Procedure: Drawing Blood Cultures | LHSC

Identify Number of Samples to be Collected

See Blood Culture Ordering Decision Tree:

1. If the patient has no intravascular lines, draw 2 sets of peripheral cultures from 2 different draws (different lines or puncture sites).

• Blood cultures drawn at the time of line insertion can be considered "venipunctures".
• Once the line has been previously accessed for blood samples, it cannot be considered a venipuncture sample.
• If a patient is hypotensive or in shock, do not delay blood culture sampling while awaiting line placement. Obtain two peripheral cultures and start antibiotics STAT.
• If blood cultures cannot be obtained quickly in a patient in shock, do not delay administration of antibiotics.

2. If the patient has intravascular lines in place that are > 24-48 hours, draw cultures and request a "CAB" assessment as follows:

• Collect one set of blood cultures from a Peripheral Stab AND from EACH indwelling line (arterial, central line, PICC).
• Each set of blood cultures consists of one anaerobic and one aerobic bottle.
• Cultures from all sites should be drawn within 15 minutes.
• Dialysis lines should also be cultured, however, cultures must be drawn by a nurse approved for CRRT or hemodialysis.
• For multilumen central venous catheters, obtain blood culture from distal lumen whenever possible.
• If a patient has an implanted central venous catheter (e.g. Portacath for oncology), it must be accessed by a Vascular Access or Oncology nurse. 

3. If the patient has a previously established line that is being removed and obtain cultures from the line and at least one other site and send the tip for culture (done semiquantitatively).

NOTE:

A Catheter Associated Bacteremia (CAB) assessment will only be performed if a venipuncture sample is included (and labeled as a venipuncture sample). It required lab notification for appropriate setup of cultures.

If any indwelling line becomes positive more than 2 hours before the venipuncture culture first became positive, the blood stream infection (bacteremia) is unidentified as a CATHETER ASSOCIATED BLOOD STREAM INFECTION.

If all blood cultures become positive within a 2 hour window, the infection is not considered to be catheter associated.

All samples must go to the lab at the same time so that they can be setup together.

A newly established line can be considered a "peripheral stab" ONLY if it is newly established and has not been previously used for blood drawing. If the sample is drawn at the time of insertion, identify this as a "peripheral culture" in the lab orders.

If a peripheral culture cannot be obtained, report this under "Comments" in Power Chart (see item 7) and document in the AI flow sheet. (A CAB assessment will not be performed without a sample that is labeled as "venipuncture").

Simultaneous results from multiple sites aids in the interpretation of the results (e.g., differentiates contamination, colonization and clinical infection).  Multiple samples also increase the yield and potential for culture growth.

Mortality increases 8% with every 1 hour delay in the administration of appropriate antimicrobial therapy (ie. covers the actual organism).

The initial pre antibiotic blood culture is often the only one that shows the causative organism. 

TIP Cultures:

A positive tip culture with > 15 CFUs of an organism is used to identify that the catheter is the likely source of the positive culture (indicates high burden of organism attached to the catheter tip).