Utility of intra-operative ultrasound in choosing the appropriate site for blood pressure monitoring in Takayasu's arteritis
A 35-year-old woman with the following characteristics was posted for emergency caesarean delivery in view of intra-uterine growth retardation and foetal tachycardia: Second gravida at 35 weeks of gestation with TA, AR and hypertension for 5 years, on treatment with tablet methyldopa 500 mg, amlodipine 5 mg and extended release metoprolol 50 mg, each, twice daily.\nHer pulse rate was 114/min and BP was 183/78 mmHg in right arm supine position. Volume of upper limb pulses appeared to be bilaterally equal on palpation. However, right radial pulse was collapsing in nature along with radio-femoral delay. Grade four early diastolic murmur, loudest in aortic area, with palpable thrill-radiating to left sternal border was present. Examination of other systems and investigations were unremarkable. Two dimensional (2D) echocardiogram revealed narrowing of thoracic and abdominal aorta to 9 mm with a high blood flow velocity of 2.0 m/s. Ascending aorta and aortic arch were dilated along with moderate AR. Left ventricular ejection fraction was 58% with normal biventricular systolic function and normal pulmonary artery pressure. Doppler performed 5 years back showed high resistant flows in common, internal and external carotid arteries bilaterally, with possible proximal stenosis of right subclavian artery (SCA).\nBaseline vitals in the operating room were as follows: Heart rate of 115/min, non-invasive blood pressure (NIBP) of 188/78 mmHg in right upper limb and SPO2 of 97% [].\nAnaesthetic plan was lumbar epidural anaesthesia with invasive radial arterial BP monitoring prior to placing the epidural. Since the doppler report showed possible stenosis of right SCA, left radial arterial line was secured and the invasive BP (IBP) was 112/55 mmHg. Lower limb arterial monitoring was not considered due to narrowing of thoraco-abdominal aorta. Epidural catheter was secured in L1-L2 intervertebral space, and the position was confirmed with test dose of 3 ml of 2% preservative free lignocaine. Patient was positioned supine with a wedge under the right buttock. To achieve a sensory block up to T6 level, 10 ml of 0.5% ropivacaine was given in 5-ml increments every 10 minutes. There was a drop in IBP to 80/40 mmHg along with a drop of NIBP to 122/60 mmHg after the epidural over 10 minutes. We treated the drop in IBP with 6 mg ephedrine boluses to avoid any cerebral or utero-placental hypoperfusion. There was ill-sustained increase in IBP and NIBP after each bolus (3 boluses provided). BP increased up to 122/64 mmHg, while the NIBP increased up to 198/94 mmHg after the third bolus of ephedrine. Patient complained of headache after each bolus of ephedrine. Possibility of over treating IBP leading to headache was considered after ruling out possibilities of monitoring error. On-table doppler ultrasound of upper limb arteries was performed specifically looking at the luminal diameter and amplitude of pulsations. Both were reduced in the left radial and axillary artery when compared to the right radial and axillary artery. Right radial pulsation was collapsing in nature, which is expected in AR. Thereafter, we considered treating using the NIBP values of the right upper limb. Meanwhile, the baby delivered was shifted to neonatal intensive care unit in view of prematurity. Rest of the intra-operative period was uneventful. Postoperatively, the patient was monitored in a high dependency unit. Post-operative aortogram revealed normal right SCA and diffuse disease of the left distal SCA, which confirmed our intra-operative findings.