Anaesthesia In brachycephalics will get the hearts of most vets racing but, whether we like it or not, the general public’s desire for these airway challenged breeds means we are having to do more and more of these particularly high risk anaesthetics. So last week’s webinar delivered by European specialist in anaesthesia and analgesia, Carl Bradbrook BVSc CertVA DipECVAA MRCVS RCVS & EBVS, proved particularly invaluable in this daunting era of the Pug, French bulldog and English bulldog.
As an example of how challenging these anaesthetics can be, Carl discussed the particular difficulties posed by these breeds with their Brachycephalic Obstructive Airway Syndrome (BOAS) being the most obvious concern. The effects of BOAS are perpetuated even further by the muscle relaxant effects of general anaesthesia. Also gastro-oesophageal disease has to be taken into account as many brachycephalics will regurgitate and may have hiatus hernias predisposing them to aspiration pneumonia, oesophagitis and oesophageal strictures. Temperature monitoring to ensure they neither get too cold or too hot and minimising stress in these patients are additional concerns.
These considerations are a lot to take on board, but Carl methodically went through each challenge, advising on what we can do to minimise the risks for our patients. For example minimising stress in our patients can be achieved by performing pre op tests such as bloods the day before they undergo any procedures. Carl also advises sedating these patients early on with appropriate agents. Obvious premed choices usually include either ACP based or alpha-2 agonist based sedations alongside an appropriate opioid such as methadone or buprenorphine. Interestingly Carl stated that studies have shown Pugs seem to sedate better with alpha-2 agonist based sedatives and French bulldogs tend to sedate better with ACP based sedatives. Carl also noted that anecdotally these breeds seem nauseous once an opiate is administered and as a result Carl usually administers maropitant pre-operatively to minimise this effect.
The risks associated with regurgitation can be minimised by using prophylactic gastrointestinal protection. Omeprazole at a dose on 1mg/kg can be given either per os four hours prior to inducing anaesthesia or can be given intravenously at the same dose just prior to induction. Omeprazole should be continued for five days post general anaesthesia. Carl also explained that pro-kinetics can also be utilised by administering an intravenous infusion of metoclopromide. Carl explained these breeds seem to have slow gastric emptying times which adds to the lack of ventilation and increases the risk of gastrointestinal complications. Using prokinetics such as metoclopromide in high risk patients may help to reduce these complications.
In order to perform induction of anaesthesia in these high risk patients as safely as possible, Carl advises that preparation is key. Carl discussed using a safety check list pre-induction, pre-procedure and on recovery. Carl delivered some examples of check lists within this webinar and highly recommended their use after an audience poll discovered that only 26% of participants were using them. Carl also stated that IV access was mandatory for patient safety and advised that he often found the use of EMLA cream helpful and would usually use the saphenous vein in preference to the cephalic as it appeared to be better tolerated by these patients. Ensuring you have a fully stocked airway box in case of an emergency is also necessary and should include laryngoscopes, stylets, dog urinary catheters (to aid in intubation), tracheostomy tubes, induction agents as well as several sizes of endotracheal tubes. During induction, Carl advises always giving induction agents to effect and to utilise the induction agent you are most familiar with. He recommends placing the dog in sternal recumbancy and elevating the head by about 30 degrees. It is important to intubate and check the cuff prior to placing the head back down on the table below the level of its abdomen where the patient is then at risk of regurgitation. Nasal oedema which causes a dripping nose and further airway obstruction can be seen when brachycephalics are placed in dorsal recumbancy and when ties are placed around their muzzle or behind their ears. Carl recommends using nasal congestants to prevent nasal oedema as they cause vasoconstriction of the nasal mucosa. Carl places half a ml of nasal congestant into each nostril.
Recovery is a high risk period for any patient following anaesthesia but even more so for the brachycephalic patient. Carl advises leaving the endotracheal(ET) tube in place for as long as possible. Often these patients tolerate their ET tubes being in place even when conscious and to ensure they have sufficient return of upper respiratory tract muscle function, ideally the patient should be able to lift their head up prior to removal of the tube. Continual monitoring of these patients is key with the use of pulse-oximetry as a bare minimum alongside regular body temperature checks. Carl also advises the use of sedation as required using low doses of either ACP or alpha 2 agonists. If after removal of the ET tube the patient shows signs of airway obstruction, oxygen should be administered, the tongue should be gently pulled forward and suction administered. If necessary general anaesthesia should be induced and the patient re-intubated. Carl also finds nebulisation with adrenaline useful in these cases as it causes vasoconstriction and bronchodilation. The procedure for performing this was fully explained within the webinar.
Carl delivered an information packed practical webinar which should offer greater confidence to even the most risk adverse vet when dealing with these evermore popular breeds and so for all the small animal vets who are undoubtedly having to deal with these patients on a more regular basis, this is a webinar that should not be missed.