Extradural pain relief in labour: bupivacaine sparing by extradural fentanyl is dose dependent.
The minimum local analgesic concentration (MLAC) of bupivacaine in labour is defined as the effective concentration in 50% of subjects (EC50). We have used the technique of double-blinded sequential allocation to quantify the bupivacaine sparing effect of the addition of four different doses of extradural fentanyl in 223 labouring women. There were five groups: (1) plain bupivacaine (control); (2) bupivacaine with fentanyl 1 microgram ml-1; (3) bupivacaine with fentanyl 2 micrograms ml-1; (4) bupivacaine with fentanyl 3 micrograms ml-1; and (5) bupivacaine with fentanyl 4 micrograms ml-1. The MLAC of bupivacaine were 0.069% w/v, 0.057% w/v, 0.048% w/v, 0.031% w/v and 0.015% w/v, respectively. We observed a reduction in MLAC of 18%, 31% (P = 0.03%), 55% (P < 0.0001) and 72% (P < 0.0001) with fentanyl 1, 2, 3 and 4 micrograms ml-1, respectively, demonstrating a significant negative linear trend (P < 0.0001) with increasing fentanyl dose. The incidence of pruritus was increased significantly with fentanyl 4 micrograms ml-1 (P = 0.0015). Because of this, fentanyl 3 micrograms ml-1 may be the optimal dose when the aim is bupivacaine sparing extradural analgesia during labour.
Lyons
G
G
St James's University Hospital, Leeds.
Columb
M
M
Hawthorne
L
L
Dresner
M
M
D000293:Adolescent; D000328:Adult; D015360:Analgesia, Epidural / Q000379:methods*; D016362:Analgesia, Obstetrical / Q000379:methods*; D000701:Analgesics, Opioid / Q000008:administration & dosage* / Q000009:adverse effects; D000779:Anesthetics, Local / Q000008:administration & dosage; D002045:Bupivacaine / Q000008:administration & dosage; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D004338:Drug Combinations; D005260:Female; D005283:Fentanyl / Q000008:administration & dosage* / Q000009:adverse effects; D006801:Humans; D011247:Pregnancy; D011537:Pruritus / Q000139:chemically induced
D000701:Analgesics, Opioid; D000779:Anesthetics, Local; D004338:Drug Combinations; D005283:Fentanyl; D002045:Bupivacaine