ADAM Health Encyclopedia

Pericardial fluid gram stain

Definition

Pericardial fluid gram stain is a method of staining bacteria from fluid in the sac surrounding the heart to diagnose bacterial infections.

Alternative Names

Why the Test is Performed

The test is performed when the doctor suspects an infection of the heart, or if you have a pericardial effusion with an unknown cause.

How the Test is Performed

First, fluid is taken from the sac surrounding the heart. Some people may have a cardiac monitor placed before the test to check for heart disturbances. Patches called electrodes are put on the chest, similar to during an ECG. You might have a chest x-ray or ultrasound before the test.

The skin of the chest is cleaned with antibacterial soap. A trained physician, often a cardiologist, will take the sample.

A small needle is inserted into the chest between the ribs and into the pericardium, which is the thin sac that surrounds the heart. A small amount of fluid is taken out. You will feel pressure and some pain as the needle is inserted into the chest.

You may have an ECG and chest x-ray after the procedure. Sometimes the pericardial fluid is taken during open heart surgery.

A drop of the pericardial fluid is then placed in a very thin layer on a microscope slide -- this is called a smear. The specimen is stained with a series of stains, together called a gram stain. The stained smear is then examined under the microscope for the presence of bacteria.

The color, size, and shape of the cells help make it possible to identify the bacteria.

How to Prepare for the Test

You will be asked not to eat or drink anything for several hours before the test. A chest x-ray or ultrasound may be done before the test to identify the area of fluid collection.

How the Test Will Feel

You will feel some pressure and discomfort when fluid is removed from the sac surrounding the heart. Your doctor should be able to give you enough pain medicine so that the procedure does not hurt very much.

Risks

There is a risk of puncturing the heart or the lung with this procedure. Introducing infection into the area is another rare, but potential, risk.

Considerations

Other tests may be performed on the pericardial fluid sample.

Normal Results

Results are normal when no organisms are found in the gram stain test.

What Abnormal Results Mean

If bacteria are present, you may have an infection of the pericardium or heart. Further testing, such as bacterial culture, can identify the specific organism causing the infection. Sometimes blood testing can help with the diagnosis.