2-CHLOROPROCAINE ANTAGONISM OF EPIDURAL MORPHINE ANALGESIA

Background: 2-chloroprocaine (2-CP) used for lumbar epidural anesthesi a (LEA) reportedly decreases the efficacy of epidural morphine (EM) ad ministered for post-cesarean section (CS) analgesia. The amount of sup plemental i.v. morphine self-administered by the patient via the patie nt-controlled-analgesia device (PCA) is used to study the interaction between EM and 2-CP. Methods: Forty-two patients scheduled for electiv e CS were randomly divided into 3 equal groups, and received 2-CP, 2-C P+epinephrine (Epi, 5 mu g.ml(-1)) or 2% lidocaine (Lido) with Epi for LEA. All patients received 5 mg EM and i.v. PCA morphine for postoper ative pain. Cumulative amount of i.v. morphine used in the first 24 ho urs as well as the amount of the drug used during each 2-h period were noted. Nonparametric analysis of variance and Chi-squared analysis we re used for statistical comparisons. Results: The mean cumulative 24-h i.v. PCA morphine requirement in the 2-CP, 2-CP+Epi and Lido+Epi grou ps respectively was 20.5+/-24, 33.1.5+/-27 and 4.07+/-6.3 (mean+/-SD). The Lido+Epi group used significantly less morphine (P=0.01) compared to either of the 2-CP groups with no significant difference between t he 2-CP groups. The maximum i.v. PCA morphine use occurred in the firs t 4 hours following surgery in all three groups. Conclusion: Analgesic efficacy of EM is decreased when 2-CP is used for LEA compared to whe n Lido+Epi is used.