The aim of this prospective study was to evaluate the usefulness of stroke volume variation (SVV) derived from NICOM® to predict fluid responsiveness in the prone position. Forty adult patients undergoing spinal surgery in the prone position were included in this study. We measured SVV from NICOM® (SVVNICOM) and FloTrac™/Vigileo™ systems (SVVVigileo), and pulse pressure variation (PPV) using automatic (PPVauto) and manual (PPVmanual) calculations at four time points including supine and prone positions, and before and after fluid loading of 6 ml kg-1 colloid solution. Fluid responsiveness was defined as an increase in the cardiac index from Vigileo™ of ≥12 %. There were 19 responders and 21 non-responders. Prone positioning induced a significant decrease in SVVNICOM, SVVVigileo, PPVauto, and PPVmanual. However, all of these parameters successfully predicted fluid responsiveness in the prone position with area under the receiver-operator characteristic curves for SVVNICOM, SVVVigileo, PPVauto, and PPVmanual of 0.78 [95 % confidence interval (CI) 0.62-0.90, P = 0.0001], 0.79 (95 % CI 0.63-0.90, P = 0.0001), 0.76 (95 % CI 0.6-0.88, P = 0.0006), and 0.84 (95 % CI 0.69-0.94, P < 0.0001), respectively. The optimal cut-off values were 12 % for SVVNICOM, SVVVigileo, and PPVauto, and 10 % for PPVmanual. SVV from NICOM® successfully predicts fluid responsiveness during surgery in the prone position. This totally non-invasive technique for assessing individual functional intravenous volume status would be useful in a wide range of surgeries performed in the prone position.
Keywords: Cardiac output; Fluids therapy; Heart; Intraoperative; Monitoring; Prone position; Spinal surgery.