Evaluation of topical epidural morphine for postoperative analgesia following hemilaminectomy in dogs.

A randomized prospective study was conducted in dogs undergoing hemi-laminectomy procedures for Hansen type I disk protrusion to compare postoperative analgesia achieved with topical spinal application of morphine versus saline. An absorbable gelatin sponge was placed in the defect next to the dura and soaked with either preservative-free morphine (0.1 mg/kg) or saline (0.1 ml/kg) just before wound closure. For 48 hours after surgery, dogs were monitored for pain using visual analog and numeric descriptive scales and given rescue analgesia according to study guidelines. A Kaplan-Meier survival analysis revealed that dogs in the morphine group had a longer (13.3 +/- 3.6 hours) duration of postoperative analgesia than those in the control saline group (5.3 +/- 1.8 hours), and dogs in the morphine group also required fewer doses of additional pain medication. Preservative-free morphine administered topically via an absorbable gelatin sponge appears to be a promising method to alleviate postoperative pain in dogs undergoing hemilaminectomy procedures.