We hypothesized that onset of sensory block is delayed in infected versus healthy tissues within the same nerve distribution after axillary brachial plexus block (ABPB) and that clonidine added to mepivacaine would enhance anesthesia and postoperative analgesia. Forty-one outpatients undergoing thumb/index paronychia surgery under ABPB were randomly assigned to receive in a double-blind fashion 400 mg mepivacaine plus either 100 &mgr;g clonidine (clonidine group, n = 21) or 2 mL saline (placebo group, n = 20). Onset of sensory block in the infected area was delayed compared with healthy areas of the same nerve distribution (24.7 ± 5.5 min versus 21.3 ± 7.2; P = 0.02 for median and 21.6 ± 7.8 min; P = 0.04 for radial) within the placebo group. In the clonidine group, when compared to placebo i) onset of sensory block in both the median and radial nerve territories was accelerated (11.1 ± 5.6 and 10.5 ± 5.2 versus 21.3 ± 7.2 and 21.6 ± 7.8 min, respectively; P < 0.001), ii) onset of sensory block in the region of infection was accelerated (9.1 ± 1.9 versus 24.7 ± 5.5 min; P < 0.001), iii) duration of anesthesia (275 ± 75 versus 163 ± 57; P = 0.04) and time to first analgesic requirement (279 ± 87 versus 197 ± 84 min; P = 0.002) were prolonged with decreased visual analog scale scores at this time (30 ± 18 versus 70 ± 24; P < 0.001), and iv) verbal numeric rating scores were decreased at 24 h (1.7 ± 2.2 versus 4.1 ± 3.0; P = 0.002) and 48 h (0.1 ± 0.5 versus 1.5 ± 2.4; P = 0.01) postoperatively. Our findings suggest that in the setting of distal infected tissue surgery under ABPB infected tissues are resistant to anesthesia compared with healthy areas within the same nerve distribution and clonidine added to mepivacaine enhances both anesthesia and postoperative analgesia.

Iohom, G.; Machmachi, A.; Diarra, D. P.; Khatouf, M.; Boileau, S.; Dap, F.; Boini, S.; Mertes, P. M.; Bouaziz, H. Author Information

To date, results of studies evaluating the efficacy of opioids and local anesthetic combinations in the brachial plexus are inconclusive. We examined whether increasing sufentanil in doses of 5, 10, and 20 &mgr;g decreased onset time or increased duration of an axillary brachial plexus block. Ninety-two patients scheduled for carpal tunnel release under axillary brachial plexus block were enrolled in the study. Patients were randomized to receive axillary plexus block with 40 mL 1.5% mepivacaine and saline (Group 1), sufentanil 5 &mgr;g (Group 2), 10 &mgr;g (Group 3), or 20 &mgr;g (Group 4). Onset and duration of sensory and motor block were measured. Opioid-related side effects were recorded. The addition of sufentanil did not improve speed of onset or increase the duration of sensory or motor block. Paradoxically, duration of sensory and motor block was longest in the control group: sensory, 241 min (188–284) and motor, 234 min (128–305), and decreased with increasing 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 belonging to Groups 2 and 4, and in 60% of the patients in Group 3. In contrast, only 10% of the patients reported side effects in the control group. We conclude that sufentanil added to mepivacaine does not increase the onset or prolong the duration of an axillary plexus block. Furthermore, the addition of sufentanil was associated with a frequent incidence of side effects. Implications This study demonstrates that the addition of sufentanil in a dose-dependent manner to 1.5% mepivacaine in the axillary plexus does not improve onset or duration of blockade, and that this admixture is associated with an increased incidence of side effects.