The Impact of Aneurysm Location on Incidence and Etiology of Hyponatremia Following Subarachnoid Hemorrhage

BACKGROUND: Hyponatremia is the most common electrolyte abnormality in patients with aneurysmal sub-arachnoid hemorrhage (aSAH). Syndrome of inappropriate antidiuretic hormone secretion (SIADH) and cerebral salt wasting (CSW) are the most common etiologies. Whether or not the location of the ruptured aneurysm is associated with the etiology of hyponatremia is unknown. We sought to determine whether or not the incidence of SIADH and CSW after aSAH differed based on aneurysm location. METHODS: Retrospective analysis of 335 consecutive patients who presented with aSAH at a single institution was performed. Patients were included if they developed hyponatremia before postbleed day 14. Electronic health records were reviewed to obtain data regarding aneurysm location, treatment, etiology of hyponatremia, and modified Rankin Scale score at hospital discharge. RESULTS: Inclusion criteria were met by 114 patients. There were 67 (59%) anterior circulation aneurysms and 47 (41%) posterior circulation aneurysms. Of patients, 85 (75%) had hyponatremia owing to SIADH, 14 (12%) had CSW, and 15 (13%) did not fit either etiology. SIADH was more common than CSW in anterior circulation aneurysms (90%) compared with posterior circulation aneurysms (75%). This trended toward, but did not reach, statistical significance (P = 0.08). More severe Hunt and Hess grades were associated with the development of CSW rather than SIADH (P = 0.002). CONCLUSIONS: SIADH is much more common than CSW in patients with aSAH. Anterior circulation aneurysms may be associated with a higher rate of SIADH than posterior circulation aneurysms.