PMLS2 LEC - CAPILLARY PUNCTURE

• Capillary puncture


  Obtaining drops of blood for testing by puncturing or making an incision in the capillary bed in the dermal layer of the skin with a lancet or other sharp device

  
• Capillary specimen collection

  Especially useful for pediatric patients where removal of larger quantities of blood by venipuncture can have serious consequences
• Sites for capillary specimen collection

  • Finger (fingerstick) for adults and children over 1 year
  • Heel (heelstick) for infants less than 1 year and occasionally toddlers

  
• Lancets


  • Sterile, disposable, sharp-pointed or bladed instrument that either punctures or makes an incision in the skin to obtain capillary blood specimens
  • Available in a range of lengths and depths to accommodate various specimen collection requirements
  • Specifically designed for either finger puncture or heel puncture and must have OSHA-required safety features

  
• Microcollection containers/microtubes


  • Special small plastic tubes used to collect the tiny amounts of blood obtained from capillary punctures
  • Often referred to as "bullets" because of their size and shape
  • Most have color-coded bodies or caps/stoppers that correspond to color coding of ETS blood collection tubes, and markings for minimum and maximum fill levels typically measured in microliters (μL)
• Microhematocrit tubes and sealants


  • Disposable, narrow-bore plastic, or plastic-clad glass capillary tubes that fill by capillary action and typically hold 50 to 75 μL of blood
  • Used primarily for manual hematocrit (Hct), also called packed cell volume (PCV), determinations
  • The tubes come coated with ammonium heparin, for collecting Hct tubes directly from a capillary puncture, or plain, to be used when an Hct tube is filled with blood from a lavender-top tube
  • Plastic, clay, or wax-type sealants that come in small trays are used to seal one end of microhematocrit tubes
• Capillary blood gas equipment


  • Collection tubes are long thin narrow-bore capillary tubes, normally plastic for safety and available in a number of different sizes to accommodate volume requirements of various testing instruments
  • The most common CBG tubes are 100 mm in length with a capacity of 100 μL, with the inside coated with heparin, identified by a green band on the tube
  • Stirrers (e.g., small metal bars) are inserted into the tube after the blood is collected to aid in mixing the anticoagulant
  • A magnet is used to mix the specimen after both ends of the tube have been sealed
  • Plastic caps or closures are used to seal CBG tubes and maintain anaerobic conditions in the specimen
• Microscope slides


  • Occasionally used to make blood films for hematology determinations
• Warming devices


  • Increase blood flow as much as seven times, especially important when performing heelsticks on newborns
  • Provide a uniform temperature that does not exceed 42°C, or a towel or diaper dampened with warm tap water can also be used to wrap a hand or foot before skin puncture
• Capillary blood

  A mixture of arterial, venous, and capillary blood along with interstitial fluid (i.e., tissue fluid from spaces between the cells) and intracellular fluid (fluid within the cells) from the surrounding area
• Composition of capillary blood

  Contains a higher proportion of arterial blood than venous blood, especially if the area has been warmed as this increases arterial flow into the area
• Reference values for capillary blood

  May differ from venous blood, with typically higher concentrations of glucose and potassium, and lower concentrations of bilirubin, calcium, chloride, sodium, and total protein
• Indications for capillary puncture


  • Available veins are fragile or must be saved for other procedures
  • Several unsuccessful venipunctures have been performed
  • Large quantities of blood removed rapidly can cause cardiac arrest
  • Obtaining blood from infants and children by venipuncture is difficult and may damage veins and surrounding tissues
  • Puncturing deep veins can result in hemorrhage, venous thrombosis, infection, and gangrene
  • An infant or child can be injured by the restraining method used while performing a venipuncture
  • Capillary blood is the preferred specimen for some tests, such as newborn screening tests

  
• Capillary puncture is generally not appropriate for patients who are dehydrated or have poor circulation to the extremities from other causes, such as shock, because specimens may be hard to obtain and may not be representative of blood elsewhere in the body
• Tests that cannot be collected by capillary puncture

  • Erythrocyte sedimentation rate methods
  • Coagulation studies that require plasma specimens
  • Blood cultures
  • Tests that require large volumes of serum or plasma
• Order of draw for collecting multiple capillary specimens

  1. Blood gas analysis

  2. Slides (smears)

  3. EDTA (fill first before other microcollection tubes)

  4. Other microcollection tubes with anticoagulants/additive

  5. Serum microcollection tubes
• General steps in capillary puncture

  1. Review and accession test request

  2. Approach, identify, and prepare patient
• Accession


  The process of recording a specimen in the order received and taking steps to unmistakably connect the specimen and the accompanying paperwork with a specific individual
• Patient identification


  The most important step in specimen collection, verifying the patient's name and date of birth, checking ID bracelets, and performing a three-way ID check
• Misidentifying a patient or specimen can be grounds for dismissal and can even lead to a malpractice lawsuit
• If there are any discrepancies in patient identification, the nurse must be notified and the specimen must not be obtained until the issue is addressed and the patient's identity is verified
• For a sleeping patient, informed consent cannot be obtained, so the specimen should not be collected until the patient can be properly identified and consent obtained
• Patient Identification


  The process of verifying a patient's identity, the most important step in specimen collection
• Misidentifying patient or specimen can be grounds for dismissal of the person responsible and can even lead to a malpractice lawsuit against that person
• Px ID: Verifying Name and DOB

  1. Patient must actively be involved in the identification process

  2. Ask patient to state his/her full name and DOB

  3. CLSI recommends patient spell the last name
• Px ID: ID Bracelets

  ID band or bracelet; also called arm band or wrist band
• Px ID: Three-Way ID

  1. Patient verbal ID statement

  2. Checking of ID band

  3. Visual comparison of labeled specimen with the patient's ID before leaving the bedside
• Px ID: Discrepancies

  Notify the nurse, and specimen must not be obtained until addressed and px ID has been verified
• Px ID: Missing ID

  Ask nurse for verification before collecting the specimen
• Px ID: Sleeping Patient


  Wake the patient gently, informed consent cannot occur
• Px ID: Unconscious Patient

  1. Ask a relative, nurse, or physician to identify patient and record the name of that person

  2. Speak to the patient as you would to someone who is alert
• Px ID: Emergency Room ID Procedures

  1. Assign temporary number to patient and record it on the test request form

  2. Fill out labels by hand or computer and apply to them the test request and specimens after collection

  3. When a permanent number is issued, it must be cross-referenced to temporary number
• Px ID: ID of Young, Mentally Incompetent, or Non-English Speaker


  Ask the nurse, attendant, relative or friend
• Px ID: Neonates and Other Infants

  1. ID bands on lower legs under 2 years of age

  2. Ask the nurse, relative, or guardian and record them on the requisition
• Patient Preparation


  Explaining the procedure, addressing patient inquiries, handling patient objections, handling difficult patients, addressing needle phobia, addressing objects in patient's mouth
• Never attempt to explain the purpose of a test to a patient. Because a particular test can be ordered to rule out a number of different problems, any attempt to explain its purpose could mislead or unduly alarm the patient.
• If a patient truly objects and refuses, write requisition stating that patient refused to have blood withdrawn, and notify appropriate personnel.
• For cognitively impaired or combative patients, it is essential for an additional person or employee to be enlisted to assist if necessary. Make an unobstructed exit route in case it is needed. Be mindful of where you place your equipment.
• For patients in altered mental states, ask for assistance and consult facility protocol for guidance.
• Addressing Needle Phobia

  1. Have only the most experienced and skilled phlebotomist perform venipuncture

  2. Have patient lie down during the procedure with elevated legs

  3. Apply ice pack to the site for 10-15 minutes before venipuncture