Pre-operative ultrasonographic evaluation of inferior vena cava collapsibility index and caval aorta index as new predictors for hypotension after induction of spinal anaesthesia A prospective observational study

BACKGROUND Hypotension after spinal anaesthesia is a common side effect that may be harmful. Patients' susceptibility to intra-operative hypotension can be affected by many pre-operative factors. OBJECTIVES The current study aimed to evaluate the efficacy of both pre-operative inferior vena cava collapsibility index (IVCCI) and inferior vena cava to aorta diameter (IVC : Ao) index for predicting postspinal anaesthesia hypotension (PSAH). DESIGN Prospective observational blinded study. SETTING Operating room from June 2017 to February 2018. PATIENTS One hundred adult patients of both sexes, American Society of Anesthesiologists' physical status 1 or 2 scheduled for elective surgery under spinal anaesthesia were included in this study. INTERVENTIONS Patients received spinal anaesthesia performed at the level of L3 to 4 or L4 to 5 intervertebral space with the patient in the sitting position then placed in the supine position immediately after neuraxial block and kept supine throughout the study period (30 min). IVCCI and IVC : Ao index were assessed pre-operatively. Baseline non-invasive blood pressure was recorded before administration of spinal anaesthesia then every minute after spinal blockade for 30 min. MAIN OUTCOME MEASURES The primary outcome was to evaluate the predictive values of both IVCCI and IVC : Ao index for detecting PSAH and the secondary outcomes were to compare the predictive values of both IVCCI and IVC : Ao index and to detect other clinical predictors for PSAH using logistic regression analysis. RESULTS Forty-five patients developed PSAH (45%). IVCCI was significantly higher in patients who developed PSAH than in patients who did not, while IVC : Ao index was significantly lower in patients who developed PSAH than in patients who did not. Hypotension after induction of spinal anaesthesia was defined as an absolute value of SBP less than 90 mmHg, a decrease in SBP more than 30% of the baseline value or an absolute value of arterial blood pressure less than 60 mmHg. Logistic regression analysis revealed that IVCCI and IVC : Ao index were good predictors of the occurrence of PSAH. Receiver operating characteristic curve analysis showed that IVC : Ao index had a sensitivity of 96%, a specificity of 88%, and an accuracy of 95% to predict PSAH at a cut-off point less than 1.2. IVCCI had a sensitivity of 84%, a specificity of 77%, and an accuracy of 84% to predict PSAH at a cut-off point more than 44.7%. CONCLUSION Pre-operative IVCCI and IVC : Ao index are good predictors of the occurrence of PSAH. However, IVC : Ao index is a more powerful predictor than IVCCI.