The effect of epidurally administered dexamethasone with lignocaine for post-operative analgesia in dogs undergoing ovariohysterectomy. A dose-response study

Purpose: To evaluate the postoperative analgesic and adverse effects of three doses of dexamethasone, administered epidurally in combination with lignocaine, in dogs undergoing ovariohysterectomy (OVH). Methods: Twenty-four female dogs undergoing ovariohysterectomy were pre-medicated with acepromazine and general anaesthesia was induced and maintained with propofol. Animals were randomly allocated into four groups of six. The control group was given lignocaine 2% (LI) and the treatment groups were given lignocaine with either 2 mg dexamethasone (LIDEX2), 4 mg dexamethasone (LIDEX4) or 8 mg dexamethasone (LIDEX8) administered at the lumbosacral epidural space. Duration of postoperative analgesia, first analgesic rescue, motor blockade, heart rate, blood pressure, respiratory rate, and rectal temperature were evaluated. Results: The duration of postoperative analgesia was 19.5 (SD 6) hours for LIDEX8 (p=0.001), 10 (SD 2) hours for LIDEX4 (p=0.002), 4 (SD 2) hours for LIDEX2 (p=0.074) treatments compared with values for the LI control treatment 2.2 (SD 1.6) hours. All treatments had significant cardiovascular and respiratory alterations but they were within acceptable range in these clinically healthy female dogs. Conclusion: Dexamethasone added to epidural lignocaine significantly extends the postoperative analgesia after ovariohysterectomy in female dogs.