PMLSMOD Capillary Puncture

• Selection of lancets depend on:

  • age of the patient
  • collection site
  • volume of specimen required
  • puncture depth needed to collect an adequate specimen without injuring bone
• Lasette

  • cleared by the FDA for use on the fingers of adults and children 5 years of age and older
• lasette

  • use on children younger than 5 years of age is subject to a physician's discretion
• another term for microcollection containers

  microtubes
• markings of measurement in microtubes

  microliters (uL)
• BD Microtainer MAP has a penetrable septum for use with automated hematology systems
• microhematocrit tubes and sealants


  used primarily for manual hematocrit (Hct) / packed cell volume (PCV)
• Heparin tubes typically have a red or green

  band on one end
• nonadditive tubes have a blue band
• Plastic or clay sealants that come in small trays are used to seal one end of microhematocrit tubes.
• Because of safety concerns, it is now recommended that sealing methods be used that do not require manually pushing the tube into the sealant or products be used that measure Hct without centrifugation.
• The magnet typically has an opening in the center or side so that it can be slipped over the capillary tube and moved back and

  forth along the tube length, pulling the metal stirrer with it, and mixing the anticoagulant into the blood specimen
• coated with ammonium heparin


  for collecting HCT tubes from a capillary puncture
• coated plain


  used when an Hct tube is filled with blood from a lavender top tube
• heparin band


  red or green
• sodium heparin band


  green
• nonadditive tubes


  blue
• Warming the site increases blood flow as much

  as seven times.
• Capillary specimens are a mixture of

  • arterial
  • venous
  • capillary blood
  • interstitial fluid (fluid in the tissue spaces between the cells)
  • intracellular fluid (fluid within the cells) from the surrounding tissues
• the concentration of glucose is normally higher in capillary blood specimens, whereas total protein (TP), calcium (Ca2+), and potassium (K+), concentrations are lower
• A properly collected capillary specimen can be a practical alternative to venipuncture when small amounts of blood are acceptable for testing.
• capillary puncture is an appropriate choice if:

  • The patient is apprehensive or has an intense fear of needles.
• capillary puncture is an appropriate choice if:

  • To obtain blood for POCT procedures such as glucose Monitoring
• capillary puncture for infants because:

  • Infants have a small blood volume; removing quantities of blood typical of venipuncture or arterial puncture can lead to anemia.
• capillary puncture for infants because:

  • According to studies, for every 10 mL of blood removed, as much as 4 mg of iron is also removed.
• capillary puncture for infants because:

  • Large quantities removed rapidly can cause cardiac arrest. Life is threatened if more than 10% of a patient’s blood volume is removed at once or over a short period.
• capillary puncture for infants because:

  • Obtaining blood from infants and children by venipuncture is difficult and may damage veins and surrounding tissues
• capillary puncture for infants because:

  • Puncturing deep veins can result in hemorrhage, venous thrombosis, infection, and gangrene.
• capillary puncture for infants because:

  • An infant or child can be injured by the restraining method used while performing a venipuncture.
• capillary puncture for infants because:

  • Capillary blood is the preferred specimen for some tests, such as newborn screening tests.
• TESTS THAT CANNOT BE COLLECTED BY CAPILLARY PUNCTURE:

  • most erythrocyte sedimentation rate methods
  • coagulation studies that require plasma specimens
  • blood cultures
  • tests that require large volumes of serum or plasma.
• Specimens must be collected quickly to minimize the effects of platelet clumping and microclot formation and to ensure that an

  adequate amount of specimen is collected before the site stops bleeding.
• Hematology specimens are collected first because they are most affected by the clotting process.
• Serum specimens are collected last because they are supposed to clot.
• The CLSI order of draw for capillary specimens is as follows:

  • Blood gas specimens (CBGs)
  • EDTA specimens
  • Other additive specimens
  • Serum specimens
• finger puncture

  A young child is typically held in the lap by a parent or guardian who

  restrains the child with one arm and holds the child’s arm steady with the other.
• Specific locations for capillary puncture include fingers of adults and heels of infants.
• The puncture site should be in the

  • central
  • fleshy portion of the finger
  • slightly to the side of center
  • perpendicular to the grooves in the whorls (spiral pattern) of the fingerprint
• General site selection criteria

  • warm
  • pink or normal color
  • free of scars, cuts, bruises, or rashes
  • should not be cyanotic (bluish in color)
  • NOT edematous (swollen), or infected.
• Do not puncture fingers of infants and children under 1 year of age. The amount of tissue between skin surface and bone is so small that

  bone injury is very likely. Infection and gangrene have been identified as complications of finger punctures in newborns.