A pig hemorrhagic shock model: Oxygen debt and metabolic acidemia as indicators of severity

"Uncontrol led bleeding," "a controlled prefixed bleeding volume," or "cont rolled decrements in blood pressure" are traditional models of experimental hemorrhagic shock. They are influenced by compensatory mechanisms and do n ot adequately reflect the severity of the cellular insult as a major target for therapeutic strategies. The aim of this study was to develop an animal model that uses oxygen debt (OD) and metabolic acidemia as indicators of h emorrhage severity. Twenty-five female pigs (mean weight: 23.8 kg) were ane sthesized and randomized to 1 of 5 groups of increasing OD (< 50 through > 120 mL/kg). The predetermined OD was accrued by hemorrhage uniformly over 6 0 min and followed by retransfusion. The animals were allowed to recover un der anesthesia for 200 min and were then observed for 3 days. The extent of metabolic derangements were quantified by arterial base excess (BE) and pl asma lactate (LAC) measurements. OD, BE, and LAC were shown to be superior as predictors of outcome in comparison with traditional variables ("bleedin g volume," "blood pressure," "cardiac output") in correlation and regressio n. Of the analyzed predictors of outcome, BE and LAC showed the highest cor relation to levels of OD (r = -0.78, 0.8 respectively; P < 0.0001), and reg ression models were developed. The LD50 for OD was 95.0 mL/kg, for BE -15.3 mmol/L. and for LAC 7.7 mmol/L. By using the developed regression models, it is possible to estimate accurately the actual level of OD from BE and LA C values obtained during hemorrhagic shock. OD, BE, and LAC appear to be op timal indicators of severity for a pig hemorrhagic shock model.