By Stephanie Krein, DVM, DACVAA
Angell Animal Medical Center
Brachycephalic breeds, including Pugs, French bulldogs, English bulldogs, American bulldogs, and Boston Terriers, can be some of the most difficult animals to anesthetize and present unique challenges that do not exist amongst other breeds. This article will discuss the anatomic and physiologic differences that can affect the outcome of anesthesia and ways to deal with these differences.
Brachycephalic dogs have anatomic considerations that may affect anesthetic outcome (1). Many brachycephalic breeds suffer from brachycephalic airway syndrome (BAS) which includes the presence of stenotic nares, elongated soft palate, everted laryngeal saccules, and hypoplastic trachea and have narrower and smaller upper airways than dogs with a normal anatomy (2, 3, 4). These narrow airways increase resistance and the work of breathing. This becomes particularly important during times of stress when the respiratory rate increases and the flow becomes turbulent, further increasing the work of breathing. It is important when anesthetizing a brachycephalic dog to be prepared at all times for upper airway obstruction. These dogs must be monitored closely after premedication, throughout anesthesia, into the post-operative period, and after extubation into the recovery period. An oxygen source and endotracheal tube should always be readily available, even after extubation. Regurgitation or reflux is always a concern when sedating or anesthetizing brachycephalic dogs and one should be prepared if this should happen. Preventative measures should be taken with all brachycephalic dogs undergoing sedation or anesthesia, although these measures have not been shown definitively to reduce regurgitation. Steps that can be taken in attempts to prevent regurgitation include adding metoclopramide to the premedication, administration of Cerenia at least one hour prior to premedication, and the addition of other centrally acting antiemetics such as dolasetron or ondansetron to the protocol. Although these additions have not been shown to reliably reduce regurgitation they do reduce nausea and vomiting associated with drugs and anesthesia and this ultimately will lead to a better anesthetic experience for both the dog and their owner.
Designing the perfect anesthetic protocol for brachycephalic dogs can be difficult to say the least. The proper sedation should allow the patient to breathe slowly and calmly without causing excessive respiratory depression. Many brachycephalic dogs respond well to sedatives such as acepromazine or dexmedetomidine in conjunction with an opioid, but the sedative dose should be half of what is used in the non-brachycephalic dog. Full mu opioids can be used but may cause excessive respiratory depression so a reversal agent should be available. Butorphanol, a kappa agonist and mu antagonist opioid, can be used and provides reliable sedation but short acting analgesia. Buprenorphine, a partial mu agonist, provides moderate analgesia and minimal sedation and can also be used as part of the premedication. Dexmedetomidine, an alpha-2 agonist, may be used in these dogs if no cardiovascular disease exists but due to the presence of high vagal tone the dose used should be reduced. Dexmedetomidine when used in lower doses provides good sedation, is fully reversible, and provides analgesia (6). Acepromazine, a phenothiazide sedative, is commonly used in many brachycephalic breeds due to its anxiolytic properties. Acepromazine provides reliable sedation in these dogs but is not reversible so should be used in low doses. There are several websites stating that acepromazine cannot be used in French bulldogs but these websites are not backed by any reliable scientific evidence or studies and should be followed with caution. In fact, French bulldogs are often highly stressed and excited when presenting for anesthesia and can actually benefit from the addition of acepromazine to the protocol. The goal of premedication in brachycephalic dogs is to provide enough sedation and anxiolysis to allow intravenous catheter placement with minimal stress.
The induction agent chosen should allow for smooth rapid induction and intubation thereby protecting the airway and providing a source of oxygen as quickly as possible. The induction agent should also allow for rapid loss of consciousness and rapid return of consciousness. There are several induction agents that can be chosen including propofol or alfaxalone. Preoxygenation is always recommended before induction of dogs with BAS (3, 4, 5). Intubation should be performed as rapidly as possible and mask inductions should be avoided (4, 5). Due to the everted laryngeal saccules and small tracheal size, most BAS breeds require a smaller size endotracheal tube than would be expected for a patient of the same weight so it is important to have a large variety of sizes of endotracheal tubes available during induction (7). Due to the common occurrence of obesity in brachycephalic breeds, controlled or mechanical ventilation is often necessary. It is not uncommon for regurgitation to occur during the induction period and it is of good practice to have active suction available for rapid suction of the airway. The intra-operative period is usually similar to that of other breeds, although if surgery is to be performed on the airway itself it may be indicated to administer an injectable steroid such as dexamethasone to reduce post-operative swelling.
Most problems occur during the induction and recovery periods and this is a particular problem in the recovery period when patients are poorly monitored. It is important to postpone extubation until the patient is bright, alert, swallowing, and even chewing on the endotracheal tube (5). If extubation is attempted while the patient is sedate and groggy from anesthesia there is an increased risk for upper airway obstruction. If an upper airway obstruction does occur, the patient may need to be reintubated so extra laryngoscopes, induction agent, and tubes should be available. Once extubation occurs the patient should be observed for breath sounds and signs of obstruction such as inflation of the abdomen with collapse of the thorax on inspiration and lack of breath sounds. The patient should be placed in sternal recumbency during recovery and pulse oximetry should be monitored as long as possible. The airway may also be opened by extending the head, opening the mouth and pulling out the tongue of the patient. It is often enough just to prop up the head of the patient maintaining a patent airway while they are still groggy. If reversible sedatives were used then the antagonist can be given to try and lessen the sedation levels. Once the patient is taking good breaths and awake they should be monitored closely for the next few hours or transferred to the intensive care unit. Brachycephalic patients should never be left alone in the recovery period. The key to a successful anesthetic recovery is a calm, comfortable patient and a calm, prepared anesthetist. Although sedation and anesthesia of BAS patients can be difficult and stressful, with proper precautionary steps and drug choice it can be done safely and successfully.
For more information, please contact Angell’s Anesthesiology Service at 617-541-5048 or firstname.lastname@example.org.
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