Description
Brachycephalics patients are a commonly encountered within veterinary practice, and require special consideration for anaesthesia due to the anatomical abnormalities which feature in these breeds. These abnormalities include: stenotic nares, an elongated soft palate, laryngeal collapse, hypoplastic trachea, and laryngeal saccule eversion. These abnormalities have been grouped together into what is known as brachycephalic syndrome. Clinical signs of brachycephalic syndrome are typical of upper airway obstructive disease and can include stridor, snoring, exercise intolerance, cyanosis and collapse.When selecting pre-anaesthetic agents for these patients it is preferable to avoid those which may cause deep sedation as this can be associated with excessive relaxation of the upper airway muscles and result in worsening of obstruction. Any sedatives administered should be used at low doses.Analgesic agenst should be selected for all surgical procedures, e.g. opioids, and should not be avoided due to concerns over respiratory depression, that said, as with all patients, brachycephalics should be closely observed once premedicants have been administered. Brachycephalic breeds tend to have a higher vagal tone than other breeds. Impulses from the vagus nerve result in parasympathetic effects such as bradycardia, bronchoconstriction, and excessive saliva formation. For these reasons it would be worth calculating the dosage of an anticholinergic should these effects become severe. It is highly recommended that brachycephalic patients are "pre-oxygenated" prior to induction of anaesthesia. Administration of 100% oxygen before induction of anesthesia prolongs the time to onset of arterial hypoxemia. This technique increases the body's oxygen stores, primarily in the functional residual capacity (FRC) of the lungs. Induction should be rapid in order to gain control over the airway. When intubating a brachycephalic patient, expect to use a much smaller endotracheal tube, a wide variety of tube sizes should be selected. A laryngoscope is a necessary tool for intubation, as the amount of redundant tissue in the pharynx may reduce the visibility of the laryngeal opening. While under anesthesia patients can be maintained with inhaled anesthetic such as isoflurane or sevoflurane in 100% oxygen. Sevoflurane is metabolized faster than isoflurane allowing for a faster recovery. This may be an attractive choice when anesthetizing a brachycephalic patient. The recovery period is critical time for all patients undergoing anaesthesiam but particularly for the brachycephalic breeds. The timing of extubation in these patients is an important factor in the recover of these patients and it is important to remember that brachycephalics can sometimes desaturate during recovery, so a portable pulse oximeter is a useful tool during this period. Brachycephalic ideally should be recovered in sternal recumbency with their head slightly elevated. Many clinicians like to wait for brachycephalic patients to be awake and reacting to the presence of an endotracheal tube before it is removed. It is important to have additional induction agent and additional endotracheal tubes ready in recovery in the event that airway obstruction and re-intubation is needed.