dermal

• Collection of blood samples

  Venipuncture is the most frequently performed phlebotomy procedure, but dermal puncture is appropriate in certain circumstances due to advances in laboratory instrumentation and point-of-care testing
• Reasons for using dermal puncture in infants and children under 2 years

  • Locating superficial veins is difficult
  • Deep veins can be dangerous
  • Drawing excessive blood can cause anemia
  • Certain tests require capillary blood
• Adult patients requiring dermal puncture

  • Burned or scarred patients
  • Patients receiving chemotherapy
  • Patients with thrombotic tendencies
  • Geriatric or other patients with fragile veins
  • Patients with inaccessible veins
  • Obese patients
  • Apprehensive patients
  • Patients requiring home glucose monitoring and point-of-care tests
• It may not be possible to obtain a satisfactory sample by dermal puncture from severely dehydrated patients, those with poor peripheral circulation, or swollen fingers
• Certain tests may not be collected by dermal puncture due to the larger amount of blood required, such as some coagulation studies, erythrocyte sedimentation rates, and blood cultures
• Correct collection techniques are critical in dermal puncture due to the smaller amount of blood collected and the higher possibility of sample contamination, microclots, and hemolysis
• Hemolysis is more frequently seen in samples collected by dermal puncture than in those collected by venipuncture
• Hemolysis interferes with tests affected by it and with newborn bilirubin determination
• Reasons for hemolysis in dermal puncture

  • Excessive squeezing of the puncture site
  • Increased RBC fragility in newborns
  • Residual alcohol at the site
  • Vigorous mixing of microcollection tubes after collection
• Blood collected by dermal puncture comes from capillaries, arterioles, and venules, making it a mixture of arterial and venous blood with small amounts of interstitial and intracellular fluids
• Warming the site before sample collection increases blood flow, producing a sample closer in composition to arterial blood
• Chemical differences between arterial and venous blood include higher glucose concentration in blood obtained by dermal puncture and lower concentrations of potassium, total protein, and calcium
• Alternating between dermal puncture and venipuncture should not be done when results are to be compared
• Dermal puncture equipment


  • Skin puncture devices
  • Microsample collection containers
  • Glass slides
  • Heel warmer
• Items in a phlebotomy collection tray or drawing station

  • Skin puncture devices
  • Microsample collection containers
  • Glass slides
  • Heel warmer
• Phlebotomy collection tray or drawing station

  • Contains skin puncture devices, microsample collection containers, glass slides, and possibly a heel warmer for use in performing dermal punctures
• Dermal Puncture Devices


  • Commercially available in varying lengths and depths
  • Must have Occupational Safety and Health Administration (OSHA) required safety devices that retract and lock after use
  • Many studies have been performed comparing the various devices with respect to efficiency of collection, sample hemolysis, and the formation of ecchymoses (bruising) at the collection site
  • No single method appears to be superior
• Depth of puncture


  Critical to prevent contact with bone
• Incision depth for heelsticks

  Should not exceed 2.0 mm according to the Clinical and Laboratory Standards Institute (CLSI)
• There is concern that even an incision depth of 2.0 mm may be too deep in certain infants, particularly premature infants
• Width of incision


  More important than the depth of the puncture to produce adequate blood flow
• The major vascular area of the skin is located at the dermal-subcutaneous junction
• Sufficient blood flow should be obtained from incision widths no larger than 2.5 mm
• Longer incisions should be avoided as they will produce unnecessary damage to the heel or finger
• Several color-coded lancets are available in varying depths and widths to accommodate low, medium, and high blood flow requirements
• The type of lancet selected depends on the age of the patient, the amount of blood sample required, the collection site, and the puncture depth
• Color-coded lancets


  • BD Microtainer Contact-Activated Lancet (Becton Dickinson)
  • BD Quikheel Lancets
  • Unistik 2 safety lancets (Owen Mumford, Inc)
• By documenting that the sample was collected by dermal puncture, the health-care provider can consider the collection technique when interpreting results
• Puncture devices


  • Unistik 2 Extra for tougher skin/larger sample
  • Unistik 2 Super for multitest situations and optimal blood flow
  • Unistik 2 Neonatal for heelsticks on newborns
• Heel incision devices


  • Tenderfoot toddler (pink), newborn (pink/blue), preemie (white), and micro-preemie (blue)
• Lancets


  • Tenderlett Toddler, Junior, and Adult lancets
• Capillary blood sampling devices

  • Unistik 2 Comfort, Normal, Extra, Super, and Neonatal
• Laser lancets


  • Lasette Plus (Cell Robotics International, Inc., Albuquerque, NM)
• Laser lancets are approved by the Food and Drug Administration (FDA) for adults and children older than 5 years
• Laser light penetrates the skin 1 to 2 mm, producing a small hole by vaporizing water in the skin
• Laser lancets create a smaller wound, reduce the pain and soreness associated with capillary puncture, and allow up to 100 µL of blood to be collected
• Major sample containers for microsamples

  • Microcollection tubes
  • Capillary tubes
• Capillary tubes


  Small tubes used to collect approximately 50 to 75 µL of blood for performing a microhematocrit test
• Capillary tube types


  • Plain tubes
  • Heparinized tubes
• Heparinized tubes should be used for hematocrits collected by dermal puncture, and plain tubes are used when the test is being performed on blood from a lavender stopper ethylenediaminetetraacetic acid (EDTA) tube