Impact of Hyponatremia on Morbidity, Mortality, and Complications After Aneurysmal Subarachnoid Hemorrhage: A Systematic Review

Background Hyponatremia is a common metabolic disturbance after aneurysmal subarachnoid hemorrhage (SAH), and it may worsen outcomes. This review aims to characterize the effect of hyponatremia on morbidity and mortality after SAH. Objectives We sought to determine the prevalence of hyponatremia after SAH, including in subgroups, as well as its effect on mortality and certain outcome measures, including degree of disability and duration of hospitalization. Methods A search of terms “hyponatremia” and “subarachnoid hemorrhage” was performed on PubMed, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, and EMBASE. Studies were included if they reported prevalence of hyponatremia and if they discussed outcomes such as mortality, duration of stay, functional outcomes (e.g., Glasgow Outcomes Scale), or incidence of complications in patients with aneurysmal SAH. Two independent researchers assessed the titles and abstracts and reviewed articles for inclusion. Results Thirteen studies met inclusion criteria. The prevalence of at least mild hyponatremia was 859 of 2387 (36%) of patients. Hyponatremia was associated with vasospasm and duration of hospitalization, but it did not influence mortality. Conclusion Hyponatremia is common after SAH, and there is evidence that it is associated with certain poorer outcomes. Larger, prospective studies are needed to assess these findings and provide further evidence.