References
Endotracheal intubation of small exotic mammals
Abstract
The veterinary nurse or technician plays an important role in avian and exotic anaesthesia, often inducing, intubating, and maintaining an anaesthetic while the veterinary surgeon prepares for a procedure. Gone are the days of avian and exotic specialists being the only source of veterinary care for companion rodents; with an increase in the ownership of these species comes an increase in general practitioners undertaking routine or preventative health procedures. Owners of these pets expect the same standard of care afforded to dogs and cats, and consequently veterinary staff may be required to provide the same standard of intensive anaesthetic management. Successful anaesthetic management requires an awareness of patient limitations, and one such limitation in small exotic mammals is the difficulty of endotracheal intubation. Intubation allows for better respiratory control while minimising the risk of aspiration and is particularly important for procedures lasting longer than 30 minutes, during which hypoventilation and respiratory obstruction are most likely to occur. Regardless of procedure length or complexity, intubation should be the routine standard of care if it can be done in a swift and safe manner.
Guinea pigs and rabbits are obligate nasal breathers that are unable to regurgitate, and therefore have a minimal risk of aspiration under general anaesthesia (Cantwell, 2001). This unique physiological trait has been a longstanding reason for the use of an appropriately fitting face mask for the provision of oxygen and inhalant anaesthetic in place of an endotracheal (ET) tube. However, using a face mask in these species on the basis that they cannot regurgitate negates the many other benefits of intubation. Tracheal intubation is indicated for maintaining and controlling a patent airway in an unconscious patient and to provide mechanical ventilation in a hypoventilating or apnoeic patient (Cantwell, 2001). Intubation also allows for the use of airway monitors and for an unobstructed surgical approach to the cranial aspect of a patient (Johnson, 2010). However, intubation is easier said than done. Rodents and rabbits have a small oropharyngeal cavity, large tongue, large molars, a large soft palate that obscures the epiglottis, a small larynx, a predisposition to laryngospasm and profuse respiratory secretions that can contribute to the risk of aspiration (Johnson, 2010). Guinea pigs also have a palatial ostium; the soft palate and tongue are continuous, forming a ring of tissue between the pharynx and oropharynx. This tissue is highly vascular and can become easily traumatised, resulting in profuse haemorrhaging (Cantwell, 2001). Difficult, prolonged, or traumatic intubation can result in laryngeal or tracheal inflammation, which can lead to obstruction and death. To minimise the risk of this iatrogenic damage, intubation attempts should be limited to two or three tries (Pollock, 2011).
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