Effect of intrafragmentary bupivacaine (haematoma block) on analgesic requirements in dogs undergoing fracture repair

Objective

To test the efficacy of intraoperative intrafragmentary administration of bupivacaine (haematoma block) in controlling postoperative pain in dogs undergoing osteosynthesis of long-bone isolated diaphyseal fractures.

Study design

Randomized, ‘blinded’, placebo-controlled, prospective study.

Animals

A total of 23 client-owned dogs with isolated long-bone fractures.

Methods

Dogs were allocated randomly to two groups: bupivacaine group (B) or placebo group (P). Group B dogs (n = 11) were administered an intraoperative intrafragmentary injection of 0.5% bupivacaine (1.1 mg kg^–1) just before fracture fixation, whereas group P dogs (n = 12) were administered normal saline. Postoperative pain evaluations using the University of Melbourne Pain Scale (UMPS) and algometer were performed upon arrival to the recovery room and 1, 2, 4, 6, 8, 20 and 32 hours later. Algometer measurements were performed on: the incision site, a healthy region near the fracture line and the contralateral healthy limb. When the pain score exceeded 14 points in the UMPS, rescue analgesia was administered. The time-standardised area under the curve (AUCst) was used to compare UMPS scores and mechanical pain thresholds between the two groups.

Results

None of the group B dogs required rescue analgesia, whereas eight of the 12 group P dogs did (p = 0.001). The pain threshold AUCst at the incision line was higher in group B [16.3 (2.9–41.6) N] than in group P [5.6 (2.5–17.4) N] (p = 0.029). The mean UMPS score AUCst was lower in group B (3.7 ± 1.8) than in group P (9.4 ± 4.6) (p = 0.016). In a small number of animals of both groups that were evaluated radiologically, adequate bone healing was noted.

Conclusions and clinical relevance

An intraoperative bupivacaine haematoma block is a simple, quick and effective method that can be used to aid in postoperative pain control in dogs submitted to long-bone osteosynthesis.