Isoflurane-induced hypotension in orthognathic surgery

The effect of isoflurane-induced hypotension on reduction of blood loss, improvement of surgical field, and postoperative edema was investigated in 52 patients undergoing combined maxillary and mandibular osteotomies. Anesthesia was maintained with fentanyl, N2O, O2, and isoflurane. Deliberate hypotension was induced by increasing isoflurane inspired concentration. Blood loss in the hypotensive group (MAP 55-65 mm Hg) was significantly less than that in the control group (MAP 75-85 mm Hg); 454.0 +/- 211.3 mL versus 755.3 +/- 334.6 mL (P less than 0.001). Fewer patients had to be transfused in the hypotensive group, 12.0% versus 44.4% (P less than 0.02). The surgical field was significantly improved by the hypotensive technique, but operative time was not shortened. Subjective and objective measurements of postoperative edema failed to show any effect of deliberate hypotension. Our data suggest that isoflurane-induced hypotension effectively reduces blood loss and the number of transfusions in orthognathic surgery.