The Effect of Intravenously Administered Dexmedetomidine on Perioperative Hemodynamics and Isoflurane Requirements in Patients Undergoing Abdominal Hysterectomy

The effects of two doses of dexmedetomidine (0.3 or 0.6 micrograms.kg-1), fentanyl 2.0 micrograms.kg-1, or saline as a single intravenous bolus administered 10 min prior to the induction of anesthesia were assessed in double-blind, randomized study in 96 women undergoing abdominal hysterectomy. In each patient, anesthesia was induced with thiopental 4.0 mg.kg-1, and after the effect of succinylcholine had dissipated, isoflurane 0.3% end-tidal concentration in 70% nitrous oxide was begun to maintain anesthesia. The isoflurane concentration was adjusted to maintain blood pressure and heart rate within 20% of preoperative values, and fentanyl was given if the end-tidal isoflurane concentration exceeded 1.5%. In all groups, blood pressure and heart rate increased after tracheal intubation. However, the increase in blood pressure and heart rate was significantly less in the higher dexmedetomidine (0.6 micrograms.kg-1) group than in the saline group (P less than 0.01). Also, the postintubation increase in heart rate was significantly less (P less than 0.05) in the dexmedetomidine 0.6 micrograms.kg-1 group (increase of 18 +/- 3 beats per min) compared to the fentanyl group (increase of 26 +/- 3 beats per min). In patients receiving dexmedetomidine 0.3 micrograms.kg-1, the increase in blood pressure or heart rate did not differ from that of the saline group. The mean end-tidal isoflurane concentration was significantly less in the women receiving the higher dose of dexmedetomidine (0.35%) than in those receiving saline (0.47%) or fentanyl (0.48%), although the reduction was not clinically important.(ABSTRACT TRUNCATED AT 250 WORDS)