Role of inferior vena cava collapsibility index in the prediction of hypotension associated with general anesthesia: an observational study

Background Intraoperative hypotension increases 30-day mortality and the risks of myocardial injury and acute renal failure. Patients with inadequate volume reserve before the induction of anesthesia are highly exposed. The identification of latent hypovolemia is therefore crucial. Ultrasonographic measurement of the inferior vena cava collapsibility index (IVCCI) is able to detect volume responsiveness in circulatory shock. No current evidence is available regarding whether preoperative measurement of the IVCCI could identify patients at high risk for hypotension associated with general anesthesia. Methods A total of 102 patients undergoing elective general surgery under general anesthesia with standardized propofol induction were recruited for this prospective observational study. The IVCCI was measured under spontaneous breathing. A collapsing (IVCCI >= 50%) (CI+) and a noncollapsing (CI-) group were formed. Immediate postinduction changes in systolic and mean blood pressure were compared. The performance of the IVCCI as a diagnostic tool for predicting hypotension (systolic pressure < 90 mmHg or a >= 30% drop from the baseline) was evaluated by ROC curve analysis. Results A total of 83 patients were available for analysis, with 20 in the CI+ and 63 in the CI- group, we excluded 19 previously eligible patients due to inadequate visualization of the IVC (7 cases), lack of adherence to the protocol (8 cases), missing data (2 cases) or change in anesthesiologic management (2 cases). The mean decrease in systolic pressure in the CI+ group was 53.8 +/- 15.3 compared to 35.8 +/- 18.1 mmHg in CI- patients (P = 0.0001). The relative mean arterial pressure change medians were 34.1% (IQR 23.2-43.0%) and 24.2% (IQR 17.2-30.2%), respectively (P = 0.0029). The ROC curve analysis for IVCCI showed an AUC of 64.8% (95% CI 52.1-77.5%). The selected 50% level of the IVCCI had a sensitivity of only 45.5% (95% CI 28.1-63.7%), but the specificity was high at 90.0% (78.2-96.7%). The positive predictive value was 75.0% (95% CI 50.9-91.3%), and the negative predictive value was 71.4% (95% CI 58.7-82.1%). Conclusion In spontaneously breathing preoperative noncardiac surgical patients, preoperatively detected IVCCI >= 50% can predict postinduction hypotension with high specificity but low sensitivity. Despite moderate performance, IVCCI is an easy, noninvasive and attractive option to identify patients at risk and should be explored further.