Plasma renin and angiotensin II levels in subarachnoid haemorrhage

Abstract

Plasma renin and angiotensin II concentrations, urinary catecholamines, plasma sodium concentration and blood pressure were measured before and after neurosurgical intervention in 5 patients who had sustained a spontaneous subarachnoid haemorrhage (SAH). The results were interpreted in conjunction with information obtained from carotid angiography (to show the presence or absence of cerebral arterial spasm) and serial electrocardiograms (ECG). Significant correlations were found between urinary normetanephrines (NMN) excretion and both plasma renin concentration ( r=0.42, n=21, 0.05 > P > 0.001) and plasma angiotensin II concentration ( r=0.65, n=20, P < 0.001); and between urinary metanephrines (MN) excretion and plasma angiotensin II concentration ( r=0.58, n=20, 0.01 > P > 0.001). Plasma renin and angiotensin II concentrations were abnormally elevated in 2 of the 3 patients with abnormal ECGs. Although no clear and significant relationship existed between the various biochemical parameters on the one hand and cerebral vasospasm on the other, the 1 patient who developed spasm post-operatively had a simultaneous rise in plasma renin, angiotensin II and urinary normetanephrine concentrations with the onset of spasm. The mechanism by which the renin/angiotensin II system may be activated in SAH and its interrelationship with the sympathetic nervous system in the production of ECG changes and cerebral arterial spasm, are discussed.