• Conor S Gillespie, Anca Mihaela-Vasilica, Jasneet Dhaliwal, Keng Siang Lee, Alex E Henney, Munashe Veremu, Youssef Chedid, Elena Roman, Lana Al-Nusair, Justyna O Ekert, Musa China, William H Cook, Ali M Alam, Mohammad Ashraf, Jonathan P Funnell, Carly Grandidge, Lawrence Best, and Samir Matloob.
• Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK; Department of Neurosurgery, Addenbrooke's Hospital, Cambridge, UK.
• World Neurosurg. 2025 Jan 31; 195: 123616123616.

ObjectiveHyponatremia after aneurysmal subarachnoid hemorrhage (aSAH) is common; however, the incidence, and association with vasospasm, morbidity, and mortality, has yet to be defined. We aimed to identify incidence of hyponatremia after aSAH, and quantify its association with measurable outcomes.MethodsA Preferred Reporting Items for Systematic Reviews and Meta-Analyses-compliant systematic review and meta-analysis was conducted (international prospective register of systematic reviews ID CRD42022363472). Articles published in MEDLINE, Embase, and Cochrane Library between January 1990 and January 2024 were included. Hyponatremia definitions, incidence during admission, and association among vasospasm, length of hospital stay, and poor outcome (Glasgow Outcome Scale 3 or less) were identified. Pooled incidence rates and binary and continuous outcomes were calculated using random effects meta-analysis models.ResultsIn total, 52 studies (10,512 patients) were included. Most studies included patients admitted to tertiary neuroscience centers (61.5%, N = 32), or critical care units (23.1%, N = 11). Sodium of less than 135 mmol/L was the most commonly used hyponatremia definition (84.6%, N = 44). The pooled incidence of hyponatremia was 37.0% (95% confidence interval [CI]: 31.7%-42.4%). Hyponatremia increased the risk of vasospasm (15 studies; odds ratio: 2.93; 95% CI: 1.77-4.84), and length of hospital stay (3 studies, 16.4 days vs. 8.0 days, mean difference 8.5 [95% CI: 4.6-12.4]), but was not associated with poor outcome (10 studies; odds ratio 1.15; 95% CI 0.44-3.02). These findings remained when carrying out sensitivity analysis for different hyponatremia and outcome definitions, bias, and aSAH populations.ConclusionsHyponatremia is common in aSAH, may increase the likelihood of vasospasm, but in isolation does not appear to affect overall outcomes. Managing hyponatremia effectively should be a priority for treating clinicians.Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.

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