[Peridural analgesia with high doses of fentanyl: failure of the method for early postoperative kinesitherapy in knee surgery].

Following orthopedic surgery of the lower limb, ten patients were given fentanyl 5 micrograms . kg-1 in a single epidural injection. Almost complete analgesia (P less than 0.001) was rapidly obtained. The total period of analgesia was rather short (182.3 +/- 32.1 min). The maximal analgesia period was 87 +/- 8.34 minutes. Despite this high dose of fentanyl (245 to 450 micrograms), in five patients the passive mobilization of the knee following surgery was extremely painful and, for that matter, impossible in three of them. Such high doses of fentanyl entail the risk of respiratory depression as respiratory rate is decreased (P less than 0.01) and the Pco2 is increased (P less than 0.01). Fentanyl should not be used at such high dosage and should probably not be preferred to morphine, considering that the duration of analgesia is short, that the analgesic score is identical to that obtained with lower doses or with longer lasting narcotics, that it does not prevent passive mobilization pains and that it entails a definite risk of respiratory depression.