Intraoperative Mannitol Administration Increases the Risk of Postoperative Chronic Subdural Hemorrhage After Unruptured Aneurysm Surgery

Although mannitol is used widely to facilitate brain retraction in cases of ruptured aneurysms, there is no consensus about the intraoperative administration of mannitol in the case of unruptured aneurysms. Accordingly, this study was conducted to identify an intraoperative mannitol administration strategy.Mannitol was administered routinely to patients (n = 90) from January 2015 to April 2016 and not administered to patients (n = 97) from May 2016 to June 2017. The patient groups with and without mannitol administration were then compared based on the patient medical records, radiologic data, and digital recordings from an intraoperative microscope.The patient groups with and without mannitol administration were comparable regarding patient age, number of elderly patients, sex, and aneurysm locations. No between-group difference was identified in terms of the intradural procedural time, retraction-induced cortical injury, postoperative electrolyte imbalance, symptomatic infarction, and postoperative epidural hematomas. However, the patient group without mannitol administration showed a significantly lower incidence of chronic subdural hematomas (CSDHs)50 mL (13.3% vs. 3.1%, P = 0.010). Moreover, a multivariate analysis revealed that an advanced age (P = 0.019), male sex (P0.001), and mannitol administration (P = 0.040) were all statistically significant risk factors for a postoperative CSDH50 mL following unruptured aneurysm surgery.Withholding the administration of mannitol during a pterional or modified procedure for unruptured aneurysms was found to reduce the postoperative occurrence of a CSDH without increasing the operative difficulties or other postoperative complications.