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ANESTHETIC PHARMACOLOGY

Effect-Site Concentration of Propofol for Recovery of Consciousness Is Virtually Independent of Fentanyl Effect-Site Concentration

Hiroko Iwakiri, MD^*, Osamu Nagata, MD^*, Takashi Matsukawa, MD, Makoto Ozaki, MD^*, and Daniel I. Sessler, MD

*Department of Anesthesiology, Tokyo Women’s Medical University, Tokyo, Japan; Department of Anesthesiology, Yamanashi Medical University, Yamanashi, Japan; OUTCOMES RESEARCH^TM Institute, Department of Anesthesiology and Pharmacology, University of Louisville, Louisville, Kentucky; and Ludwig Boltzmann Institute, University of Vienna, Vienna, Austria

Address correspondence and reprint requests to Makoto Ozaki, MD, Department of Anesthesiology, Tokyo Women’s Medical University, Tokyo 162-8666, Japan. Address e-mail to mozaki{at}anes.twmu.ac.jp

Fentanyl reduces the amount of propofol necessary to prevent responses to surgical stimuli. However, opioids have relatively little effect on consciousness. We, therefore, tested the hypothesis that fentanyl minimally alters the effect-site concentration of propofol associated with awakening. Fifty women having gynecologic laparotomy with propofol anesthesia were randomly allocated into the following target effect-site fentanyl concentrations: 0.8, 1.0, 1.4, 2.0, and 3.0 ng/mL. Fentanyl was continued at the designated rate through the initial postoperative phase. The propofol effect-site concentration associated with eye opening in response to verbal command was regarded as the awakening concentration. The estimated propofol effect-site concentrations at awakening did not differ significantly among the groups and were 1.9 ± 0.5 µg/mL with a fentanyl effect-site concentration of 0.8 ng/mL; 1.6 ± 0.4 µg/mL with 1.0 ng/mL of fentanyl; 1.6 ± 0.2 µg/mL with 1.4 ng/mL of fentanyl; 1.7 ± 0.4 µg/mL with 2.0 ng/mL of fentanyl; and 1.6 ± 0.34 µg/mL with 3.0 ng/mL of fentanyl (mean ± SD). Seventy percent of the subjects in the 0.8 ng/mL fentanyl group spontaneously complained of pain, whereas none of the patients in the 2 or 3 ng/mL groups did. Five (56%) of 9 women in the 3 ng/mL group had a postoperative respiratory rate <6 breaths/min. Heart rate in one of these women decreased to <40 bpm. These data suggest that the optimal fentanyl effect-site concentration in patients recovering from gynecologic laparoscopy is between 1.4 and 2.0 ng/mL.

IMPLICATIONS:The effect-site concentration for propofol at awakening was virtually independent of the fentanyl effect-site concentration over the range of 0.8 to 3.0 ng/mL; however, 0.8 ng/mL of fentanyl was associated with inadequate postoperative analgesia, and 3.0 ng/mL of fentanyl was associated with respiratory toxicity. The optimal postoperative fentanyl effect-site concentration during recovery from propofol general anesthesia for laparotomy thus appears to be near 2 ng/mL.

This article has been cited by other articles:

				H. Iwakiri, N. Nishihara, O. Nagata, T. Matsukawa, M. Ozaki, and D. I. Sessler Individual Effect-Site Concentrations of Propofol Are Similar at Loss of Consciousness and at Awakening Anesth. Analg., January 1, 2005; 100(1): 107 - 110. [Abstract] [Full Text] [PDF]