Irreversible shock is not irreversible: A new model of massive hemorrhage and resuscitation

Background: Existing shock models do not address the patient with massive h emorrhage(> 1 blood volume). Such patients often die from irreversible shoc k. This model simulates the clinical scenario of massive hemorrhage and res uscitation (MHR) to determine if irreversible shock can be reversed. Methods: Lewis rats were bled at a rate of 1 estimated blood volume (EBV) p er hour for 2 hours with simultaneous infusion of resuscitation mixture (RM ) consisting of red blood cells and crystalloid,:Blood pressure was maintai ned at a mean arterial pressure (MAP) of 50 mm Hg during the 2 hours of hem orrhage, Hemorrhage was stopped and resuscitation continued for 1 hour unti l 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 follow ed by resuscitation to MAP > 90 mm Hg for 1 hour with crystalloid alone, Tw o-meek survival was compared using a x(2) test. Results: Control animals (n = 13) were hemorrhaged 48% +/- 5% of EBV and ha d a mortality rate of 23%. R INR animals had severity and duration of hypot ension identical to that of controls but were hemorrhaged 214% +/- 8% of EB V, Despite receiving 390 mL/kg of RM and a final hematocrit of 37%, 14 of 1 5 animals resuscitated with 6 x EBV died from "irreversible" shock (mortali ty, 93%; p < 0.001 vs. controls). When very large volumes of resuscitation were used, survival rates improved significantly. The 10 x EBV group receiv ed 120% of lost red blood cells and 530 mL/kg of crystalloid and had 64% su rvival at 2 weeks (p < 0.01 vs. 6 x EBV group.) Conclusion: This MHR model is much more lethal than a traditional severe he morrhage model and reproduces the clinical picture of irreversible shock, T his irreversible shock can be reversed with very large volumes of resuscita tion.