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

alpha alpha -Cross-linked hemoglobin (alpha alpha Hb) is an example of a he moglobin-based oxygen carrier (HBOC) with significant cardiovascular activi ty. This may compromise the safety and efficacy of this HBOC by causing sys temic 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 effe cts. 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 pol ynitroxylated 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 thi s study urethane-anesthetized rats were hemorrhaged to a mean arterial pres sure (MAP) of 35-40 mmHg and maintained for 30 min. Animals were resuscitat ed with solutions of(1) 10%; PN-alpha alpha Hb (43 mmHg), (2) 10% alpha alp ha 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). Hemodynam ics and regional blood circulation was measured at baseline, following hemo rrhage, and at 30 and 60 min postresuscitation using a radioactive microsph ere technique. Base deficit (BD) was measured at baseline, following hemorr hage, and at 60 min following resuscitative fluid infusion. Finally surviva l was determined as the time following resuscitation until secession of hea rt rhythm. Saline and 300% RL resuscitation did not improve BE, systemic he modynamics, or regional blood circulation PN-alpha alpha Hb, alpha alpha Hb , and albumin significantly improved these parameters, however, only PN-alp ha alpha Hb and alpha alpha Hb improved survival. PN-alpha alpha Hb was fou nd to be less hypertensive than alpha alpha Hb due to blunted increases in both cardiac output and systemic vascular resistance. This study demonstrat es that, by using alpha alpha Hb as a scaffold for polynitroxylation, impro vement in vasoactivity and resuscitative efficacy may be possible. in concl usion, the addition of antioxidant activity in the form of polynitroxylatio n of a low molecular weight Hb (alpha alpha Hb) may create a safe and effic acious resuscitative fluid. (C) 2000 Elsevier Science Inc.