BLOOD CULTURE CONTAMINATION

IN-SERVICE

AUGUST 2008

J.WIIEFEL

BLOOD CULTURE CONTAMINATION

SKIN ANTISEPSIS

This is the most important part of the blood culture collection procedure. Failure to follow sterile technique can introduce skin surface bacteria into the blood culture bottle and interfere with interpretation of results.

Microbiology must report all microorganisms isolated form blood cultures. If an organism is misinterpreted as pathogenic, it could result in inappropriate treatment.

GLOVES MUST BE WORN FOR ALL VENIPUNCTURES.

Do not put on gloves until you are ready to do the venipuncture. If your cart, supplies, the patient bed, armband, PDA and the patient is touched with your gloves, you have picked up many organisms on your gloves. These organisms will be introduced to the blood culture.

Blood culture contamination is most likely to occur during attempts to relocate difficult-to-find veins by palpation after a site has been sterilized if you must go back and feel for the vein prior to the venipuncture and after the venipuncture site has been cleaned, #1 Do not touch the actual site that you will stick. Feel above or below the area on the vein that you have chosen. If you touch where you will stick, you must re-do the chloraprep sterilization process and let the area dry completely. #2 Clean the tip of your glove on the finger that you will feel for the vein with chloraprep just as you did the patients arm.

If the specimen collector uses poor collection technique, they can introduce organisms into blood culture bottles.

Do not palpate the venipuncture site after the site has been prepared without first cleaning the gloved finger.

Failure to wipe the tops of the bottles with alcohol and allow to dry.

Using too little or too much blood for the culture can result in a false negative/positive cultures.

Injection of air into the anaerobic bottle can cause the death of some anaerobic microorganisms and, again, result in a false-negative culture.

This is the reason the anaerobic bottle must be filled first.

Remove the cap at bedside so as not to introduce air into the vials and cause contamination.

Only use syringes.

Use the correct order of draw. Always collect the blood cultures first.

anaerobic aerobic

The results of such organisms can be measured in both financial and human terms. One study showed that contaminated blood cultures can increase a patient’s hospital stay as much as 4.5 days and add more than $5,000 to the cost of treatment. (Adjusted for inflation-May 2000). Incorrect data can keep patients from rejoining their families and their jobs and from reclaiming their daily lives.

SKIN PREP

Chlorhexidine antisepsis reduces the rate of blood culture contamination. chlorhexidine is effective against all nosocomial pathogens, and primary bacterial resistance is rare.

Apply to dry skin by scrubbing with back and forth strokes for 30 seconds being careful to maintain contact with the skin. Skin bacteria are found in the first five layers of the skin, and concentric circles are not effective in removing these organisms. Scrubbing allows for more friction and better antisepsis. You then allow the site to air dry for 30 seconds. The applicator contains 2% chlorhexidine gluconate and 70% isopropyl alcohol, allowing for a fast dry time.

WRONG CORRECT

BLOOD CULTURE BOTTLE TOP PREP

Clean the blood culture bottle tops with alcohol. Allow the tops to dry. Do not touch after they have been cleaned.

LABELING

Label the blood culture bottles at bedside Do not Cover the Barcodes on the bottles. If you are drawing more than one set, the bottles must be labeled as which set with the date and time of collection. The initials of the person collecting the specimen is required to be on the bottle.

Label bottles with the appropriate patient information label. Ensure that barcodes on the bottles are not covered by additional labels.

COLLECTING ADEQUATE VOLUMNS

The volumn of blood collected is the Key to a good blood culture

The optimal volume for blood culture collections from adults is considered to be 20mL of blood per set, distributed between 2 bottles, and not to exceed 8 mL to 10 mL per bottle. Overfilling the bottles will trigger the instrument detectors with an alarm, indicating a positive (growth of bacteria) blood culture. This is a false positive. You may also get false-negative results if you do not put in the required amount of blood by overwhelming the media in the bottle and the bacteria die.

Filling bottles directly through a needle/tube-holder assembly is not recommended because of the risk of reflux of the broth media back into the vein and the difficulty of assessing the volume of blood drawn. It is a good idea to mark a fill line on the blood culture bottle prior to collection.

DO NOT COLLECT SPECIMENS WITH A VACUTAINER.

When drawing blood cultures using a "butterfly" needle, the aerobic culture should be drawn first. Aerobic refers to bacteria that grow in the air and anaerobic refers to bacteria that do not grow in the air. Since there is air in the "butterfly" needle tubing anaerobic specimens cannot be drawn without first removing the air from the tubing. The tops of any containers used when drawing a blood culture should be sterilized with the use of a alcohol scrub that is allowed to dry.

SETS

Most orders are for blood cultures times two. Never collect the second blood culture from the same site. Using two different sites increases the likelihood of capturing sparse and transient populations of microorganisms, it is also better for the patient to use two sites, lessening trauma to the vein and avoiding hematomas.

Drawing multiple sets from a single puncture is unacceptable and makes interpretation impossible should the culture be contaminated by poor site preparation. Multiple bottles filled from the single venipuncture should be regarded as a single blood culture.

Step one: Skin preparation

Wash your hands with soap and water then dry

Clean any visibly soiled skin on the patient with soap and water then dry.

Apply a disposable tourniquet and palpate to identify vein

Release tourniquet

Clean skin with a ChloraPrep® swab and allow to dry

Step two: Preparation

Clean the tops of culture bottles with an alcohol swab and allow to dry

Sample Collection:

Wash and dry your hands again or use alcohol hand rub and apply clean gloves

Apply tourniquet. Do not palpate again after cleaning. Collect sample and release tourniquet

Cover the puncture site with an appropriate dressing.

If blood is being collected for other tests, always inoculate the blood culture bottles first. Inoculate the anaerobic bottle first.

Discard needle and syringe in a sharps container.

Wash hands after removing gloves