Wednesday 7 March, 2007

Collect blood in the serum tube first

Posted in Emergency Dept., General Practice, Michael Tam, Procedures, Wards at 22:00 by Michael Tam

Original article by: Michael Tam :: Printer friendly

Vacutainer system

This short article is relevant for those people or institutions that use vacuumed tubes for venepunction and does not apply to using a needle and syringe.

One of the disadvantages of using a vacuumed tube system for directly withdrawing blood is that there is always a possibility that the needle dislodges or that the vein collapses before all the necessary tubes are filled.

For a long time, this would involve an apology from myself to my patient and a second venepuncture to collect the necessary blood. This is actually a reason that to this day, I still prefer using a plain needle and syringe (despite the increased needlestick risk) for patients with either difficult access or who require blood in many tubes.

However, this is a trick that I learnt from experience:

Always collect blood in the serum tube first.

The reason for this is simple: there are no additives in the serum tube and you can withdraw blood out of it to redistribute if necessary.

Despite the serum tube being usually quite large, only a couple of mililitres of blood are necessary for most simple tests (e.g., UEC, LFTs, Ca, Mg, PO4). If you have already collected 5-6 mL of blood and the vein collapses, you can easily (but carefully) redistribute this blood from the serum tube into any other necessary tubes (e.g., EDTA tube for FBC).

You must be quick, however, as once the blood as coagulated (usually 1-2 minutes), this trick is no longer feasible.

Please read the disclaimer


  1. Hildy said,

    My current technique for patients with potentially difficult access / many tubes worth of blood is to use a syringe and butterfly – my workplace uses sheathing butterflies which reduce the needlestick risk, and I find it much easier to hold the needle steady and apply negative pressure when the syringe and needle aren’t rigidly coupled.

    do you have a suggestion on how to couple the vacutainer+blue needle (adapter) system to a syringe easily? I’ve been popping the lids off the vacutainers and using no needle on the syringe, but I don’t really like doing that.

    • Robyn said,

      put the tubes in a stand then you can use needle and syringe to put the blood in (this is better than holding in your hand). Although I do think the safest option is to pop the lids off.

  2. Michael Tam said,

    My preferred technique is to use butterfly needle and syringe as well for safety reasons. However, there is absolutely nothing like the control you get with a needle on a syringe. With a needle and syringe (once you get the technique right), you can puncture the skin and withdraw blood with a single one hand. The other hand can be used to keep the skin taut and keep the arm steady (in the case of an uncooperative patient).

    Insofar as putting the blood from the syringe into the pre-vacuumed tubes, I usually just inject through the rubber (bad!), or when I’m feeling safety conscious, I pop off the tops.


  3. Hildy said,

    Something I tried today was keeping a tube rack (really a cut up piece of the foam the tubes come in) in my bag and leaving the tubes in that, so that I can inject through the rubber with no needlestick risk. It works reasonably well, but I don’t know how long the foam will last in my bag.

  4. Gasboy07 said,

    That’s a good one – I’ve never thought about doing it that way. Fill the serum tube first… will keep that one in mind.

    I’m naughty. I just stick the needle through the rubber.

    For difficult patients, I try a butterfly. If that fails there’s always the good old arterial jab…

  5. Hildy said,

    gasboy: if you’re in a hospital, though, I almost never use serum tubes (heparin tubes are preferred by my local lab for the standard tests).

    my crazy foreign-trained resident uses a technique with the brachial artery where he goes from lateral at a fairly shallow angle and tries to hit the vena comitans; if he misses it and goes into the brachial artery, then you still get blood (but have to press on it for longer).

  6. Michael Tam said,

    I cannot say what is in hospitals now, but they certainly had standard serum (i.e., gel) tubes when I was in hospital, and that wasn’t that long ago. Actually, how can you even get a UEC with a heparinised tube? (don’t you need to separate out the serum first??)

    Maybe different hospitals have different machines.

    As for your resident, that is definitely craziness and I would advise strongly against it. That technique sounds like high risk for the formation of an A-V fistula!

    If you need arterial blood, go for the radial artery preferentially. If you do need to go for the brachial, aim directly for the big pulsating thing! ;-)

  7. Hildy said,

    we have serum tubes, but for the majority of basic tests (UEC, CMP, LFT, etc) my local lab prefers heparin tubes to serum tubes for inpatients only. The rationale is that a hep tube can be centrifuged to obtain serum, whereas the serum tube must wait for the hour or two for it to be adequately clotted.

    I often go for a saphenous vein, but that doesn’t work in patients with pedal oedema (ie most of the sick ones).

  8. Neelkumar Gopikrishna said,

    How to handle Vacum System what are the dif., between Syrings & Vac Tube

  9. gasana paul said,

    this nice of collecting vein blood but i want to know more bout the anticoalant used in different analysis of blood

  10. Hildy said,

    having now worked in a place which uses serum tubes, I think this is bad advice – many serum tubes have clot activator which will really screw with the measurements of other things.

    the tube rack works well.

  11. Michael Tam said,

    The price of progress unfortunately.

    Yep, tubes with anything in them other than gel will screw up your blood results. It wasn’t so long ago that most serum tube had nothing in them apart from a gel to separate out the serum from the cellular component on centrifuge.

    If you need to take blood from someone with dodgy venous access, then I recommend collection into a syringe first.

  12. Whitey said,

    And I’m going to vote for the butterfly and syringe for difficult venepuncture also. What has not been mentioned is that this should be a two operator procedure. You get someone else to hold the syringe and generate some gentle negative pressure, and then you can concentrate 100% on getting the tip of the butterfly in the lumen of the vein, and then holding it there for as long as it takes.

    It’s a technique that I use probably 1% of the time, but there has never been a patient who I couldn’t get blood from with this technique.

  13. Landulpho said,

    Quando acontece da veia colapsar comigo a unica coisa que eu faço é soltar um pouco o torniquete… tentem isso e verão como poderão encher quantos tubos forem necessarios…
    Boa coleta para todos…

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