Reported morbidities following 861 anaesthetics given at four equine hospitals.

POSTANAESTHETIC morbidity prolongs convalescence, thus increasing costs to the client, and can lead to death. Most information available on postanaesthetic morbidity in horses relates to musculoskeletal disorders, such as postanaesthetic myopathy or fractures (Richey and others 1990, Young and Taylor 1993). More recently, the prevalence of postanaesthetic colic after non-abdominal procedures has been estimated retro spectively (Senior and others 2004, 2006, Andersen and others 2006). Information relating to other types of postanaesthetic morbidity is scarce. This short communication describes a multi-centre prospective study conducted to estimate the prevalence of and identify risk factors for reported morbidities in horses undergoing non-abdominal procedures at four equine hospitals in the UK. The hospitals were chosen on the basis of staff affiliations and their ability to record data and to reflect different horse populations and caseloads. Data were collected prospectively on all horses admitted to each centre for non-abdominal procedures requiring general anaesthesia between April 2004 and June 2005. The in-house data collection systems at each of the four centres were modified to incorporate the additional admission, hospitalisation and discharge data required for the study. Case definitions of specific morbidities were agreed at the beginning of the study by the participating centres (Table 1). At the end of the study, the records at each centre were collated by one investigator (R. A.). Data were collected from a total of 861 anaesthetics. The frequency of each type of morbidity is shown in Table 2. The overall prevalence of reported morbidities was 13·7 per cent; the most commonly reported morbidity was post anaesthetic colic (5·2 per cent), defined as any recognised sign of abdominal pain (Tinkler and others 1997) that could not be attributed to any concurrent disease. In 31 of the 45 colic cases (68·8 per cent) the cause of the signs of colic was undiag nosed, so it is possible that some cases were misdiagnosed even though a large proportion responded to medical therapy for colic. Postanaesthetic lameness, for example, due to myopathy, neuropathy or fractures, was reported in seven cases (0·8 per cent); this is in contrast to previous, retrospective, estimates of prevalence of 1·4 per cent (Young and Taylor 1993) and 6·4 per cent (Richey and others 1990). However, the results from previous studies may be outdated; it is widely considered that improved understanding of the risk factors involved in the development of postanaesthetic myopathy, and the availability of more effective prophylactic measures, appears to have reduced the incidence of postanaesthetic lameness. The present study appears to support this theory. The prevalence of some of the morbidities varied between the centres. There were two mortalities that were directly related to the anaesthesia. One horse died from a fractured neck, and one horse was euthanased because of a fractured left proximal humerus, giving a mortality rate of approximately 0·2 per cent.