Using a retrospective case–control design, Basali et al. studied the relation between perioperative blood pressure (BP) increase and postoperative intracranial hemorrhage (ICH). The authors first searched their institution’s database for all cases of craniotomy from 1976 to 1992. Of 11,214 patients undergoing craniotomy, they identified 86 (0.77%) in whom postoperative ICH had developed. Of those patients, 69 met inclusion criteria for the study. The authors then compared this group of 69 patients with a matched control group of 138 patients (2:1) who had no postoperative cranial bleeding after craniotomy.
Blood pressure records from preoperative, intraoperative, emergence from anesthesia, and immediate postoperative periods were studied. The authors defined postoperative hypertension as one recorded instance of systolic BP more than 160 mmHg or diastolic BP more than 90 mmHg before ICH. Hypertension in the intraoperative period was defined as at least two consecutive occurrences of BP more than or equal to 160/90 mmHg. In their review, the authors also collected the following data: type of anesthetic, estimated surgical blood loss, type of intraoperative fluids, duration of procedure, and body temperature at the end of surgery.
Approximately 50% of the cases of ICH occurred in the immediate postoperative period, 0–20 h after surgery. Of the patients who experienced ICH, 62% had intraoperative hypertension, whereas only 34% of control patients had intraoperative hypertension. Not surprisingly, duration of hospital stay and mortality were significantly greater in the ICH group than in the control group. Because of limitations resulting from its retrospective design and because of the lack of sufficient BP readings for control patients, the study showed an association, but not a causal relation, between acute intraoperative or early postoperative hypertension and ICH.