Blood loss and hypotensive anesthesia in oral-facial corrective surgery.

To evaluate accurately changes in blood volume during oral-facial corrective surgery, double-tagged radioisotope blood volume studies were performed preoperatively and postoperatively. Unexpectedly large RCV deficits that were not consistent with EBL were observed in studies conducted at two separate facilities. Hypotensive general anesthesia was used for the intended purpose of reducing blood loss in oral-facial corrective surgery. Various physiological parameters were measured preoperatively, intraoperatively, and postoperatively to evaluate patient response to this anesthetic method. The MAP was reduced from 89.94 +/- 2.13 to 72.79 +/- 1.63 mm Hg under the influence of NaN infusion supplemented with halothane. No dose-response relationship existed between NaN and the intraoperative MAP. A 44% reduction in the measured red cell volume was observed in comparison to a previously studied group of patients who underwent similar surgical procedures under normotensive anesthesia. It is concluded from an extensive review of the literature that the most vulnerable period for serious complications is in the immediate postoperative period. No significant complications or adverse effects were observed in this study. It cannot be emphasized too strongly that the safety of this hypotensive technique lies in constant and careful monitoring of the patient and meticulous attention to all details of anesthetic management.