GENERAL ANAESTHESIA OF SHEEP LAMBS USING FOUR SELECTED ANAESTHETIC PROTOCOLS

Abstract

This study was conducted using 16 healthy sheep lambs to investigate the reliability and safety of selected general anaesthetic protocols namely:- 1) xylazine Hcl + ketamine Hcl 2) xylazine Hcl + thiopentone sodium 3) medetomidine Hcl + ketamine Hcl 4) medetomidine Hcl + thiopentone sodium The animals were randomly divided into two groups, eight animals in each group. Xylazine Hcl (XY) at a dose rate of 0.05 mg/kg and medetomidine at a dose rate of 10 micro-grams/kg were used as pre-anaesthetic medications and were injected intravenously. Ketamine hydrochloride at a dose rate of 2 mg /kg and thiopentone sodium (TH) at a dose rate of 10 mg/kg were used as anaesthetic agents in the above mentioned anaesthetic protocols and were injected intravenously. Respiratory rate, heart rate and rectal temperature were monitored using standard methods. The different phases of anaesthesia (anaesthetic phase, narcosis phase, lateral recumbency phase, sternal recumbency phase, standing phase, and total recovery time) were monitored and recorded. Regaining times of selected reflexes (Palpebral, pedal, swallowing, cough and tongue reflexes) were also determined. Respiratory rate was found to be non-significantly affected following induction of anaesthesia with all protocols except when medetomidine was used in combination with ketamine Hcl. Induction of anaesthesia with the different selected anaesthetic protocols resulted in a significant bradycardia. Rectal temperature was found to be non-significantly affected with all protocols except when xylazine was used in combination with thiopentone sodium. The anaesthetic protocols involving either xylazine or medetomidine with thiopentone sodium resulted in a significant prolongation of the duration of anaesthetic phase and the total recovery time when compared with other tested protocols. A significant difference in the duration of the narcosis phase was observed with the anaesthetic protocol xylazine – thiopentone sodium. The mean regaining times of the pedal and tongue reflexes were found to be of significantly longer durations with both xylazine – thiopentone sodium and medetomidine - thiopentone sodium anaesthetic protocols. Palpebral, cough and swallowing reflexes were shown to persist throughout the course of anaesthesia with xylazine-ketamine. Apnea was reported only with xylazine – thiopentone sodium and medetomidine - thiopentone sodium anaesthetic protocols. This study confirmed the fact that all anaesthetic protocols proved to be safe in sheep since a single death case was not reported. Ketamine Hcl - containing anaesthetic protocols were shown to be of very negligible effects on respiration and hence they are relatively more safer than thiopentone sodium containing protocols.