References
Monitoring anaesthetics in exotics
Abstract
Anaesthetic death rate is higher in exotic patients than in dogs and cats. Unfamiliarity with monitoring and inability to intubate are frequently cited reasons for higher death rate. Ability to hide signs of illness, and fewer healthy, elective aneasthetic procedures likely influence death rate as well. Direct vascular support can be challenging. For some patients, small size or unique anatomic features present unique challenges. Sophisticated monitoring equipment (e.g. capnographs, blood pressure monitors) designed for canine/feline use must often be adapted for exotic patients, and is more likely to fail when used in exotic patients. For this reason, the anaesthetist must develop a plan for addressing equipment failure, and have a backup monitoring device ready, if applicable. Anecdotally, it appears that changes in respiratory and cardiovascular parameters may occur more rapidly than in canine and feline patients. While careful patient preparation and monitoring are important for any anaesthetic patient, particular attention to detail may help improve anaesthetic survival rate in exotic species.
A recent survey of veterinary hospitals in the UK indicated that anaesthetic death rate was higher in all exotic patients than in dogs and cats (Brodbelt et al, 2008). Amongst studied species, sample death rates were listed as: dogs, 0.17%; cats, 0.24%; rabbits, 1.39%; guinea pigs, 3.8%; rats, 2.01%; budgerigars, 16.33%; and reptiles, 1.49%. Reasons listed by survey participants as possible explanations for exotic patient deaths included unfamiliarity with monitoring, and inability to intubate. While principles for patient monitoring are the same for all patients, applying these to exotic patients requires experience, practice, and some modifications in both technique and equipment.
Pre-surgical patient preparation includes the gathering and organisation of all monitoring equipment, heat sources, emergency drugs and other supplies prior to induction of anaesthesia. Vascular support (intravenous (IV) or intraosseous (IO) catheterisation) is recommended for all patients undergoing anaesthesia, but especially for surgeries expected to last beyond 20 minutes, and for ill or unstable patients. Catheterisation is straight forward in rabbits and ferrets, and moderately challenging in larger guinea pigs. In smaller patients where vascular support is desired, IO catheterisation can be utilised using the humerus, femur or tibia in mammals and reptiles with legs, and distal ulna or proximal tibiotarsus in birds (Figure 1) (Gunkel and Lafortune, 2005)). Catheterisation is described in detail elsewhere.
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