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SUBJECT: Sampling for arterial blood gas analysis

(Blood is drawn anaerobically from a peripheral artery (radial, brachial, femoral, dorsalis pedis, or posterior tibial) via a single percutaneous needle puncture, or from an indwelling arterial cannula or catheter for multiple samples. Either method provides a blood specimen for direct measurement of partial pressures of carbon dioxide (PaCO2) and oxygen (PaO2), hydrogen ion activity (pH), total hemoglobin (Hbtotal), oxyhemoglobin saturation (HbO2), and the dyshemoglobins carboxyhemoglobin (COHb) and methemoglobin (MetHb)).

PURPOSE:

  1. To evaluate the adequacy of ventilatory (PaCO2) acid-base (pH and PaCO2), and oxygenation (PaO2 and SaO2) status, and the oxygen-carrying capacity of blood (PaO2, HbO2, Hbtotal, and dyshemoglobins).
  2. To quantitate the patient's response to therapeutic intervention and/or diagnostic evaluation (e.g., oxygen therapy, exercise testing).
  3. To monitor severity and progression of a documented disease process.

POLICY:

  1. Arterial blood gases are done on a physicianís order only.
  1. Sample will not be submitted if it is contaminated by air, improper anticoagulant or inappropriate anticoagulant concentration, flush solution (if sample is drawn from an indwelling catheter), or venous blood. The sample clots because of improper anticoagulation of the collection device, improper mixing, or exposure to air. If there has been delay of > l5 minutes for samples held at room temperature or > 60 minutes for samples held at 2-4įC.
  • The following should be monitored as part of arterial blood sampling:
    1. Inspired oxygen percentage and flowrate
    2. Proper application of patient device (e.g., venturi mask, partial rebreather or cannula)
    3. Mode of supported ventilation and relevant ventilator feedback (e.g. actual minute ventilation)
    4. Pulsatile blood return and appearance of puncture site after direct pressure has been applied and before application of pressure dressing for potential hematoma formation
    5. Presence or absence of air bubbles or clots in syringe or sample
    6. Patient's temperature
    7. Position and /or level of activity (if other than resting)
    8. Patient's clinical appearance and ease of (or difficulty with) blood sampling.

    EQUIPMENT:

    PROCEDURE:

    1. Obtain needed equipment.
    2. Perform Allenís test (both the radial and ulnar arteries should be compressed at a level approximately 1 centimeter proximal to the wrist joint while the patientís hand is squeezed for approximately 5 seconds then relaxed. The palmar surface of the hand should be blanched. Release compression on the ulnar artery. It is normal for the palmar surface to flush within 5 seconds. Prolonged delay before flushing indicates decreased ulnar artery flow. Radial arteries lacking collateral ulnar circulation should be avoided as puncture sites if possible. In adults if the radial artery is unsuitable as a puncture site, the brachial artery is the second choice, followed by the femoral artery).
    3. The skin over the puncture site is cleaned with 70% isopropyl alcohol or other suitable antiseptic solution.
    4. Palpate the site trying to stabilize the artery. Slight hyperextension of the wrist or elbow can be achieved by placing a rolled up towel under the joint; this can aid palpation and stabilization of the artery.
    5. Hold the syringe so the bevel of the needle faces upward, keeping the needle at a 25į to 45į angle to the artery. Insert the needle through the skin into the artery taking care not to puncture the posterior wall of the artery (if any venous blood is obtained the procedure should be restarted with a new syringe). If the artery is not entered immediately the needle may be slightly pulled back then redirected into the artery
    6. Arterial pressure should cause the blood to flow into the syringe.
    7. Withdraw the needle when an adequate sample has been obtained. Immediately place dry gauze or cotton over the puncture site and apply pressure.
    8. Maintain pressure over puncture site for a minimum of 5 minutes (longer if the patient has taken aspirin or anticoagulants).
    9. Single-handedly cap needle then remove from syringe.
    10. Expel any air bubbles from the sample and cap the syringe.
    11. Mix sample by rolling and tilting syringe.
    12. If not analyzed immediately, store the sample in ice (2-4įC). Iced samples should be analyzed within 3 hours.
    13. The puncture site should be compressed for a minimum of 5 minutes, longer if the patient is taking anticoagulant therapy, aspirin or has a prolonged prothrombin time. After 5 minutes, the puncture site should be inspected for several seconds to ensure that clotting has taken place. During this inspection, palpate the pulse proximal and distal to the puncture site to assess the presence of arterial spasm.
    14. A sterile bandage should be placed over the puncture site to keep the puncture site clean while healing. A bandage is not a substitute for compression of the puncture site.

    Technique for obtaining sample from infants and children:

    1. Obtain needed equipment (heparinized syringe should be 1 ml with a 25-guage needle or you may use a 25-guage butterfly infusion kit).
    2. Perform Allenís test (Radial: The patientís hand is squeezed by the clinician. The clinician then occludes the radial and ulnar arteries by compressing them at the patientís wrist with the middle and index fingers of both hands and forefingers. While both arteries are still occluded, the fist is unclenched. The palmar surface of the hand should be blanched. Release compression on the ulnar artery. It is normal for the palmar surface to flush within 5 seconds. Prolonged delay before flushing indicates decreased ulnar artery flow. Radial arteries lacking collateral ulnar circulation should be avoided as puncture sites if possible. If the radial artery is unsuitable as a puncture site, the dorsalis pedis artery is the second choice, followed by the posterior tibial artery. Femoral artery punctures are performed only in emergency situations in children and never in neonates)(Dorsalis pedis: The foot is elevated and both the dorsalis pedis and posterior tibial arteries are compressed. Pressure is released from the artery that will not be punctured, and the nailbeds and the sole of the foot are assessed for return of blood flow which would confirm collateral circulation).
    3. Follow number 3-14 in procedure.

    Technique for obtaining sample from arterial line:

    1. Turn stopcock off to patient.
    2. Remove the sterile cap from stopcock.
    3. Attach sterile syringe to stopcock.
    4. Open stopcock to syringe and intra-arterial catheter. Aspirate 3 ml of blood.
    5. Turn stopcock to the half-closed position, quickly remove syringe, and replace with heparinized syringe.
    6. Open stopcock to syringe and intra-arterial catheter and obtain arterial blood gas sample.
    7. Close stopcock to the syringe and remove syringe containing blood sample.
    8. Activate flush device to clear arterial line.
    9. Turn stopcock off to the patient and flush side port of stopcock into sterile syringe until all blood is cleared from stopcock.
    10. Close stopcock and replace sterile protective cap.
    11. Prepare arterial sample by holding syringe upright and remove air bubbles.
    12. Immediately seal syringe with cap.
    13. Roll and tilt syringe gently to ensure heparin mixing.

    If not analyzed immediately, store the sample in ice (2-4įC). Iced samples should be analyzed within 3 hours.

    CONTRAINDICATIONS:

    Contraindications are absolute unless specified otherwise.

    HAZARDS/COMPLICATIONS:

    LIMITATIONS OF METHOD/VALIDATION OF RESULTS:

    Limitations:

    Validation of results:

    INFECTION CONTROL:

    Sources/References:

    1. AARC Clinical Practice Guideline - Sampling for Arterial Blood Gas Analysis. Respir Care 1992;37:913-917
    2. Barnhart SL, Czervinske MP. Perinatal and Pediatric Respiratory Care, 1995; WB Saunders Company