Effect of preoperative epidural morphine administration on desflurane requirements during gynecologic surgery.

BACKGROUND AND

OBJECTIVES

The goal of this study is to examine the influence of epidural morphine on the end-tidal desflurane concentration titrated to maintain the bispectal index (BIS) values between 40 and 60 during gynecologic surgery.

METHODS

Forty patients undergoing transabdominal hysterectomy under general anesthesia were randomly and prospectively assigned to 1 of 2 study groups: group saline (group S) and group morphine (group M). After placing an epidural catheter at L3-4 or L4-5, patients received either 10 mL of saline or 4 mg of morphine in 10 mL of saline approximately 60 minutes before anesthesia induction. Anesthesia maintenance was provided with desflurane and nitrous oxide in oxygen with a ratio of 2:1 by an anesthesiologist blinded to the group. Measurements included BIS value, end tidal desflurane concentration, heart rate, and blood pressure before surgery and every 10 minutes during surgery.

RESULTS

Although there was a tendency to slightly lower end-tidal desflurane concentrations in the morphine group, this difference did not reach statistical significance at any time. In the morphine group, the heart rate was lower than in the saline group at 20, 30, 40, and 50 minutes of surgery (P < .05). BIS values were similar throughout surgery.

CONCLUSIONS

Preoperative administration of epidural morphine does not reduce desflurane requirements in patients undergoing gynecologic surgery.