Experimental subarachnoid hemorrhage in rats: Effect of intravenous α- α diaspirin crosslinked hemoglobin on hypoperfusion and neuronal death

Background. Hemodilution with diaspirin crosslinked hemoglobin (DCLHb) ameliorates occlusive cerebral ischemia. However, subarachnoid hemoglobin has been implicated as a cause of cerebral hypoperfusion. The effect of intravenous DCLHb on cerebral perfusion and neuronal death after experimental subarachnoid hemorrhage was evaluated. Methods: Rats (n = 48) were anesthetized with isoflurane and subarachnoid hemorrhage was induced by injecting 0.3 ml of autologous blood into the cistema magna. Each animal received one of the following regimens: Control, no hematocrit manipulation; DCLHb, hematocrit concentration decreased to 30% with DCLHb; or Alb, hematocrit concentration decreased to 30% with human serum albumin. The experiments had two parts, A and B. In part A, after 20 min, cerebral blood flow (CBF) was assessed with ¹⁴C-iodoantipyrine autoradiography. In part B, after 96 h, in separate animals, the number of dead neurons was determined in predetermined coronal sections by hematoxylin and eosin staining. Results: Cerebral blood flow was greater for the DCLHb group than for the control group; and CBF was greater for the Alb group than the other two groups (P < 0.05). In one section, CBF was 45.5 ± 10.9 ml · 100 g^-1. min^-1 (mean ± SD) for the control group, 95.3 ± 16.6 ml · 100 g^-1 min^-1 for the DCLHb group, and 138.1 ± 18.7 ml · 100 g^-1 · min^-1 for the Alb group. The number of dead neurons was less in the Alb group (611 ± 84) than in the control group (1,097 ± 211), and was less in the DCLHb group (305 ± 38) than in the other two groups (P < 0.05). Conclusions: These data support a hypothesis that hemodilution decreases hypoperfusion and neuronal death after subarachnoid hemorrhage. The data do not support the notion that intravascular molecular hemoglobin has an adverse effect on brain injury after subarachnoid hemorrhage.