Increased Sympathetic Nervous Activity in Patients With Nontraumatic Subarachnoid Hemorrhage

TLDR

Activation of the sympathetic nervous system, raising catecholamines, contributes to cerebral vasospasm and cardiac complications after subarachnoid hemorrhage, yet testing has relied on indirect methods. The study employed an isotope dilution method to quantify sympathoadrenal activation over time in 18 subarachnoid hemorrhage patients. Patients exhibited a roughly three‑fold rise in total‑body norepinephrine spillover within 48 hours, which persisted for 7–10 days before normalizing at six months, confirming massive sympathetic activation after subarachnoid hemorrhage.

Abstract

Background and Purpose —Activation of the sympathetic nervous system, which leads to elevation of circulating catecholamines, is implicated in the genesis of cerebral vasospasm and cardiac aberrations after subarachnoid hemorrhage. 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 subarachnoid hemorrhage exhibited an approximately 3-fold increase in total-body norepinephrine 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 sympathetic 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 nervous activation occurs in patients after subarachnoid hemorrhage. This overactivation may relate to the well-known cardiac complications described in subarachnoid hemorrhage.