[Hyponatremia and cerebral vasospasm in patients with aneurysmal subarachnoid hemorrhage]

We studied retrospectively the relationship between hyponatremia and cerebral vasospasm in 121 consecutive patients with aneurysmal subarachnoid hemorrhage. In 19 patients sodium levels fell below 130 mEq/l on at least two consecutive days. Hyponatremia developed at average 8.9 hospital day and lasted for 4.4 days. It was mild (126 to 130 mEq/l) in 15 patients, moderate (121 to 125 mEq/l) in 3 patients, and severe (116 to 120 mEq/l) in 1 patient. Cerebral vasospasm was evaluated by angiography, symptoms and CT finding. Angiographical vasospasm was found in 57 patients, symptomatic vasospasm in 38 patients and low density area on CT in 20 patients. Angiographical vasospasm developed in 15 of the 19 patients (78.9%) with hyponatremia, symptomatic vasospasm in 16 patients (84.2%), low density area on CT in 8 patients (42.1%), the difference being significantly high. (respectively, p < 0.01, p < 0.001 and p < 0.01 by chi-square test) Polyuria of 2500 ml or more immediately before the onset of hyponatremia developed in 14 patients (87.5%). When symptomatic vasospasm and hyponatremia coincided, there were only 4 patients in which symptomatic vasospasm was preceded by hyponatremia. So, it is difficult to predict the development of vasospasm from that of hyponatremia. This study found incidence of cerebral vasospasm after aneurysmal subarachnoid hemorrhage to be significantly higher in patients who developed hyponatremia, which raised suspicion about the presence of dehydration. Hyponatremia with central origin generally remains asymptomatic, but it is important to treat positively when the pathology of cerebral vasospasm is taken into consideration.