Preoperative ultrasonographic evaluation of inferior vena cava collapsibility index versus subclavian vein collapsibility index as a predictor of hypotension following induction of general anaesthesia:An observational study

Hypotension is very common intraoperatively in patients under anaesthesia and may cause many adverse effects which leads to extended hospital stay of patients.[1] After induction of general anaesthesia, patients are at particular risk of developing hypotension because of the cardiovascular depressant and vasodilatory effects of anaesthetic agents more seen in patients with hypovolemia and lack of compensatory response.[2].Other factors include American Society of Anaesthesiologists physical status (ASA) III and IV, baseline mean arterial pressure lower than 70 mmHg, age more than 60 years, use of propofol, and high fentanyl dose [3]. Preoperative volume status depends on various factors like physical status, comorbidities, bowel preparation and fasting period of patient[2]. Intra operative hypotension may lead to adverse events like myocardial infarction, heart failure, stroke, acute renal failure, prolonged hospital stay, increased mortality[2]. Assessing intravascular volume status is a challenge for clinicians. Traditional static parameters like central venous pressure are invasive and not accurate. Ultrasound assessment of inferior vena cava diameter (DIVC) with respiration, passive leg raise test and IVC collapsibility index (IVC-CI) are used as a reliable, non invasive tool to assess intravascular volume and predict intraoperative hypotension.[1,3,4,5] But IVC assessment is difficult in patients having abdominal distension, tenderness, guarding, ascites, morbid obesity and patients having abdominal dressing. [2] Hence Subclavian vein (SCV) which is located adjacent to the pleura and upstream of the superior vena cava can be easily visualized in most patients with a linear probe.[2] Studies have shown that SCV assessment can be used as reliable adjust to IVC for measurement of intravascular volume status[1,2,4]. Also, Collapsibility Index of Subclavian Vein (SCV-CI) was able to predict post general anaesthesia hypotension in deep inspiration[1]. We hypothesize that pre operative ultrasonographic SCV-CI is a reliable and a better alternative to IVC-CI in predicting hypotension following induction of general anaeasthsia.