The tidal volume challenge improves the reliability of dynamic preload indices during robot-assisted laparoscopic surgery in the Trendelenburg position with lung-protective ventilation

Background The reliability of pulse pressure variation (PPV) and stroke volume variation (SVV) is controversial under pneumoperitoneum. In addition, the usefulness of these indices is being called into question with the increasing adoption of lung-protective ventilation using low tidal volume (V-T) in surgical patients. A recent study indicated that changes in PPV or SVV obtained by transiently increasing V-T (V-T challenge) accurately predicted fluid responsiveness even in critically ill patients receiving low V-T. We evaluated whether the changes in PPV and SVV induced by a V-T challenge predicted fluid responsiveness during pneumoperitoneum. Methods We performed an interventional prospective study in patients undergoing robot-assisted laparoscopic surgery in the Trendelenburg position under lung-protective ventilation. PPV, SVV, and the stroke volume index (SVI) were measured at a V-T of 6 mL/kg and 3 min after increasing the V-T to 8 mL/kg. The V-T was reduced to 6 mL/kg, and measurements were performed before and 5 min after volume expansion (infusing 6% hydroxyethyl starch 6 ml/kg over 10 min). Fluid responsiveness was defined as >= 15% increase in the SVI. Results Twenty-four of the 38 patients enrolled in the study were responders. In the receiver operating characteristic curve analysis, an increase in PPV > 1% after the V-T challenge showed excellent predictive capability for fluid responsiveness, with an area under the curve (AUC) of 0.95 [95% confidence interval (CI), 0.83-0.99, P < 0.0001; sensitivity 92%, specificity 86%]. An increase in SVV > 2% after the V-T challenge predicted fluid responsiveness, but showed only fair predictive capability, with an AUC of 0.76 (95% CI, 0.60-0.89, P < 0.0006; sensitivity 46%, specificity 100%). The augmented values of PPV and SVV following V-T challenge also showed the improved predictability of fluid responsiveness compared to PPV and SVV values (as measured by V-T) of 6 ml/kg. Conclusions The change in PPV following the V-T challenge has excellent reliability in predicting fluid responsiveness in our surgical population. The change in SVV and augmented values of PPV and SVV following this test are also reliable.