Evaluation of epidural morphine or ketamine analgesic effect in dogs by von Frey filaments

Pre-emptive analgesic effects of epidural ketamine or morphine were compared using the von Frey filaments (VF). Fourteen mixed breed male or female dogs, weighing 12.5kg, divided into G1 (morphine, 0.1mg/kg; n=7) and G2 (ketainine, 0.2mg/kg; n=7) groups were used. Under sevoflurane anesthesia epidural injections were made by spinal needle inserted at lombo-sacral space. Subsequently, a 1.5cm cushion incision was made and immediately closed with a simple interrupted nylon suture and the inhalatory anesthesia was closed. Thirty minutes after the suture, the postincisional pain was measured by VF filaments at 0.3cm around the incision. These procedures were repeated every 30 min until 120 min and at 3, 4, 5, 6 and 24 hours after suturing. The VF filaments force expressed in grants were analyzed by non-parametric tests (Kruskal-Wallis or Mann-Whitney, Pless than or equal to0.05). No response to VF filaments was observed in G1 dogs. The VF force was reduced progressively in the G2 dogs,from 90 min to 24 hours. It was concluded that VF filaments evaluation showed that pre-emptive epidural morphine produced more effective and lasting postincisional analgesia than ketamine.