• Tsunehisa Sato, Mutsuhito Kikura, and Shigehito Sato.
• Staff Anesthesiologist, Department of Anesthesiology, Hamamatsu Rosai Hospital, Hamamatsu, Japan.
• J Opioid Manag. 2013 Sep 1; 9 (5): 335-42.

ObjectiveTo examine the characteristics of postoperative fentanyl effect-site concentrations during intravenous analgesia in patients requiring or not requiring a fentanyl bolus and in patients with or without postoperative nausea and vomiting (PONV).DesignRetrospective observational study.SettingUniversity-affiliated general hospital.PatientsSixty patients who underwent posterior lumbar spine fusion.Main Outcome MeasuresThe authors simulated the fentanyl effect-site concentration for 48 postoperative hours and compared it between patients who did and did not require a fentanyl bolus and between patients who did and did not experience PONV.ResultsAt the end of anesthesia, the fentanyl effect-site concentration was similar between 37 (61.7 percent) patients requiring and 23 (38.3 percent) patients not requiring a postoperative fentanyl bolus (p=0.97). Within the first 12 postoperative hours, the concentration decreased in both groups (p < 0.01). The fentanyl effect-site concentration was higher in patients requiring a postoperative fentanyl bolus (within 12 hours, 1.4 ± 0.32 ng/mL vs 0.89 ± 0.35 ng/mL; between 12 and 48 hours, 0.94 ± 0.19 ng/mL vs 0.57 ± 0.09 ng/mL) (p < 0.05). PONV occurred in 22 (36.6 percent) patients, but more so in women (68.2 percent; p < 0.01); PONV was similar between patients requiring and not requiring a fentanyl bolus (p=0.78). Between the 12th and 48th postoperative hours, fentanyl effect-site concentrations were higher in patients with PONV (0.61 ± 0.10 ng/mL vs 0.57 ± 0.10 ng/mL, p=0.03).ConclusionsPatients needing a postoperative fentanyl bolus require a higher fentanyl effect-site concentration possibly because of individual variations, and PONV depends on the postoperative fentanyl effect-site concentration.

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