Has plasma renin activity a prognostic significance in subarachnoid haemorrhage?

The possible relationship between plasma renin activity and neurological deficits was examined in ten patients with spontaneous subarachnoid haemorrhage in a prospective clinical study. The patients were examined daily, particular attention being given to signs of brain stem dysfunction. The degree of impaired consciousness was assessed using the Glasgow Coma Score. Plasma renin activity was determined on days 1-5, 7, 9, 11, 13, 15 and 21 after the initial bleeding episode using an Angiotensin-I-radioimmunoassay. Six of seven patients with signs of brain stem dysfunction displayed a marked increase in plasma renin activity. Thus a significant negative correlation between the degree of consciousness and the plasma renin activity resulted. An explanation for this correlation may be found in the localization of the autonomous centres and the high concentrations of renin in the hypothalamus and brain stem. The individual changes in plasma renin activity have prognostic significance, whereas single estimated plasma renin activities show great inter-individual differences and have only limited prognostic value.