Nursing Student
New Grad

02.03 Blood Cultures

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  1. Purpose
    1. Obtaining blood cultures for testing without contaminating the sample

Nursing Points


  1. Supplies needed
    1. All supplies for venipuncture
      1. Antiseptic scrub
    2. Two sets of blood culture bottles
    3. Alcohol pads
    4. Needle or transfer device for getting blood into the bottles
    5. Patient labels

Nursing Concepts

  1. Steps and Nursing Considerations
    1. Perform all proper steps for venipuncture
    2. If obtaining via venipuncture, scrub skin with antiseptic scrub for a FULL minute and let dry
    3. Do NOT touch the skin after cleansing
    4. If using a butterfly directly from patient into bottle:
      1. Fill aerobic bottle first
      2. Minimum 5 mL in each
    5. If using syringe method
      1. Attach needle and purge air out of needle until a drop of blood is seen
      2. Fill anaerobic bottle first
      3. Minimum 5 mL in each
    6. Do NOT allow large air bubbles to enter the anaerobic bottle
    7. Label the bottles
      1. Patient identifiers
      2. Time and date of draw
      3. Your initials
      4. Location of draw (i.e. Rt arm, Lt AC)
  2. Blood cultures should be drawn from two sites, preferably on opposite sides if possible
  3. Blood cultures should NEVER be drawn off an existing line without explicit orders from a provider
    1. A positive culture from an existing line assumes the line itself is infected

Patient Education

  1. Purpose for blood cultures
  2. Preliminary results in 24 hours, final results in 48-72 hours

Reference Links

Study Tools

Video Transcript

In this video, we’re going to look at the priorities when drawing blood cultures. Specifically, in the drawing blood lesson we talked about how to do a venipuncture. One of the most important things you need to take from that lesson, though, is that when you’re drawing blood for cultures, you MUST scrub the site with an antiseptic scrub for a FULL minute. The #1 source of contamination in blood cultures is the bacteria found on the skin.

So, go back and watch that video if you need to. Right now we’re going to talk specifically about how to get the blood INTO the blood culture bottles appropriately. In school they tell you “pink then green, because ladies first” or something they want you to memorize. Well, you guys know we’re not all about that. We want you to UNDERSTAND the why behind the what and how to know which bottle to do first. One bottle will be for aerobic bacteria – that’s bacteria that can survive in air. The other bottle will be for anaerobic bacteria – ones that CAN’T survive in air. So when you’re thinking about which bottle to do first – always think about where the AIR is!!
If you’re using a butterfly needle like this and you’re going to insert it into the patient’s arm and then directly into the bottle – where is ALL of this air going to go?? Right into the bottle. So if I put it into the anaerobic bottle – all those bacteria are going to die and I’m not going to be able to test them, right? So in THIS case, you start with aerobic.
Now let’s think about if you had a syringe full of blood with a needle that you were going to insert into the bottles. If I turn this syringe upside down, where did the air bubbles go? They went to the top, right? So if I put 4 or 5 mL of blood in each bottle from the same syringe, the AIR will go in the second bottle. So which one do I do first? Anaerobic!
Now, let’s show you what this looks like. You really only need 5 mL of blood in each bottle, so if you have a syringe with 10 mL of blood, you’re going to split it. But that vacuum is SUPER strong, so you have to watch closely. First, clean the tops of the blood culture bottles – each with their own alcohol pad so you don’t cross contaminate. Then, purge any air out of the needle JUST until you see a drop of blood at the end. Then, insert the syringe first into the anaerobic bottle – as SOON as it drops down to 5 mL, pull straight out. Then, insert it into the aerobic bottle and let the rest of the blood go into that one.
When you’re done, of course you’re going to carefully place the syringe and needle directly into a sharps container.
When you draw blood cultures, you’re going to be using two different sites, usually from opposite arms. So when you label the bottles, you put the patient information, time, date, your initials, AND the location you drew that blood from – like “right arm” or “Left AC”. We NEVER draw blood cultures out of a line without explicit orders from the provider.
Then bag them up and send them to the lab as you normally would! You should get preliminary results in about 24 hours!
We hope that was helpful for blood cultures. Make sure you check out the “drawing blood” video to learn about venipuncture. And remember with Blood Cultures, we’re trying to avoid contamination at all costs, so clean the site REALLY well and don’t touch the site before you stick it, and clean the tops of the bottles with their own alcohol scrub! And, of course, make sure you don’t put air into the Anaerobic bottle.

We love you guys! Go out and be your best selves today. And, as always, happy nursing!