Inferior Venacaval Ultrasonography to Detect Pre-Operative Hypovolemia as a Predictor of Postinduction Hypotension

Abstract

Background: Hypotension is a common side effect of general anaesthesia, and when severe, it may lead to adverse outcomes. Ultrasonography of Inferior Vena Cava (IVC) is an effective, non-invasive method of assessment of intravascular volume status and hence the risk of hypotension at induction of anaesthesia. This study investigated whether preoperative ultrasound guided IVC measurements could predict hypotension after induction of anaesthesia. Methods: After ethical committee approval, this study was conducted at Sri Ramakrishna Hospital, Coimbatore. Written and informed consent was obtained. Forty six (46) adult patients, conforming to American Society of Anaesthesiologists physical status I to II, scheduled for elective surgery under general anaesthesia were recruited. Maximum IVC Diameter (dIVCmax) and Collapsibility Index (CI) were measured preoperatively. Before induction, Mean Blood Pressure (MBP) was recorded. After induction, MBP was recorded for 10 consecutive minutes. Hypotension was defined as greater than 30% decrease in MBP from baseline or MBP less than 60 mmHg. Results: IVC could not be visualized in 6 patients. Data from remaining 40 patients were analysed, of whom 26 patients (65%) developed hypotension. The incidence of hypotension in patients with CI>40% was 100% and when CI<40% it was 4%. The mean value of IVC maximum diameter was 1.60 cm and the mean value of IVC minimum diameter was 1.02 cm. The optimal cut-off value was 40% for CI among the patients who developed hypotension. CI was positively associated with a percentage decrease in MBP. Conclusion: Preoperative ultrasound IVC-CI measurement is a reliable predictor of hypotension after induction of general anaesthesia, and CI greater than 40% was highly significant in causing post induction hypotension.