Pulse pressure variation as a guide for volume expansion in dogs undergoing orthopedic surgery.

Abstract

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 (15&#xa0;mL&#xa0;kgin 15 minutes) was administered in mechanically ventilated dogs (tidal volume 10&#xa0;mL&#xa0;kg) with hypotension [mean arterial pressure (MAP)&#xa0;<&#xa0;65&#xa0;mmHg]. The volume expansion was considered effective if cardiac output (CO; transesophageal Doppler) increased by &#x2265; 15%. Cardiopulmonary data were analyzed using two-way ANOVA, receiver operating characteristics (ROC) curves and Spearman coefficient; p&#xa0;<&#xa0;0.05 was considered significant. RESULTS: Effective volume expansion, mean &#xb1; standard deviation 42 &#xb1; 4% increase in CO (p < 0.0001) was observed in 76% of the dogs, resulting in a decrease in PPV (p&#xa0;<&#xa0;0.0001) and increase in MAP (p&#xa0;<&#xa0;0.0001), central venous pressure (CVP; p&#xa0;=&#xa0;0.02) and ejection fraction (p&#xa0;<&#xa0;0.0001) compared with before the fluid challenge. None of these changes occurred when volume expansion resulted in a nonsignificant CO increase of 4&#xa0;&#xb1;&#xa0;5%. 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&#xa0;=&#xa0;-0.65; p&#xa0;<&#xa0;0.0001) but absolute values of CO and PPV were not correlated. The PPV performance (ROC curve area: 0.89&#xa0;&#xb1;&#xa0;0.06, p&#xa0;=&#xa0;0.0011) was better than that of CVP (ROC curve area: 0.54&#xa0;&#xb1;&#xa0;0.12) and MAP (ROC curve area: 0.59&#xa0;&#xb1;&#xa0;0.13) 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.