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Practical approach to the cat with respiratory distress

IntroductionThe cat presenting with respiratory distress poses unique challenges to the veterinary clinician. Not only do clini-cal signs often appear to occur suddenly, creating an emotional situation for owners, but the cat is often in an unstable condition where decompensation can occur because of the stress associated with handling and procedures. Intensive care and support are vital, but the number and frequency of procedures must be mini-mised in order to promote patient stability. The clinician must maintain a logical and calm approach, by formulating a list of differential diagnoses that is revised on an ongoing basis as diagnostic test results are revealed. The aim of this article is to describe a framework for veterinary practitioners to use in approaching these difficult cases and to help formulate and refine a list of differential diagnoses for respiratory distress in cats.

Presenting signs, initial stabilisation and historical findingsMost cats with respiratory distress present acutely, often at an inconvenient time and with little notice. We recommend that the patient is provided with supportive oxygen therapy as soon as they are known to have respiratory distress (Figure 1). As a result, history taking is often curtailed early on, but this can be resumed once initial stabilisation is under way. Whilst the clinician is working with the cat, a third party (possibly a veterinary nurse) should obtain a signed consent form for stabilisa-tion and initial procedures, including thoracocentesis.

It is imperative that the dyspnoeic cat is handled minimally, in a quiet and calm

environment, with adequate oxygen pro-vision. Intravenous access or blood work is often contraindicated early in the timeline of case management. Sedation should be considered if the patient is distressed. Pharmaceuticals that dramatically alter systemic vascular resistance or promote bronchoconstriction should be avoided. The author typically uses butorphanol (0.2-0.4mg/kg IM, SC or IV if access is present), and avoids using medetomidine or ketamine because of their profound effects on systemic vascular resistance.

Observation of respiratory pattern is a very useful way of narrowing the list of possible differential diagnoses in cats with respiratory distress (Table 1). It can be performed whilst the cat is in a carrier, whilst they are receiving oxygen, and without any patient restraint which may contribute to stress. It is worth noting that a paradoxical pattern represents non-specific respiratory fatigue, although it is common in patients with pleural space disease and diaphragmatic rupture. Respiratory fatigue is a concern, because further decompensation may be associated with respiratory failure. When clinical signs of respiratory distress in cats are accompanied by postural adaptations (for example, orthopnoea, represented by a sternal recumbency with an extended neck and abducted elbows to reduce the resistance to airflow) or persistent open mouth breathing, the situation should be considered grave and the patient highly unstable. Owners and other staff handling the patient should be cautioned, and equipment for endotracheal intubation and cardiopulmonary resuscitation should be prepared.

Kieran Borgeat BSc(Hons) BVSc MVetMed CertVC DipACVIM (Cardiology) DipECVIM-CA (Cardiology) MRCVS American and European Specialist in Veterinary Cardiology

Kieran graduated from the University of Bristol in 2005 and after 6 years in first opinion practice and achieving his RCVS Certificate in Cardiology he moved to the Royal Veterinary College (RVC) where he completed a residency and masters degree. He is a Diplomate of the American and European Colleges of Veterinary Internal Medicine (Cardiology) and currently works in private referral practice and as a visiting lecturer at the RVC and Bristol. Kieran’s interests include interventional image-guided procedures and feline cardiomyopathies.

Highcroft Veterinary Referrals 615 Wells Road Whitchurch Bristol BS14 9BE

Tel: 01275 838473

www.highcroftvetreferrals.co.uk

The feline patient with respiratory distress is often a challenging and emotionally-fuelled emergency presentation. Minimising patient stress is crucial, and it can be difficult to obtain the appropriate diagnostics with which to make decisions about how to best treat patients. A calm, logical approach is vital, employing observational skills, thoracic ultrasonography, cardiac biomarker testing and focused echocardiography. In most cases, this protocol narrows the list of differential diagnoses sufficiently for empirical treatment to be administered, and successful stabilisation to be achieved.

Key words: feline, cardiomyopathy, critical care, dyspnoea, congestive heart failure (CHF).

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Once the cat is settled in a calm, oxygen rich environment, a full history can be obtained from the owner. Alternatively, this may be carried out by another vet-erinarian or experienced veterinary nurse whilst the primary clinician is overseeing initial stabilisation. In most cases it is appropriate for owners to be provided with reassurance that their cat is being cared for appropriately whilst they wait. In the event that an owner has left the prem-ises, a telephone call to update them and take a history should suffice, provided that signed consent was previously obtained.

As always, a thorough history and estab-lishing a timeline of events is vital in achieving a diagnosis and formulating an appropriate treatment plan. The duration, intensity and progression of respiratory signs should be interrogated thoroughly, as should any concurrent clinical signs. His-torical reports of a persistent or chronic cough should assist in identifying lower airway disease, but may also be attributable to respiratory tract neoplasia. Coughing is rare in cats with congestive heart failure (CHF), which tend to present primarily with tachypnoea. Retching or gagging is highly suggestive of nasopharyngeal or laryngeal disease, but the sounds are easily confused with a cough by owners. For this reason, we would encourage clinicians

Pattern Description Localisation Common differentialsDiagnostic tests to consider

Inspiratory

(Video 1)

Long, slow inspiratory phase, often accompanied by stridor

Upper respiratory tract Nasopharyngeal obstruction (polyp, foreign body)Laryngeal obstruction (mass lesion, paralysis)

Upper respiratory tract visualisation and imaging

Restrictive

(Video 2)

Rapid, shallow pattern with even effort on inspiration and expiration

Pleural space, alveoli, pulmonary interstitium

Pleural fluid (effusion, haemothorax, pyothorax)PneumothoraxPulmonary oedema (CHF)

Thoracic ultrasonography

Obstructive (Video 3)

Near-normal rate with disproportionate expiratory effort, often involving an expiratory abdominal push

Lower airway disease Lower airway obstruction (chronic bronchitis, asthma)

Thoracic radiography or computed tomography

Paradoxical (Video 4)

Caudal thorax and cranial abdomen move in opposite directions during both phases, often fast rate

Non-specific; represents respiratory fatigue Common in pleural space disease

Pleural space disease,Pulmonary oedema (CHF),Lower respiratory tract diseaseDiaphragmatic rupture

Thoracic ultrasonography

Panting (Video 5)

Paroxysmal: open mouth, rapid, short, shallow breaths

Non-specific; may not represent true respiratory distress if respiratory pattern normal between episodes

StressHyperthyroidismRight-to-left shunting cardiovascular disease

Dependent on other clinical findings

Table 1: The observation of respiratory pattern can be used to help localise the disease and narrow the list of differential diagnoses.

Figure 1: Commonly used methods of oxygen supplementation in cats (clockwise from top left): flow-by oxygen, provided using an anaesthetic circuit (with or without a mask) to deliver oxygen flow over the external nares; a collapsible oxygen tent; an incubator, and a specifically designed oxygen kennel. A rudimentary version of the latter can be produced for temporary use by passing oxygen into a standard kennel using an anaesthetic circuit and covering the kennel bars with cling film.

“Once the cat is settled in a calm, oxygen rich environment, a full

history can be obtained”

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