Pus in the pericardium

Fluid sometimes accumulates in a patient's pericardium. If there is only a little, you can leave it there (if indeed you are aware of it at all), unless you need it for diagnosis. But if there is much, it embarrasses the action of his heart (cardiac tamponade) and may kill him, so you may have to remove it urgently! The fluid can be blood after a cardiac injury (65.9) or an effusion from many causes, either infected or sterile. Elsewhere in the body, you drain pus to treat an infection. In his pericardium, you are mainly draining it to overcome its mechanical effects.

He is unlikely to present with symptoms that immediately suggest a pericardial effusion. He is more likely to be admitted with a variety of medical diseases and be observed to have some of the following signs: (1) Grossly distended neck veins, (2) pulsus paradoxus (a reduction of arterial pressure of [mt] 10 mm and of pulse pressure on inspiration), (3) pulsus alternans (QRS complexes of alternately varying voltage), and (4) a large cardiac shadow. He is obviously ''ill', and may be febrile. He has signs of a low cardiac output with a poor peripheral circulation; he has a small pulse volume, tachycardia, a low normal or subnormal blood pressure, and soft heart sounds. Early on you may hear a pericardial rub, but the accumulation of fluid soon separates his pericardial surfaces and stops the rub. He has the signs and symptoms of heart failure, and an increased area of cardiac dullness. The severity of the signs of cardiac tamponade are related more to the rate at which fluid accumulates in his pericardium than to the volume of fluid in it. The diagnosis may be obvious, or if fluid has accumulated slowly, it may be difficult.

There are problems: (1) Any cause of cardiac failure may have distended his neck veins. (2) Although pulsus paradoxus strongly suggests a pericardial effusion, not all patients show it. (3) The X-ray finding of a large globular heart can also be due to gross cardiac enlargement without there being any fluid in his pericardium.

The great danger in putting a needle into his pericardial cavity to drain it is that: (1) You can easily penetrate his right ventricle, cause bleeding, increase the fluid in his pericardial cavity, and kill him rapidly. (2) You may cause ventricular fibrillation with the tip of the needle. Even so, in spite of these dangers, not aspirating his pericardium may be more dangerous than aspirating it.

Fig. 6-2a ASPIRATING THE PERICARDIUM. Insert the needle in his epigastrium immediately to the left of his xiphisternum. Incline it 45[de] to the horizontal and 10[de] towards the left. In this way, if it does prick his heart it is more likely to meet his thicker left ventricle than his thinner right auricle.

PUS IN THE PERICARDIUM See also Section 65.9 for cardiac tamponade as the result of trauma.

X-RAYS. A very large globular heart, often with venous congestion. Depending on what is causing his pericarditis, you may see basal shadows in his lungs, or pneumonia obscuring his heart.

ECG. Tachycardia, usually sinus rhythm, a raised S-T segment (nonspecific), an inverted T wave (late, nonspecific), low voltage QRS complexes (highly suggestive), pulsus alternans (highly suggestive).

THE DIFFERENTIAL DIAGNOSIS of the causes of pericardial effusion which may lead to tamponade is as follows in probable order of frequency in most of the Third World:

Suggesting tuberculosis[md]a history of cough, bloody sputum, weight loss and malaise. Patients with AIDS and tuberculosis are particularly likely to develop tuberculous pericarditis and pleural effusions.

Suggesting viral myocarditis[md]an influenza-like illness with generalized muscle pains. Early, you may hear a pericardial friction rub.

Suggesting a pyogenic bacterial cause[md]some other site of infection, such as pneumonia, meningitis, or measles with secondary staphylococcal infection. Often, there is some obvious site of infection, but not always (primary pericarditis).

Other causes of pericardial effusion that might cause tamponade include: uraemia, malignant deposits (only if they bleed seriously), collagen diseases, and the rupture of an amoebic abscess into the pericardium (rare).

Here are some causes of a large heart without fluid in the pericardial cavity:

Suggesting rheumatic heart disease (common) [md]valvular lesions; these are usually easily diagnosed.

Suggesting cardiomyopathy [md]an enlarged heart clinically and radiologically. The cardiac outline may be globular and closely simulate fluid in the pericardium.

Suggesting endomyocardial fibrosis (EMF)[md]atrioventricular incompetence left and right is usual. Eosinophilia.

PREPARATION. Find two assistants, one to watch the patient's ECG, or his pulse, and ready to resuscitate him if necessary, and another to fetch anything more that might be needed for resuscitation. Have the full resuscitation equipment available: laryngoscope, tracheal tubes, a sucker, oxygen, and an anaesthetic machine or an Ambu bag. Do an ECG while you are aspirating, or failing this ask someone to feel his pulse continuously.

EQUIPMENT. A needle inside a plastic cannula (''needle- inside-cannula', A 15.2), a 3-way tap (less satisfactorily a 2- way one), and a 20 or 50 ml syringe.

ASPIRATION. Insert the cannula in his epigastrium immediately to the left of his xiphisternum. Incline it 45[de] to the horizontal and 10[de] towards the left. In this way, if it does prick his heart, it is more likely to meet his thicker left ventricle than his thinner right auricle.

DRAINAGE. Incise his linea alba and proceed upwards in the extraperitoneal plane until you reach his pericardium. Cautiously incise this and insert a drain.

CAUTION ! If he deteriorates suddenly with a pulse which you cannot feel: (1) Immediately remove the cannula. (2) Start external cardiac massage (A 3.6). (3) While you stop external cardiac massage briefly, ask your assistant to intubate him. Continue to control his ventilation (A 13.1).