Risk Factors for Cerebral Vasospasm After Subarachnoid Hemorrhage: A Systematic Review of Observational Studies

Cerebral vasospasm (CV) following subarachnoid hemorrhage (SAH) remains one of the leading causes of high mortality and poor outcomes. Understanding the risk factors associated with CV is pivotal to improving patients' outcomes. We conducted an extensive search for analytical observational studies that analyzed the correlation between various variables and the likelihood of CV development among adult patients with SAH (age >= 18 years). Five scholar databases were used, namely, PubMed, EBSCO, Web of Science, Science Direct, and Google Scholar. Relevant studies published between January 1st, 2016, and August 9th, 2023, were included. The Newcastle-Ottawa Scale was adopted to assess the risk of bias among included observational studies. A total of 33 studies met the inclusion criteria. Of the 24,958 patients with SAH who were identified, 6,761 patients had a subsequent CV (27.1%). Several statistically significant risk factors were reported across the literature. Younger age, female sex, smoking, alcohol intake, modified Fisher grade 3-4, higher Hunt and Hess grading, and the presence of multiple comorbidities (diabetes, hypertension, congestive heart failure, and history of stroke) were among the well-established risk factors for CV. Additionally, leukocytosis was consistently reported to be a significant predictor in multiple studies, providing compelling evidence for its association with CV. Even though single studies reported an association between CV and certain variables, further research is necessary to investigate the implications of these findings. These include arterial tortuosity, hypokalemia, potassium to glucose gradient, hypoalbuminemia, anemia, von Willebrand factor and vascular endothelial growth factor, use of desflurane, and hemodynamic stability. Overall, this systemic review provides a comprehensive summary of the current data that evaluates the potential risk factors for the development of CV after SAH. However, because of data heterogeneity, certain factors require further validation in their correlation with CV development. Larger-scale observational and clinical trials are mandatory to extensively investigate the significant predictors of CV to lay the scientific foundation for improving outcomes in susceptible patients with SAH.