A new severity predicting index for hemorrhagic shock using lactate concentration and peripheral perfusion in a rat model.

Forty percent of trauma deaths are due to hemorrhage, with 33% to 56% occurring in the prehospital environment. This study proposes a new index (NI) based on the ratio of serum lactate concentration (LC) to peripheral perfusion (PP) as an indicator of hemorrhage-induced mortality during the prehospital stage. Thirty-six anesthetized rats were randomized into three groups according to volume of controlled blood loss. We measured heart rate (HR), systolic and diastolic blood pressures (SBP and DBP), mean arterial pressure (MAP), pulse pressure (PPR), respiration rate (RR), temperature (TEMP), LC, PP, shock index (SI = HR/SBP), and proposed the new hemorrhage-induced mortality index (NI = LC/PP). Peripheral perfusion, defined as peripheral tissue perfusion and skin microcirculation, was continuously monitored by laser Doppler flowmetry. All parameters were analyzed for changes between prehemorrhage and posthemorrhage to investigate the effects of hemorrhage on mortality. Areas under a receiver operating characteristic curve (AUCs) in descending order for NI, SI, PP, SBP, MAP, PPR, DBP, TEMP, LC, RR, and HR were 0.975, 0.941, 0.922, 0.919, 0.903, 0.884, 0.847, 0.816, 0.783, 0.744, and 0.672, respectively. The correlation coefficients with mortality for NI, SI, PP, SBP, MAP, PPR, DBP, TEMP, LC, RR, and HR were -0.818, -0.759, 0.726, 0.721, 0.694, 0.662, 0.597, 0.544, -0.487, 0.420, and -0.296, respectively, with the same order as the AUC. NI was shown to be an optimal independent mortality predictor on multivariable logistic regression analysis. In conclusion, the newly proposed hemorrhage-induced mortality index, based on blood lactate/PP ratio, was a better marker for predicting mortality in rats undergoing acute hemorrhage in comparison to the other parameters evaluated in this study.