A prospective randomized, double-blinded clinical study evaluating the efficacy and safety of bupivacaine versus morphine-bupivacaine in caudal epidurals in cats with urethral obstruction.

Objective: To investigate the efficacy and safety of the caudal epidural technique in cats with urethral obstruction (UO).

Design: Prospective, double-blinded, randomized, sham-controlled study.

Animals: Eighty-eight male cats with UO.

Interventions: Thirty cats randomized to bupivacaine epidural (BUP), 28 cats to bupivacaine-morphine epidural (BUP/MOR), and 30 cats to sham epidural (SHAM).

Measurements And Main Results: Time to perform the epidural and efficacy of the epidural was assessed by evaluation of tail and perineal responses. The amount of propofol for urinary catheterization and time to administration of rescue analgesia (buprenorphine) was recorded. Cats were monitored for epidural complications. The median time to perform the epidural was 2 min (range, 0.2-13 min and range, 0.5-13 min), with an epidural success rate of 70%. The median amount of propofol administered for urinary catheterization was significantly less in the BUP (2.1 mg/kg; range, 0-7.5 mg/kg) and MOR/BUP cats (1.85 mg/kg; range, 0-8.6 mg/kg) as compared to SHAM cats (4 mg/kg; range, 0-12.7 mg/kg) (P = 0.006, P = 0.0008, respectively). The median time to administration of rescue analgesia was also significantly longer in the BUP (10 h; range, 2-32 h) and MOR/BUP cats (10 h; range, 4-45 h) as compared to SHAM cats (4 h; range, 2-36 h) (P = 0.0026, P = 0.0004, respectively). There were no recognized complications related to the epidural.

Conclusion: Caudal epidural appears to be safe, may reduce the amount of IV anesthesia needed to facilitate urinary catheterization, and can be used to provide long-term analgesia in the hospital.