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ItemA comparison of the incidence of apnoea following induction of anaesthesia with propofol or alfaxalone in dogsBigby, Sarah Elizabeth ( 2018)Animals are often given combinations of drugs that produce sedation prior to the use of agents that induce general anaesthesia. Following sedation, induction of general anaesthesia can cause a period of apnoea (cessation of ventilation) which is commonly referred to as post-induction apnoea. If post-induction apnoea persists it can pose significant risk to animals undergoing anaesthesia. This thesis examines the effect of intramuscular premedication drugs acepromazine and dexmedetomidine combined with methadone, commonly used to produce sedation in canines prior to anaesthesia, and the effect of the anaesthetic induction drugs propofol and alfaxalone on the incidence and duration of post-induction apnoea in healthy dogs. In addition, the effect of the rate of administration of propofol and alfaxalone on the incidence and duration of post-induction apnoea in healthy dogs is also described. Prospective, randomised clinical trials identified no difference in effect of the premedication drugs acepromazine and dexmedetomidine on post-induction apnoea when using propofol or alfaxalone. The results of the trials conducted also did not identify a difference in incidence or duration of post-induction apnoea following either propofol or alfaxalone; however, a significant effect of rate of administration of these drugs on incidence and duration of post-induction apnoea was detected. The duration of apnoea following propofol or alfaxalone was significantly longer when these drugs were given rapidly. Based on these findings, propofol and alfaxalone cause significant post-induction apnoea and the rate of administration of both drugs should be reduced where possible. The incidence and duration of apnoea does not appear to be influenced by the use of acepromazine or dexmedetomidine in combination with methadone for premedication. Monitoring of respiration is recommended when using these premedication and induction agent combinations.