ABSTRACT
OBJECTIVE: To compare the anti-nociceptive effect of tramadol, a combination of tramadol-lidocaine, and lidocaine alone when administered in the epidural space. STUDY DESIGN: Experimental randomized cross-over study. ANIMALS: Seven healthy male goats, aged 9-11 months, weight 17.5-25.5 kg. METHODS: Treatments were lidocaine, 2.86 mg kg(-1), tramadol-lidocaine (1 mg kg(-1) and 2.46 mg kg(-1), respectively) and tramadol (1 mg kg(-1)) given into the epidural space. The volume of all treatments was 0.143 mL kg(-1). Nociception was tested by pin prick and by pressure from a haemostat clamp. Times to the onset and duration of anti-nociception in the perineal region were recorded. Recumbency and ataxia were noted. Rectal temperature, heart rate and respiratory rate were recorded before and at 15 minute intervals for 2 hours after the administration of each treatment. Statistical comparison used one-way anova with a post hoc Duncan's test as a post hoc. Significance was taken as p < 0.05. RESULTS: Times (mean ± SD) to onset of and duration of loss of sensation, respectively in minutes were; lidocaine, 3 ± 1 and 85 ± 11), tramadol-lidocaine 4 ± 1 and 140 ± 2; tramadol 12 ± 1 and 235 ± 18. Onset and duration times were significantly longer with tramadol than the other two treatments. Duration was significantly longer with tramadol-lidocaine than with lidocaine alone. With lidocaine treatment all goats were severely ataxic or recumbent, after tramadol-lidocaine mildly ataxic, and after tramadol not ataxic. Rectal temperature, heart and respiratory rates did not differ significantly from baseline after any treatment. CONCLUSIONS AND CLINICAL RELEVANCE: The combination of tramadol-lidocaine given by epidural injection produced an anti-nociceptive effect in the perineal region, which was rapid in onset and had a longer duration of action than lidocaine alone. This combination might prove useful clinically to provide analgesia in goats for long-duration obstetrical and surgical procedures but surgical stimuli were not investigated in this study.
