Fentanyl in 2% mepivacaine compared with fentanyl in 0.5% bupivacaine: two parallel controlled double blind studies.

The efficacy of epidural mepivacaine and bupivacaine, combined with fentanyl to enhance blockade, was compared in two parallel controlled, double-blind clinical trials. Patients in the studies (n = 91) were scheduled for orthopedic surgery of the legs and a tourniquet was used in all cases. Those patients receiving mepivacaine attended day surgery only, whereas patients receiving bupivacaine were hospitalised. Epidural puncture was performed with a Tuohy needle at the L3-4 level in the lateral decubitus position. Levels of sensory and motor blockade were assessed; adverse reactions and pain during surgery were recorded. There were four groups of patients: 1) 26 received 2% mepivacaine with placebo; 2) 26 received 2% mepivacaine with 0.1 mg fentanyl; 3) 19 received 0.5% bupivacaine with placebo and 4) 20 patients received 0.5% bupivacaine with 0.1 mg fentanyl. The levels of the sensory blockade was comparable in all groups. The degree of motor-blockade was more intense in the mepivacaine groups, but the blockade by mepivacaine lasted shorter. Addition of fentanyl did not change the sensory and motor blockade. Intraoperative pain was reported by: 7 patients in the mepivacaine/placebo group; 4 patients in the mepivacaine/fentanyl group; 4 patients in the bupivacaine/placebo group; and by one patient in the bupivacaine/fentanyl group. These results indicate that fentanyl enhances the quality of epidural blockade when combined with either mepivacaine or bupivacaine.