P. 512

An Urban Experience
L. O’Dwyer1
1VetsNow, Anaesthesia & ECC, Manchester, United Kingdom
Louise O’Dwyer MBA BSc(Hons) VTS(Anesthesia&ECC) DipAVN(Medical & Surgical) RVN
Clinical Support Manager, VetsNow, Manchester, U.K.
Brachycephalics are 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.
Anaesthesia of dogs suffering from Brachycephalic Obstructive Airway Sydrome (BOAS) should be managed using a. minimal sedative premedication, pre-oxygenation and rapid intubation following induction. The problem with these dogs is often in the recovery period, as they reach a point where they are suf ciently ‘light’ that they will start to chew the ET tube, but not suf ciently awake that they can adequately maintain a patent airway. It is essential in these patients to realise a rapid recovery
with minimal hangover, so appropriate drugs should be selected to achieve this - this means avoiding long-acting drugs (such as acepromazine) or using only very low doses, and perhaps choosing a maintenance agent with a fast recovery pro le (e.g. sevo urane; although we use des urane for these cases, as recovery is even faster).
Irrespective of the species, upper airway abnormalities result in a reduction in airway diameter and an associated increase in upper airway resistance. To compensate
for the latter, a greater negative intrathoracic pressure
is created to generate adequate inspiratory air ow. In addition to the increase in the work of breathing, the dynamic pressure changes can further exacerbate the collapse of upper airway structures into the air passages and further increase the airway resistance. In severe cases, airway dysfunction is associated with in ammation and oedema of the pharyngeal tissues. In addition to the respiratory problems, cardiovascular and gastrointestinal abnormalities may be present in brachycephalic animals.
Of the abnormalities listed above the most commonly seen with brachycephalic breeds are stenotic nares and an elongated soft palate. Stenotic nares is a condition
in which the nostrils are malformed. These nostrils are narrow and sometimes collapse inward during inhalation making it dif cult for the patient to breathe through their nose. An elongated soft palate is a condition where the soft palate is too long and the tip of it protrudes into the airway and interferes with inspiration of air into the lungs. Brachycephalic breeds tend to learn to compensate
for these respiratory insuf ciencies, but sedation and anaesthesia remove these compensatory mechanisms. It then becomes the job of the anaesthetist to monitor and protect the airway.
Adequate pre-anaesthesia planning for these patients
is essential. The aim of the preoperative evaluation is to determine if there is any disease present that will affect the uptake, action, metabolism, elimination, and safety of the anaesthetic. Primarily the cardiopulmonary, nervous, renal and hepatic are the systems of greatest concern. The history and physical examination are the best determinants of disease. Laboratory tests should only be performed on the basis of history/physical examination. It has been shown that the use of extensive laboratory screening has not improved outcome in human or veterinary medicine.
The reference ranges, ‘normal’ for laboratory tests
are presumed to be within +/- 2 standard deviations
of the mean, and therefore 5% of normal animals fall outside this range. The upper and lower values do not represent a cut off between normal and disease. Indeed, a normoglycaemic diabetic, or an animal with cirrhosis with normal hepatic enzymes and bilirubin will seem unremarkable on screening and therefore fall into the ‘normal’ category when that is far from the case.
Brachycephalic breeds are particularly prone to airway obstruction during the perianesthetic period. They are prone to obstruct and die if left unattended after having been given sedatives or anesthetic drugs. Short-acting agents that leave little residual drug effect should allow these dogs to wake up rapidly and get back airway control. These cases are high risk and should be labor intensive to ensure a good outcome.
Deep sedation of these patients can be associated
with excessive relaxation of the upper airway muscles and worsened airway obstruction. Unless a patient is aggressive or dangerous to you, use lower doses of premedications. Also note that analgesic agents should always be used for surgical procedures. Opioids are
the most frequently used pre-anaesthetic analgesic agents. Opioids are not contraindicated simply because the patient is brachycephalic. Although it is thought

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