Increased sympathetic nervous activity in patients with nontraumatic subarachnoid hemorrhage

Background and Purpose-Activation of the sympathetic nervous system, which leads to elevation of circulating catecholamines, is implicated in the gene sis of cerebral vasospasm and cardiac aberrations after subarachnoid hemorr hage. To this juncture, sympathetic nervous testing has relied on indirect methods only. Methods We used an isotope dilution technique to estimate the magnitude and time course of sympathoadrenal activation in 18 subarachnoid patients. Results-Compared with 2 different control groups, the patients with subarac hnoid hemorrhage exhibited an approximately 3-fold increase in total-body n orepinephrine spillover into plasma within 48 hours after insult (3.2+/-0.3 and 4.2+/-0.7 versus 10.2+/-1.4 nmol/L; P<0.05 versus both). This sympathe tic activation persisted throughout the 7- to 10-day examination period and was normalized at the 6-month follow-up visit. Conclusions-The present study has established that massive sympathetic nerv ous activation occurs in patients after subarachnoid hemorrhage. This overa ctivation may relate to the well-known cardiac complications described in s ubarachnoid hemorrhage.