Stroke volume variation does not predict fluid responsiveness in patients with septic shock on pressure support ventilation

BACKGROUND: Stroke volume variation (SVV)--as measured by the pulse contour cardiac output (PiCCO) system--predicts the cardiac output response to a fluid challenge in patients on controlled ventilation. Whether this applies to patients on pressure support ventilation is unknown. METHODS: Thirty consecutive patients with septic shock were included. All were on pressure support ventilation, monitored using the PiCCO system and receiving 500 ml of colloid on clinical indications. Arterial pulse contour SVV and the transpulmonary thermodilution cardiac index were measured before and after fluid challenge. RESULTS: Forty-seven per cent of the patients were defined as fluid responders by an observed increase of > 10% in the cardiac index after fluid. Prior to fluid challenge, the cardiac index was lower in responders compared with non-responders (mean +/- SD, 3.0 +/- 0.6 vs. 4.0 +/- 1.2 l/min/m2, P < 0.01). In contrast, pre-infusion values of SVV were similar between subsequent responders and non-responders (13 +/- 5 vs. 16 +/- 6%, P =0.26). The mean areas under the ROC curves were 0.77 (95% confidence interval, 0.60-0.94) and 0.52 (0.30-0.73) for pre-fluid cardiac index and SVV, respectively, indicating a predictive power of only the cardiac index. CONCLUSIONS: SVV did not predict the response in cardiac output to fluid challenge in patients with septic shock on pressure support ventilation.