Does the induction agent affect the course of halothane anaesthesia in horses?

The confidential enquiry into perioperative equine fatalities (CEPEF): mortality results of Phases 1 and 2

“…It has been widely reported that death in colic horses is not entirely unexpected because of the existing disease process (Tennant et al 1972;Pearson et al 1975;Huskamp 1982;Ducharme et al 1983;Parry 1983;Pascoe et al 1983;Reeves et al 1986;White & Lessard 1986;Phillips & Walmsley 1993). The information from this large, multicentre data set is in general agreement with several smaller single clinic studies in reporting a death rate of around1% of horses undergoing routine anaesthesia (Mitchell1969; Lumb & Jones1973;Tevick1983; Clarke & Gerring 1990;Young & Taylor 1993, Mee et al 1998a. CEPEF has now con¢rmed beyond all reasonable doubt that equine anaesthesia carries a high risk of mortality and merits further investigation into the causes and remedyof this risk.The data presented have highlighted a number of factors associated with an increased risk of anaesthetic-related death which should allow a rational approach to attempts to improve the mortality rate.…”

“…A combination of diazepam and ketamine or guiaphenesin and thiopentone were the most commonly used, but a few others such as thiopentone or ketamine alone, and guiaphenesin and ketamine were also used on occasion (Table 7). Taylor & Young (1993) reported that the induction agent had little affect on the course of halothane anaesthesia and considered that the overwhelming cardiovascular depressant effects of halothane outweighed any minor effects of the induction agents. This view is supported by the data from CEPEF.…”

“…However, experience from many equine clinics indicates a notable mortality rate in horses without systemic illness undergoing routine surgery. A number of reports from single clinics report a mortality rate in horses between 0.63 and 1.8% which increases up to 5% if systemically ill animals are included (Mitchell 1969;Lumb & Jones1973;Tevik1983, Clarke & Gerring 1990Young & Taylor 1993;Mee et al1998a,b). These data were collected from retrospective analysis of clinic records over 3^5 years.…”

Equine anaesthesia-associated mortality: where are we now?

“…Recovery quality is influenced by the same factors that affect mortality [age, ASA physical status, surgery, body position, anaesthesia duration and out‐of‐hours surgery (Young & Taylor ; Taylor & Young ; Dugdale et al. )].…”

“…The longer the period of anaesthesia maintenance with volatile agents, the less likely the anaesthetic induction agents are to affect the course of anaesthesia and recovery (Taylor & Young ) . A recent abstract reported poorer recoveries in six horses when midazolam was used in conjunction with ketamine for anaesthesia induction than when propofol was used in conjunction with ketamine, before 1 hour of isoflurane anaesthesia (Jarrett et al.…”