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While most dog breeds do well with anesthesia, brachycephalic dogs face a greater risk of complications. The term brachycephalic is Greek for "short head" and refers to dogs whose faces appear pushed in, such as bulldogs and pugs. Their unusual facial appearance can causes a number of changes to the dogs’ airways, a condition known as brachycephalic airway syndrome, which can lead to problems when they are anesthetized.
Brachycephalic Airway Syndrome
Brachycephalic airway syndrome describes four possible abnormalities in the respiratory systems of some brachycephalic breeds. Brachycephalic airway syndrome can include narrow nostrils (stenotic nares), longer and looser soft palate, narrowed windpipe (tracheal stenosis) or inside out ventricles on the larynx (everted laryngeal saccules). These conditions can cause obstruction of the upper respiratory system under normal conditions. If your brachycephalic dog has trouble cooling off by panting in the heat, she probably suffers from brachycephalic airway syndrome.
Sedating Before Anesthetizing
Because stress can increase upper airway obstructions in brachycephalic breeds, sedating your dog prior to the actual anesthetizing can help to reduce the risk of complications. However, too much sedative before the operation can depress the respiratory system too much. According to Dr. Stephanie Krein and Dr. Louis Wetmore of Tufts University, combining acepromazine (an anti-anxiety medication given to cats and dogs) with an opioid can be used to keep the dog relaxed without that risk.
Medications and Vagal Tone
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In addition to respiratory system abnormalities, brachycephalic breeds can have a high vagal tone. According to Merriam-Webster, the vagal tone refers to "impulses from the vagus nerve producing inhibition of the heartbeat." Therefore, if a dog has a high vagal tone, he has a reduced heart rate. Christina Braun, anticholinergics can be given to dogs before anesthetia to keep their vagal tone lower. These drugs also reduce saliva production, which can be useful as well.
Propofol is one of the drugs recommended for anesthetizing brachycephlic breeds. Dr. Lyon Lee of the Center for Veterinary Health Sciences points out that the drug is fast acting and leaves the body quickly. Using these types of drugs is preferable to using a mask for anesthetizing dogs who have brachycephalic airway syndrome. Once the dog is unconscious, the doctor should use small endotracheal tubes for intubation - the process of using tubes to keep the dog's airways open - because of the risk of tracheal stenosis (extremely narrow windpipe). Some brachycephalic dogs, particularly those who are obese or in critical condition, also may need ventilation, which can increase the risk of complications.
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According to Dr. Patty Khuly, more than half of dog deaths related to anesthesia actually occur post-surgery. In fact, she points out that the risks to brachycephalic breeds are greater during recovery than at other times in the process. Often the problem is caused by premature extubation - the removal of the tube that kept the dog's airways open. With dogs who have brachycephalic airway syndrome, removing the tube too early can cause an obstruction and if the dog is not being properly monitored during recovery, he can die from a lack of oxygen. Instead, extubation should not be done until the dog is conscious and alert.