Postoperative analgesic effects of either a constant rate infusion of fentanyl, lidocaine, ketamine, dexmedetomidine, or the combination lidocaine-ketamine-dexmedetomidine after ovariohysterectomy in dogs

ObjectiveTo evaluate the postoperative analgesic effects of a constant rate infusion (CRI) of either fentanyl (FENT), lidocaine (LIDO), ketamine (KET), dexmedetomidine (DEX), or the combination lidocaine-ketamine-dexmedetomidine (LKD) in dogs. Study designRandomized, prospective, blinded, clinical study. AnimalsFifty-four dogs. MethodsAnesthesia was induced with propofol and maintained with isoflurane. Treatments were intravenous (IV) administration of a bolus at start of anesthesia, followed by an IV CRI until the end of anesthesia, then a CRI at a decreased dose for a further 4hours: CONTROL/BUT (butorphanol 0.4mgkg(-1), infusion rate of saline 0.9% 2mLkg(-1)hour(-1)); FENT (5gkg(-1), 10gkg(-1)hour(-1), then 2.5gkg(-1)hour(-1)); KET (1mgkg(-1), 40gkg(-1)minute(-1), then 10gkg(-1)minute(-1)); LIDO (2mgkg(-1), 100gkg(-1)minute(-1), then 25gkg(-1)minute(-1)); DEX (1gkg(-1), 3gkg(-1)hour(-1), then 1gkg(-1)hour(-1)); or a combination of LKD at the aforementioned doses. Postoperative analgesia was evaluated using the Glasgow composite pain scale, University of Melbourne pain scale, and numerical rating scale. Rescue analgesia was morphine and carprofen. Data were analyzed using Friedman or Kruskal-Wallis test with appropriate post-hoc testing (p<0.05). ResultsAnimals requiring rescue analgesia included CONTROL/BUT (n=8), KET (n=3), DEX (n=2), and LIDO (n=2); significantly higher in CONTROL/BUT than other groups. No dogs in LKD and FENT groups received rescue analgesia. CONTROL/BUT pain scores were significantly higher at 1hour than FENT, DEX and LKD, but not than KET or LIDO. Fentanyl and LKD sedation scores were higher than CONTROL/BUT at 1hour. Conclusions and clinical relevanceLKD and FENT resulted in adequate postoperative analgesia. LIDO, CONTROL/BUT, KET and DEX may not be effective for treatment of postoperative pain in dogs undergoing ovariohysterectomy.