Comparing intramuscular ketamine with peri-incisional bupivacaine with or without ketamine in dogs undergoing hemilaminectomy.

Abstract

Objective: To investigate whether infiltrating bupivacaine with ketamine into the epaxial muscles improves quality and duration of analgesia perioperatively compared with bupivacaine alone or ketamine intramuscularly.

Study design: Prospective blinded randomized clinical study.

Animals: A group of 66 dogs randomized into three groups (n = 22).

Methods: Before surgery, bupivacaine 0.5% 2 mg kg^-1 alone (group B) or combined with ketamine 2 mg kg^-1 (group BK) was infiltrated peri-incisionally into the epaxial muscles. Group K received ketamine 2 mg kg^-1 injected intramuscularly into a cervical muscle without infiltration. Meloxicam 0.2 mg kg^-1 was given intravenously (IV) before moving to theatre. Cardiovascular variables: heart rate and systolic, mean and diastolic blood pressure were recorded. Intraoperative fentanyl 5 μg kg^-1 IV was administered if these variables increased by 20% from baseline. Fentanyl continuous infusion (5 μg kg^-1 hour^-1) was started if more than three boluses were required. The Glasgow Composite Pain Scale-Short Form was used pre- and postoperatively for acute pain assessment at different time intervals; methadone 0.2 mg kg^-1 IV was administered if scores were greater 5/20. Analgesia requirements, time to first administration, pain scores, total opioids interventions, need for sedation, first food intake and adverse effects were recorded. Continuous, normally distributed and non-normally distributed variables were analysed using ANOVA or Kruskal Wallis test, respectively.

Results: No significant difference was found for cardiovascular variables between groups over time, intra- or postoperative analgesia requirements, time to administration, pain scores total opioids, time to first food intake, sedation and occurrence of adverse effects.

Conclusions and clinical relevance: No difference in perioperative rescue analgesia was found between groups.