DERMAL LEC

• Capillary blood is a mixture of arterial and venous blood, and may contain small amounts of interstitial and intracellular fluids
• Dermal puncture devices include lancets and microsample containers like capillary tubes and microtainers
• Depth of the puncture:

  • Newborns: 0.35 to 1.6 mm below the skin
  • Adults: 3.0 mm
• Microhematocrit tubes are small tubes used to collect approximately 50 to 75 µL of blood for performing a microhematocrit test
• Microtainers provide a larger collection volume and present no danger from broken glass, designed to hold approximately 600 µL of blood
• Phlebotomist preparation includes carrying only necessary equipment to the patient area, wearing gowns and gloves, and extensive hand washing
• Patient identification and preparation involve requisition form, verbal identification, and ID band, with verbal identification of pediatric outpatients possibly obtained from parents
• Patient position:

  • Seated or lying down with the hand supported on a firm surface, palm up, and fingers pointed downward for fingersticks
  • Infants lying on the back with the heel in a downward position for heelsticks
• Site selection:

  • Heel and distal segments of the third and fourth fingers are common sites
  • Performing dermal punctures on earlobes is not recommended
  • Areas selected should not be callused, scarred, bruised, edematous, cold, cyanotic, or infected
• Heel puncture sites are recommended for infants younger than 1 year, avoiding other areas of the foot to prevent damage
• Finger puncture sites are suitable for adults and children over 1 year of age, with fleshy areas near the center of the third and fourth fingers on the palmar side of the nondominant hand
• Cleansing the site involves using 70% isopropyl alcohol in a circular motion, allowing it to dry for maximum antiseptic action
• Warming the site dilates blood vessels and increases arterial blood flow, done by moistening a towel with warm water or using a commercial heel warmer for 3 to 5 minutes
• Puncture device disposal requires placing the used device in an appropriate sharps container, with a new device needed for additional punctures
• Performing the puncture:

  • The heel or finger should be well supported without squeezing the puncture area
  • Massaging the area before the puncture may increase blood flow
• Sample collection involves wiping away the first drop of blood, ensuring blood flows freely from the puncture site without milking the surrounding tissue
• Capillary tubes and micropipettes are held horizontally while being filled to prevent air bubbles, and sealed with sealant clay or designated plastic caps
• Microcollection tubes are slanted down during collection, with blood allowed to run through the capillary collection scoop and down the side of the tube
• Order of collection:

  • Capillary blood gases
  • Blood smear
  • EDTA tubes (lavender)
  • Other anticoagulated tubes
  • Serum tubes (red/yellow)
• Labeling the sample requires the same information as venipuncture samples
• Bandaging the patient involves applying pressure to the puncture site with gauze, elevating the finger or heel, and confirming bleeding has stopped before removing pressure
• Completion of the procedure includes disposing of used materials, removing gloves, washing hands, and thanking the patient or parents for their cooperation