Hyponatremia Following Mild/Moderate Subarachnoid Hemorrhage Is Due To SIAD and Glucocorticoid Deficiency and not Cerebral Salt Wasting

Context: Hyponatremia is common after acute subarachnoid hemorrhage (SAH) but the etiology is unclear and there is a paucity of prospective data in the field. The cause of hyponatremia is variously attributed to the syndrome of inappropriate antidiuresis (SIAD), acute glucocorticoid insufficiency, and the cerebral salt wasting syndrome (CSWS). Objective: The objective was to prospectively determine the etiology of hyponatremia after SAH using sequential clinical examination and biochemical measurement of plasma cortisol, arginine vasopressin (AVP), and brain natriuretic peptide (BNP). Design: This was a prospective cohort study. Setting: The setting was the National Neurosurgery Centre in a tertiary referral centre in Dublin, Ireland. Patients: One hundred patients with acute nontraumatic aneurysmal SAH were recruited on presentation. Interventions: Clinical examination and basic biochemical evaluation were performed daily. Plasma cortisol at 0900 hours, AVP, and BNP concentrations were measured on days 1, 2, 3, 4, 6, 8, 10, and 12 following SAH. Those with 0900 hours plasma cortisol