Tramadol added to mepivacaine prolongs the duration of an axillary brachial plexus blockade

Tramadol is an analgesic drug that is antagonized by alpha(2)-adrenoceptor antagonists, as well as opioid antagonists. We hypothesized that tramadol m ight produce effects on an axillary brachial plexus blockade similar to tho se of clonidine. We designed a prospective, controlled, double-blinded stud y to assess the impact of tramadol added to mepivacaine on the duration of an axillary brachial plexus blockade. After institutional approval and info rmed consent, 60 patients (ASA physical status I or II) scheduled for forea rm and hand surgery after trauma under brachial plexus anesthesia were incl uded in the study. Patients were randomly assigned to receive either 40 mt of mepivacaine 1% with 2 mt of isotonic sodium chloride solution (Group A, n = 20); 40 mt of mepivacaine 1% with 100 mg of tramadol (Group B, n = 20); or 40 mt of mepivacaine 1% with 2 mt of isotonic sodium chloride solution and 100 mg of tramadol IV (Group C, n = 20). Sensory block, motor block, an d hemodynamics were recorded before and 5, 10, 30, 60, 120, 180, and 360 mi n after local anesthetic injection. Duration of sensory and motor block was significantly longer (P < 0.01; P < 0.05) in Group B (299 +/- 84 and 259 /- 76 min) than in Group A (194 +/- 35 and 181 +/- 24 min) and Group C (187 +/- 35 and 179 +/- 16 min). There was no difference in onset of sensory an d motor blockade among groups. Hemodynamics remained unchanged in all patie nts throughout the study period. We conclude that the addition of tramadol prolongs the duration of brachial plexus block without side effects. Tramad ol may be an alternative to epinephrine or clonidine as an adjuvant to loca l anesthesia for an axillary block. Implications: This study demonstrates t hat the admixture of 100 mg of tramadol with mepivacaine 1% for brachial pl exus block provides a pronounced prolongation of blockade without side effe cts. Our data support a specific analgesic effect of tramadol on peripheral nerves.