Postoperative analgesic effects of epidural administration of neostigmine alone or in combination with morphine in dogs undergoing orthopedic surgery of the pelvic limbs.

OBJECTIVE To evaluate the postoperative analgesic effects of epidural administration of morphine and neostigmine, either alone or in combination, in dogs. ANIMALS 30 dogs undergoing orthopedic surgery on a pelvic limb. PROCEDURES Anesthetic protocols were standardized. At the end of surgery, 10 dogs each received 1 of 3 epidural treatments: morphine (0.1 mg/kg), neostigmine (5 μg/kg), or morphine plus neostigmine (0.1 mg/kg and 5 μg/kg, respectively). Postoperative pain scores and the need for rescue analgesia were evaluated for 24 hours. RESULTS Pain scores were higher in the neostigmine group, compared with scores for the morphine-neostigmine group, at 2 and 24 hours after surgery and higher in the morphine group than in the morphine-neostigmine group at 2 and 4 hours. During 24 hours, rescue analgesia was provided for 4, 7, and 2 of 10 dogs each in the morphine, neostigmine, and morphine-neostigmine groups, respectively. The number of dogs given rescue analgesia was significantly different among groups at 2, 3, 4, and 6 hours after surgery. Dogs in the morphine and morphine-neostigmine groups had a lower probability of receiving rescue analgesia within 24 hours than did dogs in the neostigmine group. CONCLUSIONS AND CLINICAL RELEVANCE When administered epidurally, morphine alone or in combination with neostigmine provided effective postoperative analgesia in most dogs after orthopedic surgery, whereas neostigmine alone did not. Findings for this study suggested a potential role for neostigmine as an adjuvant for epidural analgesia in dogs undergoing orthopedic surgeries on the pelvic limbs.