Irreversible Shock Is Not Irreversible: A New Model of Massive Hemorrhage and Resuscitation

Abstract

BACKGROUND: Existing shock models do not address the patient with massive hemorrhage (> 1 blood volume). Such patients often die from irreversible shock. This model simulates the clinical scenario of massive hemorrhage and resuscitation (MHR) to determine if irreversible shock can be reversed. METHODS: Lewis rats were bled at a rate of 1 estimated blood volume (EBV) per hour for 2 hours with simultaneous infusion of resuscitation mixture (RM) consisting of red blood cells and crystalloid. Blood pressure was maintained at a mean arterial pressure (MAP) of 50 mm Hg during the 2 hours of hemorrhage. Hemorrhage was stopped and resuscitation continued for 1 hour until 6, 8, or 10 x EBV of RM was infused. Control animals were subjected to a traditional fixed pressure hemorrhage to MAP of 50 mm Hg for 2 hours followed by resuscitation to MAP > 90 mm Hg for 1 hour with crystalloid alone. Two-week survival was compared using a chi2 test. RESULTS: Control animals (n = 13) were hemorrhaged 48% +/- 5% of EBV and had a mortality rate of 23%. MHR animals had severity and duration of hypotension identical to that of controls but were hemorrhaged 214% +/- 8% of EBV. Despite receiving 390 mL/kg of RM and a final hematocrit of 37%, 14 of 15 animals resuscitated with 6 x EBV died from "irreversible" shock (mortality, 93%; p < 0.001 vs. controls). When very large volumes of resuscitation were used, survival rates improved significantly. The 10 x EBV group received 120% of lost red blood cells and 530 mL/kg of crystalloid and had 64% survival at 2 weeks (p < 0.01 vs. 6 x EBV group). CONCLUSION: This MHR model is much more lethal than a traditional severe hemorrhage model and reproduces the clinical picture of irreversible shock. This irreversible shock can be reversed with very large volumes of resuscitation.