PMLS LEC MODULE 6

• Evacuated tube system (ETS)


  The preferred method of blood collection today
• Syringe system


  Consists of a sterile syringe needle called a hypodermic needle and a sterile plastic syringe with a Luer-lock tip and a barrel

  
• Syringe needles


  • Come in a wide range of gauges and lengths for many different uses
  • Those appropriate for phlebotomy procedures are generally gauges 21 to 23, in 1- or 1.5-in. lengths
  • When used to draw blood, a syringe needle must have a resheathing feature to allow it to be safely covered and removed so that a transfer device can be attached to the syringe to fill the evacuated tubes

  
• The syringe procedure fell mostly out of favor due to the fact that it requires multiple "sticks" when needing to collect more than one tube of blood
• A syringe system is sometimes used for patients with small or difficult veins

  
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• Hypodermic Needle


  Syringe needles come in a wide range of gauges and lengths for many different uses. Those appropriate for phlebotomy procedures are generally gauges 21 to 23, in 1- or 1.5-in. lengths.
• Syringe needles used to draw blood

  • Must have a resheathing feature to allow it to be safely covered and removed so that a transfer device can be attached to the syringe to fill the evacuated tubes

  
• Syringe Barrel and Plunger


  Syringes come in a variety of sizes for various uses. Routine blood collection: 5ml, 10ml

  
• Syringe Transfer Device


  Blood collected in a syringe must be transferred into evacuated tubes. This device allows the safe transfer of blood into the tubes without using the syringe needle or removing the tube stopper.
• Syringe Transfer Device


  • Greatly reduces the chance of accidental needlesticks
  • Confines any aerosol or spraying of the specimen that may be generated as tubes are removed from it

  
• Comparing the syringe method with the evacuated tube system, the syringe plunger is used by drawing the plunger backwards which creates a vacuum that draws blood into the syringe barrel when the needle is inserted into a vein. Unlike the evacuated tube system, the vacuum created by applying pressure to the plunger is gradual and can be controlled by the phlebotomist so that sufficient pressure can be applied to draw blood into the barrel without causing the vein to collapse.

  
• Depending on the amount of blood required for testing, and the number of different blood collection tubes that the blood must be transferred to, more than one syringe may have to be filled.
• Unsafe Practices are also observed when using the syringe method since needle sticks are far more possible compared to the evacuated tube system. Such practices in the past were poking of the syringe needles through the tube stopper, or removing the tube stopper and ejecting blood from the syringe into the tube.

  
• Pros of the syringe method

  • Controlled aspiration of blood
  • You can change the needle gauge for smaller/thinner veins
  • Easily maneuvered
  • Cheap

  
• Cons of the syringe method

  • The volume of syringe used limits the fluid dispensing volume
  • Excessive resistance may lead to the build-up of pressure and eventual failure of the syringe pump
  • Needle pricks
  • Time consuming in transferring blood from one tube to another
• If the needle is too large for the vein for which it is intended, it will tear the vein and cause bleeding–hematoma.
• If the needle is too small, it will damage the blood cells during sampling, and laboratory tests that require blood cells, or hemoglobin may be invalid.
• Using a Syringe Transfer Device

  1. Attach the syringe transfer device to the syringe

  2. Place the evacuated tube into the transfer device

  3. Advance the tube onto the needle until blood flows into the tube

  4. Additional tubes can be filed as long as there is enough blood in the syringe
• Order of Draw


  • Sterile Tube (blood culture)
  • Blue-top coagulation tube
  • Serum tube (with or without clot activator, with or without gel)
  • Heparin tube (with or without gel plasma separator)
  • EDTA tube
  • Glycolytic inhibitor tube
• Additive


  May affect enzyme reactions
• Sodium fluoride


  • Destroys many enzymes
• Cellular constituents


  An additive may alter them
• As a future Medical Technologist, it is important that you develop an understanding on the materials and procedures for specimen collection
• Aside from technical skills, communication and rapport-building skills are essential in a successful specimen collection
• Each combination of additives is distinguished by a different colored top
• Different manufacturers may use slightly different color-coding schemes
• Sterile tube


  • Tests: Blood culture
  • Additive/s: Sodium polyanethol sulfonate
  • Number of inversions: 8 – 10 times
  • Specimen: Whole blood
• Coagulation tubes


  • Tests: Coagulation tests
  • Additive/s: Sodium citrate (3.2% or 3.8%) – because of the preservation of labile factors
  • Number of inversions: 3 - 4 times
  • Specimen: Whole blood
• CTAD tube


  • Test: Specialized platelet testing
  • Contains sodium citrate, theophylline, adenosine and dipyridamole
  • Minimizes in vitro platelet activation and the artificial entry of platelet factors into plasma
• Thrombin and soybean trypsin inhibitor tube


  Providing serum for determinations of certain fibrin degradation products
• 3.2% sodium citrate is CLSI recommended for coagulation tests on patients with polycythemia or hematocrit reading greater than 55% which requires that the anticoagulant to be decreased due to the rationale that if there is an excess sodium citrate, it will interfere with coagulation tests
• 1. 1 ratio of blood-to-anticoagulant should be maintained (e.g.: 4.5 mL blood and 0.5 mL sodium citrate)
• Overmixing can activate platelets and cause erroneous coagulation test results
• Red top tube


  • Tests: Stat and routine chemistry tests, ammonia, electrolytes, arterial blood gases
  • Additive/s: Silica (clot activator), none in glass
  • Number of inversions: 5 times for plastic tubes; none for glass tubes
  • Specimen: Serum after centrifugation
• Serum-separator tubes


  • Tests: Most chemistry tests; "stat" tests
  • Additive/s: Spray-coated silica (to increase platelet activation) and a polymer barrier gel
  • Number of inversions: 5 times, complete clotting within 30 minutes
  • Specimen: Serum after centrifugation
• Fibrin fibers in the serum of incompletely clotted centrifuged SSTs may cause blockages in the tubing of analyzers
• SSTs are used for most chemistry tests and prevent contamination of the serum by cellular chemicals and products of cellular metabolism
• SSTs are not suitable for use in the blood bank and for certain immunology and serology because the gel may interfere with immunological reactions
• SSTs are not recommended for therapeutic drug testing