Reversal of cerebral vasospasm via intravenous sodium nitrite after subarachnoid hemorrhage in primates Laboratory investigation

Object. Subarachnoid hemorrhage (SAH)-induced vasospasm is a significant underlying cause of aneurysm rupture-related morbidity and death. While long-term intravenous infusion of sodium nitrite (NaNO2) can prevent cerebral vasospasm after SAH, it is not known if the intravenous administration of this compound can reverse established SAH-induced vasospasm. To determine if the intravenous infusion of NaNO2 can reverse established vasospasm, the authors infused primates with the compound after SAH-induced vasospasm was established, Methods. Subarachnoid hemorrhage-induced vasospasm was created in 14 cynomolgus macaques via subarachnoid implantation of a 5-ml blood clot. On Day 7 after clot implantation, animals were randomized to either control (saline infusion, 5 monkeys) or treatment groups (intravenous NaNO2 infusion at 300 mu g/kg/hr for 3 hours 1.7 monkeys) or 8 hours [2 monkeys]). Arteriographic vessel diameter was blindly analyzed to determine the degree of vasospasm before, during, and after treatment. Nitric oxide metabolites (nitrite, nitrate, and S-nitrosothiols) were measured in whole blood and CSF. Results. Moderate-to-severe vasospasm was present in all animals before treatment (control, 36.2% +/- 8.8% [mean +/- SD]; treatment, 45.5% +/- 12.5%; p = 0.9). While saline infusion did not reduce vasospasm, NaNO2 infusion significantly reduced the degree of vasospasm (26.9% +/- 7.6%; p = 0.008). Reversal of the vasospasm lasted more than 2 hours after cessation of the infusion and could be maintained with a prolonged infusion. Nitrite (peak value, 3.7 +/- 2.1 mu mol/L), nitrate (18.2 +/- 5.3 mu mol/L), and S-nitrosothiols (33.4 +/- 11.4 mu mol/L) increased significantly in whole blood, and nitrite increased significantly in CSF. Conclusions. These findings indicate that the intravenous infusion of NaNO2 can reverse SAH-induced vasospasm in primates. Further, these findings indicate that a similar treatment paradigm could be useful in reversing cerebral vasospasm after aneurysmal SAH. (DOI: 10.3171/2011.7.JNS11390)