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Vacutainer

2007 Schools Wikipedia Selection. Related subjects: General Chemistry

   A range of Vacutainer tubes containing blood.
   A range of Vacutainer tubes containing blood.

   Vacutainer is a brand of test tube specifically designed for
   venipuncture. It was developed in 1947 by Joseph Kleiner., and is
   currently marketed by Becton, Dickinson and company.

Principles

   Tiger top vacutainer filled with blood.
   Enlarge
   Tiger top vacutainer filled with blood.

   The vein is first punctured with the hypodermic needle, which is
   connected to a translucent plastic holder. The needle actually has a
   second, smaller needle, and when a Vacutainer test tube is pushed down
   into the holder, its rubber cap is pierced. The vacuum in the tube
   sucks blood though the needle and fills itself. The tube is then
   removed and another can be inserted and filled the same way. It is
   important to remove the tube before withdrawing the needle, as there
   may still be some suction left, causing pain upon withdrawal.

   The test tubes are covered with a colour-coded plastic cap. They often
   include additives that mix with the blood when collected (see below),
   and the colour of the tube's plastic cap indicates which additives that
   tube contains.

   The plastic caps are opaque for tubes with a normal vacuum.
   Translucent-topped tubes contain a weaker vacuum in the same sized
   tube, and will obtain less blood. The weaker suction makes them more
   suitable for smaller sized veins. Because of the standardised suction
   of the tubes, they may cause the veins of elderly people, or those with
   delicate veins, to collapse. In this case a syringe should be used
   instead.

Contents of tubes

   A large SST vacutainer.
   A large SST vacutainer.

   The tubes may contain additional substances that preserve the blood for
   processing in the medical laboratory. Using the wrong tube may
   therefore make the blood sample unusable.

   The substances may include anticoagulants (EDTA, sodium citrate,
   heparin) or a gel with intermediate density between blood cells and
   blood plasma. When the tube is centrifuged, the blood cells sink to the
   bottom of the tube, are covered by a layer of the gel, and the plasma
   (or serum) is left on top. The gel enables the tube to be tipped
   upside-down and transported without the blood cells remixing with the
   plasma.

   The meaning of the different colors are standardized across
   manufacturers. For more details on the meaning of these different
   colors, see , , or the bottom of .

   The Order of Draw refers to the sequence in which these tubes should be
   filled. The needle which pierces the tubes can carry additives from one
   tube into the next, and so the sequence is standardized so that any
   cross-contamination of additives will not affect laboratory results .

Containers containing coagulants

     * Gold - A serum-separating tube (SST). These contain particles that
       cause blood to clot quickly, as well as a gel to separate blood
       cells from serum. (Because the blood has clotted before it has been
       centrifuged, the liquid part is called serum not plasma.)
     * Orange - These tubes contain thrombin which makes the blood clot
       extremely rapidly. This allows the serum to be analysed in a
       shorter time.

Containers containing anticoagulants

     * Green - Contains the lithium salt of heparin, an anticoagulant.
       Also may contain ammonium or sodium salts of heparin.
     * Purple or lavender - contains EDTA. This is a strong anticoagulant
       and these tubes are usually used for full blood counts and blood
       films. Can also be used for blood banks.
     * Grey - These tubes contain fluoride and oxalate. Fluoride prevents
       enzymes in the blood from working, so a substrate such as glucose
       will not be gradually used up during storage. Oxalate is an
       anticoagulant.
     * Light blue - Contain a measured amount of citrate. Citrate is a
       reversible anticoagulant, and these tubes are used for coagulation
       assays. Because the liquid citrate dilutes the blood, it is
       important the tube is full so the dilution is properly accounted
       for.
     * Dark Blue - Contains the sodium salt of heparin, an anticoagulant.
       Also can contain EDTA as an additive or have no additive. These
       tubes are used for trace metal analysis.
     * Pink - Similar to purple tubes (both contain EDTA) these are used
       for ABO grouping and cross-matching.

Other

     * Red - Contains no additives. Tests for antibodies and drugs often
       require these.
     * Light yellow - Used in HLA phenotyping. Also contains SPS, used for
       blood cultures.
     * Speckled top - no anticoagulant. Also called a "tiger top" tube.
       Contains clot activator.

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