Risk Factors for Cerebral Vasospasm in Aneurysmal Subarachnoid Hemorrhage: A Population-Based Study of 8346 Patients

Background: A recent systematic review and meta-analysis found that there was a lack of consensus regarding risk factors for cerebral vasospasm in aneurysmal subarachnoid hemorrhage (aSAH). Objective: To identify risk factors associated with increased likelihood of cerebral vasospasm after aSAH using the largest, all-payer, inpatient database in the United States. Methods: The Nationwide Readmissions Database (2016) was queried using International Classification of Diseases, Tenth Revision codes to identify patients (age ≥18 years) treated (coiling or clipping) for aSAH. Exposure variables included demographics, comorbidities, location and clinical grade of aSAH, treatment type, and laboratory anomalies. Multivariable analysis was conducted to identify factors independently associated with cerebral vasospasm (ICD-10 code I67.84). Results: The rate of vasospasm was 28.1% in 8346 patients with treated aSAH. In multivariable analysis, vasospasm risk was inversely proportional to age (P < 0.001). Substance abuse, particularly tobacco smoking and cocaine, was associated with vasospasm (P < 0.05). Advanced SAH severity (Hunt and Hess grade ≥2) approximately doubled risk of vasospasm (P < 0.001). Poor hemodynamic status, including anemia (odds ratio [OR], 1.8), hypovolemia (OR, 1.6), and hypotension (OR, 1.4), was correlated with vasospasm. Laboratory abnormalities, including leukocytosis (OR, 1.3), hyponatremia (OR, 1.4), and hypokalemia (OR, 1.3), were associated with vasospasm (all P < 0.05). Conclusions: In the first nationwide analysis of cerebral vasospasm, risk factors included younger age, female sex, smoking history, hemodynamic compromise, and clinical severity of aSAH. Recently proposed biomarkers, including leukocytosis and hypokalemia, were supported by our findings. This study may assist risk stratification and earlier detection of vasospasm.