Clinical Notes: Sophie

Sophie, an eight year old neutered female Dachshund, was bright and happy until three days ago. Then she started vomiting. She now just lies there not wanting to move or eat.

Learning Objectives

  1. Identification of life-threatening abnormalities in a collapsed patient.
  2. Prioritising treatment of abnormalities detected.
  3. Arriving at an accurate diagnosis and formulating a long-term care and treatment plan.
  4. Understanding the aetiology and management of pericardial effusion.

Clinical Condition

The pericardium is a fibrous sac that surrounds the heart. This sac is composed of two layers. Between the two layers of the pericardium a few millilitres of fluid lie in the pericardial space. This fluid serves to lubricate the movement of the heart within the pericardial sac. This sac is attached to the great veins at the heart base.

Because of its fibrous nature the pericardium is not very distensible or accommodating of sudden changes of its volume. This can be protective, for example in preventing acute distension of the myocardium. However if there is a sudden change in the volume of fluid within the pericardium the inelastic nature of the pericardium can lead to sudden increases in pressure within the pericardial space and compression of the ventricles. The majority of disease that we see associated with the pericardial sac results in accumulation of excessive fluid within the pericardial space. Clinical signs observed reflect the effects that this has on the circulatory system.

The walls of the right side of the heart are much thinner than those of the left side. This makes the right side more susceptible to compression as pressure within the pericardial sac increases. Compression of the right side of the heart will have significant effects of the hearts ability to relax and fill normally during diastole and signs of right sided heart failure will develop. This compression of the heart is termed cardiac tamponade. The amount of blood entering the pulmonary circulation from the right ventricle dictates the potential for filling the left side of the heart and thus cardiac output. Therefore, even though the left side of the heart is not directly compressed its output is compromised and there is a fall in systemic arterial blood pressure. In an attempt to restore cardiac output to normal the body responds by increasing the heart rate and retaining fluid at the kidneys. However this compensation is not enough and a reduction in tissue perfusion occurs. This results in clinical signs of heart failure.

Case Management

Important points in management of collapsed patients

  1. Rapid assessment of the patient to identify which body system(s) are primarily involved.
  2. Obtaining intravenous access.
  3. Characterising arrhythmias detected.
  4. Obtaining appropriate laboratory samples before initiating treatment.

Management of pericardial effusion

  1. Relieve cardiac tamponade to restore cardiac output
  2. Determine nature of effusion
  3. Carry out imaging studies to help determine the cause of the effusion
  4. Appropriate fluid therapy to maintain hydration without risking pulmonary hypertension due to volume overloading

Pericardiocentesis

bla bla bla

Suggested Management Plan for Sophie

  1. ABC - Airways, Breathing, Circulation. Identify any abnormalities involving the cardiovascular or respiratory systems. These are the conditions that are most likely to result in the death of your patient. Now consider how you might identify the cause of the abnormalities detected (initially these were tachycardia and poor peripheral perfusion).
  2. Either record an ECG or obtain a blood sample primarily for...
  3. The ECG in this case showed a very fast but regular rhythm. The complexes appear normal in conformation. It is likely that this is a supraventricular rhythm. Possible causes would include pain, hypercapnia, hypotension, reduced myocardial contractility, reduced cardiac output secondary to poor cardiac filling or poor oxygen delivery to the tissues secondary to anaemia.
  4. If not already obtained a blood sample should be collected. At this point rapid assessment of PCV and total protein are useful to assess degree of anaemia or dehydration. The measurement of BUN can indicate if acute renal failure has occurred secondary to the cardiac failure. A full haematology and biochemistry is useful, but can wait.
  5. Imaging - Radiography and ultrasonagraphy have important roles in the diagnosis of pericardial disease. Radiography:- the cardiac sillotte is usually enlarged and rounded. In cases of acute onset pericardial effusion where the volume of effusion is small this may not be readily appreciable. Echocardiography will readily confirm the presence of a pericardial effusion. Where the patient is suffering from tamponade this may be identified on echocardipgraphy as collapse of the right atrium during dyastole. Careful searching may reveal the presence of a mass within the pericardial space. These frequently involve the right atrial appendiage or the heart base. The mass may be visable extending through the pericardial sac or into adjacent cardiac chambers. The presence of some fluid within the pericardial sac will make it easier to determine the margins of a mass.
  6. Pericardiocentesis should be performed as outlined above. This will serve to relieve the compressing on the right ide of the heart, improving cardiac output and provide samples for analysis. Rapid draining of large volumes should be avoided and patients should be closely monitored for signs of rapid re-effusion as can occur especially where a haemorragic mass is the cause of the effusion. In such cases a drain may need to be placed to allow repeated drainage without the discomfort associated with repeated pericardiocentesis.
  7. Decision making. Once a diagnosis has been reached the findings have to be discussed with the client. As veterinary surgeons our prime concern is for the welfare of the patient. In this case the prognosis is hopeless. The mass cannot be resected. The patient is clearly uncomfortable and the effusion is recurring rapidly. The only realistic option for the management of this case is euthansia. However immediate euthansia may not be possible if the client cannot be contacted, or is unwillnig to give immediate permission without 'time to think' or consultation with other family members. It may be necessary to administer fluid therapy, antiemetics, or repeatedly drain the pericardial sac to keep the patient comfortable until the client is able to give permission to euthanise.

Further Reading

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