Pathogenesis of hyponatremia following subarachnoid hemorrhage due to ruptured cerebral aneurysm.
BACKGROUND
Hyponatremia following subarachnoid hemorrhage (SAH) occurs due to the inappropriate secretion of antidiuretic hormone (SIADH). However, this condition is also sometimes associated with certain dehydration states.


METHODS
To clarify the pathogenesis, daily values of urine volume, water balance, and sodium balance (Na Bal) were correlated with plasma levels of atrial natriuretic peptide (ANP), antidiuretic hormone (ADH), and plasma renin activity (PRA) in 31 cases of SAH.


RESULTS
Na Bal was markedly negative on days 2 and 3. Cumulative Na Bal showed continuous negative values until day 10 following SAH. ANP values showed a consistent elevation, while ADH showed only an initial surge. PRA, as the gross indicator of circulatory volume, showed a lack of suppression, indicating no increase in the circulatory volume.


CONCLUSIONS
Hyponatremia following SAH therefore appears to be the result of increased natriuresis, due to the inappropriate elevation of ANP rather than SIADH. In this situation, water restriction should not be recommended, since the circulatory volume is decreased.
Kurokawa
Y
Y
Department of Neurosurgery, Kushiro City General Hospital, Japan.
Uede
T
T
Ishiguro
M
M
Honda
O
O
Honmou
O
O
Kato
T
T
Wanibuchi
M
M
D000328:Adult; D000368:Aged; D017542:Aneurysm, Ruptured / Q000150:complications*; D009320:Atrial Natriuretic Factor / Q000097:blood; D001834:Body Water / Q000378:metabolism; D003681:Dehydration / Q000209:etiology / Q000503:physiopathology; D005260:Female; D006801:Humans; D007010:Hyponatremia / Q000097:blood / Q000209:etiology* / Q000652:urine; D002532:Intracranial Aneurysm / Q000150:complications*; D008297:Male; D008875:Middle Aged; D009318:Natriuresis / Q000502:physiology; D012083:Renin / Q000097:blood; D013345:Subarachnoid Hemorrhage / Q000150:complications*; D014667:Vasopressins / Q000097:blood
D014667:Vasopressins; D009320:Atrial Natriuretic Factor; D012083:Renin