Patient-controlled lumbar epidural fentanyl compared with patient-controlled intravenous fentanyl for post-thoracotomy pain

Thirty-four patients undergoing thoracotomy were entered into a randomized, double-blind, placebo-controlled study to compare the effects of patient-controlled, lumbar epidural (PCA-E) fentanyl with patient-controlled intravenous (PCA-i.v.) fentanyl with respect to drug requirements, analgesic efficacy and respiratory function. Prior to chest closure patients received fentanyl 2 micrograms.kg-1 by the epidural or i.v. route. In the recovery room further doses of epidural or i.v. fentanyl, 50 micrograms, were administered by the patients who controlled two PCA pumps. Background fentanyl infusion rates were increased by 10 micrograms.hr-1 each time the patient administered a drug bolus and were decreased by 10 micrograms.hr-1 whenever visual analogue scale (VAS) pain scores were less than 2 on a maximum 10 scale. Twenty-nine patients completed the study. Patients in the PCA-E group (n = 14) required less total fentanyl than those in the PCA-i.v. (n = 15) group (1857 +/- 693 micrograms vs 2573 +/- 890 micrograms respectively, P less than 0.05). Fentanyl infusion rates were lower in the PCA-E group at most measurement times. There were no differences between groups in respiratory rates, PaCO2, VAS pain scores or changes in pulmonary function as measured by FVC and FEV1. It is concluded that satisfactory patient-controlled analgesia can be achieved with both epidural and i.v. fentanyl after thoracotomy but that fentanyl requirements are less when given via the epidural route. This supports a direct spinal cord site of action for lumbar epidural fentanyl.