Activity of peripheral sympathetic efferent nerves in experimental subarachnoid haemorrhage

Abstract

The origin and pathomechanism of vegetative disturbances in patients suffering from subarachnoid haemorrhage are not completely clarified. Since some of these alterations in vegetative functions may well be attributed to acute changes in sympathetic activity, we initiated a study to investigate this modality in experimentally induced subarachnoid haemorrhage. Experiments were performed on 51 cats, anaesthetized with alpha-chloralose and urethane, immobilized and artificially ventilated. Compound electrical discharges of the left vertebral, cardiac and renal sympathetic nerves, ECG, EEG, end-tidal CO2, systemic arterial blood pressure and intracranial pressure were recorded on a polygraph. Subarachnoid haemorrhage was simulated by the injection of 1-5 ml of fresh, autologous blood into the cisterna magna. Mock cerebrospinal fluid was also injected as a control. Our results showed that in induced subarachnoid haemorrhage, not the blood itself but the intracranial pressure elevation might be responsible for the strong increase in sympathetic efferent activity. With the direct recording of the electrical activity of the three sympathetic nerves, we were able to verify the sympathetic overactivity underlying the cardiovascular disturbances during intracranial pressure elevation. Regarding the mechanism of the overactivity, most probably not the ischaemia or hypoxia, but the mechanical distortion of the medulla could be the adequate stimulus of the sympathetic overactivity and the Cushing response during intracranial pressure elevation.

Pattern of elevation of urine catecholamines in intracerebral haemorrhage

“…Experimental work in cerebrovascular disease yielded controversial results: Graf and Rossi 9 emphasized the epinephrines as mediator between sympathetic activation and clinical symptoms and signs. Hachinski and colleagues 12 14 and other authors22, 25,28,30,34 found that norepinephrines after stroke or intracranial space-occupying processes were more important. In this study the fact that there was no isolated elevation of metanephrine proved the importance of the normetanephrines.…”

An Experimental Brain Missile Wound: Ascertaining Pathophysiology and Evaluating Treatments to Lower Mortality and Morbidity

“…The most basic effect of an increase in ICP is a massive increase in sympathetic nerve activity causing a sympathetic pressor response (16,44,77,100,116,140). We have demonstrated that ICP elevations and the pressor response are also associated with biogenic amine changes (particularly EPI and NE) in the hypothalamus and brain stem.…”

Intraoperative jugular bulb desaturation during acute aneurysmal rupture

“…Computed tomography of head was negative for subarachnoid hemorrhage, but angiography revealed a large aneu- tension has been described to be a result of the reflex increase of catecholamine secretion, [6][7][8] and a result of the sympathetic overactivity due to brainstem compression, 9 or due to craniocaudal ischemia. [10][11][12][13] Some animal studies suggest Cushing's response is a late feature, when ICP approaches mean arterial pressure, signalling breakdown of cerebral autoregulation.…”