Comparison of Noninvasive Dynamic Indices of Fluid Responsiveness Among Different Ventilation Modes in Dogs Recovering from Experimental Cardiac Surgery

Abstract

BACKGROUND Fluid resuscitation is a cornerstone of minimizing morbidity and mortality in critically ill patients, but the techniques for predicting fluid responsiveness is still a matter of debate. In this study, we aimed to evaluate the utility of noninvasive stroke volume variation (SVV), pulse pressure variation (PPV), and systolic pressure variation (SPV) as a dynamic predictor for assessing fluid responsiveness during different ventilation modes in anaesthetized, intubated dogs recovering from cardiac surgery. MATERIAL AND METHODS Thirty-six adult Beagle dogs undergoing experimental surgery for isolated right ventricular failure were monitored for SVV, PPV, and SPV simultaneously using electrical velocimetry device. The relationships between each indicator and SVI before and after volume loading were compared in 3 ventilatory modes: assist control (A/C), synchronized intermittent mandatory ventilation (SIMV), and continuous positive airway pressure (CPAP). Responders were defined as those whose stroke volume index increased by ≥10%. RESULTS In all of the indices, the baseline values were greater in responders than in nonresponders (P<0.01) under A/C and SIMV. Receiver operating curve analysis confirmed the best predictive value during A/C [area under the curve (AUC): SVV, 0.90; PPV, 0.88; SPV, 0.85; P<0.05] followed by SIMV (AUC: SVV, 0.86; PPV, 0.83; CPAP, 0.80; P<0.05), with their sensitivities and specificities of ≥7 5%. By contrast, no statistically significance detected in any parameter during CPAP (AUC: SVV, 0.71; PPV, 0.66; CPAP, 0.65; P>0.05). CONCLUSIONS SVV, PPV, and SVV are all useful to predict cardiac response to fluid loading in dogs during A/C and SIMV, while their reliabilities during CPAP are poor.

Figure 1

Schematic experimental design of fluid challenge in intubated anesthetized dogs after experimental cardiac surgery. EV-derived hemodynamic parameters were measured before and after the fluid loading (arrows) during one of the 3 ventilation modes: A/C (Group 1), SIMV (Group 2), or CPAP (Group 3) (n=12 per each group).

Figure 2

Box-and-whisker plots of SVV (A), PPV (B), and SPV (C) in dogs ventilated by A/C, SIMV, and CPAP before fluid challenge in responders and nonresponders (n=12 per each group). Data are expressed as median values and interquartile ranges with scatter plots.

Figure 3

Prediction of fluid responsiveness (increase in SVI ≥10%) by receiver operating characteristic of SVV, pulse pressure variation (PVV), and systolic pressure variation (SPV) in dogs ventilated by A/C (A), SIMV (B), and CPAP (C) (n=12 per each group). The 45-degree diagonal line indicates the reference line of no-discrimination.