Role of inferior vena cava collapsibility index in the prediction of hypotension associated to general anesthesia: an observational study
Abstract Background: Intraoperative hypotension increases 30-day mortality, risk of myocardial injury and acute renal failure. Patients having inadequate volume reserve before induction of anesthesia are highly exposed. Identification of subclinical hypovolemia is therefore crucial. Ultrasonographic measurement of inferior vena cava collapsibility index (IVCCI) is able to detect volume responsiveness in circulatory shock. Ther is a lack of current evidence whether preoperative application could identify high risk patients for hypotension associated to general anesthesia. Methods: 102 patients (conforming ASA status I-III, without significant cardiac pathology) undergoing elective abdominal surgery under general anesthesia with standardized propofol induction were recruited to this prospective observational study. IVCCI was measured under spontaneous breathing. A collapsing (IVCCI≧50%) (CI+) and a non-collapsing (CI-) group were formed. Immediate postinductional changes in systolic and mean blood pressure were compared. Performance of IVCCI’s 50% cut-off as a diagnostic tool for predicting hypotension (systolic pressure below 90 mmHg or >30% drop from baseline) was evaluated by ROC curve analysis. Results: A total of 83 patients were evaluated, 20 in the CI+ and 63 in the CI- group. Mean decrease of systolic pressure in CI- group was 35.8±18.1 mmHg compared to 53.8±15.3 mmHg of CI+ patients (P=0.0001). Relative decrease in systolic pressures differed significantly as well: CI- patients had a mean of 24.7±11.3% while this was 36.4±9.1% in CI+ group (P<0.0001). Relative mean arterial pressure change medians were 24.2% (IQR 17.2%-30.2%) and 34.1% (IQR 23.2%-43.0%) respectively (P=0.0029). The ROC-curve analysis for IVCCI showed an AUC of 64.8% (95%CI 52.1-77.5%). Selected 50% level of IVCCI had a sensitivity of only 45.5% (95%CI 28.1-63.7%) but specificity was high: 90.0% (78.2-96.7%). Positive predictive value revealed as 75.0% (95%CI 50.9-91.3%) and negative predictive value was 71.4% (95%CI 58.7-82.1%). Conclusion: Preoperatively detected IVCCI≧50% is a moderately useful test to identify patients susceptible to postinductional hypotension. However, due to its low sensitivity, it has a low value in excluding it. Keywords: Anesthesia, hypotension, propofol, vena cava, inferior, echocardiography