Influence of Tramadol on Anaesthetic Indices and Physiological Parameters of Epidural Lignocaine in West African Dwarf Sheep Undergoing Laparo-Ovariectomy

Summary: The influence of tramadol on the anaesthetic indices and physiological parameters of epidural injection of lignocaine was evaluated in West African Dwarf (WAD) sheep undergoing laparo-ovariectomy. Ten female sheep weighing (16.2 ± 1.3 kg) were randomly allocated into anaesthesia with epidural injection of lignocaine (4mg/kg) (LIG), or lignocaine (2mg/kg) and tramadol (2mg/kg) (LIG-TRA). Following anaesthesia, they were aseptically prepared and subjected to laparo-ovariectomy. Behavioural changes were noted as they occur, and onset of drug action (OAN) (time between epidural injection and loss of pedal reflex), duration of analgesia (DAN) (time between disappearance and reappearance of pedal reflex) were determined. Also, duration of recumbency (DRC) (time between loss of righting reflex and returns to sternal recumbency) and recovery time (RCT) (time between re-appearance of pedal reflex and when the animal was able to stand without ataxia) were determined. Rectal temperatures (RT), respiratory rates (RR) and heart rates (HR) were determined every ten minutes for two hours. Results were expressed as mean ± standard error of mean. Anaesthetic indices were compared with Student’s t-test, while physiological parameters were compared with analysis of variance (ANOVA) for repeated measures. In this study, one sheep anaesthetized with LIG-TRA had bloat while none in sheep anaesthetized with LIG had bloat. The OAN was significantly (p < 0.05) shorter in LIG-TRA (1.4 ± 0.5 mins) than with LIG (4.4 ± 2.8 mins). Although DAN and DRC were longer in LIG-TRA (133 ± 19.5 mins, 192.6 ± 43.6 mins) than LIG (119.4 ± 52.5 mins; 166.2 ± 30.6 mins) respectively, values were not statistically significant (p = 0.863). In addition, RCT was longer in LIG-TRA (56.0 ± 48.6 mins) than LIG (34.0 ± 20.6 mins). The RT, RR and HR did not differ significantly (p > 0.05) between LIG-TRA and LIG, and as well as throughout the duration of study. It was therefore concluded that tramadol did not appear to improve the anaesthetic indices of epidural lignocaine injection in sheep but increased the duration of recumbency with the tendency to cause bloat.