Abstract
Digoxin was measured by radioimmunoassay in the plasma of 25 patients with aneurysmal subarachnoid haemorrhage who had not received digoxin treatment. After heating the plasma an endogenous substance cross reacting with antibodies to digoxin was identified in 18 cases. The presence of this substance was significantly related to the total amount of blood and to the presence of blood in the frontal interhemispheric fissure and could not be explained by hypertension or intake of water and sodium. A negative sodium balance and volume depletion occurred more often in patients who were positive for digoxin, but this relation did not reach statistical significance. It is concluded that a digoxin-like natriuretic factor is released in response to a subarachnoid haemorrhage, probably as a result of hypothalamic damage.