A retrospective study of subdural hematoma was conducted in 36 patients ranging in age from 2 months to 9 years. Hypotension occurred in 41% of the children during the evacuation of the subdural hematoma. This study suggests that hypovolemia was caused, in part, by the blood loss into the subdural hematoma. In patients with hematoma larger than 8% of the intravascular volume, the frequency of the hypotension was high (88%). Infants, in particular, had larger hematomas, ranging in size from 8–27% of intravascular blood volume and, therefore, were at high risk to develop hypotension. These larger hematomas may be due to the infants' higher ratio of subdural space to the body weight. The study also suggests that the preoperative infusion of adequate fluid and blood is a significant factor in preventing hypotension during the hematoma evacuation.