Lesson 7

• Lancet


  Sterile, disposable, sharp instrument that either punctures or makes an incision in the skin
• Microcollection containers


  Microtubes or bullets - Special small plastic tubes used to collect the tiny amounts of blood
• Microcollection containers


  • Plastic - has anticoagulant
  • Have color-coded stoppers
  • Measured in µL (250 and 500)
• Microhematocrit tubes


  Disposable, narrow-bore plastic-clad glass capillary tubes that hold 50 to 75 µL of blood
• Microhematocrit tubes


  • Used for manual hematocrit (Hct) or packed cell volume (PCV) determinations
  • Coated with ammonium heparin (red or green band) or plain (blue band)
• Sealants


  Plastic or clay used to seal one end of microhematocrit tubes
• Microscope slides


  Used to make blood films for hematology determinations
• Warming devices


  Warm the site to increase blood flow by as much as seven times, but temperature must not exceed 42°C
• Capillary Blood Gas (CBG) equipment


  • CBG collection tubes - Long thin narrow-bore capillary tubes, most common 100 mm in length (100 µL), green band (sodium heparin)
  • Stirrers - Small metal bars or filings that aid in mixing the anticoagulant
  • Magnet - Used to mix the specimen
  • Plastic caps - Used to seal CBG tubes, either white or black
• Thick blood smear


  Qualitative - Identify what type of malaria is in the blood
• Thin blood smear


  Quantitative - Count of malaria species
• Capillary specimens are a mixture of arterial, venous, and capillary blood, along with interstitial fluid and intracellular from the surrounding tissues
• Interstitial


  Fluid in between cells
• Intracellular


  Within cells
• Capillary blood contains a higher proportion of arterial blood than venous blood
• Reference values for capillary blood differ from venous blood
• Glucose is higher in capillary blood than venous blood
• Total protein, calcium, and potassium are lower in capillary blood than venous blood
• Indications for capillary puncture


  • Available veins are fragile or must be saved for other procedures
  • Several unsuccessful venipunctures have been performed
  • The patient has thrombotic or clot-forming tendencies
  • The patient is apprehensive or has an intense fear of needles
  • There are no accessible veins
  • To obtain blood for POCT procedures such as glucose monitoring
• Reasons capillary puncture is preferred for infants and young children

  • Infants have a small blood volume (risks such as anemia and cardiac arrest)
  • Infant or child venipuncture is difficult and can damage veins and surrounding tissues
  • An infant or child can be injured by the restraining method used during venipuncture
  • Puncturing deep veins can result in hemorrhage, venous thrombosis, infection, and gangrene
• Capillary blood is the preferred specimen for some tests, such as newborn screening tests (NBS)
• Tests that cannot be collected by capillary puncture

  • Erythrocyte sedimentation rate (ESR)
  • Coagulation studies
  • Blood cultures
  • Tests that require large volume specimen requirement (e.g. liver profile, kidney function, lipid profile)
• Order of draw (CLSI)

  • Blood gas specimens (CBGs)
  • EDTA specimens
  • Other additive specimens
  • Serum specimens
• Specimens for newborn screening tests should be collected separately
• If patient is less than 6 years old, DO NOT EXTRACT, refer to pediatrics
• Capillary puncture steps


  1. Review and accession test request

  2. Approach, identify and prepare patient

  3. Verify diet restrictions and latex sensitivity

  4. Sanitize hands and put on gloves

  5. Position patient

  6. Select the puncture/incision site

  7. Warm the site if applicable

  8. Clean and air-dry site

  9. Prepare equipment

  10. Puncture the site and discard lancet

  11. Wipe away the first blood drop

  12. Fill and mix tubes/containers in the order of draw

  13. Place gauze and apply pressure

  14. Label specimen and observe special handling instructions

  15. Check the site and apply bandage

  16. Dispose of used and contaminated materials

  17. Thank patient, remove gloves, and sanitize hands

  18. Transport specimen to the laboratory
• According to the CLSI standards, capillary puncture must not be performed on the fingers or earlobes of newborns or other infants under 1 year of age

  
• Warming the site increases blood flow and produces an arterialized specimen
• Residual alcohol from cleaning the site causes rapid hemolysis of red blood cells
• The first drop of blood is contaminated with excess tissue fluid and may also contain alcohol residue that can hemolyze the specimen
• Hematology specimens should be collected first, followed by other anticoagulant containers, and serum specimen last
• If bleeding persists beyond 5 minutes, notify the patient's nurse or physician
• Bleeding should stop within 15 minutes after applying pressure and a bandage
• Newborn screening tests are collected by heel stick
• For malaria testing, collect blood when the patient is febrile (has a fever)
• Cold hands can cause vasoconstriction, which affects blood flow
• For bleeding time, do not wipe away the first drop of blood, as it takes 3-5 minutes for normal bleeding to stop