Background: Although preemptive analgesia has been shown to decrease postinjury pain in animals, studies in humans have provided controversial results. The authors studied whether surgical epidural anesthesia with local anesthetics could affect postoperative pain and analgesic demands, when compared with general anesthesia.
Methods: Male patients scheduled for radical retropubic prostatectomy were randomly assigned to receive epidural anesthesia only (EA, n = 34), combined epidural and general anesthesia (EG, n = 32), or general anesthesia only (GA, n = 30). A lumbar epidural catheter was inserted and tested in all patients. In the EA group, an induction dose of 0.25 ml/kg epidural bupivacaine (0.5%) was followed during surgery by a continuous infusion of 0.1 ml.kg-1.h-1 0.125% bupivacaine. In the EG group, 0.2 ml/kg epidural bupivacaine (0.5%) was injected after induction of general anesthesia but before surgery, followed by epidural infusion of 0.1 ml.kg-1.h-1 0.125% bupivacaine. In the GA group, anesthesia was maintained with morphine, isoflurane, and N2O. Epidural patient-controlled analgesia (PCA) was provided with bupivacaine and fentanyl for all patients in the postoperative period. Postoperative pain scores and analgesic requirements were examined and compared between groups every 4-8 h for 3-5 postoperative days.
Results: Intraoperatively, EA patients received significantly more epidural bupivacaine than EG patients (129 +/- 6 mg vs. 98 +/- 6 mg, respectively. Recovery room median residual sensory level in EA patients (T6 +/- 2) was significantly higher than in EG patients (T10 +/- 2). PCA demand was greater in the GA and EG groups when compared with the EA group in postoperative days 2 (126 +/- 9 ml, 112 +/- 9 ml, 90 +/- 6 ml, respectively; P = 0.01) and 3 (89 +/- 10 ml, 83 +/- 9 ml, 48 +/- 5 respectively; P = 0.005). There was no difference in PCA demand between the GA and EG groups in the postoperative period. No significant clinical differences in postoperative mean pain scores were recorded in the first 5 days after surgery in the three anesthetic groups (range 0-2/10).
Conclusions: In patients undergoing lower abdominal surgery, the neuraxial blockade and surgical anesthesia achieved by epidural local anesthetics was associated with decreased postoperative analgesic demands. Lower postoperative analgesic requirements in the EA group, when compared with both the EG and GA groups, indicate that: (1) EA patients had less postoperative pain, and (2) an efficient intraoperative blockade of noxious afferent signals to the central nervous system is fundamental in reducing postoperative pain.