Comparison of 3 blind brachial plexus block techniques during maintenance of anesthesia and postoperative pain scores in dogs undergoing surgical procedures of the thoracic limb.

Abstract

The degree of analgesia provided by blind techniques for brachial plexus blocks (BPBs) has not been compared in clinical cases undergoing surgery of the thoracic limb. The objective of this study was to evaluate the anesthetic conditions and postoperative analgesia resulting from 3 different BPB local anesthetic techniques in canine patients undergoing such surgery. Twenty-four client-owned dogs received a standardized premedication/induction protocol (hydromorphone and acepromazine/propofol), maintained with isoflurane in oxygen using mechanical ventilation, in a prospective, randomized, blinded clinical trial. Before surgery, dogs received 1 of 3 anatomical BPB techniques: traditional, perpendicular, or axillary, with 0.2 mL/kg body weight (BW) of bupivacaine 0.5%. Cardiorespiratory variables and isoflurane end-tidal concentrations were recorded throughout anesthesia. Scores for anesthetic maintenance (0-best to 4-responsive), recovery quality (0-not responsive to 3-responsive), and Glasgow pain scale were recorded for up to 24 h postoperatively. All dogs recovered uneventfully from anesthesia and no differences in the measured variables or scores were noted among groups, during and after anesthesia. When thoracic limb amputations in each of the 3 groups (= 9; 4 in traditional, 3 in perpendicular, 2 in axillary) were compared to the other surgical procedures (= 15); however, scores for anesthetic maintenance were higher [0 (0 to 1)0 (0 to 0); median (interquartile range)], recovery [1 (0 to 2)0 (0 to 0)], and pain [2.4 (2.4 to 3.0)1.6 (1.4 to 2.2)] in the first 3 h post-extubation. Surgery times were also longer with amputations [115 min (100 to 138 min)50 min (41 to 90 min)]. The 3 BPB techniques provided similar anesthesia and postoperative pain scores. Despite higher pain scores in thoracic limb amputations than in less invasive surgeries, the BPB appeared to provide significant comfort.