title: Does intrathecal fentanyl produce acute cross-tolerance to i.v. morphine?
abstract: We have examined the hypothesis that intrathecal fentanyl at operation can increase postoperative i.v. morphine requirements. We studied 60 patients undergoing Caesarean section. All received intrathecal 0.5% plain bupivacaine 2 ml combined with either fentanyl 0.5 ml (25 micrograms) (group F) (n = 30) or normal saline 0.5 ml (group S) (n = 30). In addition, 10 ml of an extradural solution (fentanyl 1 ml (50 micrograms) combined with 0.5% bupivacaine 9 ml) was administered after delivery. Extradural solution was only given before delivery if the intrathecal injection failed to produce a block above T6 or the patient required further analgesia. Postoperative analgesia was provided with i.v. morphine patient-controlled analgesia. At operation, intrathecal fentanyl reduced the need to administer extradural solution before delivery, increased the anaesthetist's satisfaction with analgesia and reduced nausea, but increased pruritus. Up to 6 h after delivery there was no difference in postoperative morphine requirements or pain scores. Between 6 h and 23 h there was a 63% increase in morphine requirements in group F. We consider the most likely explanation for this finding to be that intrathecal fentanyl induced acute spinal opioid tolerance.
authors.affiliation: Department of Anaesthetics, South Cleveland Hospital, Middlesbrough.
authors.forename: D W
authors.initials: DW
authors.lastname: Cooper
authors.forename: S L
authors.initials: SL
authors.lastname: Lindsay
authors.forename: D M
authors.initials: DM
authors.lastname: Ryall
authors.forename: M S
authors.initials: MS
authors.lastname: Kokri
authors.forename: S S
authors.initials: SS
authors.lastname: Eldabe
authors.forename: G A
authors.initials: GA
authors.lastname: Lear
mesh_terms: D016058:Analgesia, Patient-Controlled; D000701:Analgesics, Opioid / Q000494:pharmacology*; D000773:Anesthesia, Obstetrical; D000775:Anesthesia, Spinal; D002585:Cesarean Section; D004311:Double-Blind Method; D004334:Drug Administration Schedule; D004361:Drug Tolerance; D005260:Female; D005283:Fentanyl / Q000494:pharmacology*; D006801:Humans; D009020:Morphine / Q000494:pharmacology*; D010149:Postoperative Pain / Q000188:drug therapy; D011247:Pregnancy
chemical_list: D000701:Analgesics, Opioid; D009020:Morphine; D005283:Fentanyl