Simple main effects analysis showed that time had a statistically significant effect on changes in ICW (p < 0.01), ECW (p < 0.01), SMM (p < 0.01) and FM (p < 0.01), while fluid intake did not have a significant effect. Our results highlight the importance of a standardized pre-measurement nutrition, with particular attention to hydration status when using a BIA for the evaluation of body composition.Bioelectrical impedance analysis (BIA) has proven to be particularly useful due to its inexpensive and rapid assessment of total body water and body density. However, recent fluid intake may confound BIA results since equilibration of fluid between intra- and extracellular spaces may take several hours and furthermore, ingested fluids may not be fully absorbed. Therefore, we aimed to evaluate the impact of different fluid compositions on the BIA. A total of eighteen healthy individuals  performed a baseline measurement of body composition before they consumed isotonic 0.9% sodium-chloride (ISO), 5% glucose (GLU) or Ringer (RIN) solutions. During the visit of the control arm (CON), no fluid was consumed. Further impedance analyses were conducted every 10 min after the fluid consumption for 120 min. We found statistically significant interactions between the effects of solution ingestion and time for intra- (ICW,  Body composition analysis is a relevant tool to assess the hydration and nutritional status in both health and diseases ,2,3. A cTo date, only few investigations have addressed in detail the acute effects of volume expansion via orally administered fluids containing osmotically active components such as sodium and chloride, and a less osmotically active component such as glucose. Additionally, taking fluid absorption into account would allow for a more precise statement as to whether volume expansion alone or combined with electrolyte administration is more likely to influence changes in intra- and extracellular water and thus body composition.Therefore, the aim of this randomized, controlled crossover pilot trial was to investigate the influence of isotonic sodium chloride, Ringer and glucose solution on changes in body composition until 120 min post-fluid administration assessed via BIA in healthy individuals. We hypothesized that all solutions due to their osmotically active components impact total body water and thus the calculation of body composition.This was a single-center, randomized, controlled crossover pilot trial, assessing the impact of different orally administered solutions on body composition measured by bioelectrical impedance analysis . The local ethics committee of the University of Bayreuth (Germany) approved the study protocol . The study was conducted in conformity with the Declaration of Helsinki and guidelines for Good Clinical Practice. Before any trial-related activities, potential participants were informed about the study protocol and participants gave their written informed consent.−2 (both inclusive). This age range was chosen to exclude age-related confounding factors such a diminution of total body water [−1.Eligibility criteria included male or female individuals aged from 18–35 years with a body mass index (BMI) of 18.0–29.9 kg·mdy water  or menopdy water . IndividInclusion and exclusion criteria were assessed by an investigator during the screening visit prior to the start of the study.® (1:1:1:1) [After inclusion in the study, participants were assigned to ascending numbers and then allocated to the order in which the trial visits were conducted following a cross-over randomized fashion set by a software Research Randomizer1:1:1:1) . Based o10, Roche Deutschland Holding GmbH, Grenzach-Whylen, Germany). Subsequently, the participants remained in a seated position for 10 min before a duplicate baseline analysis of body composition was conducted using BIA according to the manufacturer’s specifications . This body composition analyzer emits a multitude of frequencies from 1 kHz to 1 MHz using the multi-frequency technology which separates the intra- from the extracellular water, thereby minimizing the probability of errors caused by individual variations in the distribution of the total body water or its changes over a given time period.Prior to the start of each trial visit, participants had to fast for at least 12 h and refrain from any strenuous physical activity for at least 48 h. Participants were also not allowed to consume alcohol within 24 h before each visit. Upon arrival at the research facility of the University of Bayreuth in the morning after an overnight fast, participants were asked to use the bathroom for bowel emptying, if necessary. A urine specific gravity test was performed to ensure an euhydrated status (Comburrest), participants received 12 mL per kg body mass of either isotonic sodium chloride , 5% glucose , or Ringer’s solution  and then every 10 min for a total period of 120 min (t10–120). Any other form of food and fluid intake was not permitted during each of the trial visits. Between the measurements, the participants remained in a seated position at standardized room temperature (22 °C) and humidity (50%).To determine changes in body composition, the following compartments were analyzed: Intra- (ICW) and extracellular water (ECW), total body water (TBW), skeletal muscle mass (SMM), body fat mass (FM) and visceral fat area (VFA). Following the duplicate baseline measurements , and 95% confidence intervals (CI). Within-group changes were analyzed using a repeated measures ANOVA, Friedman test or mixed-effects model followed by a post hoc Tukey multiple comparisons test. For between-group analyses, a two-way ANOVA or a mixed-effects model was performed. Statistical analyses were conducted using GraphPad Prism Software version 8.0 .−2. All screened participants were eligible to take part in the study, from which no participant had to be excluded; furthermore, no participant had to leave the study prematurely.In total, 18 healthy individuals  were included with a mean ± SD age of 23.1 ± 1.8 years, height of 176 ± 10 cm, body mass of 69.5 ± 12.5 kg and BMI of 22.2 ± 2.1 kg·mp > 0.99), equaling a ~2% increase in TBW.Based on the individual body mass on the days of the fluid conditions, participants consumed 831.6 ± 148.9 mL of ISO, 835.3 ± 151.3 mL of GLU and 832.7 ± 149.4 mL of RIN (p < 0.01). Simple main effects analysis showed that time (p < 0.01) but not fluid intake (p = 0.90) had a statistically significant effect on changes in intra-cellular water (ICW).A two-way ANOVA revealed that there was a statistically significant interaction between the effects of fluid ingestion and time .Intracellular water did not show any changes over the 120 min in the CON and GLU trial arms. In the ISO trial arm, ICW demonstrated significant increases from t0, ICW was significantly increased in both the ISO and RIN trial arms when compared to CON and GLU (p < 0.01); however, no changes were found between ISO and RIN (p = 0.55). At t10, ISO was significantly increased when compared to CON (p < 0.05) but not to RIN (<0.99) or GLU (p = 0.11).At tp < 0.0001). Simple main effects analysis showed that time (p < 0.01) but not fluid intake (p = 0.82) had a statistically significant effect on changes in extra-cellular water (ECW).We found a statistically significant interaction between the effects of fluid ingestion and time , but not ISO and GLU. At t30, both the RIN (p < 0.01) and ISO (p < 0.05) trial arms were significantly increased compared to CON, but not GLU with only the RIN trial arm showing significant increases in the further course until t120 (p < 0.001), while in the ISO trial arm significant increases were also found between t70 and t120 compared to CON (p < 0.01).From tp < 0.08) were found. Simple main effects analysis showed that neither time (p = 0.08) nor fluid intake (p = 0.88) had a statistically significant effect on changes in total body water (TBW).No statistically significant interaction between the effects of fluid ingestion and time . In the RIN trial arm, TBW was significantly increased between trest and t0 (p < 0.0001), and between t0 and t10, t30, t40, t50, t90, t100 and t120 , respectively.TBW showed no significant differences within the CON and GLU trial arms. For the ISO trial arm, TBW was significantly increased between t0, TBW was significantly increased in the RIN trial arm when compared to CON (p < 0.05), but not the other trial arms (p < 0.05). At t10, both RIN (p < 0.05) and ISO (p < 0.05) were significantly increased compared to CON, but not GLU (p = 0.05 and p = 0.25). In the RIN trial arm, TBW was significantly increased until t120 when compared to CON (p < 0.05).At tp < 0.001). Simple main effects analysis showed that time (p < 0.01) but not fluid intake (p = 0.90) had a statistically significant effect on changes in skeletal muscle mass (SMM).We found a statistically significant interaction between the effects of fluid ingestion and time , whereas at t20 only the RIN trial arm was significantly higher compared to GLU (p < 0.05), but not to CON (p = 0.07) and ISO (p = 0.77).At tp < 0.01). Simple main effects analysis showed that time (p < 0.01) but not fluid intake (p = 0.32) had a statistically significant effect on changes in FM.With regard to body fat mass (FM), we found a statistically significant interaction between the effects of fluid ingestion and time , and between trest and t90 and t120, respectively (p < 0.05). In the GLU trial arm, FM was significantly increased between trest and t10 (p < 0.0001) and in the further course until t40. Additionally, percentage changes in body fat mass can be obtained from FM showed no significant changes in the CON and ISO trial arm D. In the0 (p < 0.01), t10 and t20 (p < 0.05), FM was significantly higher in the GLU compared to CON and RIN. No significant differences were found between the CON and ISO trial arms.At tp = 0.0001). Simple main effects analysis showed that time (p < 0.0001) but not fluid intake (p = 0.90) had a statistically significant effect on changes in VFA.For visceral fat area (VFA), we found a statistically significant interaction between the effects of fluid ingestion and time  and between trest and t40 and t70, respectively (p < 0.05). In the RIN trial arm, VFA was significantly increased between trest and t10 (p < 0.01) and further time points until t120.For VFA, no significant differences were observed in the CON trial arm. In the ISO trial arm, VFA was significantly increased between t0 (p < 0.01), t10 and t20 (p < 0.05), VFA was significantly higher in the GLU trial arm compared to CON and RIN. Between the CON and ISO trial arms, and RIN and ISO trial arms, respectively, no significant differences were found.At tThe aim of this randomized, controlled crossover pilot trial was to investigate the influence of an isotonic sodium chloride, Ringer and glucose solution on changes in body com-position until 120 min post-fluid administration assessed via bioelectrical impedance analysis in healthy individuals. While the CON trial arm demonstrated no significant differences in any of the analyzed body compartments, our results indicated that all fluids independent of their osmolarity exerted a significant influence on body composition with the RIN solution mainly affecting intra- and extracellular water and visceral fat area, while the ISO primarily affected intra- and extracellular water. In contrast, GLU mainly affected body fat mass including visceral fat area.40. Moreover, we cannot confirm the postulated underestimation of TBW as a result of the fluid intake when using the BIA. One possible explanation for these conflicting results may be the amount of fluid administered to increase TBW, which was 3% as compared to the 2% in our study. Moreover, we cannot conclusively explain whether other previously mentioned factors such as skin temperature, blood flow or food or fluid intake other than the fluids within the study may have affected the impedance measurements [Previous studies have demonstrated that acute fluid consumption affected measures of impedance and estimated percentage body fat using segmental bioelectrical impedance analysis ,23,24,25urements ,27. Howeurements . It also−1), the latter has led to greater changes in body composition. This was particularly true for the elicited changes in FM. RIN led to a significant increase in VFA which was detectable directly after the fluid consumption and persisted throughout the entire 2 h period. While it was postulated that rapid increases in impedance about 20 min after the fluid intake are due to the redistribution of blood volume from the periphery to the core in response to a large volume of fluid entering the stomach and gastrointestinal tract [120 could be the result of the intestinal absorption and subsequent dilution of body fluid electrolytes [0 and persisted until t120. However, changes in the ICW were not detected by the BIA except for the time points t0 and t10 immediately after the fluid intake. This is noteworthy as there are not likely to be any changes in the ICW at these early time points, but rather an increased volume within the core as mentioned earlier.Although the ISO and RIN have the same osmolarity , no differences in body water distribution or body fat mass were found after the carbohydrate-enriched drink administration [As far as the GLU is concerned, to the best of our knowledge only a limited number of studies have investigated the effect of a carbohydrate drink on changes in body composition. For instance, Kuklinski et al. found that after the ingestion of a 400 mL carbohydrate drink containing 50.4 g of maltodextrin and fructose (240 mOsm∙Lstration . Becauserest and t40 as a result of a carbohydrate-enriched fluid consumption, are of clinical relevance as the mean differences lie below 1%. This is also supported by the fact that in the CON trial arm, values for percentage body fat mass fluctuated by up to 0.7% between trest and t120. This ultimately also applies to the other parameters, as the measured changes triggered by the fluid consumption were rather small and possibly within the error of the impedance technique, as was outlined previously [While our and previous findings indicated statistical significance, it remains uncertain whether these increases in body fat mass, e.g., between teviously . It was eviously , to estieviously  as well eviously . This waeviously , which iOur results demonstrated that all fluids may impact conductivity and thus the calculation of body compartments. The RIN and ISO mainly affected increases in extracellular water, while the RIN also affected body fat mass. The GLU solely seems to affect changes in body fat mass including visceral fat area, leading to significant overestimations. We conclude that for the standardized analysis of total body water, skeletal muscle mass and fat mass via a bioelectrical impedance analysis, measurements should take place without any recent fluid intake, while controls are in place for other confounding variables, even though the differences are likely to be clinically insignificant.


Fluids are the cornerstone of therapy in all critically ill patients. During the last decades, we have made many steps to get fluid therapy personalized and based on individual needs. In patients with lung involvement—acute respiratory distress syndrome—finding the right amount of fluids after lung surgery may be extremely important because lung tissue is one of the most vulnerable to fluid accumulation. In the current narrative review, we focus on the actual perspectives of fluid therapy with the aim of showing the possibilities to tailor the treatment to a patient’s individual needs using fluid responsiveness parameters and other therapeutic modalities. A 63-year-old man with a history of arterial hypertension was admitted to the intensive care unit (ICU) for hypoxemic respiratory failure. For five days, he suffered a high fever and cough with progressive dyspnea. At admission, he was somnolent, extremely exhausted, and with an oxygen saturation of air at 68%. The chest X-rays that were performed showed bilateral opaque infiltrates, and he tested positive for SARS-CoV2. Because of progressive respiratory insufficiency coupled with decreased mentation, he was sedated, intubated, and admitted to the ICU. Under mechanical ventilation with intermediate positive end-expiratory pressure and increased inspiratory oxygen fraction, his saturation of arterial blood with oxygen improved, but his blood pressure dropped significantly. The treating physician was in doubt about whether to follow the sepsis-surviving recommendation of administering intravenous fluid resuscitation of 30 mL per kg body weight to reverse the possible hypovolemia or whether he should be rather restrictive in order to spare the lung tissue and start the infusion of norepinephrine. Therefore, he performed several examinations using ultrasonography of the vena cava and echocardiography of the heart. Initially, he used a concomitant small dose of vasopressors with 500 mL of Ringer’s lactate to reach an acceptable blood pressure target of mean arterial pressure of 65 mmHg. Afterwards he repeated the ultrasonography examination and performed several tests of fluid responsiveness too to titrate 250 mL fast infusions to reach the state of optimal preload and heart performance. However, the small dose of norepinephrine remained. The cumulative fluid balance of the patient during the first two days was 3.5 L positive, but his oxygenation as well as peripheral perfusion and also diuresis improved. This enabled the down-titration of the fluid infusion to enable a daily zero fluid balance, and after his lungs’ functions improved, the patient started weaning off the ventilation support. At that time, a small dose of diuretics was used to reach a negative fluid balance regardless of the need for a discrete dose of vasopressors. An echocardiographic examination demonstrated physiological variability of vena cava diameter and the patient was successfully extubated after the first spontaneous breathing trial.Since Latta’s first application of saline in the late 18th century, fluid therapy remains the cornerstone of our treatments in the ICU. However, the way we perform fluid management has evolved throughout these decades. It oscillated between liberal and conservative strategies, using artificial colloids or albumin, saline or balanced crystalloids. It took some years to recognize that fluids, as well as any other treatment, may induce harm either by changing the homeostasis , or by aIn patients with lung involvement, i.e., patients with acute respiratory distress syndrome (ARDS) or those after lung surgery, targeting appropriate fluid loading may significantly affect their outcome. Since the publication of Wiedemann’s FACCT trial , more daFor decades, the body fluid compartmentalization between intra- and extravascular space has been described using the old paradigm of Starling . Recent However, EG is an extremely fragile structure. Its shedding exposes the endothelial cells with their ligand structures and enables an unopposed leak of the intravascular protein-rich plasma into the interstitium. The role of EG shedding in sepsis and viral infections has been demonstrated recently . In addiMoreover, the protective roles of EG are not limited to the fluid’s compartmentalization only. The proteoglycan endothelial surface layer serves as an effective mechanotransducer. This helps to cope with the capillary structure of the constant mechanical stress induced by the shear forces between the inside of the circulating blood-filled capillary and external mechanical strain caused by alveolar distension. In addition, this gelatinous layer impedes direct contact between plasma proteins or circulating blood elements and endothelium. EG-shedding exposes endothelium and subendothelial structures, enabling blood clotting via the interaction of plasmatic proteins and platelets with tissue factor, collagen, or von Willebrandt monomers . It has When treating the critically ill, we can recognize the typical timing and aggressivity of the therapy, but not the source of the disease. For the time evolution of fluid treatment and accumulation, the R-O-S-E acronym  has been2) of patients in the first trial were 47% and those in recent ones around 70%. From this point of view, the resuscitation phase is a salvage momentum at the last minute. Without a reasonable attempt to restore circulating blood volume, and/or managing his cardiovascular functions using drugs (mostly catecholamine), the patient is virtually doomed. The goal of resuscitation is the restoration of the minimal perfusion acceptable for the brain and heart, similar to the resuscitation of gas exchange by maintaining the airway patency and mechanically venting oxygen in and carbon dioxide out. However, the side effects of the treatments we perform at this moment are not irrelevant, especially when such an impact may be long-lasting. Massive fluid resuscitation with extravascular leak and edema formation may serve as an example. Multiple recent trials demonstrate lower cumulative fluid balance or better outcomes in those with a less aggressive initial resuscitation [It has been demonstrated multiple times that initial aggressive care in patients with critical illness creates a potential for faster reversal. We have mentioned Latta’s salvage of cholera patients using saline infusion in the introduction. However, aggressive resuscitation only makes sense in those patients who are crashing. The difference between outcomes described by early goal-directed therapy in the famous Rivers study  and thoscitation ,25. Thercitation . The remThe treating physician frequently pays more attention to managing gas exchange in lung-compromised patients, but hemodynamic parameters cannot lie behind. Intubation and connection to positive pressure ventilation significantly change the conditions within the thorax and may result in hemodynamic compromise . Typical2 and veno-atrial difference of carbon dioxide tension (PvaCO2)). After protracted hypoperfusion, recovery of organ failure  may be delayed and should not be regarded as imminent treatment failure.Once the patient is out of the worst, further treatment should be extremely judicious. These steps aim to improve the whole body’s conditions and restore normal homeostasis and balance at the lowest cost of side effects. The patient’s background—i.e., comorbidities, nature of the disease, and time the critical illness developed—should be considered. In lung-compromised patients, this means careful titration of lung protective ventilation and using other rescue therapies first. From the cardiovascular perspective, we should try to reach the patient’s normal blood pressure values and reverse low cardiac output using a combination of fluids, vasopressors, and inotropes. Our aim should be the normalization of peripheral perfusion  and reaching near-normal levels of serum lactate coupled with other laboratory markers of adequate cardiac output . PEEP i2O ). Some dmaneuver . The latmaneuver , which iAll previously listed tests are dependent on the HLI. Therefore, they may be affected by right ventricle dysfunction and pulmonary hypertension. Under such conditions, left ventricle preload may be limited, but fluid infusion will not improve cardiac output. Vice versa, it may increase right-sided congestion—observable by an increased central venous pressure (CVP) or IVC diameter. A real volume challenge may be necessary as a second step in case HLI tests are positive. This may be done using passive leg raising  or via fluid infusion. Performing passive leg raising is not without limitations , but cliTo some extent, vasoactive medication may further decrease the need for fluids. Especially in the vasodilatory shock state, norepinephrine has been demonstrated to reduce the number of fluids administered to control the shock state . VasopreThe transition between optimization and stabilization sometimes seems slightly blurred. The best marker of patients’ stabilization is the absence of a need to escalate vital organ support . On the other hand, support of some other organs  may be necessary throughout this phase due to initial failure. The stabilization process may last days or weeks, and outbursts of complicating conditions may require repeated titration of ventilator setting and cardiovascular supports. Still, the overall picture is of a patient who is not significantly worsening further on. From day two to three, fluids given to optimize preload are not the primary driver of cumulative fluid balance. On the contrary, maintenance and dilution account for most fluid intake . Based oThe FACTT protocols demonstrate that reaching zero fluid balance during stabilization is favorable. However, in some patients, diuretics cannot maintain fluid balance. Oliguria due to acute kidney injury after a shock state is frequent among the critically ill . In optiUsually, the disease gets under control after several days and vasoactive medication may be slowly weaned off. Some patients start to mobilize the retained water and spontaneously increase diuresis, but in most of them, active evacuation speeds up this process. This may be necessary, especially in patients with impaired gas exchange  and those with signs of fluid accumulation syndrome (FAS). Venous excess ultrasound score (VExUS) has been proposed recently to help to monitor the risk of FAS , and VExIndividualizing fluid therapy in patients with ARDS or other lung involvement and impaired gas exchange is challenging. Maintaining the notion that fluids are drugs and should be used with caution and only in doses absolutely needed is critical for the success of the treatment. Up to date, we do not have a specific monitoring tool to assess the fluid loading conditions and amount of accumulated water. Currently, our possibilities of monitoring are expanding, having bioimpedance monitoring tools to evaluate the body water composition ,64 and i


The application of pathophysiologic tenets has created significant changes in our approach to hyponatremia and hyponatremia-related conditions. This new approach incorporated the determination of fractional excretion (FE) of urate before and after the correction of hyponatremia and the response to isotonic saline infusion to differentiate the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) from renal salt wasting (RSW). FEurate simplified the identification of the different causes of hyponatremia, especially the diagnosis of a reset osmostat and Addison’s disease. Differentiating SIADH from RSW has been extremely difficult because both syndromes present with identical clinical parameters, which could be overcome by successfully carrying out the difficult protocol of this new approach. A study of 62 hyponatremic patients from the general medical wards of the hospital identified 17 (27%) to have SIADH, 19 (31%) with reset osmostat, and 24 (38%) with RSW with 21 of these RSW patients presenting without clinical evidence of cerebral disease to warrant changing the nomenclature from cerebral to renal salt wasting. The natriuretic activity found in the plasma of 21 and 18 patients with neurosurgical and Alzheimer’s disease, respectively, was later identified as haptoglobin-related protein without signal peptide (HPRWSP). The high prevalence of RSW creates a therapeutic dilemma of deciding whether to water-restrict water-logged patients with SIADH as compared to administering saline to volume-depleted patients with RSW. Future studies will hopefully achieve the following: 1. Abandon the ineffective volume approach; 2. Develop HPRWSP as a biomarker to identify hyponatremic and a projected large number of normonatremic patients at risk of developing RSW, including Alzheimer’s disease; 3. Facilitate differentiating SIADH from RSW on the first encounter and improve clinical outcomes. Recent studies in hyponatremia and hyponatremia-related conditions have significantly altered our diagnostic and therapeutic approaches that need to be updated in a review and developed in the future. These changes were made possible by abandoning the inaccurate categorization of hyponatremia that is based on the status of the extracellular volume. This approach has been in existence for over 50 years despite a general awareness that we cannot accurately determine the volume status by clinical criteria in non-edematous patients . The newTable listing identical clinical and laboratory findings in SIADH except for their volume status. All parameters are used clinically to characterize both diseases. One key difference that can-not be assessed clinically is the volume status, being increased in SIADH and decreased in RSW.Both SIADH and RSW present with hyponatremia, normal renal, thyroid and adrenal function, hypouricemia, concentrated urine defined as urine osmolality (Uosm) being greater than the plasma osmolality (Posm), urine sodium concentration (UNa) usually exceeding 30 mmol/L and high fractional excretion (FE) of urate. Due to the divergent therapeutic goals of water-restricting water-logged patients with SIADH and administering salt and water to volume-depleted patients with RSW, it is essential to differentiate between these two syndromes with identical clinical parameters. This differentiation would be unnecessary if RSW was indeed a rare condition. The identification of patients with RSW, which included patients without clinical evidence of cerebral disease, suggested that a study of hyponatremic patients from the general medical wards of the hospital would test our increasing awareness that RSW might be more common than perceived ,3,4. TheThis study unexpectedly found 24 (38%) of 62 hyponatremic patients recruited from the general medical wards of the hospital to have RSW. The absence of cerebral disease in 21 of these 24 patients supported our proposal to change cerebral to RSW to justify this important change in the nomenclature . These sOur recent identification of the natriuretic protein, haptoglobin-related protein without signal peptide (HPRWSP), found in the plasma of salt wasting patients with neurosurgical and Alzheimer’s diseases, has the potential of serving as a biomarker to simplify the identification of RSW patients on the first encounter to improve clinical outcomes .The recent report of a high prevalence of RSW in the general medical wards of the hospital by the application of well-developed pathophysiologic principles provided sufficient data of high credibility to abandon the ineffective volume approach. It took 30 years to generate consistently reproducible data to propose this new approach. There are two pathophysiologic phenomena that eventually led to the identification of HPRWSP as the likely natriuretic factor that induces RSW.Investigations into the unique relationship between serum sodium and FEurate can now reliably differentiate SIADH from RSW. As noted in Urate is freely filtered at the glomerulus and is transported exclusively in the proximal tubule of the kidney by reabsorbing and secretory transporters where there is normally a net reabsorption of 89–96% of the filtered load of urate, leaving 4–11% of the filtered load to be excreted in the final urine and designated as FEurate . FEurateUtilizing FEurate to identify the different causes of hyponatremia is especially useful in identifying patients with a reset osmostat, which occurs in about 30% of patients with hyponatremia. It is also useful in identifying patients with Addison’s disease. This elusive disease presents with nondescript symptoms such as weight loss, fatigue, nausea, vomiting, postural dizziness and hyperpigmentation where 50% of patients with Addison’s disease are diagnosed at a time of adrenal crisis . The chaDifferences in response to an isotonic saline infusion between SIADH and RSW patients can be best explained by the physiologic differences in the mechanisms that increase ADH secretion. ADH levels in SIADH do not respond to changes in the extracellular volume or plasma osmolality and is caused by the autonomous and inappropriate secretion of ADH as compared to a predictive appropriate response to both volume and osmolar stimuli in RSW ,17. InfuAs noted in We tested the response to an isotonic saline infusion in patients by making certain we had correctly made the diagnosis of SIADH and RSW. Two patients had SIADH with increased blood volume as determined by radioisotope dilution methods and decreased plasma renin and aldosterone levels and one patient had RSW with decreased blood volume and increased plasma renin and aldosterone levels. As depicted in The undetectable ADH level at the time the urine osmolality was dilute at 152 mosm/kg was recently challenged, claiming that the ADH was still present because the urine was not maximally dilute at an expected 50 mosm/kg . This coAnother example of a failure to apply established physiological phenomena is the study of 49 hyponatremic patients with a subarachnoid hemorrhage . The diaOrrhage actually had RSW, which is an accepted common cause of RSW. Two editorials agreed that all 49 hyponatremic patients had SIADH but failed to acknowledge the well-established physiologic observations that isotonic saline does not correct the hyponatremia in SIADH but typically does correct it in RSW ,18,23,24The determination of FEurate and the response to isotonic saline infusions in hyponatremic patients identified an unexpectedly high rate of RSW in hyponatremic patients from the general medical wards of the hospital . Of the Seventeen (27%) had SIADH based on five with baseline high FEurate which normalized after correction of their hyponatremia . Eleven Nineteen (31%) had a reset osmostat based on a normal FEurate on all patients and eight excreted a diagnostic dilute urine on a spontaneously excreted urine.Twenty-four (38%) had RSW with eleven demonstrating a persistent increase in FEurate after correcting their hyponatremia. Nineteen diluted their urine within 24 h after initiating isotonic saline infusions with two demonstrating undetectable levels of ADH when their urine was dilute. Ten patients excreting dilute urines required infusions of 5% dextrose in water to prevent correcting serum sodium by more than 6 mmol/L over a 24 h period to reduce the risk of developing osmotic demyelination ,25. Of gAn additional unexpected finding was the surprisingly low baseline UNa in a significant number of patients. Thirteen patients with RSW had baseline UNa less than 30 mmol/L as compared to three with SIADH and six with a reset osmostat. Because patients with hyponatremia are usually seen when they are in an equilibrated stage of their disease when urine output of sodium matches sodium intake, patients with RSW probably lost their appetite because of more serious comorbid conditions. Determinations of Una, therefore, appear to be less important in our approach to hyponatremic patients, especially when the algorithms do not consider SIADH or even RSW unless their UNa exceeds 30 or 40 mmol/L ,28.The study of 62 hyponatremic patient from the general medical wards can be legitimately criticized because of the labor-intensive nature of attempting to determine FEurate before and after correction of their hyponatremia or whether they diluted their urine after initiating isotonic saline infusions. This was only possible because the funded study included a research coordinator whose sole function was to carry out the protocol as precisely as possible, especially when there were so many levels of function that had to be coordinated and at a time when the length of stay was a major issue. The ultimate value of this study was to introduce the importance of considering RSW as a common cause of hyponatremia and to engage those involved in hyponatremia and hyponatremia-related diseases to contribute to a better understanding and improving clinical outcomes for these patients.As part of our quest to identify the physiologic mechanisms that contribute to clinical diseases, we decided to develop strategies to identify a natriuretic protein that might cause RSW. It became evident that the utilization of an animal model would be most informative because it allowed many competing variables to be expressed as compared to an in vitro model where a limited number of variables are controlled in an in vitro setting. We decided to perform rat clearance studies by infusing plasma from prospective patients with RSW. The most likely candidates were neurosurgical patients where the blood volume studies demonstrated RSW to be very common and in Alzheimer’s disease (AD) where they were hypouricemic, most likely due to an increase in FEurate ,30. BecaBecause there was a dose response of FElithium to increasing doses of plasma, the blood levels of the natriuretic protein must have been increasing, suggesting that blood levels of the natriuretic factor and dehydration from RSW were increasing as the patient became more demented. It is, thus, likely that all demented patients below an MMSE score of less than 12 were volume depleted from RSW. It is interesting to note that FEurate increased modestly from 6.6 in the control group to 9.7% in the patients with AD . The meaAttempts to identify the natriuretic factor(s) that was present in the plasma of patients with neurosurgical and Alzheimer’s disease in 1993 was possible when the analysis of proteins had developed to a point where every protein could be identified with precision in small sample sizes. We modified the protocol of the previous rat renal clearance studies by injecting 0.5 mL of serum in 1.5 min instead of 0.5 mL given intraperitoneally followed 90 min later by a constant infusion of 2 mL administered over a 3 h period ,32,33. WAtrial natriuretic peptide (ANP) has been implicated as the natriuretic peptide that causes RSW. The low normal value of the baseline ANP of 35 pg/mL is consistent with the decreased blood volume in the unequivocal case of RSW presented above b 4]. Th. Th4]. TIt is evident from the foregoing discussion that there is a dire need to develop simpler ways to differentiate SIADH from RSW. It is anticipated that HPRWSP will not be increased in patients with Addison’s disease, Bartter’s or Gittelman’s syndromes. Developing HPRWSP as a biomarker will allow us to differentiate SIADH from RSW on the first encounter with the patients, correctly select the diametrically opposite therapeutic options and improve clinical outcomes. SIADH and RSW occur commonly in hyponatremic patients in the general medical wards of the hospital but there is an untapped potential of identifying RSW in normonatremic patients as well.There is an underemphasis of the need to have a sufficiently high water intake to induce hyponatremia. The loss of approximately 500 mL/day of pure water loss by insensible means will induce hypernatremia if there is inadequate water intake. This is especially true of patients with AD who were all normonatremic except for one patient because they did not drink enough water to develop hyponatremia due to a decrease in thirst with aging and their dementia. We should also be aware of the studies of administering daily injections of pitressin to normal subjects and dogs where hyponatremia did not develop without consciously providing sufficient water intake ,37. ThisAs discussed earlier, 18 of 19 patients with advanced AD had progressively increasing FElithium levels as they became more demented or as the MMSE decreased below 12. The dose-dependency of FElithium excretion rates suggests that the blood concentration of HPRWSP was rising as the dementia worsened  6,33]. ,33. 6,33The goal for treating volume-depleted patients with RSW is to return them to a euvolemic state. The intuitive solution is to provide sufficient salt and water to improve the quality of life by establishing a euvolemic state at the expense of increasing urine output, especially sleep-depriving nocturia. This may be tolerable in patients whose RSW appears to subside after the successful treatment of their coexisting comorbid condition, although there are few who require salt and water supplementation for longer periods of time. This does not appear to be applicable to patients with AD, who seem to have a more permanent form of RSW. Developing an inhibitor would most effectively treat all RSW patients, especially those with a more persistent form of RSW as in AD.The difference in duration of the salt wasting syndrome between those encountered in the hospital and AD raises interesting questions about the factors that control the upregulation of genes that control the production of HPRWSP. It appears that HPRWSP is normally produced at low rates with minimal or no clinical effects until there is an intercurrent illness that upregulates the gene that produces HPRWSP. Under normal conditions, therefore, the production of HPRWSP can be equated to a leaky faucet, which opens up for variable periods of time to induce RSW and reverts back to a less leaky state with the resolution of the comorbid condition. In AD, however, the faucet appears to be indefinitely open without an endpoint, suggesting that there is not only a prolonged or permanent upregulation of the gene but factors that also influence the rate of production of the putative factor. A permanently open faucet will, thus, indefinitely expose all organs of the body to the putative factor with no foreseeable endpoint.Future investigations should include identification of the factors that affect the upregulation of the gene, production rates of HPRWSP and long-term exposure of all organs of the body to HPRWSP, especially the brain. Treatment of RSW in AD, therefore, introduces different challenges that require the development of an inhibitor of HPRWSP or that genetically downregulate its production once the diagnosis has been established instead of trying to create a euvolemic state by increasing salt and water intake and reducing the quality of life by the polyuria and nocturia. Inhibiting HPRWSP or reducing production of HPRWSP would have the greater benefit to the patient by eliminating any effects HPRWSP might have in other organs of the body, especially the dementia in AD. It appears that patients with an MMSE score less than 12 become progressively more volume depleted as their dementia worsens  33]. Fu. Fu33]. Haptoglobin-related protein (HPR) is a relatively unknown primate-specific 45 kDa plasma protein that is produced by the liver and has a 91% sequence homology to haptoglobin phenotype Hp1-1 . The newWe described the derivation and clinical utility of a superior approach to hyponatremia and hyponatremia-related diseases that should replace the archaic and ineffective volume approach. The intricate nuances exposed by this labor-intensive pathophysiologic approach has improved our ability to identify many of the causes of hyponatremia, the most important being the differentiation of SIADH from RSW and the high prevalence of RSW. The presence of natriuretic activity in the plasma of neurosurgical diseases and AD led eventually to identification of HPRWSP as the natriuretic factor in both groups of patients. Because haptoglobin-related protein with the signal peptide had no natriuretic activity, there is a need to determine whether HPR is present only without the signal peptide or with variable levels of the signal peptide. There is a need to simplify methods to determine HPRWSP levels in plasma that will serve as a much-needed biomarker for RSW in hyponatremia and hyponatremia-related diseases and to apply the appropriate therapy that will improve clinical outcomes. HPRWSP has multiple clinical applications that have been recently reviewed .


Acinetobacter baumannii-calcoaceticus complex (CRABC) is recognized as an urgent/critical antimicrobial resistant threat by the Centers for Disease Control and Prevention and World Health Organization. The development of new antibiotics targeting CRABC is an urgent unmet medical need that Roche is tackling through development of a novel antimicrobial compound . A significant challenge for the planned pathogen-focused clinical trial is the need to rapidly identify eligible patients with CRABC infections. Here, we describe a prototype assay for the rapid detection of CRABC causing HAP/VAP or bloodstream infections (BSI).Carbapenem-resistant A. baumannii- calcoaceticus complex (ABC) organisms harboring the most prevalent associated carbapenemases genes . This work entailed the assay design and optimization for use on the automated, high-throughput (HTP) cobas® 5800/6800/8800 Systems, including primers/probes, sample processing, and result interpretation for three sample types . The assay utilizes the commercially available cobas omni Utility Channel Kit, a defined oligo pool, controls, and an off-instrument analysis package. Assay inclusivity, exclusivity, limit of detection (LoD), and specificity were evaluated using archived or contrived clinical specimens.This prototype assay was developed for the qualitative detection of in silico and wet lab testing. Using preliminary interpretive cutoffs, high specificity (100%) was observed with negative clinical samples  and LoDs of 5280 (95% CI: 4010-9166), 6180 (95% CI: 4548-11285) and 1250 CFU/mL (95% CI: 1050-1750) were observed for BAL, sputum and positive blood culture, respectively.The CRABC prototype assay had 100% inclusivity for ABC and claimed resistance markers and 100% exclusivity for other bacteria commonly found in respiratory or positive blood culture samples based on cobas® 5800/6800/8800 Systems could be adopted to rapidly identify patients with CRABC-associated HAP/VAP or BSI for enrollment in a pathogen-focused clinical trial.This CRABC prototype assay for use on the automated, HTP Natacha Martins Sorenson, PhD, Roche: Grant/Research Support Hai Nguyen, n/a, Roche: Grant/Research Support Arrash Moghaddasi, n/a, Roche: Grant/Research Support Aishwarya Sathish, n/a, Roche: Grant/Research Support Indira Somanathan, n/a, Roche: Grant/Research Support Letong Jia, n/a, Roche: Grant/Research Support Patrick Lin, n/a, Roche: Grant/Research Support Xun Zhuang, PhD, Roche: Grant/Research Support Colin Lam, n/a, Roche: Grant/Research Support Brian Lee, MD, GE Healthcare: Stocks/Bonds|Invitae: Stocks/Bonds|Merck: Stocks/Bonds|OPKO Health: Stocks/Bonds|Roche Diagnostics: Employment|Roche Diagnostics: Stocks/Bonds|Spero Therapeutics: Stocks/Bonds Kyle C. Cady, PhD, Roche: Grant/Research Support|Roche: Stocks/Bonds


Lung cancer remains the major cause of cancer‐related deaths worldwide. Early stages of lung cancer are characterized by long asymptomatic periods that are ineffectively identified with the current screening programs. This deficiency represents a lost opportunity to improve the overall survival of patients. Serum biomarkers are among the most effective strategies for cancer screening and follow up.Using bead‐based multiplexing assays we screened plasma and tumours of the KrasG12D/+; Lkb1f/f (KL) mouse model of lung cancer for cytokines that could be used as biomarkers. We identified tissue inhibitor of metalloproteinase 1 (TIMP1) as an early biomarker and validated this finding in the plasma of lung cancer patients. We used immunohistochemistry (IHC), previously published single‐cell RNA‐seq and bulk RNA‐seq data to assess the source and expression of TIMP1in the tumour. The prognostic value of TIMP1 was assessed using publicly available human proteomic and transcriptomic databases.We found that TIMP1 is a tumour‐secreted protein with high sensitivity and specificity for aggressive cancer, even at early stages in mice. We showed that TIMP1 levels in the tumour and serum correlate with tumour burden and worse survival in mice. We validated this finding using clinical samples from our institution and publicly available human proteomic and transcriptomic databases. These data support the finding that high tumour expression of TIMP1 correlates with an unfavorable prognosis in lung cancer patients.TIMP1 is a suitable biomarker for lung cancer detection. Lung cancer remains the major cause of cancer‐related deaths worldwide. We found that the tissue inhibitor of metalloproteinase 1 (TIMP1) is a tumour‐secreted protein with high sensitivity and specificity for aggressive cancer, even at early stages in mice. We show that TIMP1 levels in the tumour and serum correlate with tumour burden and worse survival in mice. We validated this finding using clinical samples from our institution and publicly available human proteomic and transcriptomic databases. These data support the finding that high tumour expression of TIMP1 correlates with an unfavorable prognosis in lung cancer patients. In fact, cancer cells represent only a fraction of the total tumour mass.The immune system may also influence tumour growth by modulating the interaction of the tumour with the ECM. Tumours with aggressive behaviors are associated with high expression of matrix metalloproteases (MMP), capable of degrading the ECM to facilitate regional invasion and metastasis.In this study, we hypothesized that tumour‐secreted cytokines and chemokines could serve as biomarkers for lung cancer and predict prognosis. We performed a discovery screen in a well‐established murine model of lung cancer and found that TIMP1 is highly expressed in the tumours of mice, reaching levels high enough in the serum to be used as an early detection biomarker. TIMP1 levels correlated with tumour burden and predicted overall survival in mice and humans with lung cancer.22.1G12D/+; Lkb1f/fKras mouse model of lung cancer has been previously described.7 p.f.u. of Adenovirus CMV‐Cre (Ad5CMV‐Cre) purchased from the University of Iowa Gene Transfer Vector Core . Mice were euthanized when they reached 30% weight loss or developed a poor body composition score (2 or less).The 2.2Blood from mice was collected by cardiac puncture and centrifuged at 10 000 × g for 10 min at 4°C; then the serum was stored at −20°C until further analysis. During euthanasia some lungs were dissected to isolate tumours which then were flash frozen in liquid nitrogen and stored at −80°C. To measure cytokines, they were homogenized using a custom‐made lysis buffer . For the initial 44‐ plex screening of cytokines both serum and tumour lysates were sent to Eve Technologies . Any other TIMP1 measurements were performed using Luminex kits purchased from R&D.2.3Mice lungs were perfused and fixed in 4% paraformaldehyde (PFA) for 24 h and then switched to 70% ethanol prior to paraffin embedding and sectioning at 4 μm. Human tumours were fixed, embedded, and sectioned by the Department of Pathology and Laboratory Medicine at Weill Cornell according to standard of care procedures. Tumours from the KL mice were fixed in 4% PFA overnight and then preserved in 70% ethanol until paraffin embedding, sectioning (4 μm), H&E staining and scanning at Histowiz . For immunohistochemistry, the slides were dewaxed in Histoclear , re‐hydrated and exposed to antigen retrieval using citrate buffer  in a pressure cooker for 10 min. The endogenous peroxidase activity was quenched using 3% hydrogen peroxide in PBS for 5 min. Sections were then blocked using 5% rabbit serum. Slides were incubated for 2 h at room temperature with an anti‐TIMP1 antibody . Biotinylated secondary antibody, avidin/biotin reagents (PK‐4100) and DAB peroxidase substrate (SK‐4100) were purchased from Vector Laboratories. Slides were imaged either using an Aperio AT2 (Leica Biosystems) at Histowiz or a Zeiss Axioscope Imager. Tumour area in the lungs of the KL mice was automatically quantified using scanned whole H&E slides and QuPath (0.4.2).2.4https://www.innov‐research.com/).Plasma samples (K2 EDTA) and FFPE tissue blocks from lung cancer patients were obtained from New York Presbyterian Hospital/Weill Cornell Medical College in accordance with a protocol approved by the Institutional Review Board (IRB) (IRB#19‐11021135). Lung adenocarcinoma and adjacent normal tissue used for qPCR analysis were obtained from New York Presbyterian Hospital/Weill Cornell Medical College in accordance with IRB approved protocol number 1008011221. Plasma samples (K2‐EDTA) from healthy donors were obtained from Innovative Research  followed up by an additional clean‐up step using RNeasy kit (Qiagen). cDNA was synthesized using SuperScript VILO Master Mix (Thermo Fisher). TIMP1 qPCR was done using Applied Biosystems SYBR Select Master Mix (Thermo Fisher) and previously published primers (5′−3′ AGCGCCCAGAGAGACACC and CCACTCCGGGCAGGATT).2.6t‐test of qPCR data in Figure https://kmplot.com/analysis/).https://www.cbioportal.org/). Epidemiological data in Tables p < 0.05, **p < 0.01, ***p < 0.001 and ****p < 0.0001. Graphical abstract was created using Biorender.com.All data were analyzed using RStudio 2023.03.0+386) running R version 4.0.5) unless stated otherwise. Paired .0.5 unle.03.0+3862.7KrasG12D/+; Lkb1f/f tumours was previously published and is available at the GEO Database (GSE107470).The bulk RNA‐sequencing of the 2.8https://zenodo.org/record/7400873#.ZGO1RuyZP0o. All graphs were created using RStudio (2023.03.0+386) running R (version 4.0.5).Imputed and library‐size normalized expression data of eight primary tumour samples were segmented from data provided in Laughney et. al.33.1G12D/+Kras and flox/floxStk11/Lkb1 (KL) alleles, a well‐established genetically engineered mouse model that develops aggressive lung cancer.We performed a screen for tumour‐secreted cytokines and chemokines using mice carrying inducible N = 127) and confirmed that it continued to be specifically elevated in tumour‐bearing mice  analysis of these cytokines in the serum to assess their performance as biomarkers and found that TIMP1 had an area under the curve (AUC) of 0.90, the highest of all the analyzed Figure . Next, we Figure  and perfe Figure . The sere Figure , a good e Figure , suggeste Figure  and H. T3.2Next, we sought to determine if TIMP1 levels could be used to predict overall survival in mice. We measured TIMP1 in serum and tumour lysates from KL mice and performed a Kaplan‐Meyer (KM) survival analysis. The mice with higher TIMP1 levels had worse overall survival rates whether it be in the tumour Figure  or serum3.3p‐value = 0.07) for squamous cell carcinomas to have higher levels of TIMP1  in resected lung tumours and its surrounding healthy tissue. In agreement with previous results,Additionally, IHC staining for TIMP1 in human lung tumours follows a cellular distribution similar to the tumours of the KL mice. Positive TIMP1 staining is observed in stromal fibroblasts and macrophages surrounding the tumour cells. Some high‐grade tumour cells also show positive cytoplasmic staining of TIMP1, particularly squamous cell carcinomas and adenocarcinomas with sarcomatous features Figure . This prTo better understand the conditions that lead to higher expression of TIMP1 in tumours, we performed a transcriptomics correlation analysis of TIMP1 using tumour RNA‐Sequencing data from the KL mice recently published by our group.Together, these data suggest that TIMP1 is produced by the tumour and surrounding stromal cells in a pro‐inflammatory milieu, and its concentration in plasma could be used as a biomarker for lung cancer detection.3.4p value = 0.0068 and 0.02, respectively). These results match those obtained by mining combined databases  of lung cancer microarrays, as depicted in Figure p value: 0.00011). Furthermore, we used a recently published dataset of lung cancer that contains overall survival and proteomics of the tumours and found that higher protein levels of TIMP1 correlate with unfavorable prognosis.To assess the role of TIMP1 as a prognostic factor in patients with lung cancer, we mined publicly available proteomic and transcriptomic datasets Figure .25 We 4Currently, there are no clinically useful serological biomarkers for lung cancer detection. In this study, we used a well‐established, genetically engineered mouse model of lung cancer to identify TIMP1 as a tumour‐secreted factor that predicts poor survival in mice and humans with lung cancer. Our results agree with those of others who found that the expression of TIMP1 correlates with poor survival in many tumour types.TIMP1 is highly expressed in a plethora of tumours including colon,The early detection of lung cancer relies on screening high risk populations using LDCT, which may lead to false positives.Our study has a few notable limitations. First, our clinical samples consisted only of subjects with NSCLC and we did not evaluate the relationship of TIMP1 to other lung cancer types. However, Jumper et al. could not identify any significant difference in TIMP1 levels between NSCLC and SCLC.M.D.G. reports personal fees from Novartis, Pfizer and Scorpion Therapeutics for work unrelated to this topic. M.D.G. is co‐founder and shareholder of Faeth Therapeutics. N.K.A. has equity in Angiocrine Bioscience. O.E. is supported by Janssen, J&J, Astra‐Zeneca, Volastra and Eli Lilly research grants. He is a scientific advisor and an equity holder in Freenome, Owkin, Volastra Therapeutics and One Three Biotech and a paid scientific advisor to Champions Oncology. T.E.M. receives research funding from Janssen and from Pfizer, Inc. B.M.S. is a consultant for Pfizer, AstraZeneca and Flame Biosciences. B.M.S. is on the advisory board or a speaker for Pfizer, AstraZeneca, BMS and Genentech and is a Board member of the Lung Cancer Research Foundation and the AATS Foundation Council. B.M.S. discloses holding stock or salary in Pfizer, PPD . B.M.S. is a consultant at Flame Biosciences and Galvanize Therapeutics. B.M.S.’s wife is an employee of and has financial interest in Xalud Therapeutics. All other authors declare no competing interests.The Lung Cancer Research Foundation, Grant Number: NIH K08 CA230318; The 2020 AACR‐ AstraZeneca Lung Cancer Research Fellowship, Grant Number: 20‐40‐12‐ DANT; The Starr Cancer Consortium; Weill Cornell Medicine.Supporting informatonClick here for additional data file.Supporting informatonClick here for additional data file.Supporting informatonClick here for additional data file.Supporting informatonClick here for additional data file.


Aggressive brain tumours, whether primary gliomas or secondary metastases, are characterised by hypervascularisation and are fatal. Recent research has emphasised the crucial involvement of endothelial cells (ECs) in all brain tumour genesis and development events, with various patterns and underlying mechanisms identified.Here, we highlight recent advances in knowledge about the contributions of ECs to brain tumour development, providing a comprehensive summary including descriptions of interactions between ECs and tumour cells, the heterogeneity of ECs and new models for research on ECs in brain malignancies. We also discuss prospects for EC targeting in novel therapeutic approaches.Interventions targeting ECs, as an adjunct to other therapies , have shown promising clinical efficacy due to the high degree of vascularisation in brain tumours. Developing precise strategies to target tumour‐associated vessels based on the heterogeneity of ECs is expected to improve anti‐vascular efficacy. 1. Interactions between endothelial cells (ECs) and tumour cells are involved in most key events during brain tumour development.2. EC heterogeneity and new research models in brain tumours have received increasing attention.3. Given the high degree of vascularisation in brain tumours, interventions targeting ECs are of particular importance. Glioblastoma (GBM) is the most frequent and aggressive primary brain tumour in adults, and brain metastasis remains a destructive complication of systemic malignancies, which affects about 20% of all cancer patients.ECs play essential parts in all critical events of the brain metastasis process, mainly the following: 1) tumour cells breakthrough from in situ locations into the vasculature (with blood flow to the brain) via intravasation, (2) entry into the blood as circulating tumour cells (CTCs), (3) tumour cell adherence and survival in the vascular niche, (4) breaching of the blood–brain barrier (BBB) and (5) intracranial colonisation and infiltration  and external glia surrounding capillaries; the resulting presence of a dense network of blood vessels and basement membrane provides an optimal environment for the vascular co‐option of tumour cells.2.4.139 have been shown to have high vessel co‐option activity. Notably, Griveau et al.Vascular co‐option has been proven to enable GBM cells to invade the brain, making the treatment of this cancer very challenging. Studies have increasingly revealed that bidirectional remodelling of ECs and GBM cells is important for GBM vessel co‐option. On the one hand, ECs facilitate the vascular infiltration of GBM cells by releasing bradykinin,2.4.2Metastatic cells in the brain are highly dependent on vascular co‐option to maintain tumour progression, particularly in the early stages of colonisation, after the course of extravasation. It is required not only for the survival of metastatic cells after extravasation but also for the growth of disseminated tumour cells upon exit from dormancy.In a word, vascular co‐option is a key step in initiating metastasis and is associated with the alteration of secretory factors, which could be considered potential diagnostic biomarkers to help clinicians dynamically detect tumour dormancy in the future. In addition, drugs that clinically target this process could be developed to avoid large metastasis formation and tumour progression. However, no effective biological strategy has been developed yet. In addition, as the early stages of metastasis are challenging to observe directly in the clinic, developing effective bionic models that mimic vascular co‐option is essential for preclinical studies.2.5Angiogenesis is generally accepted to be governed strictly by a balance of pro‐ and anti‐angiogenic factors. In tumour angiogenesis, this balance is disrupted, and the increased pro‐angiogenic factors lead to the uncontrolled promotion of angiogenesis. These angiogenesis‐related factors can be released by tumour cells and the paraneoplastic microenvironment.2.5.1Angiogenesis is thought to be triggered by hypoxia due to insufficient blood supply caused by rapid tumour growth. Hypoxia induces tumour cells to express hypoxia‐inducible factor‐1 (HIF‐1), which regulates the transcription of many angiogenesis‐related genes, such as VEGF, especially in gliomas. VEGF is the most potent angiogenic factor and the most widely studied. High levels of VEGF promote angiogenesis and tumour cell expansion, whereas low levels lead to reduced tumour vessel growth. VEGF in brain tumours functions in paracrine and autocrine manners by binding with high affinity to VEGF receptor 2/foetal liver kinase receptor 1 and VEGF receptor 1/fms‐like tyrosine kinase‐1.2.5.2Tumour cells trigger systemic alterations in the TME to create sites conducive to tumour cell seeding, survival and growth. Multiple studies have shown that various cellular components in the brain TME play important roles in angiogenesis. Astrocytes are the most numerous cells in the brain microenvironment that are responsible for the maintenance of BBB. Astrocytes are activated to tumour‐associated astrocytes in GBM,2.6Vasculogenic mimicry is the behaviour of the tumour attempting to form vascular‐like structures to supply nutrients and oxygen to itself, which is not dependent on EC‐based angiogenesis.3Recent analysis of brain tumours at the single‐cell level has revealed an unexpectedly high level of phenotypic complexity in the TME, including ECs.3.1GBM is characterised by broad intratumoural cell heterogeneity. In a native, immunocompetent mouse model of glioma, two endothelial subpopulations are determined. Tumour‐associated vessels make up the majority of the intratumoural vasculature, while tumour‐derived ECs are rare but also contribute to intratumoural vascularisation. There are molecular differences with extensive and significant cellular heterogeneity within the two EC subpopulations. In tumour‐associated vessels, heterogeneous ECs are divided into five clusters based on molecular expression characteristics. The similarity between these clusters is that canonical Wnt signalling and pathways involved in BBB integrity are significantly expressed, suggesting that targeting Wnt or BBB integrity could be used to indiscriminately inhibit tumour‐associated vessels as a routine strategy. In contrast, some potent factors  that regulate gene expressions have been found to be active in a certain cluster. It is possible that these potent factors continue to reinforce the transcription of genes that are involved in angiogenesis, such as VEGFR2, and this heterogeneity is likely to account for the failure of anti‐vascular therapies; thus, it is important to explore the mechanisms by which these potent factors regulate endothelial behaviour. Moreover, another cluster exhibits a marked immunomodulatory heterogeneity characterised by the expression of the chemokine receptor cluster of differentiation 74 and the proinflammatory chemokine CXCL10, suggesting an interaction with the immune population, which may explain the emerging immune phenotype. Tumour‐derived ECs present a much stronger infiltrative and angiogenic profile than tumour‐associated vessels, possibly because these ECs transformed by tumour cells still retain the tumour stemness.3.2A study involving the single‐cell sequencing of normal tissue, early‐stage lung cancer and metastases from 44 patients revealed eight EC subclusters. Consistent with the EC clusters in GBM mentioned above, a distinct set of tumour‐derived ECs is found in early‐stage lung cancer and lung cancer brain metastasis samples. Transcriptional sequencing indicates that VEGF and Notch signalling are strongly activated and regulate the fate decisions and development of ECs. Differential gene enrichment analysis of tumour ECs further confirms that angiogenic functions in brain metastases are significantly enhanced, indicating that brain metastasis induces analog vascular alterations to adapt to widespread angiogenesis, which has not been further elucidated. Among these differential genes, the up‐regulated insulin receptor in the intratumoural vascular is considered a potential target for therapies.In summary, heterogeneity in both expression profiles and distribution of ECs has been found in brain tumours. Similarly, tumour‐derived ECs, which show a strong neovascularisation capacity, are found in both primary and metastatic brain tumours, indicating the importance of this EC cluster in the intracranial context for brain tumour trophic growth, and targeting this EC subpopulation is expected to provide new therapeutic options for brain tumours. In addition, ECs with varying degrees of tight junction protein expression show heterogeneous spatial distributions, which reflects the influence of different tumour regions on BBB permeability. In the intratumour core region, a large number of ECs with impaired tight junctions are found. On the one hand, it reflects that the core of the tumour may retain the characteristics of the tumour‐initiating cells to a certain extent. On the other hand, it indicates that the oxygen and PH concentration gradients in the core region of the tumour may affect the BBB. Furthermore, the heterogeneity in the integrity of these ECs reflects the preference for vascular selection during the initial colonisation of the metastatic tumour cell. Therefore, protecting the integrity of the endothelial barrier is of great importance both for inhibiting the primary brain tumour's rapid intracranial infiltration and preventing the colonisation of metastases. The difference is that these EC heterogeneities do not produce exactly the same effects in primary and metastatic tumours. In GBM, more intratumour ECs exist in those patients with longer survival, and perivascular tumour cells have a reduced Ki67: CC3 ratio (a ratio that reflects active tumour proliferation) compared with tumour cells that avoid blood vessels, which might be caused by perivascular infiltration of immune cells. In contrast, Ki67 expression is significantly higher in tumour cells interacting with ECs in brain metastases.4The metabolic reprogramming of the glioma microenvironment has been found to lead to resistance to anti‐angiogenesis drugs, inducing metabolic adaptation to anaerobic glycolysis.5In traditional in vitro models, incubation (Transwell) chambers separated by substrate‐coated filters are used to study cellular interactions. However, this approach has limited functional capacity and is far from the in vivo pathological process. In vivo animal models also face ethical limitations. Hence, reliable bionic experimental models that reproduce the complex brain TME, especially vascular structures, including the BBB, are urgently needed. Many studies have recently attempted to construct better in vitro models to simulate tumour cell–EC interactions.5.1Microfluidic systems are powerful tools for studying disease pathology and have enabled the establishment of more in vitro models similar to in vivo models. This technology enables complex cellular interactions in vitro by setting up microchannels to manipulate fluids. The most common microfluidic chip model simulating tumour cell–EC interaction is usually designed with several parallel channels connected by dense and equally spaced micro gaps for molecular dissemination and communication. According to the anatomy of tumour cell–EC interactions, there is a collagen channel located between the 'tumour channel' and the 'vascular channel', which both mimic the basement membrane of blood vessels and provide a three‐dimensional (3D) environment to support the activation, outgrowth and angiogenesis of ECs in response to chemokines released by tumour cells. Park et al.5.23D bioprinting is an emerging technology in which bioactive materials are used as bioinks to construct 3D structures according to a designed model, and it holds great promise for modelling human diseases.5.3Given its complexity, the human brain is difficult to model using other organisms. Intensive research has been conducted to examine the use of in vitro organoid approaches to model human brain development and disease. Bian et al.66.1The first‐line conventional treatment for brain metastasis and GBM consists of surgical resection, radiation therapy and chemotherapy. Notably, melanoma‐derived brain metastasis responds favourably to immune checkpoint inhibitors (ICIs) therapy, and long‐term complete responses occur in some cases. Although these treatments do not directly target ECs, they cause complex effects on the vascular system, such as the cerebral vasospasm induced after surgery, the vascular remodelling, leakage and angiogenesis triggered by radiation.6.26.2.1Anti‐angiogenic therapy with the addition of bevacizumab has not been successful as a first‐line treatment for either GBM or brain metastasis, and new therapeutic strategies are urgently needed. In addition to highly abnormal angiogenesis, GBM is featured by an immunosuppressive microenvironment that hampers matured dendritic cells and the toxicity of T cells. For this reason, immune checkpoint therapy is a novel approach to its treatment. Given the success of ICIs in the treatment of melanoma and lung cancer, especially for melanoma‐derived brain metastasis,6.2.2In GBM, the expression of the mesenchymal–epithelial transition factor (MET) has been widely studied and correlates with bevacizumab resistance. However, a phase‐2 multicentre study suggested that combining bevacizumab with the MET inhibitor onartuzumab did not benefit patients with recurrent GBM.7For tumours with a high potential to metastasize to the brain , the majority of cancer patients now die not from the primary disease but from metastasis occurring 1−5 years after the surgical removal of the primary tumours; as current state‐of‐the‐art diagnostic modalities and auxiliary tools enable the precise resection of localised pre‐metastatic tumours. Unfortunately, due to the specificity of the brain microenvironment, both primary brain tumours and secondary brain metastases remain life‐threatening. Future therapeutic approaches for primary and secondary brain malignancies should target not only tumour cells but also other cells in the TME. Given the high degree of vascularisation of brain tumours, interventions targeting ECs are of particular importance. Interactions between ECs and tumour cells are involved in most key events during brain tumour development. However, existing anti‐endothelial treatment strategies are mainly anti‐angiogenic and ignore other key events involving ECs, leading to limitations in therapeutic efficacy. In addition, the heterogeneities of ECs suggest that generalised anti‐endothelial therapy may not lead to specific efficacy and that precise targeting of certain characteristic EC populations may be a better option. Moreover, focusing on the specific metabolic reprogramming that occurs in ECs in brain tumours may also facilitate precision therapies targeting tumour‐associated ECs. With the development of preventive and evidence‐based medicine for secondary brain metastases, clinicians and researchers tend to believe that preventing metastasis is easier than treating it. Therefore, the application of chemopreventive strategies before metastasis occurs provides more possibilities in clinical practice. As the endothelium is a significant driver of brain tumours, we believe that more endothelium‐related research models and preventive therapies will be proposed based on the mechanisms summarised in this review (Figure The authors have declared that no conflict of interest exists.


Elevated standardised mortality ratio of cardiovascular diseases (CVD) in patients with brain tumours may result from differences in the CVD incidences and cardiovascular risk factors. We compared the risk of CVD among patients with a primary malignant or non-malignant brain tumour to a matched general population cohort, accounting for other co-morbidities.Using data from the Secured Anonymised Information Linkage (SAIL) Databank in Wales (United Kingdom), we identified all adults aged ≥ 18 years in the primary care database with first diagnosis of malignant or non-malignant brain tumour identified in the cancer registry in 2000–2014 and a matched cohort (case-to-control ratio 1:5) by age, sex and primary care provider from the general population without any cancer diagnosis. Outcomes included fatal and non-fatal major vascular events  and venous thromboembolism (VTE). We used multivariable Cox models adjusted for clinical risk factors to compare risks, stratified by tumour behaviour  and follow-up period.There were 2869 and 3931 people diagnosed with malignant or non-malignant brain tumours, respectively, between 2000 and 2014 in Wales. They were matched to 33,785 controls. Within the first year of tumour diagnosis, malignant tumour was associated with a higher risk of VTE  and stroke . After the first year, the risks of VTE  and stroke  remained higher than controls. Patients with non-malignant tumours had higher risks of VTE , stroke  and aortic and peripheral arterial disease  within the first year of diagnosis compared with their controls.The elevated CVD and VTE risks suggested risk reduction may be a strategy to improve life quality and survival in people with a brain tumour.The online version contains supplementary material available at 10.1186/s12916-023-03153-6. Cardiovascular diseases (CVD), including coronary artery disease, stroke, aortic and peripheral arterial diseases and venous thromboembolism (VTE), are associated with malignant tumour diagnoses and their treatment –5. ThereBrain tumours are a heterogeneous group of tumours comprising over 130 different types . SurvivaThis study assessed the association between brain tumour diagnosis and CVD by tumour subtypes and estimated the incidences of CVD from tumour diagnosis compared to matched controls leveraging population-based routine healthcare data collected in Wales, UK.No formal PPI was undertaken for this study. However, the James Lind Alliance priority setting partnership on brain and spinal cord tumour identified long-term physical and cognitive effects of surgery and radiotherapy as one of the top 10 priorities. This study estimated the cardiovascular risks and VTE after brain tumour diagnosis compared to people without any cancer diagnosis. We also present these risks among brain tumour patients stratified by surgery status.This is a retrospective matched cohort study based in Wales (UK) using data from the Secure Anonymised Information Linkage (SAIL) Databank. Wales has a population of 3.1 million. The SAIL Databank contains whole-population anonymised individual-level routine healthcare data linkable to disease registries and national statistics registers via pseudonymised unique identifiers. SAIL datasets used in this study included primary care, hospital care, cancer registry and administrative datasets. All datasets have national coverage except the primary care dataset, which covers approximately 75% of the Welsh population.We used the cancer registry in SAIL Databank to identify adult patients aged ≥ 18 years with an incident primary intracranial tumour. Patients were eligible if their tumour was diagnosed between 2000 and 2014, and they had primary care data available from at least 1 year before index brain tumour diagnosis. Each patient must have had at least one matched control available, where the date of brain tumour diagnosis was not the date of death. Matched controls were people without a diagnosis of any cancer who had an active registration at a general practitioner practice during 2000 and 2014. We used the cancer registry to confirm no cancer diagnosis in the control population. Controls needed to have primary care data available at least 1 year before study entry, which was the time of tumour diagnosis of the matched patient with a brain tumour. Matching variables included date of birth within 5 years, sex and GP practice at a ratio of one brain tumour patient to up to five controls without replacement.https://doi.org/10.17605/OSF.IO/3FMY5). The primary outcome of interest was fatal and non-fatal major vascular events and VTE (deep vein thrombosis and pulmonary embolism). Major vascular events included haemorrhagic stroke , ischaemic stroke, unspecified stroke, ischaemic heart disease  and aortic and peripheral vascular disease. Events were defined as fatal if they were the direct cause of death on the death certificate or death occurred within 30 days of the outcome. We collected time-to-event data from date of study entry to date of event for all outcome variables. Patients may have more than one outcome event.Code lists for all outcome and data variables are available on Open Science Framework , medical history , hypertension, hyperlipidaemia, diabetes mellitus) and medications . For people with brain tumours, we also collected tumour behaviour , tumour types  and surgery status. WIMD is a postcode-based measure of relative deprivation in Wales published by the Welsh Government. Lower WIMD represents higher deprivation. Participants were recorded as being on a medication if there were at least 6 prescriptions of that class of medication before the date of study entry. For medical history of hyperlipidaemia, we combined those with coding of hyperlipidaemia with those on lipid lowering drugs. Diabetes status used both coding of diabetes and antidiabetic drugs. Tumour behavioural code in the International Classification of Diseases for Oncology Third Edition (ICD-O-3) determined malignancy where /3 denoted malignant tumours and /0–1 denoted non-malignant tumours. The binary surgery status was determined by data from cancer registry, procedural codes and histological diagnosis as surgery is the only means for histological diagnosis. The end of follow-up is defined as date of death, date of deregistration from primary care or end of study period (31 December 2018) for those alive and registered with primary care.https://doi.org/10.17605/OSF.IO/3FMY5). All outcomes and variables were captured using both primary care and hospital data. There was no formal sample size calculation, but the study design allowed detection of a hazard ratio of 1.20 with 80% power and 5% type 1 error in subgroup analyses. We planned to use all data available.Data sources used in this study included primary care general practitioner dataset, Welsh demographic service, Patient Episode Database for Wales, Welsh Cancer Intelligence and Surveillance Unit (cancer registry) and Annual District Death Extract. We used Clinical Terms Version 2 READ codes to extract information from primary care data. Diagnoses using the International Classification of Diseases version 10 (ICD-10) codes and procedures using the Office of Population Censuses and Surveys Classification of Surgical Operations (OPCS-4) codes were used to define variables and outcomes in hospital data. Where available, we used code lists from related publications to define our variables  using the Collett exact method. Cox regression was our primary statistical model to assess the association between brain tumour diagnosis and different CVDs. We initially fitted models including brain tumour diagnosis and the matching variables to account for the study design  and thenepiR’ (v2.0.19), ‘survival’ (v3.2–13), ‘rstpm2’ (v1.5.1) and ‘cmprsk’ (v2.2–10).We performed the same Cox models in subgroups of matched cohorts with glioblastoma and non-malignant meningioma for assessing whether incidence trends were reproducible in more homogeneous tumour groups. We did not examine effect modification because of anticipated low power in our dataset with relative few outcome events. Our primary multivariable analysis did not include body mass index (BMI) or smoking status because of relatively elevated levels of missingness . We used the STROBE checklist when writing our report.This study included 6800 patients with primary brain tumour diagnosed in Wales 2000–2014 and their 33,785 age-, sex- and GP practice-matched controls. Cohort selection is presented in Fig. p < 0.001), haemorrhagic stroke , and ischaemic stroke  but not IHD  or aortic and peripheral vascular disease . In multivariable analyses of patients surviving 1 year compared to controls, malignant brain tumour diagnosis was associated with VTE  and all stroke types combined  .Among 2869 patients with malignant tumours, 252 (8.8%) patients had at least one cardiovascular event within 1 year of diagnosis. There were 89 patients with a major vascular event and 170 patients with VTE , haemorrhagic stroke , ischaemic stroke  and aortic and peripheral arterial disease . In those surviving 1 year after tumour diagnosis, non-malignant tumour compared to controls was associated with a lower risk of haemorrhagic stroke , ischaemic heart disease  and aortic and peripheral arterial disease   patients had at least one cardiovascular event within 1 year of diagnosis. There were 265 patients with a major vascular event and 96 patients with VTE  and haemorrhagic stroke  , haemorrhagic stroke  and ischaemic stroke . Patients with meningiomas alive 1 year after tumour diagnosis had lower risk of haemorrhagic stroke , ischaemic heart disease , and aortic and peripheral arterial disease   differed from ours because they included subdural haematoma  and extradural haemorrhage . Non-traumatic extradural haemorrhage is rare. In the atraumatic setting, most subdural haematomas are subacute or chronic, which do not have shared cardiovascular risk factors and clinical management with stroke [A population matched-cohort study in England reported 906 1-year survivors of malignant central nervous system tumours had a higher hazard of stroke compared to their matched controls  . This sth stroke . Includih stroke . This diAdvances in treatment for certain cancer types have improved the survival of many patients in high-income countries . TogetheRisks of major vascular events and VTE can be reduced with antithrombotic drugs. We only presented descriptive statistics on CVD events by antiplatelet status because of few patients Table . Higher Strengths of this analysis include the availability of medical comorbidities associated with CVD. We demonstrated that risks observed for all non-malignant tumours can be applied to meningiomas; the risk profiles of malignant tumours and glioblastoma are different, suggesting that tumour subtypes should be considered separately. Our results add to the existing literature by describing the risk of CVDs from the time of brain tumour diagnosis. We were unable to include body mass index and smoking status in our primary analyses due to low-quality data availability. However, given similar effect estimates when restricted to the subpopulation with these data, it is unlikely to be a key confounder for the associations observed. This interpretation is supported by data from the English matched-cohort study , which fPatients are at higher risks of CVDs after malignant or non-malignant brain tumour diagnosis compared to age-, sex- and GP practice-matched controls without a cancer diagnosis. These risks are highest within the first year of tumour diagnosis and risk profiles differ by tumour subtypes. Future work needs to clarify the interaction between cancer treatment and CVD risks and to assess the efficacy of existing therapies in minimising CVD risks. Quantifying the benefits of cancer therapies and their associated risks can improve clinical decision-making for maximising the quality of life of brain tumour patients.Additional file 1: Table S1. Characteristics of patients with glioblastoma and meningioma and their matched controls. Table S2. Clinical management of 6800 brain tumour patients. Table S3. Cumulative incidence and relative risks of cardiovascular diseases within 1 year of study entry in brain tumour patients compared with general population in competing risk analyses. Table S4. Cumulative incidence and relative risks of cardiovascular diseases from 1 year after study entry in brain tumour patients compared with general population in competing risk analyses. Figure S1. Data completeness for smoking and body mass index data. Figure S2. Crude incidences and hazard ratios for cardiovascular events after tumour diagnosis in people with glioblastoma and meningioma diagnosis compared with their matched controls. Figure S3. Estimated incidences of major vascular events and venous thromboembolism from study entry to 1 year using flexible parametric models by surgery status. Figure S4. Risk comparisons including body mass index and smoking status in multivariable analyses. Figure S5. Risk comparisons excluding stroke occurring within 14 days of brain tumour diagnosis in people with brain tumour.


My first exposure to hemodialysis was in 1976 when, as a first-year medical student, I visited the home of a friend with kidney failure. His bedroom was transformed into a mini hospital where he made up his own Kiil dialysers, used two independent volumetric pumps to control the blood flow, which he had learned to balance since the age of 16 years, and a weigh bed to monitor his intradialytic fluid removal. It left an impression. A lot has changed since then including the case mix of people on dialysis, their expectations and priorities, treatment goals and strategies, and technological advances. This brief article will look at how these have evolved over time and speculate as to how they might continue to develop , the optimal strategy may be to set the postdialytic weight below the normally hydrated weight, that is, cause volume depletion, whereas when protecting against dialysis-related symptoms, the opposite strategy must be adopted, with its inherent risks.More controversial is the choice of surrogate clinical outcomes to use when assessing the quality of volume management. Undoubtedly, left ventricular hypertrophy is a consequence of long-standing hypertension and fluid overload and thus a legitimate target for optimal fluid management. There is, however, poor evidence that reducing left ventricular mass translates into clinical benefit9 yet it is infrequently measured and rarely considered when prescribing dialysis. This is remarkable given the survival and quality-of-life benefits associated with residual kidney function, long appreciated in peritoneal dialysis patients. Aggressive fluid management strategies that do not take residual function into account run the risk of accelerating its loss, and there is an urgent need for trials of fluid management strategies that might preserve it for as long as possible. Conversely, there are people on dialysis who are at risk of dying during the 3-day break, and it is likely that at least some of those are at risk because of fluid excess, either directly because of pulmonary edema or indirectly by cardiac damage. It is clear that a one-size-fits-all strategy for volume management cannot deliver what is needed.Perhaps most importantly, it is now recognized that preservation of residual kidney function is of value to hemodialysis patients,The single most important technological advance in volume management was the advent of volumetric ultrafiltration. The combination of a balanced pump system, a pair of pumps separated by a flexible membrane so that the dialysate flow in and out of the dialyser can be perfectly matched, with the addition of a volumetric ultrafiltration pump meant that fluid removal during dialysis could be controlled precisely. Its introduction meant that the rate of fluid removal could now be controlled, which previously was performed by monitoring weight change in response to positioning of the dialysis membrane. It had a major effect on the safety and symptoms associated with dialysis but also contributed to the drive to shorten dialysis treatments by maximizing ultrafiltration rates. The replacement of acetate with bicarbonate as the dialysate buffer also had significant benefits on intradialytic cardiovascular stability during dialysis of particular value in an increasingly comorbid population. Acetate infusion causes a drop in BP and is also associated with nausea on dialysis.Both of these innovations became well established in the 1980s, whereas later technologies designed to help with volume management have been less universally adopted. These include hemodiafiltration, reported to reduce the incidence of intradialytic hypotension and improved survival—although still the subject of major trials in Europe—and devices designed to help with fluid management. These are intended to give the clinician insight into the fluid status and so provide support in the setting of the target weight. They include intradialytic relative blood volume monitoring, bioimpedance technologies, and other methods of measuring extravascular tissue fluid accumulation such as lung ultrasound. Relative blood volume monitoring exploits the idea that removal of fluid from the circulation by ultrafiltration will increase the hematocrit unless it is matched by plasma refilling from the interstitial extravascular fluid compartment. In theory, at least, once the refilling stops catching up with the ultrafiltration then the patient is at their target weight, and pattern recognition of the relative blood volume curve can be useful. Bioimpedance exploits the fact that when an alternating current is passed through tissues, it will meet less resistance from overhydrated interstitium but will be impeded by tissues whose cell membranes act as mini capacitors. It can be used to estimate the total body water and the proportion of this that is intracellular-versus extracellular. Lung ultrasound uses comets to detect extravascular lung fluid, so identifying subclinical pulmonary edema.10 As clinicians, we can influence fluid balance through the dialysis prescription, but changing how fluid is distributed in the body is far more challenging. Trials evaluating these methods as useful guides to fluid management, including relative blood volume monitoring,1 bioimpedance,11 and lung ultrasound have not been promising overall.12 As such, these technologies should only be used in conjunction with a holistic clinical fluid assessment.10What all these methods share is an ability to identify patients at risk, and it is clear that tissue fluid excess, often subclinical, is associated with worse outcomes in hemodialysis patients. This seems to be independent of inflammation and BP but is as much a function of abnormal fluid distribution as it is of positive fluid balance (see Table 13 The answer, surely, must be by taking a risk stratification approach that can accommodate individualized patient goals. This requires accurate diagnosis of the problem—for example, is it a fluid balance or fluid distribution problem (or both, Table Given these limitations, changes in case mix and need to focus on the experience of dialysis, where are we going with volume management?