Pericardial fluid Gram stain is a method of staining a sample of fluid taken from the pericardium to diagnose a bacterial infection. This is the sac surrounding the heart. The
Gram stain of pericardial fluid
How the Test is Performed
A sample of fluid will be taken from the pericardium. This is done through a procedure called
The skin of the chest is cleaned with antibacterial soap. The doctor then inserts a small needle into the chest between the ribs and into the pericardium. A small amount of fluid is taken out.
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 spread in a very thin layer on a microscope slide. This is called a smear. A series of special stains are applied to the sample. This is called a Gram stain. A laboratory specialist looks at the stained slide under the microscope, checking for the presence of bacteria.
The color, size, and shape of the cells help identify the bacteria, if present.
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 pressure and some pain as the needle is inserted into the chest and when the fluid is removed. Your health care provider will likely give you pain medicine so that the procedure is not too uncomfortable.
Why the Test is Performed
Your provider may order this test if you have a heart infection (
The test may also be done if you have, or are suspected to have, pericarditis.
A normal result means no bacteria are seen in the stained fluid sample.
What Abnormal Results Mean
If bacteria are present on the Gram stain, you may have an infection of the pericardium or heart. Blood tests and bacterial culture can help identify the specific organism causing the infection.
Complications are rare but may include:
- Heart or lung puncture
Chernecky CC, Berger BJ. Pericardiocentesis - diagnostic. In: Chernecky CC, Berger BJ, eds. Laboratory Tests and Diagnostic Procedures. 6th ed. St Louis, MO: Elsevier Saunders; 2013:864-866.
LeWinter MM, Cremer PC, Klein AL. Pericardial diseases. In: Libby P, Bonow RO, Mann DL, Tomaselli GF, Bhatt DL, Solomon SD, eds. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. 12th ed. Philadelphia, PA: Elsevier; 2022:chap 86.
Review Date: 04/12/2022
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