The therapeutic effect of continuous intracisternal L-arginine infusion onexperimental cerebral vasospasm

Background. Recent studies on the pathogenesis of cerebral vasospasm follow ing subarachnoid haemorrhage (SAH) suggest a breakdown of the balance betwe en the vasoconstrictor and vasodilator systems. A shortage of a major cereb ral vasodilator, nitric oxide (NO), has been accused of causing this breakd own. We investigated the effect of continuous intracisternal infusion of a NO precursor, L-Arginine, in a rabbit SAH model. Method. Three experimental groups were designated: Group 1 - Cerebral blood flow (CBF) data was obtained via transorbital Doppler ultrasonography (TDU ) in 8 normal rabbits. Group 2 - Intracisternal catheter placement and TDU study during saline infusion were performed in 8 animals at the 4(th) day o f SAH, Group 3 - SAH occurred in 8 animals. 4 days later, L-Arginine was in fused intracisternally for 1 hour, while TDU was performed before and durin g infusion. CBF parameters which were obtained via TDU measurement or calcu lations, were compared. Findings. The results of TDU revealed significant vasospasm in all SAH anim als, as well as resolution of vasospasm with L-Arginine infusion. After 20 minutes of infusion, a steady and sustained vasodilation was obtained in th e third group. The analysis of CBF data revealed a significant difference i n SAH values, and no difference in control animals. Interpretation. Our results support the contribution of the "NO shortage" c oncept in the pathogenesis of cerebral vasospasm and overconsumption of L-A rginine during the post-SAH period may cause this shortage. L-Arginine trea tment may be useful for the prophylaxis and treatment of cerebral vasospasm . The intracisternal infusion method can eliminate the short action time di sadvantage of L-Arginine.