Anaesthesia of cats and dogs with cardiac disorders: the veterinary nurse's role

Cardiac disorders are a particularly important consideration in anaesthesia because many of the main side effects of most analgesic and almost all anaesthetic drugs is cardiovascular depression. In turn, heart diseases can have pharmacokinetic effects on the drugs utilised, for example poor peripheral perfusion may result in lowered drug bioavailability after sub-cutaneous or intra-muscular injection (Clutton, 2007). Heart disease can be evident in veterinary patients in many forms so it is first important to ascertain the nature of the problem. An understanding of the anatomy and physiology of the cardiovascular system is also important to critically evaluate how different anaesthetic and analgesic drugs will affect the system, and whether these effects will be beneficial or detrimental to different heart diseases. There is no single protocol that will be effective in all patients with heart disease due to the differing pathophysiology of these disorders. There are differing opinions on drugs for use in cases with heart disease between specialist veterinary anaesthetists and the recommendations provided by textbooks and continuing education articles are generally based on personal opinion as there is an extremely limited clinical evidence base. Often drugs and drug combinations that are recommended in these cases are unlicensed and veterinary surgeons and nurses may have limited experience of their use and side effect profiles. A prime example of this is the induction agent etomidate which is often recommended, but not licensed or widely available in the UK (Figure 1).