Decrease in platelet count as an independent risk factor for symptomatic vasospasm following aneurysmal subarachnoid hemorrhage

Object. Increased platelet consumption is expected in patients with cerebral vasospasm, according to data from clinical and experimental studies. The authors investigated sequential changes in platelet counts in patients with subarachnoid hemorrhage (SAH) and the difference in platelet consumption between patients with and those without symptomatic vasospasm (SV). Variables related to platelet count as well as other clinical and radiological variables were analyzed as independent predictors of SV. Methods. One hundred consecutive patients who had undergone surgery within 48 hours after SAH onset were entered in the study. Clinical and radiological variables and blood cell counts, including red blood cells, white blood cells, and platelets, after SAH were retrospectively examined. Twenty of these variables were entered into univariate and multivariate analyses to determine predictors for SV. After SAH, the platelet count decreased to a minimum and then increased rapidly to levels greater than those recorded on admission. This change was specific to SAH, and platelet consumption was more severe in patients with SV than in those without. There were three independent predictors of SV: a ratio of the lowest platelet count and the admission count greater than 0.7 (odds ratio [OR] 0.322, 95% confidence interval [CI] 0.124-0.834 p = 0.0196) and a history of hypertension (OR 0.338, 95% CI 0.126-0.906, p = 0.0311) were negatively significant (that is, decreases the occurrence of SV), and a Fisher Grade 3 (OR 4.42, 95% CI 1.48-13.2, p = 0.0077) was positively significant (that is, increases the occurrence of SV). Conclusions. The association between a decrease in platelet count and the occurrence of SV indicates the important role of platelets in the pathophysiology of vasospasm following SAH.