Single-injection caudal thoracic paravertebral block improves pain control and recovery quality in female dogs undergoing unilateral radical mastectomy: a randomized controlled trial.

OBJECTIVE: To test clinical and analgesic effects of a single-injection caudal thoracic paravertebral block (TPVB) after localization of the thoracic paravertebral space with a loss-of-resistance to air injection technique in female dogs undergoing unilateral radical mastectomy. ANIMALS: 14 client-owned dogs. PROCEDURES: Dogs were premedicated with methadone, anesthetized with propofol and sevoflurane, and randomly assigned to receive a TPVB or no block preoperatively. Rescue analgesia with fentanyl and methadone was provided on the basis of cardiovascular responses during surgery and postoperative pain scores assigned with a validated pain scale. Required dose of rescue opioids; mean end-tidal sevoflurane concentration; episodes of hypotension, bradycardia, and other complications; quality of recovery scores; and postoperative pain scores were compared between groups. RESULTS: Median intraoperative fentanyl doses were 0 µg/kg (range, 0 to 2 µg/kg) and 4 µg/kg (range, 2 to 6 µg/kg) for the TPVB and control groups, respectively. Median postoperative methadone doses were 0 mg/kg (range, 0 to 0.2 mg/kg) and 0.6 mg/kg (range, 0.4 to 0.6 mg/kg) for the TPVB and control groups, respectively. Recovery scores and pain scores assigned at the time of and 1 hour after extubation were significantly lower in the TPVB group than in the control group. CONCLUSIONS AND CLINICAL RELEVANCE: A single-injection caudal TPVB improved pain control and recovery quality in female dogs undergoing unilateral radical mastectomy. Because the TPVB involves only a single injection, does not take long to perform, and requires only readily available low-cost equipment, the technique may be a valuable option in both referral and first-opinion practice.