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The art of anesthesia in brachycephalic dogs

The latest best practices and updates

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Anesthetic management of brachycephalic dogs presents challenges before, during and after any surgical, dental or radiographic procedure, and even under sedation. We asked Andrea Looney, DVM, Dipl. ACVAA, Dipl. ACVSMR, CCPR, of Massachusetts Veterinary Referral Hospital in Woburn, Mass., for guidance about best practices and recent updates.

Q: How can we minimize stress in brachycephalic dogs? 

A: There are many nonpharmaceutical ways to minimize stress: Keep them in a cool environment, plan surgery when temperature and humidity are lower, minimize restraint. Also consider the Fear Free initiative for ideas about reduction of pre-hospital stress.

If at all possible, once patients are in the hospital, avoid cages and allow patients a wider space, such as a corner of the treatment room or a playpen. Avoid collars and leash restraint as well. Try to perform surgery in the morning. Anxiety worsens respiratory distress by increasing respiratory rate and effort, further increasing movement and edema of laryngeal and pharyngeal tissues. This can compound dehydration after fasting.

Q: How about pharmaceutical options? 

A: When necessary, the drugs of choice for sedation, anxiety and stress reduction include dexmedetomidine, midazolam, butorphanol or a combination thereof. I’m not a fan of diazepam because its preservative, propylene glycol, decreases cardiac output in large doses and doesn’t allow for intramuscular administration.

Low-dose acepromazine—0.01 to 0.03 mg/kg with a maximum dose of 1 milligram, regardless of size—works well to relax smooth and striated muscle. However, in very stressed, hypoxic brachycephalic breeds, it has too long a half-life for comfort.

Dexmedetomidine is a great option for relaxation in these cases. It is sedating, reversible and can be used in combination with opioids. In most brachycephalics, try to sedate IM first, and then place an IV catheter. Restraint can cause overheating and stress in these patients, which worsens their respiratory distress.

At home or in the hospital, trazadone is a nice anti-anxiety drug to use pre- and postop in these dogs and in most anxious breeds.

Q: Is there a reason to take pre-op thoracic radiographs routinely in these dogs? 

A: Absolutely. They might reveal cardiomegaly—indicative of congenital heart disease or congestive cardiac disease—hiatal hernia or intrathoracic collapsing trachea.

They can also help rule out aspiration pneumonia, lung lobe torsion, collapsed lung or pulmonary edema before anesthesia is performed. If money is a concern, a simple lateral view is a good start. However, two orthogonal views would be ideal.

Q: What do you prefer in a brachycephalic dog who presents in a respiratory crisis? Sedation, tracheostomy or intubation? 

A: I would avoid a tracheostomy and intubation until absolutely required. Sedation usually results in better ventilation and oxygenation. Less induction agent will be required to intubate if and when the time comes. Sedation improves ventilation in several ways:

  • By increasing large and small airway diameter via relaxation of striated and smooth muscles.
  • By improving oxygenation via reduction of excess tissue movement. This increases FiO2 and the amount of oxygen reaching the distal airways.
  • By reducing ventilation/ perfusion mismatch.
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Q: Do you recommend a steroid injection or are you concerned about possible GI side effects? 

A: I like to administer dexamethasone SP (0.1 mg/ kg) to brachycephalics, then an NSAID the next day or low-dose prednisone for one or two days postop. At this low dose, it can always be repeated if further airway issues arise.

Personally, I have no major concerns about GI side effects with such a low dose. I don’t give antacids routinely in these patients. However, if there is any regurgitation intraoperatively, I like to flush the mouth and esophagus with warm saline or water, and then give famotidine IV.

Q: What are the pros and cons of giving prokinetic and anti-vomiting medications? 

A: I am a big advocate of using maropitant pre-op in these patients. In fact, I prefer to have patients come in to the hospital on it orally for a day prior. Maropitant has been proven to counteract the nausea induced by opioids and to reduce minimal alveolar concentration. In brachycephalic dogs, we strive to reduce any excessive vagal tone or GI issues, and this drug helps.

I also use metoclopramide (0.2 mg/kg) in some brachycephalic cases. However, I will not use it in patients with renal disease or pre-existing hypotension because it blocks dopamine receptors. Dopamine is an essential neurotransmitter for blood pressure and renal perfusion.

One more tip: I often combine butorphanol (0.1 mg/ kg) coupled with a pure mu agonist in my pre-med protocol of brachycephalic patients as a sedative—not an analgesic—an antiemetic and an antitussive to help with laryngeal and tracheal issues.

An elongated soft palate in a 10-month-old bulldog.

Q: How do you feel about anticholinergics in brachycephalics? 

A: I don’t like to use them routinely or as part of a “cookbook recipe” because they increase the viscosity of salivary and respiratory secretions when stickiness is already an issue in the larynx and pharynx.

Instead, I like to flush their oral cavity with saline or warm water once intubated, and avoid anti-cholinergics unless absolutely required, to increase heart rate to fight bradycardia-induced hypotension.

Glycopyrrolate can then be administered in increments of 0.005 mg/kg IV. Anticholinergics can also cause ileus, which we don’t need in these dogs, either.

Atropine is best reserved for CPR purposes in all anesthetized and critical care patients.

Q: Which opioids do you prefer for pain management? 

A: I would prefer hydromorphone (0.1 mg/kg), methadone, oxymorphone (0.1 mg/ kg) or fentanyl for severe pain, and buprenorphine (0.02 mg/kg) for mild pain. I frequently combine pure mu agonists with butorphanol (0.1 mg/kg) to reduce the chances of vomiting, and to add a sedative to the cocktail.

Methadone is useful because it causes little nausea or vomiting, but it’s expensive, difficult to find and carries a diversion potential.

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Fentanyl is the CRI drug of choice for these patients because of its titrability. It is usually used at lessened doses of 3 to 5 mcg/kg/hr intraop and 1 to 3 mcg/kg/hr postop.

Keep in mind that brachycephalic patients have a high degree of vagal tone to begin with, so the usual opioid doses may really worsen bradycardia and add to sleep and respiratory issues.

Since opioids can also cause anxiety and nausea, it is critical in brachycephalic patients to combine these with the appropriate sedative, such as midazolam, dexmedetomidine, butorphanol or even acepromazine as a last resort, to avoid adding stress and respiratory distress to these patients.

Q: Is there a proven benefit of pre-oxygenation before anesthesia? 

A: Most anesthesia nurses and anesthesiologists use it in hope that it denitrogenates the functional residual capacity of the lung and reduces the chances of cellular hypoxia, which occurs as induction drugs are delivered. However, there is little proof that it is valuable in helping these patients, especially when we have trouble getting oxygen to the lower airways, where gas exchanges actually occur.

Q: What is your favorite way to induce brachycephalic dogs? 

A: I use alfaxalone or ketamine and a benzodiazepine (midazolam). Another option is ketofol, which is ketamine and propofol mixed together in the same syringe—2 mg/kg of each.

Propofol used by itself can cause apnea. While these brachycephalic patients survive in near hypoxic environments, they cannot tolerate much hypercapnia, which the propofol will greatly add to.

Q: How do you judge the size of the endotracheal tube, since these dogs have hypoplastic tracheae? 

A: You can try to palpate the trachea, but it can be tough in brachycephalics. So I prefer to line up two or three tubes that are smaller than what’s expected on a weight basis for the patient, and I choose the logical size once I visualize the glottis at the time of intubation.

Another feature of endotracheal tube selection is not only the diameter but also the length of the tube. This is even more important in smaller brachycephalic patients. Endotracheal tubes should end at the thoracic inlet, keeping in mind that these patients have a short neck. Ideally, the endotracheal tube should be cut to minimize dead space. It should not extend much outside the mouth. Remember, both tube length and diameter are important in these patients.

Q: When do you recommend removing the endotracheal tube? 

A: Contrary to popular belief, leaving the tube in until the patient is swallowing and coughing may cause laryngeal spasm, gagging, regurgitation and nausea. I prefer to extubate once the patient has a blink reflex and jaw tone.

The more upper airway—nares, nasopharynx, pharyngeal, laryngeal—issues the brachycephalic patient has, the later the extubation should take place. That said, I still try not to initiate any gag response by keeping the tube in too long.

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On the opposite, lower airway issues such as hiatal hernia, collapsed lung volumes and hypoplastic trachea preclude sooner extubation after blink and jaw tone return. Gastric surgery patients, patients with esophageal disease and pancreatitis patients are examples of patients with increased regurgitation risks.

After extubation, I keep a close eye on the pulse oximeter, body temperature, anxiety and pain level, and reinduce or reintubate the patient if needed.

Q: When is it safe to feed these dogs? 

A: This depends on the surgery and the opioid given. If abdominal surgery is performed, I will feed them 12 to 18 hours postop. With orthopedic cases, patients should be fed as soon as they are awake and willing, paying close attention to vomiting, nausea and laryngeal issues.

Every patient is different, so it is difficult to predict which type of food is better.

Feeding small amounts of a high-fiber, high-protein meal frequently—every two to four hours—is better than feeding one to two daily meals in post-op patients. Reducing stress, walking regularly for bathroom breaks and offering fresh water with ice cubes to reduce heavy or rapid ingestion are essential for a return to normal motility.

Q: When are you comfortable sending them home after anesthesia? 

A: Pain and stress levels increase in the hospital. So it’s ideal to send them home as soon as possible, but this will depend on what surgery is performed and how clinical the patient actually is.

Brachycephalic patients are similar to humans with sleep apnea and respiratory issues.

Sending them home too soon can precipitate common periop complications such as regurgitation, hypoxemia, pain or distress.

However, keeping them too long creates anxiety, altered GI motility, stress and may even precipitate further hypoxemic or hypercapnic issues due to stress and sleep issues.

I prefer to send brachycephalic patients home within 24 hours postop for abdominal and upper airway surgery patients, and even less—six to 12 hours—for elective orthopedic procedures.

The respiratory cases—soft palate, et cetera—are the ones that fall in between. Exactly how long to keep the patient after surgery is an art as much as a science.

Resources

For more information on the Fear Free initiative, see these Veterinary Practice News articles by Dr. Phil Zeltzman:


Dr. Phil Zeltzman is a board-certified veterinary surgeon and author. His traveling practice takes him all over eastern Pennsylvania and western New Jersey. You may visit his website at www.DrPhilZeltzman.com and follow him at www.facebook.com/DrZeltzman. Columnists’ opinions do not necessarily reflect those of Veterinary Practice News. 

Chris Longenecker, CVT, of Reading, Pa., contributed to this article. 

Originally published in the June 2016 issue of Veterinary Practice News. Did you enjoy this article? Then subscribe today! 

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