Craniotomy for supratentorial brain tumors: risk factors for brain swelling after opening the dura mater

Object. Cerebral swelling often occurs during craniotomy for cerebral tumors. The primary aim in this study was to determine risk factors (intracranial pressure [ICP], patient characteristics, histopathological features, neuroimaging characteristics, anesthetic regimen, and perioperative physiological data) predictive of brain swelling through the dural opening. As a secondary aim the authors attempted to define subdural ICP thresholds associated with brain swelling. Methods. The study population consisted of 692 patients (mean age 50 ± 15 years) scheduled for elective craniotomy for supratentorial brain tumors. Brain swelling through the dural opening was estimated according to a four-point scale. The patients were dichotomized as those without cerebral swelling (that is, brain below the dura mater [59 patients] or brain at the level of the dura mater [386 patients]) and those with cerebral swelling (that is, moderate brain swelling [205 patients] or pronounced brain swelling [42 patients]). Logistic regression analysis was used to identify subdural ICP (odds ratio [OR] 1.9, 95% confidence interval [CI] 1.72–2.1, p < 0.0001), midline shift (OR 1.06, 95% CI 1.02–1.11, p = 0.008), a diagnosis of glioblastoma multiforme (OR 2.1, 95% CI 1.01–4.3, p = 0.047), and metastasis (OR 2.9, 95% CI 1.3–6.9, p = 0.01) as independent risk factors of intraoperative brain swelling. Thresholds for ICP associated with brain swelling were defined as follows: at an ICP less than 5 mm Hg, brain swelling rarely occurred (5% probability); at an ICP greater than 13 mm Hg, brain swelling occurred with 95% probability; and at an ICP greater than 26 mm Hg, severe brain swelling occurred with 95% probability. Conclusions. Subdural ICP is the strongest predictor of intraoperative brain swelling. It is possible to define thresholds of cerebral swelling and the authors recommend subdural ICP measurement as a tool to initiate preventive measures to reduce ICP before opening the dura mater.