Comparison of pulse pressure variation versus echocardiography-derived stroke volume variation for prediction of fluid responsiveness in mechanically ventilated anesthetized dogs

Objective To evaluate the ability and accuracy of aortic flow velocity-time integral variation (Delta VTI) and peak aortic velocity variation (Delta Vpeak) compared with pulse pressure variation (PPV) to predict fluid responsiveness in mechanically ventilated dogs. Study design Prospective clinical study. Animals A group of 50 mechanically ventilated dogs with spontaneous hypotension during orthopedic or oncologic surgery. Methods Investigations were performed in the surgery room. When mean arterial pressure (MAP) decreased to <65 mmHg, measurements were performed before and after a fluid challenge (lactated Ringer 's solution 5 mL kg(-1) over 15 minutes). Responders were defined as a change in stroke volume (SV; transesophageal Doppler) >= 15%. Data were analyzed using paired/unpaired t test or Mann-Whitney/Wilcoxon test when appropriate and receiver operating characteristics (ROC) curves; a p value <0.05 was considered statistically significant. Results After the fluid challenge, 35 (70%) of 50 dogs were responders with significant increases in SV and decreases in PPV; 15 dogs were nonresponders. Delta VTI and Delta Vpeak correlated with a 15% increase in SV. The optimum cut-off value for PPV was 15.6% (sensitivity, 88%; specificity, 100%), for Delta VTI was 10.65% (sensitivity, 65%; specificity, 100%) and for Delta Vpeak was 10.15% (sensitivity, 80%; specificity, 100%). The area under the ROC curve for PPV was (0.93 +/- 0.08) and for DVpeak was (0.89 +/- 0.09), before fluid challenge. The gray zone area spread from 6.15% to 15.6% for PPV (18 dogs), 2.45% to 10.65% for DVTI (22 dogs) and 0.6% to 10.15% for Delta Vpeak (25 dogs). Conclusions When using mechanical ventilation, Delta VTI and Delta Vpeak predicted fluid responsiveness with the same ability as PPV, based on the area under the ROC curve analysis. However, PPV showed great accuracy demonstrated by a narrower gray zone that included fewer individuals.