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​Considerations for anaesthesia of the brachycephalic dog.

Considerations for anaesthesia of the brachycephalic dog.

Brachycephalic dogs pose an increased anaesthetic risk for peri-anaesthetic morbidities which is related to conformational problems and concurrent diseases. In planning for anaesthesia, we should take these into consideration and understand the impact such concerns have on our decisions for case management. 

It is important to gain certain information from the owner regarding clinical signs relating to airway obstruction and gastrointestinal (GI) disease in all brachycephalic patients. 

Exercise tolerance remains one of the best indicators of airway conformation and this can be evaluated with a 3-minute trot test. Elements of the airway that can impede passage of respiratory gases to the lungs include stenotic nares, aberrant nasal turbinates, elongated soft palate, excessive pharyngeal soft tissue, everted laryngeal saccules, laryngeal collapse and tracheal hypoplasia. All of these have potential to affect ultimate tissue oxygen delivery. These physical obstructions should be assessed in every brachycephalic undergoing anaesthesia and steps taken to correct abnormalities where possible if deemed to cause significant airway impairment. Significant improvement of GI and respiratory signs following surgical management of airway obstruction has previously been reported (Haimel & Dupré 2015, Kaye et al 2018). 

Signs of regurgitation are not always obvious and many of these dogs are silently refluxing without owners being aware that there is a problem. Look out for subtle signs such as snorting, swallowing and excessive lip licking which can be indicative of regurgitation. Breed‐specific prevalence for regurgitation and vomiting for French bulldogs was 93%, English bulldogs 58% and pugs 16% in one study (Kaye et al 2018). This is valuable information in guiding our use of anti-emetics in the peri-anaesthetic period. 

Our concern as anaesthetists is regurgitation and subsequent aspiration of GI contents during any period that the airway is not fully protected. Aspiration pneumonia is a potentially fatal outcome with oesophagitis and stricture formation similarly catastrophic. 

Anaesthetic drugs

There are no anaesthetic drugs that are specifically contraindicated in brachycephalic breeds and the veterinary surgeon is advised to adhere to the following principles;

• Airway maintenance - avoid heavy sedation which may lead to upper airway obstruction. The alpha-2-agonists medetomidine and dexmedetomidine can be used, provided close attention is paid to the patient following administration to ensure the airway remains open.  

• Reduce the incidence of regurgitation – administer methadone on an ‘as required’ basis rather than ‘by the clock’ to reduce the adverse GI effects such as regurgitation.

• Give induction agents slowly IV to effect and ensure the dog is deep enough to avoid gagging or coughing when attempting intubation. 

• Ensure analgesia is excellent. Use of NSAIDs should be assessed in light of specific GI disease but otherwise there is no reason to avoid the use of opioids, local anaesthetics and adjuncts such as ketamine. 

• Evidence does not support the routine administration of corticosteroids for airway surgery. 

Drugs & doses

There are no specific contra-indications to anaesthetic drugs and the reader is advised to be familiar with these drugs in routine healthy cases before trialling anything new with brachycephalics. Medetomidine or dexmedetomidine (1-5 mcg/kg IV) are appropriate and the IV route is preferred. Mild sedation with minimal impact on airway patency is desired. Equally, acepromazine is a valid choice and gives mild sedation. It can be used intramuscularly for those cases where IV access is not possible at doses approx. 0.02 mg/kg. If used IV the dose should be reduced to 0.005-0.01mg/kg to limit the degree of vasodilation and subsequent hypotension produced.  Both acepromazine and the alpha-2-agonists can be combined with opioids for neuroleptanalgesia. For surgery, doses of methadone ranging from 0.1-0.3mg/kg are suitable, depending on the degree of pain anticipated. For mild to moderate pain, buprenorphine 0.02mg/kg IM or IV will provide effective analgesia. Although considered to have minimal cardiovascular effects and therefore thought to be useful as premed agents, the benzodiazepines should not be used as premedicants in adult animals. 

Gastrointestinal drugs

Maropitant – the anti-emetic effect of maropitant should reduce the incidence of vomiting/regurgitation. 

Metoclopramide – the prokinetic effect of metoclopramide is used to minimise regurgitation.

Omeprazole – one study in dogs showed that 1mg/kg omeprazole PO 4 hours prior to anaesthesia reduced the incidence of regurgitation in the peri-anaesthetic period.

Oxygen provision

Preoxygenation with 100% oxygen delivered via a facemask for 3 minutes before induction of anaesthesia increases the time to desaturation. If the dog is stressed, then flow-by oxygen can be provided. With existing airway compromise plus challenges associated with tracheal intubation preoxygenation adds a safety factor during this period. Although not commonly practised in the UK, an air:oxygen mixture as the carrier gas will reduce the onset of atelectasis and may be of benefit in this patient population. Oxygen should be available during the recovery period should desaturation occur and the use of pulse oximetry in this period is recommended.  

Endotracheal tube care

Rules for ET tubes are that the largest diameter to comfortably fit the airway should be used without the length being excessive – the tube connector should be at the level of the incisors to reduce airway dead space.  Good illumination is essential for intubation. The cuff of the ETT should be inflated to create an airtight seal using the minimal inflation technique. Suction should be available should regurgitation occur. 

Post-extubation airway care

Airway patency should be ensured at all times following extubation and patients should be supervised one to one until fully recovered. Nebulised adrenaline (0.3-0.5mg/diluted in 5ml saline) can be used to reduce oedema of the upper respiratory tract with effects audible within 10 minutes of nebulisation. This is useful for both airway and non-airway surgeries and can be repeated as required. 

Anxiolysis

Anxiolysis is one of our main aims with brachycephalics as they are prone to hyperthermia which can be triggered by a minimal amount of stress. The dog’s temperament should be assessed prior to admit and a plan made to deal with stress. Trazodone, a serotonin reuptake inhibitor, has been shown to reduce signs of stress in hospitalised patients and can be administered prior to the owner leaving home and continued during hospitalisation. Additional sedation may be required at any stage post-anaesthesia and the exact drugs used depend on the patient. 

Ocular care

Brachycephalic dogs have a higher incidence of corneal ulceration and protection under anaesthesia is essential. A lubricant such as carmellose sodium (Celluvisc 0.5%) is recommended. 

Temperature management

Close attention is required to avoid hyperthermia and hypothermia. Brachycephalics have a limited ability to dissipate heat and are prone to stress-induced hyperthermia. Conversely, these dogs should not become hypothermic as this will impair ventilation in the recovery period and could increase the risk of complications. 

Creating a brachycephalic protocol for your practice is a sensible idea to ensure that optimal care is provided to these patients, with a plan that is specific to their individual requirements. A flowchart (Downing & Gibson 2018) is useful for such cases. 

Podcasts 

Downing, F (2018) Anaesthetising the brachycephalic patient  BSAVA Congress

Leece, E (2018) Anaesthesia for BOAS surgery BSAVA Congress

Article by
Matt Gurney
BVSc CertVA PgCertVBM DipECVAA MRCVS

Matt graduated from the University of Liverpool in 2003 and spent several years enjoying mixed practice before returning to Liverpool to undertake a residency in anaesthesia & analgesia. From 2009 to 2018 he developed and led the anaesthesia service at Northwest Veterinary Specialists, a multidisciplinary specialist hospital in Cheshire.

Matt is a European Veterinary Specialist and an RCVS Recognised Specialist and is currently Vice President of the European College of Veterinary Anaesthesia & Analgesia. In October 2018 Matt returned to his roots in the south and joined Anderson Moores Veterinary Specialists. His main interests lie in acute and chronic pain management.

Originally published: Thursday, 28th March 2019

References

Downing, F & Gibson, S (2018) Anaesthesia of brachycephalic dogs. Journal of Small Animal Practice 59, 725-733

Haimel, G. & Dupré, G. (2015) Brachycephalic airway syndrome: a comparative study between pugs and French bulldogs. Journal of Small Animal Practice 56, 714-719

Kaye, BM., Rutherford, L., Perridge, DJ & Ter Haar, G. (2018) Relationship between brachycephalic airway syndrome and gastrointestinal signs in three breeds of dog. Journal of Small Animal Practice 59, 670-673.

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