Resuscitative effects of polynitroxylated αα-cross-linked hemoglobin following severe hemorrhage in the rat

alpha alpha -Cross-linked hemoglobin (alpha alpha Hb) is an example of a hemoglobin-based oxygen carrier (HBOC) with significant cardiovascular activity. This may compromise the safety and efficacy of this HBOC by causing systemic hypertension and reducing blood flow to some organs. The present work is based on the hypothesis that incorporating antioxidant activity into an HBOC in the form of a covalently attached nitroxide may prevent these effects. We have tested this hypothesis by adding antioxidant activity to alpha alpha Hb with 2,2,6,6-tetramethyl-piperidinyl-1-oxyl (Tempo) to create polynitroxylated alpha alpha Hb (PN-alpha alpha Hb). The new compound PN-alpha alpha Hb acts as an antioxidant in our in vitro and in vivo assays, in this study urethane-anesthetized rats were hemorrhaged to a mean arterial pressure (MAP) of 35-40 mmHg and maintained for 30 min. Animals were resuscitated with solutions of(1) 10%; PN-alpha alpha Hb (43 mmHg), (2) 10% alpha alpha Hb (43 mmHg), (3) 7.5% albumin (43 mmHg), (4) 300% Ringers lactate (RL), and (5) 0.9% normal saline equal to the shed blood volume (SBV). Hemodynamics and regional blood circulation was measured at baseline, following hemorrhage, and at 30 and 60 min postresuscitation using a radioactive microsphere technique. Base deficit (BD) was measured at baseline, following hemorrhage, and at 60 min following resuscitative fluid infusion. Finally survival was determined as the time following resuscitation until secession of heart rhythm. Saline and 300% RL resuscitation did not improve BE, systemic hemodynamics, or regional blood circulation PN-alpha alpha Hb, alpha alpha Hb, and albumin significantly improved these parameters, however, only PN-alpha alpha Hb and alpha alpha Hb improved survival. PN-alpha alpha Hb was found to be less hypertensive than alpha alpha Hb due to blunted increases in both cardiac output and systemic vascular resistance. This study demonstrates that, by using alpha alpha Hb as a scaffold for polynitroxylation, improvement in vasoactivity and resuscitative efficacy may be possible. in conclusion, the addition of antioxidant activity in the form of polynitroxylation of a low molecular weight Hb (alpha alpha Hb) may create a safe and efficacious resuscitative fluid. (C) 2000 Elsevier Science Inc.