Venipuncture

• Dermal Puncture:

  • Composition of Capillary Blood:
  • Mixture of arterial and venous blood
  • May contain small amounts of interstitial and intracellular fluids
• Dermal Puncture Devices:

  • Lancets:
  • Depth of Puncture:
  • Newborn: 0.35 to 1.6 mm below the skin
  • Adults: 3.0 mm
  • Microsample Containers:
  • Capillary Tubes:
  • Used to collect approximately 50 - 75 µL of blood for performing a microhematocrit test
  • Color coded: RED for heparinized tubes, BLUE for plain tubes
  • Microtainer:
  • Holds approximately 600 µL of blood
  • Provides a larger collection volume and presents no danger from broken glass
• Dermal Puncture Procedure:

  • Phlebotomist Preparation:
  • Requisition Form
  • Wearing of Gowns and Gloves
  • Extensive Hand washing
  • Carrying only necessary equipment to the patient area
  • Patient Identification and Preparation:
  • Requisition form, verbal identification, and ID band
  • Excessive crying may affect the concentration of white blood cells and capillary blood gases
  • Patient Position:
  • Must be seated or lying down with the hand supported on a firm surface
  • For heel stick, infants should be lying on the back with the heel in a downward position
  • Site Selection:
  • Heel, distal segments of the third and fourth fingers
  • Performing dermal punctures on earlobes is not recommended
• Warming the Site:

  • Warming dilates the blood vessels and increases arterial blood flow
  • Moistening a towel with warm water or using a commercial heel warmer for 3 to 5 minutes effectively warms the site
  • The site should not be warmed for longer than 10 minutes to prevent altered test results
• Cleansing the Site:

  • Selected site is cleansed with 70% isopropyl alcohol
  • Alcohol should be allowed to dry on the skin for maximum antiseptic action
  • Failure to allow alcohol to dry can cause stinging sensation, sample contamination, hemolysis of RBCs, and prevent formation of a rounded blood drop
• Performing the Puncture:

  • Heel or finger should be well supported and held firmly
  • Massaging the area before the puncture may increase blood flow
  • Puncture Device Position:
  • Choose a puncture device corresponding to the size of the patient
  • Depress the lancet release mechanism and hold for a moment, then release
  • Puncture Device Disposal:
  • Place in an appropriate sharps container
  • Use a new puncture device if an additional puncture is required
• Sample Collection:

  • Wipe away the first drop of blood with clean gauze
  • Blood should be freely flowing from the puncture site as a result of firm pressure
  • Do not obtain blood by milking the surrounding tissue
  • Capillary Tubes and Micropipettes:
  • Held horizontally while being filled to prevent air bubbles
  • Tubes are sealed with sealant clay or designated plastic caps
• Order of Collection:

  I. Capillary blood gases

  II. Blood smear

  III. EDTA tubes - lavender

  IV. Other anticoagulated tubes

  V. Serum tubes - red / yellow
• Bandaging the Patient:

  • Apply pressure to the puncture site with gauze
  • Elevate the finger or heel and apply pressure until bleeding stops
• Labeling The Sample:

  • Microsamples must be labeled with the same information required for venipuncture samples
• Completion of the Procedure:

  • Dispose of all used materials in appropriate containers
  • Remove gloves, wash hands, thank the patient and/or parents for their cooperation
  • Only two punctures should be attempted to collect blood
• Venipuncture:

  • Most frequently performed procedure in phlebotomy
  • Patient Identification and Requisition Slips:
  • Requisitions must contain certain basic information to ensure correlation with the appropriate patient
• Information required on a requisition form for lab tests:

  • Patient's full name
  • Identification number
  • Patient's date of birth
  • Physician
  • Test(s) requested
  • Requested date and time of sample collection
  • Status of sample
• Other information on a requisition form:

  • Number and type of collection tubes
  • Special collection information (e.g., fasting for 8-12 hours, latex sensitivity)
  • Special patient information (e.g., areas to be avoided in collection)
• To ensure correct patient identification during blood draw:

  • Compare information obtained verbally and from the patient's wrist ID band with the information on the requisition form
  • Avoid asking yes or no questions for verification
  • Do not verify information from an ID band not attached to the patient
  • Do not attempt to collect blood from a sleeping patient
• Patient preparation for venipuncture:

  • Brief explanation of the procedure
  • Positioning the patient conveniently and safely
  • Asking about latex allergies
  • Using a pillow or towel for arm support
• Gloves and tourniquet application:

  • Gloves must be worn
  • Initial tourniquet application should be for 1 minute only
  • Tourniquet serves to impede venous blood flow and provide a larger amount of blood collection
• Site selection for venipuncture:

  • Antecubital fossa is the preferred site
  • Veins include median, cephalic, and basilic veins
  • Cleansing the site with 70% isopropyl alcohol in concentric circles
• Assembly of equipment for venipuncture:

  • Check equipment for defects
  • Ensure needle and syringe are properly screwed
  • Have extra tubes nearby
  • Do not place the collection tray on the patient's bed
• Steps for performing venipuncture:

  1. Re-apply tourniquet first

  2. Examine needle with bevel up

  3. Anchor vein

  4. Insert needle

  5. Fill tubes

  6. Remove needle before tourniquet

  7. Label tubes

  8. Bandage patient's arm

  9. Dispose of used supplies

  10. Inform the patient before leaving
• Venipuncture complications and pre-examination variables:

  • Addressing complications with sleeping or unconscious patients
  • Seeking assistance for unavailable patients
  • Ideal conditions for blood collection (basal state)
• Immediate local complications of venipuncture:

  1. Fainting (syncope)

  2. Failure of blood to enter the syringe

  3. Hemoconcentration or venous stasis

  4. Petechiae

  5. Vomiting

  6. Nerve injury
• Delayed local complications of venipuncture:

  1. Thrombosis of veins

  2. Thrombophlebitis

  3. Hematomas
• Areas to avoid during venipuncture:

  • Damaged veins
  • Hematoma
  • Edema
  • Burns, scars, and tattoos
  • Arm on the same side of a mastectomy
  • IV therapy
• Common difficulties encountered during venipuncture:

  • Hemolysis
  • Lipemia or lactescence
• Order of draw for blood collection tubes:

  • Stop Light Red Stay Put Green Light Go
  • SPS (Sterile - blood culture - yellow)
  • Sodium Citrate (Light Blue - Coagulation)
  • Clinical Chem with additive (Red non-additive - glass)
  • ImmunoSero (Clinical Chem with additive - plastic)
  • Chemistry (Serum separator - gold - gel)
  • CBC (Lavender - EDTA)
  • Glucose test (Gray - sodium fluoride/potassium oxalate)