Efficacy of inferior vena cava collapsibility index and caval aorta index in predicting the incidence of hypotension after spinal anaesthesia- A prospective, blinded, observational study

Background and Aim: Spinal anaesthesia-induced hypotension (SAIH) is a frequent side effect of spinal anaesthesia. SAIH is usually observed in patients with hypovolemia. Ultrasonography has evolved as a non-invasive tool for volume status assessment. Methods: This prospective, blinded, observational study was conducted on 75 adult patients who required spinal anaesthesia after receiving ethical approval and registering the study. Ultrasonographic evaluation of the aorta and the inferior vena cava (IVC) was done preoperatively, and the IVC collapsibility index (IVCCI) and caval aorta index were calculated. The incidence of SAIH was recorded. The strength of the association between different parameters and SAIH was calculated. To find out the value of the optimal cut-off for the prediction of SAIH, receiver operating characteristic (ROC) analysis for various ultrasound parameters was done. The bidirectional stepwise selection was utilised for multivariate analysis to choose the single best predictor. Results: SAIH was observed in 36 patients. Among demographic parameters, age, female gender, and height showed a medium correlation. Among ultrasonographic measurements, minimum IVC internal diameter (IVCmin) and IVCCI showed a strong association with SAIH. The best parameter regarding area under the ROC curve (AUC) and diagnostic accuracy was IVCCI (0.828 and 85%, respectively). On multivariate analysis, age (95% CI [1.01, 1.12], P = 0.024) and IVCCI (95% CI [1.05, 1.18], P < 0.001) were significant independent predictors. At a cut-off point of ≥43.5%, IVCCI accurately predicted SAIH (sensitivity 81% and specificity 90%). Conclusion: Preoperative ultrasonographic assessment of IVC to evaluate its collapsibility index is a convenient, cost-effective, and reproducible tool for predicting SAIH.