Sufentanil does not prolong the duration of analgesia in a mepivacaine brachial plexus block: A dose response study

To date, results of studies evaluating the efficacy of opioids and local an esthetic combinations in the brachial plexus are inconclusive. We examined whether increasing sufentanil in doses of 5, 10, and 20 mu g decreased onse t time or increased duration of an axillary brachial plexus block. Ninety-t wo patients scheduled for carpal tunnel release under axillary brachial ple xus block were enrolled in the study. Patients were randomized to receive a xillary plexus block with 40 mL 1.5% mepivacaine and saline (Group 1), sufe ntanil 5 mu g (Group 2), 10 mu g (Group 3), or 20 mu g (Group 4). Onset and duration of sensory and motor block were measured. Opioid-related side eff ects were recorded. The addition of sufentanil did not improve speed of ons et or increase the duration of sensory or motor block. Paradoxically, durat ion of sensory and motor block was longest in the control group: sensory, 2 41 min (188-284) and motor, 234 min (128-305), and decreased with increasin g doses of sufentanil in Group 4: sensory, 216 min (115-315) and motor, 172 min (115-260) (P < 0.05). Side effects occurred in 55% of patients belongi ng to Groups 2 and 4, and in 60% of the patients in Group 3. In contrast, o nly 10% of the patients reported side effects in the control group. We conc lude that sufentanil added to mepivacaine does not increase the onset or pr olong the duration of an axillary plexus block. Furthermore, the addition o f sufentanil was associated with a frequent incidence of side effects. Impl ications: This study demonstrates that the addition of sufentanil in a dose -dependent manner to 1.5% mepivacaine in the axillary plexus does not impro ve onset or duration of blockade, and that this admixture is associated wit h an increased incidence of side effects.