PREEMPTIVE LUMBAR EPIDURAL-ANESTHESIA REDUCES POSTOPERATIVE PAIN AND PATIENT-CONTROLLED MORPHINE CONSUMPTION AFTER LOWER ABDOMINAL-SURGERY

The present study tested the hypothesis that patients receiving epidur al bupivacaine before surgery would require less morphine postoperativ ely and/or report less intense pain than patients receiving epidural b upivacaine after incision but before the end of surgery. Forty-two pat ients (ASA class I-III) scheduled for lower abdominal surgery were ran domly assigned to 1 of 2 groups of equal size and prospectively studie d using a double-blind, placebo-controlled crossover design. Epidural catheters were placed in the T12-L1 or L1-L2 interspaces pre-operative ly, the position of the catheter was confirmed with 3% chloroprocaine with epinephrine 1:200,000, and sensory testing was carried out until levels had receded to below T12. Group 1 received 15 ml of 0.5% epidur al bupivacaine injected 35 min before incision followed by 15 ml of ep idural normal saline 30 min after incision. Group 2 received 15 ml of epidural normal saline injected 37 min before incision followed by 15 ml of 0.5% epidural bupivacaine 30 min after incision. General anaesth esia was induced with thiopental (4-6 mg/kg) and maintained with N2O/O -2 and isoflurane. Paralysis was achieved with pancuronium (0.1 mg/kg) . Opioids were not used as pre-medication or during surgery. Postopera tive analgesia consisted of patient-controlled (PCA) intravenous morph ine. Visual analogue pain scores (VAS) (at rest and after standardized mobilization) did not differ significantly between the 2 groups but M cGill Pain Questionnaire (MPQ) pain ratings were significantly lower i n group 1 at the 24 and 72 h assessments. Group 1 used significantly l ess morphine than did group 2 between 12 and 24 h after surgery. Cumul ative PCA morphine consumption in group 1 (55.2 +/- 4.7 mg) was signif icantly lower than in group 2 (71.7 +/- 6.1 mg) 24 h and 48 h (group 1 : 86.8 +/- 6.3 mg vs, group 2: 108.9 +/- 9.8 mg) after surgery, but no t at the 72 h assessment. Reduction in morphine dose at 24, 48 and 72 h amounted to 30%, 25% and 22%, respectively. The results suggest that single-shot pre-emptive epidural local anaesthesia is associated with a short-term morphine-sparing effect which is most pronounced between 12 and 24 h after surgery. Extending the pre-operative blockade into the postoperative period may prolong the initial advantage conferred b y pre-emptive epidural local anaesthesia.