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. Trial registration: This trial was registered with Clinicaltrials.gov, NCT03467711, 10th March 2018.