Pulse pressure variation as a guide for volume expansion in dogs undergoing orthopedic surgery.
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OBJECTIVE: To investigate whether pulse pressure variation (PPV) can predict fluid responsiveness in healthy dogs during clinical surgery. STUDY DESIGN: Prospective clinical study. ANIMALS: Thirty-three isoflurane-anesthetized dogs with arterial hypotension during orthopedic surgery. METHODS: Fluid challenge with lactated Ringer's solution (15mLkg-1 in 15 minutes) was administered in mechanically ventilated dogs (tidal volume 10mLkg-1) with hypotension [mean arterial pressure (MAP)<65mmHg]. The volume expansion was considered effective if cardiac output (CO; transesophageal Doppler) increased by 15%. Cardiopulmonary data were analyzed using two-way ANOVA, receiver operating characteristics (ROC) curves and Spearman coefficient; p<0.05 was considered significant. RESULTS: Effective volume expansion, mean standard deviation 42 4% increase in CO (p < 0.0001) was observed in 76% of the dogs, resulting in a decrease in PPV (p<0.0001) and increase in MAP (p<0.0001), central venous pressure (CVP; p=0.02) and ejection fraction (p<0.0001) compared with before the fluid challenge. None of these changes occurred when volume expansion resulted in a nonsignificant CO increase of 45%. No significant differences were observed in blood gas analysis between responsive and nonresponsive dogs. The increase in CO was correlated with the decrease in PPV (r=-0.65; p<0.0001) but absolute values of CO and PPV were not correlated. The PPV performance (ROC curve area: 0.890.06, p=0.0011) was better than that of CVP (ROC curve area: 0.540.12) and MAP (ROC curve area: 0.590.13) to predict fluid responsiveness. The best cut-off for PPV to distinguish responders and nonresponders was 15% (50% sensitivity and 96% specificity). CONCLUSIONS AND CLINICAL RELEVANCE: In mechanically ventilated, healthy, isoflurane-anesthetized dogs, PPV predicted fluid responsiveness to volume expansion, and MAP and CVP did not show such applicability.
