Cardiopulmonary hemodynamic changes during acute subdural hematoma evacuation.

The aim of this study was to clarify the mechanism of hemodynamic changes leading to intraoperative hypotension during evacuation of acute subdural hematoma. To our knowledge, little data is available about the mechanism of hemodynamic changes during surgical interventions to decrease intracranial pressure after severe head injury. The influence of preoperative hypotension on intraoperative hypotension was examined. Hemodynamic studies (pulmonary artery catheterization) were carried out in 15 patients before and after acute subdural hematoma evacuation. All patients were assessed for hemodynamic parameters, evacuated hematoma volume, and intracranial pressure measurements. Comparison between just before and after evacuation of the hematoma showed that the mean arterial pressure, pulmonary arterial pressure, systemic vascular resistance, pulmonary vascular resistance, central venous pressure, and pulmonary capillary wedge pressure all decreased after hematoma evacuation. However, the cardiac index was unchanged after hematoma evacuation. Mean arterial blood pressure is dependent on the cardiac index and vascular resistance, so the decrease in arterial blood pressure during hematoma evacuation was the result of a decline in vascular resistance. The influence of preoperative blood pressure on intraoperative hemodynamic changes was analyzed by dividing the patients into two groups, the preoperative hypotension group and preoperative nonhypotension group. The decrease in mean arterial blood pressure was more marked in the preoperative hypotension group than in the preoperative nonhypotension group. Intraoperative hypotension during evacuation of acute subdural hematoma is caused by a decrease in vascular resistance. Preoperative hypotension is a also risk factor for intraoperative hypotension.