Comparison between pulse pressure variation and systolic pressure variation measured from a peripheral artery for accurately predicting fluid responsiveness in mechanically ventilated dogs

Abstract Objective To compare pulse pressure variation (PPV) and systolic pressure variation (SPV) measured from a peripheral artery to predict fluid responsiveness in anesthetized healthy dogs. Study design Prospective study. Animals A total of 39 dogs (13.8–26.8 kg) anesthetized with isoflurane for elective ovariohysterectomy. Methods Ventilation was controlled (tidal volume 12 mL kg−1; 40% inspiratory pause). PPV and SPV were recorded from a dorsal pedal artery catheter using an automated algorithm. A fluid challenge (FC) with lactated Ringer´s solution (20 mL kg−1 over 15 minutes), was administered once (21 animals) or twice (18 animals) before surgery. Increases in transpulmonary thermodilution stroke volume index >15% from values recorded before each FC defined responders to volume expansion. Final fluid responsiveness status was based on the response to the single FC or to the second FC. Predictive ability of PPV and SPV were compared by receiver operating characteristics (ROC) curve analysis and by the range of cut-off values associated with uncertain results (gray zone). Results All animals after the single FC were responders; all animals administered two FCs were nonresponders after the second FC. The area under the ROC curve (AUROC) of PPV (0.968) did not differ from the AUROC of SPV (0.937) (p = 0.45). Best cut-off thresholds to discriminate responders from nonresponders were >11.7% (PPV) and >7.4 mmHg (SPV). The gray zone of PPV and SPV was 8.2–14.6% and 7.0–7.4 mmHg, respectively. The percentage of animals with PPV and SPV values within the gray zone was less for SPV (10.2%) than for PPV (30.8%). Conclusions and clinical relevance: PPV and SPV obtained from the dorsal pedal artery are useful predictors of fluid responsiveness in dogs. Using an automated algorithm, SPV may more accurately predict fluid responsiveness than PPV, with responders identifiable by PPV >14.6% and SPV >7.4 mmHg.