DETERMINATION OF THE MINIMUM LOCAL ANALGESIC CONCENTRATIONS OF EPIDURAL BUPIVACAINE AND LIDOCAINE IN LABOR

Authors
Citation
Mo. Columb et G. Lyons, DETERMINATION OF THE MINIMUM LOCAL ANALGESIC CONCENTRATIONS OF EPIDURAL BUPIVACAINE AND LIDOCAINE IN LABOR, Anesthesia and analgesia, 81(4), 1995, pp. 833-837
Citations number
16
Categorie Soggetti
Anesthesiology
Journal title
ISSN journal
00032999
Volume
81
Issue
4
Year of publication
1995
Pages
833 - 837
Database
ISI
SICI code
0003-2999(1995)81:4<833:DOTMLA>2.0.ZU;2-6
Abstract
The aim of this study was to devise a clinical model to determine the effective concentrations in 50% of patients (EC(50)) for bupivacaine a nd lidocaine in the first stage of labor and define EC(50) as the mini mum local analgesic concentration (MLAC). This should allow the determ ination of relative analgesic potency and, subsequently, the local ane sthetic sparing efficacy of other epidural analgesics. Parturients not exceeding 5 cm cervical dilation who requested epidural analgesia wer e enrolled. The two studies involved 81 women (bupivacaine n = 41, lid ocaine n = 40). After a lumbar epidural catheter was placed, 20 mL of the concentration of local anesthetic being tested was given. The conc entration was determined by the response of the previous patient to a higher or lower concentration using double-blinded, up-down sequential allocation. Efficacy was assessed using 100-mm visual analog pain sco res with less than 10 mm within 1 h defined as effective. MLAC was det ermined using the formula of Dixon and Massey. Results show MLAC bupiv acaine 0.065% (95% confidence interval [CI] 0.045-0.085), MLAC lidocai ne 0.37% (95% CI 0.32-0.42), equivalent to 2 and 14 mmol solutions, re spectively. Thus bupivacaine was 5.7 times more potent than lidocaine in weighted and 7 times more potent in molar ratios at analgesic EC(50 ), in the volume of local anesthetic studied.