Predictors of the Onset of Hemodynamic Decompensation During Progressive Central Hypovolemia: Comparison of the Peripheral Perfusion Index, Pulse Pressure Variability, and Compensatory Reserve Index

Introduction: As technological advances allow for the development of more sophisticated measurement of the mechanisms that contribute to compensation for loss of circulating blood volume such as hemorrhage, it is important to compare the discriminative ability of these new measures to standard vital signs and other new physiologic metrics of interest. The purpose of this study was to compare the discriminative ability of the following three measures to predict the onset of hemodynamic decompensation: peripheral perfusion index (PPI), pulse pressure variability (PPV), and the compensatory reserve index (CRI). Materials and Methods: There were 51 healthy participants who underwent a progressive simulated hemorrhage to induce central hypovolemia by lower body negative pressure (LBNP). The least-squares means and 95% confidence intervals for each measure were reported by LBNP level and stratified by tolerance status (high tolerance vs. low tolerance). Generalized estimating equations were used to perform repeated measures logistic regression analysis by regressing the onset of hemodynamic decompensation on each of the vital signs of interest. These probabilities were used to calculate sensitivity, specificity, and receiver-operating characteristic area under the curve (ROCAUC) for PPI, PPV, and CRI. Results: Compared with both PPV (ROCAUC = 0.79) and PPI (0.56), the CRI (0.90) had superior discriminative ability (P ⩽ 0.0001) to predict the onset of hemodynamic decompensation. This included higher sensitivity (0.86 vs. 0.78 and 0.71) and specificity (0.78 vs. 0.69 and 0.29) for the CRI compared with PPV and PPI, respectively. Further, CRI was the only measure with mean predicted probabilities of the onset of hemodynamic decompensation that progressively increased as the level of simulated hemorrhage increased. Discussion: There are two potential rationales for why the CRI had superior discriminative ability to predict hemodynamic decompensation. First, the CRI more accurately predicted the onset of hemodynamic decompensation at all levels of simulated hemorrhage, but especially at lower levels of hemorrhage. Second, the CRI was better able to differentiate high versus low tolerant participants. Conclusion: Consistent with previous research, the CRI had superior discriminative ability to predict the onset of hemodynamic decompensation. For those patients at greatest risk for developing impending circulatory shock, identifying the most sensitive and specific measures of the onset of hemodynamic decompensation is critical for both the early recognition and implementation of life-saving interventions.