The vascular endothelial growth factor (VEGF) signaling pathway (VSP) fulfills a cardinal role in endothelial cells and its inhibition has profound cardiovascular impact. This is true not only for the normal vasculature but also for the tumor vasculature when VSP inhibitors are used as anti-angiogenic therapies. Generalized endothelial dysfunction predisposes to vasoconstriction, atherosclerosis, platelet activation, and thrombosis . All of these have been reported with VSP inhibitors and collectively give rise to vascular toxicities, the most concerning of which are arterial thromboembolic events (ATE). VSP inhibitors include antibodies, acting extracelluarly on VEGF, such as bevacizumab and tyrosine kinases inhibitors, acting intracellularly on the kinase domain of VEGF receptors, such as sunintib and sorafenib. The addition of bevacizumab and VSP tyrosine kinase inhibitor therapy to the cancer treatment regimen is associated with a 1.5–2.5-fold and 2.3–4.6-fold increase risk of ATEs, respectively. Risk factors for ATEs while on VSP inhibitor therapy include age older than 65 years, previous thromboembolic events, history of atherosclerotic disease, and duration of VSP inhibitor therapy. In clinical practice, hypertension remains the most commonly noted vascular manifestation of VSP inhibition. Optimal blood pressure goals and preferred therapeutic strategies toward reaching these goals are not defined at present. This review summarizes current data on this topic and proposes a more intensive management approach to patients undergoing VSP inhibitor therapy including Systolic Blood PRessure Intervention Trial (SPRINT) blood pressure goals, pleiotropic vasoprotective agents such as angiotensin converting enzyme inhibitors, amlodipine, and carvedilol, high-dose statin therapy, and aspirin. Central to the vascular effects of vascular endothelial growth factor (VEGF) inhibitors are the actions on endothelial cell level. Anti-VEGF therapy targets not only endothelial cell proliferation and permeability, which is the goal to antagonize the formation of new tumor vessels, but also endothelial cellsurvival, vasorelaxation, and platelet activation. The end results are systemic hypertension, accelerated atherosclerosis, and arterial thrombotic events. Various interventions are geared to promote endothelial and vascular health and to reduce the detrimental effects of VEGF inhibitor therapy while maintaining its anti-angiogenic efficacy. •Increase in blood pressure is nearly universal with VEGF inhibitor therapy.•Optimal blood pressure goals and preferred therapeutic strategies are not defined.•Systolic Blood Pressure Intervention Trial target goals are justifiable in VEGF inhibitor-induced hypertension, given the high arterial vascular event risk.•Patients on VEGF inhibitor therapy may benefit from cardio-/nephro-oncology care. The concept that growth of tumors is related to their vascular supply was first described over 100 years ago.Since angiogenesis does not initiate but is involved in the maintenance and dissemination of the malignant process, angiogenesis inhibitors, for the most part, contain, but do not eliminate, cancers. This unique efficacy goes along with long, chronic treatment times, and evolving toxicities can become quite relevant for the individual cancer patient.12A recent meta-analysis of 77 studies reported that over 1200 patients need to be treated with VSP inhibitors for one fatal event to occur, and overall survival is not reduced.Almost all clinical trials have demonstrated that VSP inhibitors cause an increase in blood pressure, with 30%–80% of patients developing hypertension.The first report on automated ambulatory blood pressure monitoring (ABPM) in patients with mRCC on sunitinib showed an average increase in systolic and diastolic blood pressure by 14 mmHg and 11 mmHg, respectively, in the first week and by 22 mmHg and 17 mmHg, respectively, after 4 weeks .19 It alAs delineated in subsequent ABPM studies, increases in blood pressures occur rapidly, often within hours, and circadian blood pressure dynamics are typically lost or significantly attenuated. In a mixed cohort of patients receiving sorafinib, the average increase in blood pressure, within the first day of treatment, was 7/6 mmHg. A further increase was noted during days 6–10, followed by a plateau as steady-state concentrations of the drug equilibrated.2, and pre-hypertension were identified as predictors of a hypertensive response, each adding an absolute 10% increase in risk to a baseline risk without any risk factors of 30%.Even within the same study population, exposed to the same treatment regimen, considerable variability in the blood pressure response can be seen. Age ≥60years, body mass index ≥25 kg/mAwareness and monitoring are geared to recognize and appropriately manage blood pressure elevations in cancer patients on VEGF inhibitor therapy. In the general population, blood pressure management serves the purpose of primary (and secondary) prevention of CVD and events long-term. This used to rarely apply to cancer patients with limited exposure and life expectancy. This argument, however, may not hold any more with improvement in survival outcomes and chronicity of cancer treatment.While often not considered detrimental, even short-term increases in blood pressure can have serious implications in cancer patients on VEGF inhibitor therapy. The consequences include acute ischemic and hemorrhagic events, flash pulmonary edema, and reversible posterior leukoencephalopathy. Chronic blood pressure elevations stimulate a hypertrophic response in the myocardium, which is matched by a compensatory angiogenic response. In cancer patients on VSP inhibitor therapy, this compensatory response is inhibited, predisposing to myocardial maladaption to pressure load and “cardiotoxicity”. Hypertension is a potent risk factor for atherosclerosis, its complications, as well as atrial fibrillation, all of which can complicate the care of cancer patients significantly. Uncontrolled hypertension is conceivably of much greater risk in patients with additional CV risk factors and especially CVD. Interestingly, hypertension with VEGF inhibitor therapy is not a risk factor for proteinuria in patients exposed to this therapy.24It is also beyond the scope of this review to fully discuss the merit of systemic hypertension as a “biomarker” for the anticancer activity and efficacy of VEGF therapy. For instance, in patients on treatment with sunitinib for mRCC, overall survival was almost 2 years longer in those with systolic blood pressure increases to ≥140 mmHg.Another aspect of interest in this regard is the production of VEGF-A splice variants in cancers such as VEGF-A165b.30 Thus, while renal dysfyunction is not the initial cause of hypertension in patients on VEGF inhibitor therapy, inhibition of renal NO signaling is associated with a rightward shift of the renal pressure-natriuresis curve, impaired sodium excretion, and consequently fluid retention and salt-dependent hypertension.Various mechanisms for the development of hypertension with VEGF inhibitor therapy have been suggested . In a clWhile it is clear that VEGF inhibition interferes with NO signaling pathway activity, even in humans, it has remained a matter of debate how the interplay between VSP inhibitors and NO affects the vasculature and its contributions to blood pressure elevations.There is currently no formal guideline on the type of blood pressure monitoring in patients on VSP inhibitor therapy (office single reading vs. office average of multiple readings vs. home monitoring vs. ABPM). The Cardiovascular Toxicities Panel, Convened by the Angiogenesis Task Force of the National Cancer Institute Investigational Drug Steering Committee, recommended that blood pressures should be monitored weekly during the first cycle of VEGF inhibitor therapy, and once stable blood pressures are achieved, depending on the level of risk for complications, the evaluation schedule might be more conveniently aligned with home blood pressure monitoring or routine clinical evaluations, at least every 2–3 weeks for the remainder of treatment.2. Importantly, patients were required to be at increase CV risk by one or more of the following: clinical or subclinical CVD other than stroke; chronic kidney disease with an estimated glomerular filtration rate of 20 to less than 60 mL per minute per 1.73 m2 of body surface area, a 10-year risk of CVD of 15% or greater on the basis of the Framingham risk score; or an age of 75 years or older; patients with diabetes mellitus or prior stroke were excluded. Based on the results of this and several other trials, as well as meta-analyses on this subject, the American Heart Association along with 10 other societies released the 2017 guidelines for the prevention, detection, evaluation, and management of high blood pressure in adults.The same panel recommended less than 140/90 mmHg as the goal for blood pressure control in patients on VEGF inhibitor therapy in general and less than 130/80 mmHg for patients with diabetes and/or chronic kidney disease.P = .01).We propose that for cancer patients on VEGF inhibitor therapy, the same strict blood pressure goals should be pursued. This is not limited to secondary prevention efforts, and we would argue that these patients meet primary prevention criteria and face a 10-year risk of CVD of 15% or more by SPRINT criteria. In a study of prostate cancer patients undergoing therapy with bevacizumab, a history of myocardial infarction, angina, peripheral arterial disease, arterial thrombosis, transient ischemic attack, or stroke increased the risk of an ATE by a factor of 2.29 (0.83–5.68). In comparison, bevacizumab treatment was a stronger and even more robust predictor  inhibitors is somewhat a matter of debate. In agreement with a lesser role of the renin-angiotensin system in the mechanism of VSP inhibitor-induced hypertension, captopril was effective in lowering lower (10 mmHg) but not higher (35–50 mmHg) degrees of blood pressure elevations in animal models.In keeping with the outlined data and the overall goal to improve endothelial function and NO availability and to decrease pathological angiogenesis, one may argue that ACE inhibitors ± amlodipine is the preferred first line therapy for patients with new onset or worsening hypertension on VSP inhibitor therapy in the absence of any other comorbidity that would direct therapy. Carvedilol may be considered as a third step based on the additional beneficial vascular actions. For blood pressure control in patients with refractory hypertension, diuretics +/- nitrates may enhance the vasodilatory approach. An outline of a potential approach to therapy is provided in While hypertension is the most notable vascular effect, patients on VSP inhibitor therapy also encounter a higher risk of ischemic and thrombotic events. Indeed, chest pain episodes have been reported in 1%–15% of patients, ranging from stable angina to acute coronary syndrome.Two subsequent meta-analyses on 20 RCTs in patients with colorectal, breast, non-small cell lung, renal cell, and pancreatic cancer  reached the same conclusions.A subsequent meta-analysis of seven phase II and III trials RCTs, looking specifically at myocardial ischemic endpoints , arrhythmias, sudden cardiac death, or CV-related death) and including two more studies than in the analysis by Ranpura et al., confirmed an overall RR of 2.5 (95% CI 1.4–4.5). The total event rate was low, only 1%, and differed between low versus high-dose bevacizumab therapy (RR 2.1 [95% CI 1.1–4.2] vs. 4.8 [95% CI 1.0–22.4]). An elevated risk was most consistently noted in colorectal cancer patients (RR 2.1 [95% CI 1.1–4.1]).Cerebrovascular events have also been demonstrated in cancer patients on VSP inhibitor therapy. In a meta-analysis of 16 RCTs on cerebrovascular events in phase II and III trials with bevacizumab, the overall incidence was relatively low at 0.5%, but the RR was 3.3 (95% CI 2–5.5), again highest in metastatic colorectal cancer patients (RR 6.4 [95% CI 1.2–35.6]).With regard to VSP-TKIs, the first meta-analysis was conducted on 10 RCTs involving sunitinib and sorafenib with arterial thrombosis, cerebral infarct, cerebral ischemia, cerebrovascular accident, myocardial infarction, and myocardial ischemia as ATEs. The incidence was 1.4% overall and not significantly different between the two chemotherapeutics (RR 3 [95% CI 1.3–7.4]).As outlined above, several studies have evaluated the impact of VSP inhibition on vascular reactivity, and the synthesis of these studies is that VEGF inhibitors induce an imbalance in endothelium-derived vasodilatory and vasoconstricting factors. Endothelial dysfunction is a term often used to describe this condition, and paradoxical vasoconstriction is one of its hallmarks.Importantly, the vascular alterations seen with VSP inhibitor therapy extend into the microvasculature. Coronary microvascular dysfunction, that is, impairment of the endothelium-dependent and endothelium-independent vasodilatory response of the coronary microcirculation is noted after 8 days of sunitinib administration.This being said, arterial endothelial cell culture experiments showed that exposure to a pan-VEGF receptor TKI increases mitochondrial superoxide generation with uncoupling of endothelial nitric oxide synthase (eNOS) and subsequent imbalance in endothelial superoxide and NO production.Endothelial dysfunction also predisposes to perturbed hemostasis and vascular thrombosis.Based on the framework provided in their hypertension assessment and management document, the Cardiovascular Toxicities Panel of the National Cancer Institute extended the recommendations to address the aspects outlined above.The merit of vasoreactivity testing, ankle-brachial-index, or carotid-intima media thickness for risk stratification and the prediction of ATEs with VSP inhibitor therapy are unknown. Likewise, the predictive value of baseline and follow-up coronary computed tomography angiography and noninvasive stress testing is not defined in this population, neither for gauging the progression of CAD nor for predicting acute arterial thrombotic events. Another question is if those on VSP inhibitor therapy should be considered as high risk, as discussed above. All of these questions are pertinent only as much as the cancer therapy allows these patients to outlive and thus to experience the time dynamics of these adverse vascular events, most concerningly acute myocardial infarction and stroke.Retrospective analyses have outlined that the incidence of ATEs on bevacizumab therapy is significantly attenuated by aspirin in the high-risk group of patients ≥65 years with a prior ATE history (12.5% vs. 22.9% in aspirin nonusers).Taking the bleeding risk into consideration, it is unlikely that patients are advised to take dual antiplatelet therapy unless demanded by prior drug-eluting stent placement. In addition to medications outlined for optimal blood pressure control, the most potent intervention for vascular health and prevention in these patients may be statin therapy. Statins have been shown to improve NO bioavailability and eNOS activity. They have been shown to activate phosphatidylinositol-3 kinase and AKT signaling, which is suppressed by VEGF. Thus, there have been concerns that statins may reduce the antiangiogenic and anti-tumor efficacy of VEGF inhibitor. However, statins exert concentration- and cell type-dependent effects that need to be taken into consideration. Statins reduce the constitutive VEGF synthesis of microvascular endothelial cells, whereas they upregulate VEGF expression in macrovascular endothelial cells. Furthermore, at low concentrations, they are pro-angiogenic, whereas at high concentrations, they are anti-angiogenic.The benefit may be enhanced by the use of amlodipine, which is often required for blood pressure control in these patients as outlined above anyway and has been shown to reduce CV events in patients with mild CAD and even normal blood pressure along with preventive effects on coronary artery plaque progression.Finally, and even though difficult to accomplish in a cancer population, exercise should be advocated to promote endothelial and vascular health. This is mediated by increase in shear stress, a potent natural inducer of eNOS via the protein kinase B/AKT pathway. Shear stress-related effects during exercise are of relatively greater impact for the macrovasculature (and should thus spare the tumor microvasculature), even though restores the endothelial response to VEGF and improves endothelium-dependent vasodilatation in epicardial coronary vessels and in resistance vessels.If and when to resume cancer therapy in patients who have experienced a cardiac event is not defined. Clinical trials excluded patients with such an event within 6–12 months of initiation of treatment and often with any clinically significant CVD.Antiangiogenic therapy such as VSP inhibition has improved outcomes for several cancers but not without adverse effects. These include vascular toxicities, which were to be expected based on the cardinal role of VEGF in vascular function and health. At present, however, there are no studies to support any specific strategy, and expert consensus recommendations are nearly 10 years old. Hypertension is the most commonly seen “vascular side effect” in patients undergoing VSP inhibitor therapy, but again, the best management approach to these patients is not defined. The SPRINT trial, conducted in a patient population at higher CV risk, advocates for more intensive blood pressure targets (<120 mmHg systolic), and one may argue that patients undergoing VSP inhibitor therapy are by default at a higher CV risk based on VEGF-related impairment in endothelial function and should be more intensively treated for this reason. Endothelial dysfunction promotes vasoconstriction, atherosclerosis, platelet activation, and coagulation, all in favor of ATEs observed in this patient population. Patients with a prior ATE and ≥65 years of age are seemingly at highest risk. They in particular, but preferably anyone with a increased CV risk as defined, for instance, by the ASCVD risk score or prior CV history should receive optimal medical therapy with aspirin, ACE inhibitor, amlodipine, high-dose statin therapy . Exercise is furthermore promoted to improve CV health in these patients. The controversial nature of a more intensive management proposal is understood, but these patients now live long enough that CV complications can have a significant impact and so can preventive measures.


The findings of the study highlight the capability of artificial gravity (2-g at feet) created via SAHC toward evoking blood pressure regulatory controls analogous to standing, therefore, a potential utility toward mitigating deleterious effects of microgravity on cardiovascular performance and minimizing post-flight orthostatic intolerance in astronauts.Autonomic control of blood pressure is essential toward maintenance of cerebral perfusion during standing, failure of which could lead to fainting. Long-term exposure to microgravity deteriorates autonomic control of blood pressure. Consequently, astronauts experience orthostatic intolerance on their return to gravitational environment. Ground-based studies suggest sporadic training in artificial hypergravity can mitigate spaceflight deconditioning. In this regard, short-arm human centrifuge (SAHC), capable of creating artificial hypergravity of different g-loads, provides an auspicious training tool. Here, we compare autonomic control of blood pressure during centrifugation creating 1-g and 2-g at feet with standing in natural gravity. Continuous blood pressure was acquired simultaneously from 13 healthy participants during supine baseline, standing, supine recovery, centrifugation of 1-g, and 2-g, from which heart rate (RR) and systolic blood pressure (SBP) were derived. The autonomic blood pressure regulation was assessed via spectral analysis of RR and SBP, spontaneous baroreflex sensitivity, and non-linear heart rate and blood pressure causality (RR↔SBP). While majority of these blood pressure regulatory indices were significantly different ( CentralTherefore, to cope with the effects of orthostatic challenge on physiological performance, autonomic, baroreceptor, and vasomotor controls play a consequential role to various degrees. Enfeebled or impaired blood pressure regulatory controls owing to long-term microgravity exposure could lead to an abrupt decline in arterial blood pressure on assuming upright stance resulting in reduced cerebral perfusion . Thus, iGround-based experiments, performed to comprehend physiological response to microgravity simulated via bed rest immobilization  and poteIn the previous work from our group , we demoThe detailed experimental protocol has been explained in the previous work from our group . Here, wIn the centrifuge, the participant was strapped with their head near the center of 2.8-m radius centrifuge and feet outwards. The participant remained supine (Baseline) in the centrifuge for 20 min of baseline recording. After completion of baseline, the participant was transitioned with assistance into the standing position for 5 min (stand test). After the stand test, the participant lay supine (recovery) in the centrifuge for another 15 min, after which the centrifuge was ramped up to a rate that applied 1-g at feet  for 5 min and then increased to 2-g at feet  for 5 min. Following 5 min of centrifugation at 2-g, the centrifuge rotation was slowed and halted in 30 s.Table 1. Continuous blood pressure was acquired from non-invasive finger photoplethysmography cuff  using NI data acquisition  system at a sampling rate of 1000 Hz. Ethics approval for experimentation was obtained from the University of Toulouse. Experimentation complied with rules and regulations set forth by the research ethics board of the University of Toulouse. Written and informed consent form for participation was obtained from each participant prior to any experimentation.Data was acquired from 13 participants . The detailed demographic information is provided in Short-arm human centrifuge is a training tool capable of creating artificial gravity of different g-load . Brieflyleration . The cenDiastolic nadirs of each beat were first detected from the continuous blood pressure waveform to obtain diastolic blood pressure (DBP). The R-R time interval was obtained as the duration between two adjacent diastolic nadirs. Systolic blood pressure (SBP) was obtained as the maximum blood pressure between two adjacent diastolic nadirs. Beat-by-beat mean arterial pressure (MAP) was derived from blood pressure waveform as a mean value between two adjacent DBP locations. 5-min of data from each experimental condition was considered for analysis.nu = PV LF÷Total Power, LFnu = PLF÷Total Power, and HFnu = PHF÷Total Power, in case of RR signal the normalized power in only LF and HF frequency band was calculated as LFnu = PLF÷ and HFnu = PHF÷ where Total Power = PV LF+PLF+PHF in accordance with recommendation in the literature  of RR and SBP was calculated in very low frequency , low frequency , and high frequency  bands. There upon, the SBP power distributed (P) in the respective bands were normalized as VLFterature . The PSD1 similar to other research in the literature , signifying the feedforward (non-baroreflex) and feedback (baroreflex) controls of blood pressure was obtained using convergent cross mapping (CCM) similar to our previous work . Prior tpost hoc analysis using Tukey-HSD method to account for the significance of changes in the cardiovascular parameters and blood pressure regulatory indices during different experimental conditions. The test of significance was conducted using a statistical toolbox of MATLAB . The test results at α = 0.05 were considered significant. All tabular data in the article are presented as mean ± SD unless mentioned otherwise.Test for normal distribution of the mean of different variables studied in this research was conducted using Shapiro–Wilk test . A multiple comparison test was conducted using repeated measure of ANOVA  or Friedman test  followed by post hoc analysis using Tukey-HSD method was conducted to account for difference exerted by different experimental conditions on the cardiovascular parameters as well as on the blood pressure regulatory indices. Table 2 summarizes the behavior of cardiovascular parameters during baseline, standing, recovery, centrifugation of 1-g, and 2-g. Stand test or application of centrifugation inflicted no change in SBP (p = 0.13), DBP (p = 0.27), or MAP (p = 0.28). RR intervals reduced significantly during standing (p < 0.001) and 2-g (p < 0.001) compared to supine. Additionally, RR intervals reduced significantly during standing (p < 0.001) and 2-g (p < 0.001) compared to recovery as well as during 2-g (p = 0.02) compared to 1-g. No change in RR intervals was obtained during recovery (p = 0.99) and 1-g (p = 0.09) compared to baseline. Furthermore, no change (p = 0.57) in RR intervals was observed between standing and 2-g. Figure 1 shows an example of RR intervals and blood pressure dynamics in response to different experimental conditions.Test of normality resulted in data exhibiting mixed behavior given the limited sample size, therefore, Friedman test followed by Figure 2 summarizes the normalized spectral power distribution in the VLF, LF, and HF bands of SBP and LF, HF, and LF/HF ratio of RR intervals. The spectral power distribution in the respective frequency bands of SBP and RR in absolute and normalized units is summarized in Table 3. Table 4 lists the post hoc comparison p-value between experimental conditions for respective frequency bands. Significant change was observed in low-frequency SBP power both in normalized and absolute units during standing (p = 0.04 and p = 0.01) and 2-g (p < 0.001 and p < 0.001) compared to baseline. Moreover, the low-frequency SBP power  was significantly different during standing and 2-g compared to recovery. In addition, the SBPLF and SBPHF in absolute power were observed to be significantly different (p < 0.05) at 2-g compared to 1-g (Table 3). No difference (p > 0.10) was the behavior of such variable at 2-g compared to standing (Table 4).p = 0.007) and decreased (p = 0.007) significantly only at 2-g compared to baseline (Table 4). The LF/HF ratio increased significantly at 2-g (p = 0.007) compared to baseline. Moreover, the three metrics were significantly different (p < 0.05) during standing and 2-g compared to recovery (Table 3). In terms of absolute power no change (p = 0.87) was observed in the RRLF, while RRHF decreased significantly (p < 0.05) during standing and 2-g compared to baseline and recovery (Table 3). No difference (p > 0.10) in the dynamics of RR spectral power was obtained at 2-g compared to standing (Table 4).The spectral power (n.u.) in the LF and HF frequency bands of RR intervals increased  and 2-g  compared to baseline. Significant decline in BRS was observed during standing  and 2-g  compared to recovery as well as at 2-g  compared to 1-g (Table 3). No change  in BRS was observed at 2-g compared to standing (Table 4). The distribution of up slope and down slope BRS for the study participants is detailed in Figure 3.Baroreflex sensitivity decreased (both up and down slope) significantly during standing  and 1-g centrifugation (p = 0.04), a significant increase in baroreflex arm of the interaction compared to supine was observed, while no change (p = 0.26) in the non-baroreflex arm of the interaction was observed during experimental conditions. No change (p = 0.16) was observed in the baroreflex arm of the interaction at 2-g compared to baseline. Additionally, no difference between the standing and 2-g centrifugation was observed in the baroreflex arm .At supine rest, the non-baroreflex arm of the heart rate and blood pressure interaction was significantly higher than the baroreflex arm. During standing (The current research investigated the capability of centrifugation (1-g and 2-g) at feet to evoke autonomic control of blood pressure analogous to standing. The autonomic blood pressure regulation mechanisms via causal heart rate-blood pressure interaction, spontaneous baroreflex sensitivity, and spectral analysis of SBP and RR were studied. The analysis results ascertained previously contemplated yet undocumented potential of SAHC to evoke autonomic blood pressure control analogous to standing in natural gravity, therefore, a potential utility toward minimizing the adverse effects of long-term microgravity exposure on the cardiovascular performance, hence, minimizing orthostatic intolerance in astronauts upon return to Earth.The success of future inter-planetary missions to Mars depends on the design of pertinent countermeasures to mitigate the adverse effects of spaceflight deconditioning. The shift of central blood volume above thoracic leading to increased ventricular filling, stroke volume, and cerebral blood flow is an immediate consequence of physiological adaptation to microgravity. Accordingly, baroreceptor unloading, autonomic sympathetic nerve activity, and the vasomotor control remain vastly inhibited for the duration of spaceflight . The proFurthermore, decreased blood flow to the peripheral regions, especially to the calf skeletal muscles, render posture muscle group with nutritional scarcity, and is a major contributor toward skeletal muscle atrophy, bone remodeling, and decline in the calf circumference . While aThus, an external system capable of evoking autonomic control of blood pressure  and simultaneously increasing blood flow to the calf musculature to assure adequate nutritional and metabolic supply can mitigate the deterioration of cardiovascular performance associated with long-term exposure to microgravity.Exercise training and lower-body negative pressurization have been utilized as a potential countermeasure to spaceflight deconditioning. However, traditionally used aerobic exercise, resistance training, and lower-body suction has been limited in effect due to their inability to challenge multiple physiological systems that are associated with standing . ConsequTables 4. The results suggest the dynamics of studied variables were not different between the two conditions, therefore, the residual effects of standing was minimized and not likely to influence the autonomic behavior during centrifugation. The experimental conditions inflicted no change in SBP (p = 0.13), DBP (p = 0.27), or MAP (p = 0.28). This observation suggests that blood pressure was well-regulated during orthostatic challenge evoked via standing and centrifugation by active autonomic control of blood pressure. A significant decline was observed in the power distributed in the HF band of RR during standing (p = 0.02) and 2-g (p = 0.001) compared to baseline (Table 4), suggesting withdrawal of vagal nerve activity; resulting in a shift of sympatho-vagal balance toward sympathetic activity. Also, increase in LF SBP power was observed during standing and 2-g compared to supine (Table 3). Additionally, baroreflex sensitivity (both up slope and down slope) declined during standing and 2-g compared to supine (Table 3), which is the result of decreased vagal activity (Table 4) and increased heart rate or reduced RR intervals (Table 1) contributing toward maintenance of blood pressure equilibrium. While these markers of autonomic controls of blood pressure were significantly different from baseline during standing and 2-g, no change (p > 0.10) in the autonomic blood pressure control between standing and 2-g was observed (Table 4). Moreover, no change (Table 4) was observed in these indices between baseline and 1-g. This observation suggests 2-g is more closely related to standing compared to 1-g in terms of stimulating autonomic blood pressure regulatory controls.We applied external perturbation to the hemodynamic homeostasis via stand test and centrifugation of 1-g and 2-g at feet. A recovery period followed a stand test to minimize its influence on the autonomic behavior during centrifugation. The comparison result of baseline and recovery period is summarized in While the spectral analysis of SBP and RR time series and baroreflex sensitivity are well-accepted norm to account for the autonomic control of blood pressure, criticism of such approaches in the literature is also prevalent for the inability of the spectral method to account for the non-linearity of underlying physiology and BRS for not able to address the closed loop heart rate and blood pressure interaction . As suchFigure 4. No change (p > 0.05) was observed in the dynamics of non-baroreflex (RR→SBP) causality during standing or 2-g compared to supine. However, a significant increase was observed in the baroreflex (SBP→RR) causality; both during standing (p = 0.009) and 1-g (p = 0.04), Table 4. No change (p = 0.16) was observed in SBP→RR causality during 2-g compared to baseline. The slight decline in baroreflex causality at 2-g compared to 1-g (Table 3) could be due to the fact that 2-g was more stressful than standing and 1-g evident from certain study variables , which changed only at 2-g compared to baseline. Furthermore, heart rate, BRS, SBPLF, and SBPHF changed significantly at 2-g compared to 1-g (Table 3), which further hints toward 2-g being more stressful than 1-g. The RR intervals reduced at 1-g (p = 0.09) albeit not significantly but given limited sample size it does hint toward 1-g being more challenging than baseline. The baroreflex coupling is observed to decline before syncope (p = 0.80) or baroreflex (p = 0.88) causal events during centrifugation compared to standing (Table 3). Therefore, the observations of current study suggest centrifugation at feet is capable of evoking autonomic control of blood pressure analogous to standing.The results of closed loop heart rate and blood pressure interaction are detailed in  syncope , in our Table 4), which indicate 2-g was more stressful than standing. Accurate information regarding the degree of blood pooling achieved during each experimental condition will shed further light pertaining to the vigor of 2-g in relation to standing.Experimental protocol in the current study was not randomized, i.e., centrifugation always followed the stand test. Although a 15-min recovery period was adopted to minimize the effects of stand test on centrifugation, in future study randomized experimental protocol should be considered. Furthermore, due to the unavailability of the respiration signal, the role of hypergravity toward the dynamics of respiration could not be studied. Respiration is known to affect both heart rate (RR) as well as blood pressure . AdditioMoreover, additional mechanisms that account for blood pressure regulation such as skeletal muscle pump  shall also be investigated and compared in the future . FurtherCardiovascular adaptation to microgravity impairs autonomic control of blood pressure, consequently, astronauts are susceptible to orthostatic intolerance on return to gravitational environment. Sporadic training in artificial hypergravity is proposed to mitigate the effects of spaceflight deconditioning. SAHC is a promising tool for simulating artificial gravity of different g-loads. The response of blood pressure regulatory controls to simulated hypergravity in relation to standing is not well-established in the literature.Table 4). The findings of the current study lead us to conclude that 2-g centrifugation at feet via SAHC has potential to evoke autonomic control of blood pressure analogous to standing, therefore, a potential training tool toward reducing orthostatic intolerance in astronauts on their return to Earth.In the current article, we investigated the response of autonomic control of blood pressure during centrifugation (1-g and 2-g) in relation to standing. While no difference was observed in the autonomic control of blood pressure between standing and centrifugation, the blood pressure regulatory indices during standing and centrifugation (mostly 2-g) were significantly different from baseline (NG and AB conceived the centrifuge study and designed the experiment. AV and KT conceived the data analysis steps. MB, NG, and AB acquired the data. DX preprocessed the data. AV performed the data and statistical analyses, wrote the manuscript, and created the figures and tables. AV, DX, AG, NG, AB, and KT interpreted the results. All authors contributed to manuscript editing and approved the final version for publication.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


No known data in the literature assessing practice of kidney stone prevention in the emergency department (ED) is available.Assess patient perception and compliance to kidney stone prevention given within the emergency department. It also indirectly detects the attitude and practice patterns of primary care providers in kidney stone prevention.This is a qualitative study done in a single institution from January 2018 to January 2019 that includes 99 patients that were diagnosed with kidney or ureteral stone in ED and were discharged home, all of them where stone formers. They were asked to fill a self- administered questionnaire when they are able to read, or interviewed by the resident within the ED when they are unable to read.p < 0.05).The majority of patients (68%) did not receive any instructions about kidney stones prevention within the ED. Most of patients who follow instructions if it was given were educated (90%), had an insurance coverage (85%), and had an income higher than $1000 per month (76%), (Seventy one percents of patients believe in the effectiveness of stone prevention if it was provided and most of them are interested in learning about these preventive strategies (82%).Reasons for not following the instructions about kidney stones prevention measures were the cost (53.1%) following by the lack of explanation by ED physicians (18.8%).The majority of patients (62.6%) prefer to receive kidney stones prevention measures from urologists.Most of patients in our institute did not receive kidney stones prevention measures in ED despite that they declared their interest in following these measures. Most of the time they did not adhere to those measures due to socioeconomic factors and lack of clarifications. If these instructions were given within the ED, it could lead to an acceptable compliance rate.The online version of this article (10.1186/s12873-019-0263-0) contains supplementary material, which is available to authorized users. Kidney stones are becoming a ubiquitous problem in the emergency setting as both prevalence and incidence are increasing in all age groups . UrinaryIt is very important after initial evaluation of patients in the ED to follow these patients after discharge, secondary prevention of kidney stones not only decrease the patient revisit to ED but can reduce the healthcare cost and complications of kidney stones . The mosThe primary objective of this study is to assess how the patients perceive kidney stones prevention measures if they are given in the ED. The secondary objective is to evaluate how the patients are following the instructions that were given before discharge and to suggest solutions for a better compliance rate. Our study was also implemented as a qualitative study to indirectly detect the attitude and practice patterns of primary care providers in kidney stone prevention.This is a qualitative study on the current prevention instructions and education concerning kidney stones given to patients in the ED at Zahra Hospital at Beirut. The study was approved by our Institutional Review Board. We interviewed patients in the ED that were diagnosed with recurrent kidney or ureteral stones from January 2018 to January 2019. During this time frame, 99 patients were enrolled in the study, all of them agreed to participate. Symptomatic patients with Kidney or ureteral stones were diagnosed by non-contrast-enhanced computed tomography (CT).All patients were asked to fill a self-administered questionnaire  was a condition to test the goodness of fit of the model and its ability to predict the dependent variable (willingness to follow instructions). The Nagelkerke R2 was checked to assess the usefulness of the explanatory variables in predicting the dependent variable. The contribution of each determinant in the multivariable analysis was expressed as an odds ratio (OR) and a 95% confidence interval (CI).Models adequacy to data was insured by the Hosmer–Lemeshow test. Non significant (The majority of patients (68%) did not receive any instructions about kidney stones prevention before emergency room discharge. Table p < 0.05).Level of education was significantly different between patients who receive and who do not receive instructions from physicians .Most of patients who follow instructions (62%) if it was given are educated (90% vs. 10%), had an insurance coverage (85% vs. 15%), and had an income higher than $1000 per month (76 vs. 14%), than those who do not follow instructions .Twenty-six percents of patients who were asked about their knowledge of kidney stones prevention measures had no idea about this topic, but 71% of patients believe in the effectiveness of those measures if they are given and most of them showed interest in learning about prevention strategies (82%). The knowledge of patients, the perception of the effectiveness of prevention measures, and the interest of learning more about kidney stones prevention were significantly different between patients who receive and who do not receive instructions from physicians ; however, most patients who believe in the effectiveness of prevention measures receive instructions (respectively 96.9% vs. 59.7 and 98.6% vs.3.6%). Results are summarized in Table The most common reason for not obeying instructions about kidney stones prevention measures was the cost 53. 1%) following by the lack of explanation by ED physicians and difficulties to adhere to instructions (18.8%). Results are illustrated in Fig. % followiMost of the patients believe that kidney stones prevention measures in ED will be improved if ED physicians spend more time explaining preventive measures (33.3%) and providing them with written instructions (31.3%), and by being referred to urology clinic after discharge27.3%). Results illustrated in Fig. 7.3%. ResMoreover, the majority of them prefer to receive kidney stone prevention measures from Urologists (62.6%) see Fig. The lifetime prevalence of nephrolithiasis in the United States is estimated to be between 5% and 12%, with the probability of having a stone varying according to age, gender, race, and geographic location . NephrolMore than 90% of patients evaluated in EDs for stones are discharged after treatment . PreventA study identified the incidence of follow-up in patients who attended an ED for kidney stones. It shows only 48% of patients seen in the ED for kidney stones received follow-up care, in 68.3% of these cases with a urologist. Among patients who received follow-up care, the use of stone prevention strategies was higher when the care was delivered by a urologist .We found in our study that most of the patients (68%) did not receive any instructions about kidney stones prevention. Those who received instructions had an acceptable level of education. This may be related to two factors; first, the fact that educated patient will read more thoroughly about kidney stone disease and ask for clarifications about preventive measures, while on the other hand the ED physicians assumed most of the time that kidney stones prevention in illiterate patients is not important.The instruction adherence to recommendations if it were given was 62% and most of the patients who followed these instructions were educated, had insurance coverage and an income more than 1000$ per month. This indicates that the patient socioeconomic status affects patient adherence to these instructions. A study of 300 patients evaluating compliance of the recurrent renal stone former with current Canadian Urological Association (CUA) best practice guidelines showed that 45.8% of patients were compliant with CUA best practice guidelines even if they received satisfactory education from their urologist and primary care physician. In addition, 67. 1% of patients believed in the efficacy of preventative stone measures and 22.8% of patients perceived their stone disease to be severe . Dauw etThe lack of explanation and not providing written instructions can have an important role in adherence to the recommendations. Chan et al. concluded that people had poor knowledge of kidney stones, its suitable diet and the importance of more liquid consumption to prevent recurrence .Most of the patients in our study were highly motivated to learn about kidney stones prevention and showed a high adherence rate if those instructions are given within the ED.Many suggestions were made to improve kidney stones prevention strategies within the ED, highlighting the importance to give more time to patients for further explanation, urologist visit to ED for primary education as most of the patients prefer to receive kidney prevention recommendations from the urologist.At the end of the study, we asked our ED physicians about the reasons for not giving instructions for patients before discharge. From fifteen ED physicians in our hospital that were asked, six of them said that the cause of not giving instructions was the lack of communication with the urologists and nephrologists concerning kidney stone prevention, five of them said that the cause was a shortage of time to explain and four of them said they lack the experience in such practice within the ED. We think that a multidisciplinary approach between Urologists, nephrologists and ED physicians in kidney stones prevention in the ED settings will help in the prevention of recurrent kidney stones disease. Collaborative care among physicians should be the aims of future study regarding kidney stones prevention.Our study had several limitations. It describes a small number of patients at a single academic institution, thus potentially limiting its generalization to other populations. Since there were no previous studies to refer to, regarding kidney stone prevention in the primary care setting, we set a 1 year period to study this subject, where we studied 99 patients. The questionnaire distributed to participants was not validated; however, many urologists with subspecialty training in stone management formally reviewed the survey prior to recruitment.Most of the patients seen acutely in the ED for kidney stones do not receive prevention instructions by the ED physicians. If these instructions were given within the ED, it could lead to a high compliance rate. Many factors such as the socioeconomic status and medical coverage should be considered when kidney stones prevention tips were given.Additional file 1:Patients questionnaires. (DOCX 17 kb)


The Na/K ratio in urine stands for the dietary of sodium and potassium intake in patients with chronic kidney disease remains unclear for the renal progression. We aimed to determine the risk of progression of chronic kidney disease based on the Na/K ratio in a 24-hour urine collection.We determined the association between the progression of renal disease and 24-hour urinary sodium and potassium (Na/K) ratios in 2238 patients over a 5-year timespan using data obtained from the KoreaN cohort study for Outcomes in patients With Chronic Kidney Disease (KNOW-CKD). Renal events were defined as a 50% decrease in the glomerular filtration rate (GFR) below baseline, or the onset of end-stage renal disease (ESRD). Patients were divided into 4 groups based on the quartile range of the 24-hour urinary sodium and potassium ratio. We analyzed those variables in the 4 groups. Multiple logistic regression analyses were performed using the data of 1001 patients to identify the independent factors associated with renal events.Age and male sex accounted for the greatest number of patients in the group with the highest values (group 4) of the 24-hour urinary Na/K ratio (≥3.85). There was no difference in the prevalence of hypertension or diabetes mellitus, the ratio of use of antihypertensive drugs, blood pressures, or estimated GFRs. In the group with the highest urinary Na/K ratio, the 24-hour urinary Na concentration mean ± standard deviation was 188.7 ± 70.6 mmol and that of urinary K was 39.9 ± 16.1 mmol. The urinary protein excretion was highest in the group with the highest urinary Na/K ratio. In the logistic regression analysis, the effect on renal events increased with increasing urinary Na/K ratios. After adjusting for other factors, the risk of renal events was 2.48  1.30–4.90) in group 3, and 3.75 (95% CI: 1.35–11.27) in group 4. In the Kaplan–Meier analysis, the higher the urinary Na/K ratio, the higher the rate of CKD progression.Based on our analyses, we concluded that the higher the urinary Na/K ratio, the greater the risk of CKD progression. There are some studies that provide evidence for such assertions. In an 11-year observational study of 2196 women with normal renal function, a higher intake of sodium based on questionnaire results showed a faster decline in glomerular filtration rate (GFR). In a study of the effects of ramipril in 500 patients with glomerulonephritis, elevated 24-hour sodium excretions resulted in the development of end-stage renal failure (ESRD). The same result was obtained after adjusting for proteinuria associated with deterioration of renal function. However, some studies have shown that sodium intake is not associated with deterioration of renal function. Approximately 800 nondiabetic patients with nephropathy participated in the Modification of Diet in Renal Disease (MDRD) study. There was no correlation between urinary sodium excretion and ESRD or all-cause mortality. The reason for the difference in the study results was that the potassium intake was not adjusted. Because potassium intake increases the excretion of sodium thereby lowering blood pressure and reducing kidney damage, increased intake of potassium increases the excretion of sodium in the urine and decreases blood pressure. Increased potassium intake also increases Kallikrein secretion, reduces glomerulosclerosis, and inhibits tubular damage.,8 The Na/K in urine stands for the dietary of sodium and potassium intake. Therefore, a study suggested that the relationship between the urine sodium/potassium (Na/K) ratio and blood pressure in the general population. When sodium intake was high, blood pressure increased, but if potassium intake was high, there was an increase in excretion of sodium into the urine. In particular the group who had higher sodium intake experienced a greater decrease in blood pressure with higher potassium intake. However, this study was conducted in the general population, and the results of the study in patients with chronic kidney disease were different. In an analysis of 24-hour urine sodium concentrations in 3939 patients with chronic kidney disease, renal outcomes such as the onset of ESRD and 50% decreases in the estimated GFR (eGFR) occurred more frequently with increased excretion of urine sodium and potassium. In this study, the renal outcome was poor when the potassium excretion was high, which was different from that of the general population in general. Therefore, we decided to conduct a study on the progression of renal disease and its relationship to results of 24-hour urine Na/K ratios in patients with chronic kidney disease.The excessive intake of salt directly leads to worsening of hypertension.22.1 We excluded patients with a previous history of chronic dialysis or kidney transplantation, heart failure (NYHA class 3 or 4) or liver failure (Child–Pugh class 2 or 3), past or current history of malignancy, and current pregnancy. The KNOW-CKD protocol was approved by the institutional review board at each participating hospital, including Seoul National University Hospital, Yonsei University Severance Hospital, Kangbuk Samsung Medical Center, Seoul St. Mary's Hospital, Gil Hospital, Eulji Medical Center, Chonnam National University Hospital, and Busan Paik Hospital.The KoreaN cohort study for Outcomes in patients With Chronic Kidney Disease (KNOW-CKD) is a prospective cohort study of 2238 patients with nondialysis chronic kidney disease (CKD) stages 1 to 5 who were enrolled between February 2011 and January 2016 in Korea. The detailed design and methods of the KNOW-CKD were previously published.Of the 2238 patients, 1192 were excluded comprising 279 patients with missing urine sodium data and 956 with missing urine data. The outliers with respect to the urine Na/K ratio were also excluded (n=2). Ultimately, 1,001 patients were included in the final analysis , diastolic blood pressure (DBP), body mass index (BMI), medical history of hypertension and diabetes, serum creatinine, 24-hour urine Na/K, total cholesterol, triglyceride (TG), high-density lipoprotein cholesterol (HDL cholesterol), low-density lipoprotein cholesterol (LDL cholesterol), fasting blood sugar (FBS), HbA1c, the presence or absence of metabolic syndrome, and antihypertensive medication history , estimated GFR, 24 hours urine protein. The eGFR was calculated using the 4-variable CKD-EPI equation. Metabolic syndrome was defined by the presence of 3 or more of the following: abdominal obesity > 90 cm in men or > 80 cm in women, triglyceride level ≥ 150 mg/dL, or taking medication such as lipid lowering agent, HDL-C level < 40 mg/dL in men or < 50 mg/dL in women, or taking medication, systolic blood pressure ≥ 130 mm Hg and/or diastolic blood pressure ≥ 85 mm Hg, or taking medication, and fasting plasma glucose level ≥ 100 mg/dL, or taking medication. Thresholds for abdominal obesity were defined based on the Asian population. We defined renal events as a 50% decrease of the GFR from baseline and/or the start of renal replacement therapy.CKD and its stages were defined from the Kidney Disease Improving Global Outcomes (KDIGO) 2012 guidelines.Completeness in the 24-hours urine is determined by the subject's records. And also we defined appropriate urine collection as the ratio of measured 24-hour urinary creatinine to estimated 24-hour urinary creatinine of 0.75 to1.25, and patients with ratio in this range were included. If the ratio over 1.25 or below 0.75, we checked the amount of urine volume and review the urine creatinine and exclude the extreme outliers for urinary creatinine > 3 SD from mean.2.32, so we performed a subgroup analysis of the patients with GFRs from 15 to 90 mL/min/1.73 m2. A Cox proportional hazard model was also used to evaluate the significance of the uric acid level with respect to outcomes. R version 3.1.1.  was used for all data analyses. Statistical significance was considered when the P value was <.05.To determine the characteristics of the subjects, a descriptive analysis was used for continuous variables. For categorical variables, the χ2 test was performed to determine the correlation between different variables. We divided the subjects into quartile according to the 24-hour urine Na/K ratio. To compare the characteristics between the groups, an analysis of variance (ANOVA) was performed. In a multiple logistic regression analysis to determine the incidence of renal events and composite outcomes, we adjusted for the potential confounding factors of age, sex, smoking status, waist circumference, BMI, triglycerides, 24-hour urine protein, and metabolic syndrome. Potassium excretion was affected when the GFR was <15 mL/min/1.73 m33.1A total of 1001 patients were categorized 24-hour urinary Na/K ratio into quartile. Across all 4 groups, patients in the highest 24-hour urinary Na/K ratio were group 4 and them who had the lowest were group 1. The oldest patients were found in group 1 and the youngest were found in group 4. The proportion of men was the lowest in group 1 and the highest in group 4. The proportion of smokers was the lowest in group 1 and was higher in groups 2 and 3. The proportion of patients with hypertension was the highest in group 3 and that of diabetes mellitus was the highest in group 1. There was no difference in the ratio of patients with hypertension and diabetes. The use of antihypertensive medication was more than 80% on average, and the use of diuretics was the highest in group 4, but there was no significant difference among the groups. Systolic blood pressure was highest in group 3 and diastolic blood pressure was lowest in group 4. Likewise, statistical significance was not observed, as shown in Table The mean proportion of hypertensive patients with blood pressures <140/90 mm Hg was 70% overall with no difference between the groups. Waist circumferences were increased in groups 3 and 4. BMI was the highest in group 3. The proportion of patients with metabolic syndrome was lower in groups 1 and 2, but there was no significant difference among the groups. The TG level was the highest in group 4, but the other lipid levels showed no difference among the groups. FBS and glycated hemoglobin were not different among the groups2 in group 4. There was no difference in the proportion of patients with CKD among the groups. Proteinuria was the highest in group 4 (1602 mg).The average 24-hour urinary sodium was 188.7 mmol in group 4, and the average 24-hour urinary potassium was 39.9 mmol. The average GFR was 47.2 mL/min/1.73 m3.2P = .003) and 2.78 in group 4 , respectively. The higher the group was, the higher the proportion of renal outcomes that occurred. After adjusting for covariates, the odds ratio of renal outcomes was 2.48  in group 3 and 2.95  in group 4.A regression analysis of renal outcomes with respect to age, sex, smoking status, waist circumference, BMI, TG, and 24-hour urine protein was performed. Compared to group 1, the odds ratio of renal outcomes were 2.52 in group 3  1.39–4.79; 2, which affected the excretion of potassium, the renal outcomes, 50% decrease of the GFR from baseline and/or the start of renal replacement therapy, are as follows: compared to group 1, the risk of renal outcomes was higher in group 3  and higher in group 4 . After adjusting for covariates, the risk of renal outcomes was 2.30 higher in group 3 , and higher in group 4  (Table Except in cases of GFRs <15 mL/min/1.73 mP < .001), and in patients with eGFR 15–90 mL/min/1.73 m2, groups 3 and 4 had lower event-free survival probabilities than groups 1 and 2 (P = .006) . Dietary sodium and potassium intervention studies in 1906 Chinese people showed that low sodium and high potassium interventions correlated with blood pressure. People who are sensitive to sodium intake showed more effective blood pressure lowering. Increased potassium intake in people with high salt sensitivity is reported to be more effective for controlling blood pressure. In our study, the urine Na/K ratio in group 3 was more associated with renal impairment. For people at the same level as group 2, the average daily intake of sodium should be <160.1 ± 105.2 mmol/day, and potassium should be consumed in excess of 61.6 ± 42.2 mmol/day to decrease the negative effects on renal function. Sodium should be consumed in amounts < 3680 ± 2,418 mg, and potassium should be consumed in amounts >2,407 ± 1649 mg per day. This includes the WHO recommended Na/K 1:1 intake. When sodium is converted to salt, it should be consumed at <9.2 ± 6.0 g, and potassium should be consumed at the recommended daily dose of 3,000 mg. Additionally, if GFR is decreased, potassium should be consumed with caution.There is a plethora of research on the recommended daily allowance of sodium. There is a report that the intake of 1.787 to 2.391 g sodium per day lowers cardiovascular disease.After the use of a diuretic, the sodium reabsorption in the thick ascending limb is decreased, urinary sodium is increased, and urinary potassium excretion also increases. If the use of diuretics is not confirmed, the results of the study may be limited. In our study, there was no difference in diuretic use among the 4 groups in the 24-hour urine Na/K ratio. There was no significant difference in the GFR that affected the excretion of potassium among the groups. Also, there was no difference in the percentage of CKD among the groups. All the factors that might affect urinary sodium and potassium excretion were adjusted. After that, it was confirmed that if the urine sodium was high and the potassium was low, the renal function would deteriorate quickly. sex, smoking status, blood pressure, BMI, dyslipidemia, hyperglycemia, and proteinuria were different among the urinary Na/K ratio groups. In a regression analysis of renal outcomes, BMI, HbA1c, serum creatinine and proteinuria, and 24-hour urinary Na/K ratios were significant. In the Cox analysis, groups 3 and 4 showed more renal outcome than the other groups. The level of the ratio of urinary sodium and potassium in group 3 and 4 was also found to have exacerbated the worsening of renal function compared to the other factors exclude the eGFR below 15 mL/min/1.73 m2.Among the factors that could affect the deterioration of renal function, age, We did not analyze it separately, so an accurate assessment of the impact of proteinuria could not be made. However, our study was conducted by collecting 24-hour urine specimens for more than 1000 patients with CKD.The limitations of this study include the relatively short observation period and the fact that other factors affecting renal function deterioration were not properly evaluated. A re-analysis should be performed with a longer observation period. The collection of the 24-hour urine was not well evaluated, and there may have been an error in its interpretation. The amount of urine proteinuria may have affected the degree of deterioration of renal function. There is a study that divided urine proteinuria by 1 g. 2. In our study, we found that low sodium intake and high potassium intake could delay the deterioration of renal function. However, additional analysis is needed after evaluating the 1:1 ratio of urinary sodium and potassium before and after accurate urine volume assessments, and increasing the observation period.Unlike previous studies, the 24-hour urine Na/K ratio was analyzed. The benefit of this method was that both effect of sodium and potassium was considered. Also the GFR, which affects potassium excretion, was excluded, except in cases where it was <15 mL/min/1.73 m5In patients with CKD, the higher the ratio of urine sodium and potassium over a 24-hour period, the faster the deterioration of renal function.Conceptualization: Hoseok Koo.Data curation: Tae Hee Kim.Formal analysis: Hoseok Koo, Subin Hwang, Tae Hee Kim.Funding acquisition: Curie Ahn.Investigation: Kook-Hwan Oh, Curie Ahn, Yeong Hoon Kim.Methodology: Sun Woo Kang.Supervision: Kook-Hwan Oh, Curie Ahn, Yeong Hoon Kim.Writing – original draft: Hoseok Koo.Writing – review & editing: Tae Hee Kim.


Background: After a Stroke, there is an autonomic nervous system (ANS) changes. Transcranial Direct Current Stimulation (tDCS) can promote the reorganization of the affected circuits.Objective: To evaluate the effects of tDCS applied before a session of physical activity on the treadmill, in the modulation of the autonomic nervous system of post-stroke patients.Methodology: Cross-over study, were randomized 12 adult hemiparetic subjects in 2 groups, Group 1 (active tDCS before exercise on the treadmill) and Group 2 (sham tDCS before exercise on the treadmill). Stimulation times were 20 min; treadmill time was 20 min. The heart rate variability (HRV) and Variability of Systolic Blood Pressure (VSBP) were evaluated for 15 min, in 3 periods (pre and post tDCS and during exercise recovery on the treadmill).Results: There was no difference in the VSBP and the HRV between the groups, compared with the baseline data; however, in the intragroup analysis, the parasympathetic modulation after active tDCS increased by 18% over baseline by the RMSSD with IC 95% (−7.85 to −0.34). In group 1, the post-tDCS active and post-exercise periods presented a value of variance above baseline, indicating a better prognosis. In group 2, there was a significant reduction of 38% of Variance values (p = 0.003) after tDCS sham.Conclusion: tDCS does not generate immediate effects on HRV and VSBP, except for intragroup comparison, which has greater participation in parasympathetic modulation in the group receiving active tDCS. One of the most serious causes of stroke reoccurrence is the alteration in the Autonomic Nervous System (ANS) function that leads to a reduction of heart rate variability (HRV). This was due to the disbalance to the homeostasis of the autonomic control, based on cardiac interbeat intervals analyzed by the physiological information, which can lead to myocardial infarction and sudden death –3.Damages to ANS can also affect the control of blood pressure (BP). McLaren et al.  conducteAlthough the mechanisms of this cardiovascular autonomic dysregulation have not been fully understood, several studies , 5–7 sugUpon the importance of the ANS in cardiovascular control, some studies have researched the effects of Transcranial Direct Current Stimulation (tDCS) over the left temporal cortex in the ANS modulation. One of them is the study from Montenegro et al.  that appThe use of tDCS in individuals with stroke is safe and may be used during the rehabilitation to promote the reorganization of circuits affected by the lesion . HoweverWith the increase in surviving patients from stroke events, it is important to expand the comprehension of the lesions' chronic effects and that interferences in this sense, when positive, will enable better prognosis of cardiac autonomic function, reducing the possibility of a stroke relapse and sudden death and providing also better quality of daily living.Therefore, the main objective of the study was to evaluate the HRV and the Variability of Systolic Blood Pressure (VSBP) in hemiparetic patients due to stroke in basal conditions (rest), immediately after the application of active tDCS and sham (pre-exercise) and during the exercise recovery on the treadmill. As a secondary outcome, the performance of the exercise, and perception of stress was evaluated, with the cardiac parameters .This study consists of an original cross-sectional, randomized, controlled, double-blind trial study of 12 adult hemiparetic stroke patients. The study followed the norms set by the Consort.Survey participants included those with stroke hemiparesis for more than 6 months ; from 21Those with cognitive impairment  with a score below 24 points  were exchttps://clinicaltrials.gov/ct2/show/NCT02956096.This study was performed at University Nove de Julho at unit Vergueiro and approved by Ethics Committee of University Nove de Julho (protocol CAAE: 57314716.7.0000.5511), São Paulo, Brazil and registered in Clinical Trial (NCT02956096) The patients were submitted to two intervention protocols crossover (active tDCS and sham tDCS) :Evaluation of basal HRV (15 min), followed by active direct current transcranial stimulation (tDCS) (20 min). Immediately at tDCS, 15 min of HRV assessment followed by 20 min of treadmill walking, and finally another 15 min of HRV during exercise recovery.Evaluation of basal HRV (15 min), followed by sham direct current transcranial stimulation (tDCS) (20 min). Immediately at tDCS, 15 min of HRV assessment followed by 20 min of treadmill walking, and finally another 15 min of HRV during exercise recovery.Protocols (active tDCS or sham tDCS) were randomized to the first day of treatment only. On the second day (after 48 h) , the croRandomization was performed by lottery with brown, sealed envelopes to ensure reliability. The contents of each envelope determined which protocol the patient would initiate.The investigators responsible for the evaluation procedures and the patients were blinded to the treatment being applied (active tDCS or sham tDCS).2  surface electrodes, wrapped in a moist saline sponge with a 2 mA current for 20 min before exercise in running machine.The patient was seated to receive the stimulus. Stimulation was performed with the NeuroConn tDCS DC-Stimulator Plus device using two 5 × 5 cmThe anode electrode was positioned over the left temporal cortex (T3) and the cathode electrode over the middle deltoid muscle contralateral to the anode. In placebo stimulation, all lead positioning procedures were performed equally to the active tDCS procedure, but the stimulator was maintained on for 30 seconds (according to the fake device program). The patient was informed that he would feel a slight initial tingling, but would reduce, disappear or stay for 20 min after application. Thus, the patients had the initial feeling, but did not receive any stimulus in the remaining time. This procedure is a valid form of control in transcranial direct current stimulation studies .After 20 min of tDCS in a sitting position, the patients were positioned standing on the treadmill. To avoid possible falls, at least two physical therapists followed the exercise next to the patient. Cardiorespiratory parameters were monitored, such as heart rate, blood pressure, and oxygen saturation. Should these parameters be changed that put them at risk or if they expressed an interest in withdrawing from intervention, this would be immediately discontinued.The velocity and inclination of each individual were determined by a previous exercise stress test using the modified Harbor protocol . Speed w2) and blood pressure (BPA) were continuously recorded every 2 min of exercise. Dyspnea scores and perception of lower limb fatigue were measured at rest and immediately after an exercise session by the modified Borg scale ; heart rate (HR), oxygen saturation . The data HRV were evaluated immediately after exercise for 15 min (during the exercise recovery). For this, the patient was positioned in seated and told not to move or speak.For this, a Finometer hemodynamic meter  was used. It consists of equipment used to continuously monitor non-invasive cardiac pressure, which uses the technique of digital infrared photoplethysmography. For this procedure, an inflatable cuff is used around the middle finger phalanx.Hemodynamic variables such as systolic (SBP), diastolic (DBP), mean (MBP), blood pressure (BP), cardiac output (CD) and total peripheral resistance (RPF) were assessed by beating and recorded in BeatScope software., based on values derived from the blood pressure curve and information on age, gender, weight, and height.The data collection of blood pressure and its derivations such as the intervals R-R, observing the waves of high frequency (HF), low frequency (LF), and the low frequency interrelation with high frequency (HF/LF), were collected continuously in the basal periods and during the recovery from acute exercise for 15 min.The HRV analysis followed the Task Force's short-term spectral analysis in the time and frequency domain .BeatScope. The data were converted and stored in Excel files, used posteriorly for spectral analysis. A verification by visual inspection was performed by software CardioSeries, to identify and/or correct some premature or affected ectopic beats, using the linear interpolation to remove undesirable transients that alter the signal stationarity. The variations of Pulse Interval (PI) were evaluated in the time domain and the frequency domain by the linear method.The cardiac modulation evaluation was performed by the register of interval R-R (ms) with the software The linear methods were analyzed in the time domain and the frequency domain. Therefore, each RR interval was measured during a determined time interval, as described in the heart rate variability, calculating the floating transducer indexes of cardiac cycles.RR intervals were collected in three periods: pretreatment  for 15 min, immediately after tDCS application was completed (for 15 min) and during recovery from treadmill exercise (15 min).In all three periods, the patient remained seated, without speaking or moving. Only 5 min of each patient's data were used for visual inspection by CardioSeries software to identify and/or correct some premature ectopic beats or artifacts, using linear interpolation to remove unwanted transients that could alter the signal stationarity of these patients analyzes in each period.2 and is better correlated with the vagal modulation. But by the frequency domain, data were analyzed were through the high band (0.15 and 0.4 Hz), and low frequency (0.04 and 0.15 Hz) in its absolute values, and the sympathetic vagal balance.The indexes obtained by the determination of RR intervals by the time domain were the average of pulse interval RR through the absolute Variance and RMSSD that is the square root of the squared mean of the difference between the adjacent normal RR interval, in a time interval expressed in msSPSSR version 17.0 according to the distributed nature of variables, the central tendency measures, and the dispersion to be used as the averages and standard-deviation (parametric) or median and interquartile interval (non-parametric). HRV and BPV data are presented as mean ± SD or median and interquartile interval. For comparison between the applications, parametric tests (ANOVA of two repeated measure ways) and for the none-parametric tests were used (Friedman followed by the post-test Wilcoxon). P < 0.05 was considered statistically significant.The data were analyzed in the statistic program, Twenty-two patients were selected, 10 were excluded , disliking having to stand still and not talking during HRV analysis (two patients), and unable to return to another assessment (Crossover) (one patient), thus constituting a sample of 12 patients.2), blood pressure (BP), motor classification according to Fulg Meyer .To describe the demographic data of the patients, data were collected on age (years and months), topographic diagnosis of stroke, time of injury, classification (hemorrhagic or ischemic), affected hemisphere, weight (kg), height (cm), body mass index  of five individuals from the active tDCS group and five individuals from the tDCS sham group (crossover) from the pilot study.To make the total average of the standard deviation, the sum of all deviations was calculated and divided by 6, which represents the total number of periods of the two groups.* Power 3.1.9.2 program and applied F tests, with a repeated-measures ANOVA statistical test between two factors with an α = 0.05, β = 0.80, and sample correlation of 0.5 giving an n = 90.To calculate the effect size (0.2453323), these values were entered in the G The clinic-demographic characteristics of patients are presented in 2 with the average weight 72.25 ± 11.03 kg and an average height of 165 ± 9.92 cm, showing that the patients of the sample were overweight.The heart rate average in rest was in (71 ± 10.70 bpm) within the normality and the SBP (130 ± 8.42 mmHg) and DBP (76 ± 9.30 mmHg) indicating stage 1 hypertension. All hypertense patients (83%) took medication for arterial hypertension, showing, therefore, a resistance hypertension degree.Metabolic deficits such as diabetes or thyroid dysfunction were also not exclusion criteria, and of the 12 subjects participating in the study, three had drug-controlled type two diabetes.All patients in the sample were overweight, as can be seen in The result presented in In The results of The results of HRV in In the period's post, tDCS and post-exercise in the linear analysis of time-domain of HRV intra-Group were observed that the variance value in the period post active tDCS increased in respect to the basal values, but did not maintain this increase in the post-exercise period. However, in the analysis intra-Group in the period post tDCS sham is also observed an increase in the variance value in respect to the basal values; however, in the period post-exercise of the group sham, there was a significant reduction in respect to the basal values.Moreover, in the analysis intra-Groups, it was observed that RMSSD after active tDCS increased significantly and reduced after the exercise recovery period, but not significantly. In tDCS sham Groups, there was no significant difference in RMSSD.In the frequency domain, it was observed an increase of Low-frequency band after the application of tDCS active and a reduction of the low-frequency band in the period post-exercise. However, in Group tDCS sham is observed the same Standard of high and low-frequency bands of active Group.d = 0.44) was observed. There was no effect of active tDCS on HRV during the recovery period compared to baseline HRV.The effect size of active tDCS on intragroup HRV between post-tDCS periods compared to baseline HRV was calculated. As a result, an average effect size of  in the groups with and without tDCS; however, in intragroup analysis, parasympathetic modulation after active tDCS increased the RMSSD by 18% from baseline, and the post-tDCS active and post-exercise periods had a variation value above baseline and, finally, and Importantly, there was better physical performance, as assessed by the increased distance covered in the active tDCS group, suggesting a better prognosis.The research was composed of patients of both sexes , with 83The results in The values of band LF absolute, in basal condition, suggested that the sympathetic system is already increased, what is already mentioned in the literature by Constantinescu et al. , Sander 2. The normal values, of healthy individuals, present a mean LF band value of SBP around 17 mmHg2. This data suggests an exacerbated reduction of vascular sympathetic modulation, characteristic of sympathetic hyperactivity situations  that increased ~48% (despite not significant) in respect to the basal values. These results corroborate with the studies of immediate effects of anodic tDCS described by Cogiamania et al.  and PiccPiccirillo et al.  observedIn respect to HRV , our resWe also observed an increase in the RMSSD variable only in the Group active tDCS, showing a possible parasympathetic modulation by tDCS. These findings corroborate with the findings of de Paula et al.  that comIn the HVR frequency domain of linear mode, still in Another important data observed in this study was a significant increase of the distance traveled on the treadmill after active tDCS when compared to the tDCS sham, results that corroborate with the findings Okano et al.  and CICCThe literature has demonstrated that tDCS may modify the autonomic responses in healthy individuals Vandermeeren et al.  and ClanWe opted to stimulate T3 to be the area closest to the insular cortex, responsible for autonomic control  and usedWe performed more one analysis to see if the side of the lesion would affect our results , since tRegarding the positioning of the reference electrode (cathode) we opted for the extracephalic (deltoid) positioning once according to Noetscher et al.  and remoThere were no analyzes of all these data in our study regarding age. However, studies show that age alone is a cardiovascular risk factor . Aging pBonnemeier et al.  evaluateIn addition, systolic and diastolic blood pressure tends to increase with increasing age, especially in women, along with changes in peripheral and central mechanisms that help maintain adequate brain flow .However, it should be considered that in our study we evaluated fewer women than men who would have more influence on age. Moreover, the presence of established hypertension and drug use in all research subjects, besides being stroke survivors, certainly have a greater impact on cardiovascular autonomic modulation than age. However, this can be considered a limiting factor in our study.This study supplies evidence that a single stimulation with tDCS over the left temporal cortex (T3) of hemiparetic patients due to stroke may improve the cardiac parasympathetic response (RMSSD and HF band of IP). However, significant differences were not observed in the other parameters studied. These results may provide the base for future perspectives of researches about the autonomic modulation after tDCS in stroke.This study is one of the first studies purposes for evaluating the effects of tDCS over the autonomic modulation in hemiparetic patients due to stroke. Therefore, such opens a path for the betterment of a protocol purpose of verifying the best positioning of electrodes, best stimulation moment, as well as the best aerobic training protocol to be associated to electric stimulation over the cerebral cortex. We consider being important the continuity of the researches in this field for the improvement of knowledge and development of this treatment method considering the advantages listed.We consider some topics as limitations of our study:Difficulty in recruiting patients due to their limited mobility;Some patients had insecurity to walk on the treadmill. This fear may have influenced the increase in stress and, consequently, a greater parasympathetic action;Absence of other neurophysiological evaluations such as electroencephalogram or lipid analysis, to better understand the effects of treatment.Absence of complementary exams for an accurate diagnosis regarding the location and extent of the lesion. Patients with metabolic deficits such as diabetes or thyroid dysfunction were not excluded.Study data were not analyzed by age. All patients were overweight.glauber.heinz@hotmail.com.TRequests for data can be directed to Glauber Heinz, ClinicalTrials.gov–NCT02956096). The participating institutions have provided a declaration of participation and will be allowed to abandon the study at any time with no negative repercussions. The patients/participants provided their written informed consent to participate in this study.The studies involving human participants were reviewed and approved by the proposed study complies with the principles of the Declaration of Helsinki and the Regulating Norms and Directives for Research Involving Human Subjects formulated by the Brazilian National Health Council established in October 1996. The study received approval from the ethics committee of Universidade Nove de Julho  under protocol CAAE: 57314716.7.0000.5511 and is registered with the International Registry of Clinical Trials (GH and FC conceived and planned the theory and drafted the manuscript. GH and MS carried out the experiment. KD, SD, AV, FD, and JC helped supervise the project. GH, MS, and FC conceived the original idea. GH, MS, AV, and FD developed the theoretical formalism and participated in the design of the study. SD participated the performed the statistical analysis. FC oriented the project and the authors KD and SD coordinated the project. All the authors have made substantive contributions to the manuscript and assume full responsibility for its content, conceived of the study, participated in its design and coordination and helped to draft the manuscript, read and approved the final manuscript. All authors agree to be accountable for the content of the work.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


In critically ill patients, changes in the velocity-time integral (VTI) of the left ventricular outflow tract, measured by transthoracic echocardiography (TTE), are often used to non-invasively assess the response to fluid administration or for performing tests assessing fluid responsiveness. However, the precision of TTE measurements has not yet been investigated in such patients. First, we aimed at assessing how many measurements should be averaged within one TTE examination to reach a sufficient precision for various variables. Second, we aimed at identifying the least significant change (LSC) of these variables between successive TTE examinations.We prospectively included 100 haemodynamically stable patients in whom TTE examination was planned. Three TTE examinations were performed, the first and the third by one operator and the second by another one. We calculated the precision and LSC (1) within one examination depending on the number of averaged measurements and (2) between measurements performed in two successive examinations.In patients in sinus rhythm, averaging three measurements within an examination was enough for obtaining an acceptable precision  for VTI. In patients with atrial fibrillation, averaging five measurements was necessary. The precision of some other common TTE variables depending on the number of measurements is provided. Between two successive examinations performed by the same operator, the LSC was 11 [5–18]% for VTI. If two operators performed the examinations, the LSC for VTI significantly increased to 14 [8–26]%. The LSC between two examinations for other TTE variables is also provided.Averaging three measurements within one TTE examination is enough for obtaining precise measurements for VTI in patients in sinus rhythm but not in patients with atrial fibrillation. Between two TTE examinations performed by the same operator, the LSC of VTI is compatible with the assessment of the effects of a 500-mL fluid infusion but is not precise enough for assessing the effects of some tests predicting preload responsiveness.The online version of this article (10.1186/s13054-019-2413-x) contains supplementary material, which is available to authorized users. Today, transthoracic echocardiography (TTE) is widely used for evaluating the haemodynamic condition in the intensive care unit (ICU) and the operating theatre –4. In paNevertheless, such changes in cardiac output are sometimes of small amplitude. In particular, the diagnostic threshold of changes induced by tests of fluid responsiveness is relatively small, ranging from 5% , 12 to 1The first one is to know how many measurements should be averaged within one TTE examination by the same operator in order to obtain measurements of a sufficient precision level, which is usually fixed at 10% . Then, tThis study was conducted in a 25-bed medical ICU and approved by the Institutional Review Board of our institution . All patients or next of kin were informed about the study and consented to participate.We included consecutive patients with haemodynamic stability  for whom a TTE examination was planned. The dosage of norepinephrine and sedatives was unchanged during the study period. The exclusion criterion was poor echogenicity, defined as the inability to correctly align the Doppler beam to obtain reliable Doppler measurements and/or to correctly delineate the endocardium for measuring the left ventricular ejection fraction (LVEF).Three successive TTE examinations were performed by two operators, the first and the third by one operator and the second by the other. Within each examination, measurements were performed without removing the probe from the thorax.E) and atrial (A) peak velocities of the transmitral flow with pulsed Doppler, the early diastolic (e’) and systolic (s’) peak velocities of the lateral mitral annulus and the systolic peak (S) velocity of the tricuspid annulus with tissue Doppler imaging, the tricuspid annular plane systolic excursion (TAPSE) in the M-mode and the left and right ventricular end-diastolic area (LVEDA and RVEDA). From these variables, we calculated the E/A, E/e’ and RVEDA/LVEDA ratios. All contours were hand-drawn.From apical five- and four-chamber views, we measured the VTI, the LVEF calculated by the modified Simpson’s rule, the early  by four different board-certified operators  at end-expiration and according to current recommendations –20.real measurements performed, one infers from formulas the precision and the LSC for each variable. They are general characteristics to which one should refer for any measurement. The precision improves and the LSC decreases along with the number of measurements that are averaged. Since they are obtained from formulas which take the repetition of measurements into account, one can calculate them for any theoretical number of measurements averaged, even though the experimental sample that allowed the calculation of SD was made of three values only . The principle of this analysis is that, in an experimental population, a series of measurements is obtained. The value of standard deviation (SD) of these measurements is calculated for each variable Fig. a. From tnly Fig. a.Fig. 1MIn practice, at a first step, the SD was obtained from the three consecutive end-expiratory measurements that had been performed, for patients in sinus rhythm as for patients with atrial fibrillation. The corresponding coefficient of variation (CV) was calculated as CV = SD/mean of the three measurements  Fig. 1aa1a.n, where n is the number of replicates that the TTE examination performer would choose to average in theory within one TTE examination. The precision was calculated as being 2 CE [during an examination that can be considered as real and not related to the variability of the measurement.At a second step, from the CV obtained in the experimental population, we inferred the coefficient of error (CE) for each variable as CE = CV/√ing 2 CE –23. The ing 2 CE . It is uing 2 CE . The inting 2 CE , 22, 24.In addition, the intra-examination intra-observer variability, which is another way to estimate reproducibility of measurements, was expressed as the mean percentage error. It was calculated as the difference between two consecutive end-expiratory measurements within a TTE examination divided by the mean of both values.between two successive TTE examinations . The principle was the same as for the intra-examination analysis except that the SD was calculated not for the measurements performed within one examination, but for the average of the measurements obtained in each examination.This analysis was performed for determining the minimal change that can be regarded as significant In practice, at a first step, the SD was obtained from the results of the two examinations. This result was the average of three consecutive end-expiratory measurements performed within one examination in patients in sinus rhythm , 25–27 oAt a second step, from this CV, we calculated the inter-examination CE, precision and LSC of variables of interest by using the formulas cited above. All these calculations were performed for the same as well as for different operators.In addition, the inter-examination intra-observer variability was calculated as the difference between two end-expiratory measurements obtained in two consecutive TTE examinations performed by the same operator divided by the mean of both values. The inter-examination inter-observer variability was calculated as the difference between two end-expiratory measurements obtained in two consecutive TTE examinations performed by two different operators divided by the mean of both values.t test or a Wilcoxon signed-rank test. Between groups, a two-tailed Student t test, a Wilcoxon Mann-Whitney U test or a Fisher’s exact test was used. We planned a priori subgroup analyses between patients in sinus rhythm and with atrial fibrillation, and between patients with and without invasive mechanical ventilation.Normality of data was assessed by a Kolmogorov-Smirnov test. Within groups, variables were compared by a paired Student p value < 0.05 was considered statistically significant.We estimated that including 100 patients should allow us to obtain a reliable value of intra- and inter-examination SD for all the TTE variables of interest. Statistical analysis was performed with MedCalc 11.6.0 software . A p = 0.17). The proportion of patients with atrial fibrillation was 12% in patients with invasive mechanical ventilation and 22% in patients without (p = 0.17). The ICU mortality was 17%. The other baseline characteristics are summarised in Additional file One hundred and ten patients fulfilled the inclusion criteria. Among the 110 included patients, 18 had atrial fibrillation, 59 were under invasive mechanical ventilation, 31 were sedated, 37 received norepinephrine and 3 received dobutamine. Ten patients were excluded due to poor echogenicity. No patient received neuromuscular blockers nor had a pacemaker. The proportion of patients with invasive mechanical ventilation was 39% among patients with atrial fibrillation and 57% among patients in sinus rhythm .The inter-examination precision and LSC were similar between patients with sinus rhythm and atrial fibrillation for all TTE variables except the E/e’ ratio. It significantly increased for VTI to 14% if two operators performed examinations, but did not change for most other variables.For performing TTE in critically ill patients, one should know how many measurements to average within one examination and how clinicians could be confident regarding the changes they measured between two examinations. We observed that averaging three measurements within one TTE examination in patients in sinus rhythm was enough for obtaining a precision < 10%, which is usually considered as desirable , for theThe variability of echocardiographic measurements might be explained by three factors. The first is the variation in the position of the ultrasound beam with respect to cardiac structures. This factor of variability is important when the probe position has been changed, like between different examinations. The second resides in the variability, on a given image, in the placement of markers  on the Doppler profile, M-mode or 2D images. This factor is influenced by the quality of the images and signals, which is often decreased in ICU patients. The third is the intrinsic variability of the variables . Our study aimed at investigating these factors, especially by looking at the intra- and inter-examination precision of TTE variables. For this purpose, though the reproducibility of TTE is usually investigated through inter-observer and intra-observer variability , 13, 17,The LSC is the smallest change that can be considered as significant and not related to the imprecision of the method or the variability of the parameter. The intra-examination LSC is important for interpreting the relative changes in ultrasound indices when the sonographer performs measurements without removing the probe from the chest wall. This happens for instance when assessing the respiratory variation of VTI, for detecting tamponade or testing fluid responsiveness, or when performing respiratory occlusion tests , 12 and The inter-examination LSC is even more interesting to consider because it regards the several instances when one assesses changes in echocardiography variables during two different examinations, by different operators or by the same operator, but after replacing the probe on the thorax. In particular, a positive response to fluid is often defined by an increase in VTI ≥ 15% . This thThis is also the case for the passive leg raising test , 13–15 oE/e’ ratio, which precision itself depends on the precision of the measurements used for calculating them. Importantly, in order to minimise the intervention of respiratory variations in measurements during experimental data acquisition, we performed measurements at end-expiration. In this regard, the preload status of the patients should not significantly interfere with our results. The values of precision and LSC we provide are thus valid only in a similar condition.Regarding the number of measurements to average within one examination, we found that, within one examination in patients in sinus rhythm, the precision was acceptable for almost all variables if measurements were averaged over three cardiac cycles, the median and the highest value of the interquartile range being < 10% , 22. ThiIn patients with atrial fibrillation, averaging five measurements was necessary for reaching a median precision < 10% for all the variables, though the highest value of the interquartile range was higher for some of them. Current recommendations are to average measurements over a minimum of five cycles  or over A first limitation of this study was that TTE examinations were performed by four operators, which might have accounted for part of the variability. Nevertheless, whatever the TTE variables, the intra- and inter-examination precision was similar for all operators. Second, we did not investigate to which extent echogenicity is a factor that may influence precision. Third, for feasibility reasons, we did not investigate all the variables that can be measured by TTE. Fourth, only a limited number of patients with atrial fibrillation were included and further studies are required to confirm our results in such patients. Nevertheless, our results agree with the most recent recommendations.In critically ill patients in sinus rhythm, averaging three measurements within one TTE examination is enough for obtaining precise measurements for the majority of the common TTE variables. In patients with atrial fibrillation, averaging five measurements is necessary. Between two TTE examinations performed at different times by the same operator, the least change of VTI is compatible with the assessment of the effects of a 500-mL fluid infusion, but is not precise enough for assessing the effects of some tests that have been developed for predicting fluid responsiveness.Additional file 1:Table S1. Patients’ characteristics at baseline. (DOCX 33 kb)Additional file 2:Table S2. Haemodynamic parameters during the first and the third transthoracic echocardiography examinations. (DOCX 25 kb)Additional file 3:Table S3. Intra-examination least significant change of transthoracic echocardiography measurements according to cardiac rhythm. (DOCX 28 kb)Additional file 4:Table S4. Intra-examination intra-observer variability of transthoracic echocardiography measurements according to cardiac rhythm and mechanical ventilation. (DOCX 26 kb)Additional file 5:Table S5. Intra-examination precision of transthoracic echocardiography measurements in atrial fibrillation. (DOCX 26 kb)Additional file 6:Table S6. Intra-examination precision of transthoracic echocardiography measurements according to mechanical ventilation. (DOCX 28 kb)Additional file 7:Table S7. Intra-examination least significant change of transthoracic echocardiography measurements according to mechanical ventilation. (DOCX 30 kb)Additional file 8:Table S8. Precision, intra- and inter-observer variability of transthoracic echocardiography measurements between two examinations. (DOCX 31 kb)Additional file 9:Table S9. Variability of transthoracic echocardiography measurements between two examinations performed by the same operator according to cardiac rhythm. (DOCX 27 kb)Additional file 10:Table S10. Variability of transthoracic echocardiography measurements between two examinations performed by the same operator according to mechanical ventilation. (DOCX 27 kb)