Dyspnoea - Cat

Introduction

Feline respiratory emergencies are common in general practise. It is essential that these cases are handled in an appropriate way as the patients are normally very fragile and may go into respiratory arrest if they become too stressed.

The aims of the work up of a feline dyspnoea case are:

1) Stablise the patient

2) Identify the cause of the dyspnoea

3) Initiate therapy

Clinical Signs

The dyspnoeic cat presents with the following clinical signs:

• Increased respiratory rate and effort
• Abnormal posture - extended neck, abducted elbows, sternal recumbancy progressing to lateral recumbancy with impending respiratory arrest
• Open-mouth breathing
• Dilated pupils

Oxygen reserve is generally very low in dyspnoeic cats and you should avoid stressing them if at all possible. This is achieved by gentle handling, minimal procedures, and the use of a quiet, dimly-lit room.

Stabilisation

On presentation the cat should immediately be placed in an oxygen cage. This increases the animals oxygen reserve and allows it to relax following the journey to the practise. If an oxygen cage is not available then 'flow-by' oxygen should be supplied in a stress-free manner.

If the cat appears to be going into respiratory arrest then a general anaesthetic can be used to stabilise the animal, however this should be avoided if possible.

In some cases, the method of stabilisation is the same as the therapy, for example the drainage of pleural fluid.

Diagnosis

Whist the cat is in an oxygen cage, a thorough history should be taken, including the duration and progression of the dyspnoea, any previous/current medical problems and medications, husbandry, appetite and thirst of the cat and whether they may be a history of trauma.

A physical exam should then be performed to establish the location of the respiratory signs:

Parenchymal Disease

Parenchymal disease produces crackles at the end respiration. Differenial diagnoses include cardiogenic pulmonary oedema, pneumonia, contusions (post-trauma), pulmonary eosinophilic infiltration (PIE) and neoplasia.

Lower Airway Disease

Lower airway disease causes wheezing on expiration. Causes of this include FAAD.

Upper Airway Disease

Upper airway disease causes harsh inspiratory noise. This is rare in cats.

Pleural Space Disease

Lung sounds are decreased on auscultation. Causes include FIP, pyothorax, pneumothorax, neoplasia, haemothorax, chylothorax and congestive heart failure. Th history may help identify the cause of the disease.

Space Occupying Lesions

Space occupying lesions cause displacement of heart sounds caudally and loss of 'rib-spring' on palpation of the chest wall. Differential diagnoses include neoplasia, abscess and cysts.

The physical exam should be performed in the most stress-free manner possible: the cat should first be observed from a distance to identify the phase of respiration that is affected. Then the clinician should auscultate, palpate and percuss the chest to identify any respiratory or cardiac abnormalities. A full clinical exam should not be performed until the animal is more stable.

There are three differentials that are common causes of feline dyspnoea. It is important to keep these in your mind when working up the case and ruling-out each one can bring you to a rapid diagnosis:

1) Pleural Effusion

Pleural effusion produces muffles heart and lung sounds ventrally. The cat will normally have a short, shallow respiratory pattern. The presence of fluid can be rapidly confirmed using ultrasound.

2) Heart Disease

A cardiac murmur (with or without a gallop) and diffuse crackles across the thorax should be auscultated. An echocardiogram and radiography can be used to confirm the diagnosis of heart disease, however in a very unstable case with cardiac signs it is best to use frusemide as a trial therapy and monitor the response to therapy for diagnosis. Only once the cat has stabilised, or if it is responding poorly to treatment should radiography or echocardiography be performed to confirm the diagnosis.

3) Feline Allergic Airway Disease (Feline Asthma)

A cough, diffuse harsh sounding lung sounds and an expiratory wheeze may be auscultated. The diagnosis of FAAD can be confirmed by radiography, which may show a flattened diaphragm, air trapping, rib fractures and a bronchial pattern. However you as a clinician should consider the risk-benefit of this before performing the procedure as the cat may no be able to deal with the procedure with its low oxygen reserve.

Initial Therapy

Pleural Effusion

Initial treatment is thoracocentesis. This procedure also stabilises the animal. It should be noted that even if only a portion of the fluid is drained there should still be a significant improvement in respiratory signs. Cytology should be performed on the fluid to achieve a diagnosis and prognosis.

Heart Disease

Frusemide should be administered to any cat suspicious of heart disease to clear cardiogenic pulmonary oedema. Frusemide can be administered intravenously or intramuscularly and it should be given every half an hour until the respiratory rate drops below 40 breaths per minute. When appropriate, the frusemide should be given orally. Radiography can be used to monitor the response to treatment.

Feline Allergy Airway Disease (Feline Asthma)

Ideally the underlying cause of the FAAD should be identified.

Treatment involves:

• The administration of bronchodilators. Either torbultaline administered intravenously or salbutamol via nebulisation (this may be stressful for the animal).
• The administration of steroids to reduce inflammation. Either dexamethosone intravenously or fluticasone via nebulisation (this may be stressful for the animal).

Before steroids are administered it is best rule out lymphoma as the cause of the dyspnoea. The reasons behind this are; that steroids may mask the signs of the neoplasia and, since chemotherapy protocols include steroids, the effectiveness of the chemotherapy is reduced if the cat has been already treated with steroids. In addition, if the respiratory disease is infectious in origin clinical signs may worsen with steroid administration.

Summary

The management of emergency dyspnoea case is very important. The cats survival is dependent on your ability to stabilise it.

References

Adamantos, S (2011) Feline Respiratory Emergencies RVC Emergency and Critical Care Elective Course, Royal Veterinary College

RVC staff (2009) Respiratory System RVC Intergrated BVetMed Course, Royal Veterinary College