Alternate Names: Culture - blood
How Performed: In this test it is important that the blood sample does not become contaminated by organisms on the skin or equipment used in preparing the test. A strict aseptic technique is followed to obtain and prepare the specimen.
Blood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and a tourniquet (an elastic band) or blood pressure cuff is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the tourniquet to distend (fill with blood). A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the tourniquet is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.
The culture is examined for the presence of microorganisms over several days. If organisms are present, further culturing may take place to identify the organisms. A gram stain may also be done to classify the organism so that antibiotic therapy can be started before final culture results are available.
How To Prepare: No special preparation is needed. Wear a garment with loose sleeves that can be pushed up easily.
Infants and children:
The physical and psychological preparation you can provide for this or any test or procedure depends on your child’s age, interests, previous experience, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child’s age:
How It Feels: The needle prick is usually not painful.
Risks: There may be some bruising at the site of the venipuncture.
Why Performed: A blood culture is performed when an infection of the blood (bacteremia or septicemia) is suspected in the presence of fever, chills, low blood pressure, or other symptoms. The blood culture will help identify the infection’s origin. The results are used as a basis for determining appropriate antimicrobial therapy for treatment.
Normal Values: There is no growth of microorganisms in the culture medium.
Abnormal Results: Positive results mean that bacteria are evident in the bloodstream. Many organisms enter the bloodstream in the early stages of infection and can be identified so that proper treatment can be given.
Cost:
Special Considerations: Bacteremia is generally intermittent, so a series of 3 blood cultures may be performed before a negative result is confirmed.
Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.
