Effects of a transdermal lidocaine patch on indicators of postoperative pain in dogs undergoing midline ovariohysterectomy

OBJECTIVE To determine the effects of a transdermal lidocaine patch (TLP) on indicators of postoperative pain in healthy dogs following ovariohysterectomy. DESIGN Randomized, blinded controlled trial. ANIMALS 40 healthy shelter-owned female dogs admitted to a student surgery program for ovariohysterectomy. PROCEDURES Dogs were randomly assigned to receive after ovariohysterectomy a 5-cm-wide strip of TLP applied topically on both sides of the incision, for the full length of the incision and a wound dressing (n = 19) or a placebo patch (nonmedicated wound dressing; 21). All dogs underwent midline ovariohysterectomy. Immediately afterward, dogs received 2 IM morphine injections, carprofen (SC, q 12 h for 2 days), and the assigned patch (left in place for 18 hours). Postoperative comfort was evaluated by use of the short form of the Glasgow Composite Measures Pain Scale and serum cortisol concentrations measured prior to premedication and 1, 2, 4, 6, 8, 10, and 18 hours after surgery. RESULTS No significant difference in pain scores or serum cortisol concentrations was identified between dogs that received the TLP and dogs that received a placebo patch after ovariohysterectomy. CONCLUSIONS AND CLINICAL RELEVANCE The TLP provided no additional analgesic benefit to dogs treated concurrently with recommended doses of morphine and carprofen following ovariohysterectomy. Additional studies are needed to investigate whether similar results might be achieved in dogs treated concurrently with other analgesics.