Let’s talk about Frenchies (aka: brachycephalic anesthesia)!
Article by Elana Rybak, DVM, cVMA
Brachycephalic breeds have a plethora of health issues that can affect anesthesia and increase anesthetic complication risk. One of the most common issues is regurgitation in the perianesthetic period, in addition to upper airway obstruction and overheating (usually due to panting). French bulldogs also commonly have some degree of hiatal hernia present which can also exacerbate regurgitation.
Your patient:
Gretta is a 3-year-old FS French Bulldog that is presenting to your service for hind limb ataxia. Gretta is also painful around her TL spine on palpation. After evaluation by the neurologist, an MRI of the thoracolumbar spine is recommended to investigate the source of her clinical signs.
Pre-Pre-medications - Cerenia:
Before we give any other medications (if at all possible), our first goal is to get Cerenia (Maropitant) into our patient. In our practice, Cerenia is given to every anesthetic case, and almost all of our sedated procedure cases. Cerenia is a selective Neurokinin-1 receptor antagonist that inhibits the binding of substance P to NK-1 receptors, which centrally prevents triggering of the emesis center of the brain. Cerenia is a powerful antiemetic that works against both peripheral and central emetogens. It has been shown to improve post-anesthetic return to eating, and may decrease MAC requirements of inhalant anesthetics. It also may have some visceral analgesic effects which makes it a helpful adjunct for intra-abdominal procedures.
If a client has cost concerns, oral cerenia given the night before or morning of an anesthetic event can be used instead of injectable Cerenia. There is added benefit to this practice if the patient gets motion-sickness from the car ride to the clinic!
What about Ondansetron to prevent vomiting? Ondansetron is a 5HT3 serotonin receptor antagonist that mostly acts peripherally with some central effects. In one study comparing Ondansetron to Maropitant for hydromorphone-induced nausea and vomiting in dogs, Maropitant was superior in preventing nausea and vomiting, whereas Ondasetron was effective in preventing nausea but less so vomiting. Therefore, especially for Brachycephalic breeds, Cerenia is the anti-emetic of choice (and you could certainly use both medications together if needed!)
Pre-Pre-medications - ‘Brachycephalic Protocol’:
Our practice has also adopted a standard ‘Brachycephalic protocol’ of medications that we give prior to anesthetic induction (and before pre-medication if possible). Since many Brachycephalics are prone to regurgitation and aspiration, we always give a dose of Metoclopramide as well as Pantoprazole prior to anesthesia.
Metoclopramide is a GI prokinetic agent that helps to shorten gastric emptying time, so there is hopefully less chance of regurgitation of gastric contents into the esophagus and/or oral cavity.
Pantoprazole is a proton pump inhibitor which decreases acid production in the stomach and thus increases the pH of the gastric contents so that if regurgitation does occur, there is less chance of damage to the esophagus.
Other medications that may be used in a ‘Brachycephalic protocol’ could be substituting IV Pantoprazole with oral Omeprazole for at least 2 x q12hr doses prior to anesthesia, adding oral Sucralfate, and/or using Cisapride instead of or with Metoclopramide.
Fasting:
This is controversial. AAHA fasting guidelines say to withhold food and water for 6-12 hours prior to Brachycephalic anesthesia, and to consider feeding 10-25% of a normal meal 4-6 hours prior to anesthesia. This small meal feeding recommendation is to help to reduce gastric acid content and therefore possibly reduce the risk of esophagitis if regurgitation does occur. I have also seen specialist recommendations to withhold food for greater than 36 hours prior to anesthesia in Brachycephalic breeds due to their slow gastric emptying time. In our practice I have seen many Frenchies that were fasted for 12 hours that have a stomach completely full of food at time of anesthesia. Our practice’s general standard is to fast patients after midnight the night before the anesthetic event.
Premedication - pain management:
Gretta is painful so a pure Mu agonist would be indicated. Methadone or Fentanyl would be acceptable choices for her (or Buprenorphine if these are not available). In general I avoid Hydromorphone (or Morphine) in brachycephalic breeds. Hydromorphone tends to be the most emetic of the pure Mu agonists (Morphine is as well), and it tends to induce panting more than the other mentioned opioids. Since brachycephalic breeds are already prone to overheating, difficulty breathing due to their obstructive airway disease, as well as regurgitating and subsequently aspirating, we want to choose a pain medication that has the least possibility of exacerbating these issues while also offering appropriate analgesia. The benefit of Methadone in particular is that it can be given IM, so if we have a wiggly or aggressive patient, we can get some sedation and pain management on board without needing an IV catheter, and with much lower risk of unwanted side-effects.
Adjunct pre-medications:
Dexmedetomidine and Acepromazine are both good options as an adjunct to an opioid in Brachycephalics. I prefer Dexmedetomidine personally as it is reversible, offers additional analgesia, and is less likely to cause hypotension during the anesthetic period. That being said, brachycephalic breeds may have a tendency to have increased vagal tone, so starting with lower doses of Dexmedetomidine is advised since a main side-effect of this drug is bradycardia.
Midazolam could be considered for an older or very calm patient, however it often causes paradoxical excitement and therefore may cause more panting/anxiety. Use with caution.
Induction:
Pre-oxygenate for at least 3-5 minutes prior to induction. Giving 100% oxygen for 3 minutes can increase time to desaturation from 1 minute to up to 5 minutes! If your patient is fighting pre-oxygenation, I will titrate small doses of my induction agent (ex: Propofol) to get the patient quiet enough to accept pre-oxygenation.
In general, we co-induce the majority of our patients using Midazolam and Propofol. Ketamine and/or Alfaxalone could be added or substituted in this protocol as well if needed. Ketamine may have an additional benefit of increasing sympathetic tone which may counteract some of the high vagal tone in these patients.
Other considerations:
Keep the patient calm: Calming meds (Trazodone, Gabapentin, etc) given prior to coming to the clinic can help decrease anxiety, which will hopefully decrease incidence of panting/airway obstruction and will decrease sedative and anesthetic dosage requirements. Remember to include oral Cerenia in a ‘calming cocktail’ for the owner to give at home!
Pharyngeal swelling due to airway disease: It is not uncommon for brachycephalic breeds to have airway swelling from panting/due to their airway disease. DexamethasoneSP may need to be given to combat airway swelling, therefore, we usually do not give NSAIDS prior to anesthesia in these patients in case a steroid is needed.
Always be ready to intubate: These patients can go from ‘fine’ to ‘not fine’ quickly! They should be monitored very closely during their entire hospital stay.
If they are getting too worked up - sedate them.
Put a fan on them to keep cool if they are getting hyperthermic.
If they can’t breathe or can’t maintain normal SPO2 even with mask or flow-by oxygen - intubate!
We wait until these patients are very awake and essentially spitting out their own ETT before we extubate.
Brachycephalic patients tend to have hypoplastic tracheas and often need smaller endotracheal tubes than expected for their size. Have multiple sizes ready!
Since our patients are in dorsal recumbency for 40-60 minutes depending on the site being imaged, these patients often get some dependent sinus edema. Depending on the severity of this edema, I will sometimes place a drop of Phenylephrine Hydrochloride 0.5% nasal spray (ex: Neosynephrine) in each nostril and tilt the head back for a few seconds. This helps relieve some of the congestion and allows better breathing after extubation.
As Always, Make Good Choices!
These patients can be quite challenging,
but we can take many steps to help create
a safer anesthetic event for our smoosh-faced friends!