Endotracheal intubation of small exotic mammals (Proceedings)

ADVERTISEMENT

Endotracheal intubation of small exotic mammals (Proceedings)

May 01, 2011

Intubation provides better airway control than a face mask and minimizes the risk of aspiration. This is especially important for complex and prolonged procedures, when complications such as respiratory obstruction and hypoventilation are more likely to occur. Rabbits and rodents are difficult to intubate. They have a large tongue, large molars, a small larynx, and a soft palate that easily obscures the epiglottis. While intubation of small mammals is difficult, it should be the routine standard of care all patients as long as it can be done quickly and safely.

Indications

Endotracheal intubation is the placement of a tube that extends from the oral cavity into the trachea. It is indicated for the administration of oxygen and inhalation anesthesia, to ensure a patent airway in unconscious patients, to provide ventilatory assistance, and to provide a conduit into the trachea to permit diagnostic and therapeutic measures (e.g. endoscopy, tracheal wash, direct instillation of medications).

Intubation methods

Various intubation techniques have been suggested for small mammals. Some of these require specialty equipment, and all require practice. Intubation methods can be divided into those that are performed blind or with visualization of the larynx.

Blind Intubation

By properly positioning the head and neck, the pathway from the oropharynx to the trachea is straightened so that an endotracheal tube can be placed without direct visualization of the larynx. This is possible with the aid of laryngeal palpation, patient response (i.e. coughing, gagging), and listening for patient respiration through the endotracheal tube itself. Under special circumstances, a transtracheally-placed catheter may be used as a guide.

Visual Intubation

Divided into direct visualization and indirect visualization of the glottis.
     • Direct Visualization- Visualization of the larynx is aided by hyperextension of the head and neck. Usually an assistant must open the mouth with gauze placed around the upper and lower incisors, or an oral speculum is used. A small bladed laryngoscope (e.g. Miller 0 neonatal laryngoscope blade) is used to depress the tongue and elevate the soft palate. Once the vocal folds are visualized, the tube is placed. An atraumatic stylet (such as a polypropylene catheter) can be placed through the tube so its tip extends beyond the end of the endotracheal tube. Being narrower than the endotracheal tube, the stylet tip will fit easily into the trachea and help to guide the tube through the vocal folds. A canine otoscope can be used instead of a laryngoscope in smaller patients. After adequate visualization is achieved, a 5 French polypropylene urinary catheter is guided down the otoscope between the vocal folds and advanced into the trachea. At this point, the otoscope is removed and the tracheal tube is threaded over the catheter and into the larynx. The catheter guide is then removed.
     • Indirect Visualization- Visualization of the trachea can also be achieved using an endoscope. The endoscope is positioned so the larynx is in view, and an endotracheal tube is passed parallel to the scope and into the trachea. Further, with some scopes it is possible to put endoscope directly inside the endotracheal tube like a stylet, and to visually guide the scope/tube assembly into the trachea.

Endotracheal tube size/style for selected species
     • Ferret: 2-2.5mm ID (Cole or Murphy)
     • Rabbit: 2-3.5 ID (Cole or Murphy)
     • Prairie dog: 2-2.5mm ID (Cole or Murphy)
     • Guinea pig: 8-fr (urinary catheter), 2-2.5mm ID (Cole or Murphy)
     • Hedgehog: 1.5 mm ID (straight silicone)
     • Sugar Glider: 1.5 mm ID (straight silicone)
     • Chinchilla: 8-fr (urinary catheter)
     • Rat: 14ga (IV catheter)