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AMBULATORY ANESTHESIOLOGY

Can Remifentanil Replace Nitrous Oxide During Anesthesia for Ambulatory Orthopedic Surgery with Desflurane and Fentanyl?

From the Department of Anesthesiology, St. Vincent Catholic Medical Centers, St. Vincent’s Manhattan, and New York Medical College, Valhalla, New York.

Address correspondence and reprint requests to Donald M. Mathews, MD, Department of Anesthesiology, St Vincent’s Hospital, 170 West 12th St., NR 408, New York, NY 10011. Address e-mail to dmathews{at}svcmcny.org.

Abstract

BACKGROUND: The administration of nitrous oxide (N₂O) may be associated with side effects and toxicities. Remifentanil shares characteristics with N₂O, including MAC-reducing and antinociceptive effects and a rapid decrease in clinical effect when discontinued. We compared the outcome after ambulatory orthopedic surgery with desflurane and fentanyl supplemented with clinically equivalent doses of either N₂O or remifentanil.

METHODS: Seventy patients undergoing ambulatory orthopedic surgery were studied. Thirty-five received 66% N₂O and 35 received remifentanil 0.085 µg · kg^–1 · min^–1 in addition to desflurane, titrated to a bispectral index (BIS) value of 50, and a fentanyl infusion. The principle outcome measure was time to awakening to verbal stimulation. Secondary outcome measures included neuropsychological testing, time to orientation, hemodynamic values, pain and nausea visual analog scores, discharge times, and satisfaction scores. The average end-tidal desflurane concentration and fentanyl effect-site concentration were determined.

RESULTS: The median time (interquartile range) to awakening to verbal stimulation, 3.0 min (3.0–5.0 min) in the remifentanil group and 4.6 min (3.0–8.1 min) in the N₂O group was not significantly different. Median time to orientation was significantly faster in the remifentanil group: 6.0 min (5.0–8.5 min) compared with 8.0 min (5.0–12.8 min) for the N₂O group. There was no difference between groups in desflurane or fentanyl administration, neuropsychological testing, or any other outcome measure.

CONCLUSIONS: This study demonstrates that a remifentanil infusion of 0.085 µg · kg^–1 · min^–1 may be substituted for 66% N₂O during desflurane/fentanyl anesthesia without any clinically significant change in outcome.