Evacuated Tube System

• An evacuated tube system uses air pressure for propulsion.
• Venipuncture Procedure (Evacuated Tube System Method)

  1. Most common and efficient system

  2. Preferred blood collection method by the CLSI

  3. Closed system – Whole blood is not exposed to air or outside contaminants

  4. Allows multiple tube collection with a single venipuncture
• Evacuated Tube System


  • Most common and efficient system
  • Preferred blood collection method by the CLSI
  • Closed system – Whole blood is not exposed to air or outside contaminants
  • Allows multiple tube collection with a single venipuncture
  • Reduces potential exposure of healthcare worker to the specimen
• Physiologic Factors affecting Test Results

  1. Posture – Lipids, Enzymes, Proteins (Albumin)

  2. Diurnal rhythm – Cortisol, Iron, PTH, Growth Hormone

  3. Exercise - Creatinine, CHONS, creatine kinase, LDH

  4. Stress - WBC, cortisol, glucose

  5. Diet – Fasting: Glucose and lipid

  6. Smoking – WBC count, cortisol, Hemoglobin
• Composition of blood


  1. In vivo the blood Is in a liquid form, but in vitro it will clot in a few minutes

  2. Blood that is freshly drawn into a glass tube appears as a translucent, dark fluid. In minutes it will start to clot, or coagulate, forming a semisolid jelly-like mass

  3. If left undisturbed in the tube, this mass will begin to shrink, or retract, in about 1 hour

  4. Complete retraction normally takes place within 24 hours

  5. When fresh whole blood is mixed with substances that prevent blood clotting, called anticoagulants, the blood can be separated into plasma, a straw-colored fluid, and its cellular components

  6. Serum – liquid portion of whole blood that is allowed to clot normally

  7. Plasma – liquid portion of whole blood mixed with substances that prevent clotting
• Environment factors associated with evacuated Blood Collection Tubes

  • Ambient temperature
  • Altitude
  • Humidity
  • Sunlight
• Ambient temperature


  1. Low temperature - pressure of the gas inside the tubes will decrease, leading to an increase in draw volume for the evacuated tube

  2. High temperature - reduction in draw volume, negative impact on the stability of certain tube additives such as biochemicals or gels
• Altitude


  Higher altitudes (>5000 feet) - Lower blood volume draw
• Humidity


  1. Very high humidity could lead to the migration of water vapor inside a tube that contains a moisture-sensitive material, such as a lyophilized additive

  2. Very low humidity could hasten the escape of water vapor from a tube containing a wet additive
• Light


  1. A special additive mixture for coagulation testing that is sensitive to light and found only in glass evacuated tubes is called CTAD (citric acid, theophylline, adenosine, and dipyridamole)

  2. The CTAD mixture minimizes platelet activation after blood collection
• Three Basic Components


  • Multisample Needles
  • Tube Holder
  • Evacuated Tubes
• Multisample Needles


  Multisampling needles with color-coded caps - 20 gauge – yellow, 21 gauge – green, 22 gauge - black
• Tube Holders


  Needles and Tube Holders with safety feature
• Safety Features


  • Provide immediate permanent containment and can be handled using one hand, which must stay behind the needle at all times
  • Include resheathing devices such as shields that cover the needle after use, blunting devices, equipment with devices that retract the needle after use (FDA considers this as important in preventing needle stick injury)
  • Fixed safety feature that provides a barrier between the hands and the needle after use
  • Allow or require the worker’s hands to remain behind the needle at all times
  • Integral part of the device and not an accessory
• Evacuated Tubes


  It is recommended that storage for all vacutainer blood collection tubes should not exceed 25 degrees C. If plastic tubes reach higher
• Requirements for a device that provides a barrier between the hands and the needle after use


  • Allow or require the worker’s hands to remain behind the needle at all times
  • Integral part of the device and not an accessory
• It is recommended that storage for all vacutainer blood collection tubes should not exceed 25 degrees C
• If plastic tubes reach higher temperatures, the tubes may lose their vacuum or implode
• Evacuated tubes are intended for one-time use only
• Possible causes of premature loss of vacuum in evacuated tubes

  • Improper storage
  • Opening the tube
  • Dropping the tube
  • Advancing the tube too far onto the needle before venipuncture
  • Needle bevel becomes partially out of the skin during venipuncture
  • Removing the tube before the vacuum is exhausted
  • Stoppage of blood flow during the blood draw can result in an underfilled tube called a partial draw or “short draw”
• Manufacturers guarantee reliability of additives and tube vacuum until an expiration date printed on the label
• Shelf life of an evacuated tube is defined by

  • Stability of the additive
  • Vacuum retention
• Ideal Gas Law: PV=nRT
• Antiseptics used in blood collection

  • 70% ethyl alcohol
  • 70% Isopropyl Alcohol
  • Benzalkonium Chloride
  • Chlorhexidine gluconate
  • Hydrogen Peroxide
  • Povidone-Iodine (0.1%- 1% Iodine)
  • Tincture of Iodine
• If a vein cannot be located in either arm, it may be necessary to examine the veins on the dorsal side of the wrist and hand. The veins in the feet should not be used without physician permission
• If a patient refuses to have blood drawn, notify nurse and document the refusal
• Occasionally a venipuncture is unsuccessful. Do not attempt to perform the venipuncture more than two times. If two attempts are unsuccessful, notify the phlebotomy supervisor
• Problems encountered in phlebotomy: Refusal by the patient to have blood drawn, Difficulty
• Phlebotomy complications


  1. Bleeding from the site of the venipuncture and hematoma formation are the most common vascular complications

  2. The second most common complication of venipuncture is infection

  3. Iatrogenic anemia, physician-induced anemia, or anemia resulting from blood loss for testing is known as anemia

  4. Post phlebotomy patients can exhibit neurologic complications, including seizure or pain

  5. Cardiovascular complications include orthostatic hypotension, syncope, shock, and cardiac arrest

  6. The most common dermatologic consequence of phlebotomy is an allergic reaction to iodine in the case of blood donors
• Problems encountered in phlebotomy

  • Refusal by the patient to have blood drawn
  • Difficulty obtaining a specimen because the bore of the needle is against the wall of the vein or going through the vein
  • Movement of the vein
  • Sudden movement by the patient or phlebotomist that causes the needle to come out of the arm prematurely
  • Improper anticoagulant
  • Inadequate amount of blood in an evacuated tube
  • Fainting or illness subsequent to venipuncture
• Special Site-Selection Situations


  1. A limb with an IV line running should not be used for venipuncture because of contamination to the specimen. The patient’s other arm or an alternate site should be selected

  2. Edema is the abnormal accumulation of fluid in the intracellular spaces of the tissue

  3. Veins are very difficult to palpate in areas with extensive scarring or burns. Alternate sites or capillary blood collection should be used

  4. Blood should never be drawn from a vein in an arm with a cannula or fistula. The preferred venipuncture site is a hand vein or a vein away from the fistula on the underside of the arm

  5. If a mastectomy patient has had lymph nodes adjacent to the breast removed, venipuncture should not be performed on the same side as the mastectomy
• Tubes should NOT be labeled prior to blood collection. Label each specimen before leaving with the patient’s full name, patients unique identification number date and time collected, phlebotomist’s initials and their other information required by the institution
• Hospital Waste Disposal


  • Red – puncture proof: Sharps and needles
  • Yellow – infectious wastes
  • Yellow with black band – chemical wastes
  • Green - non infectious wet
  • Black – non infectious dry
  • Orange – radioactive waste