SPECIMEN COLLECTION - ARTERIAL BLOOD GAS

Arterial punctures are the responsibility of Medical Technologist, Medical Laboratory Technicians and Technical Assistant III's authorized by training and competency to perform the procedure.

 

SELECTION OF BLOOD COLLECTION SITE:

There are three main arterial sites on each side of the body, which are easily accessible for arterial puncture. Two of these sites are available to laboratory personnel- the brachial artery immediately above the crease of the elbow and, more preferably, the radial artery at its site of most palpable pulsation in the wrist. The third is the femoral artery - laboratory personnel are not authorized to use this site. The patient's physician may use the femoral artery or other sites.

The patient's nurse may draw specimens through an arterial line.

In infants without an arterial line, laboratory personnel may be requested to draw an arterialized capillary specimen by heel stick.

 

HANDLING CONDITIONS:

To store blood samples for later analysis, place the syringe in ice. Blood gas values may change within five to ten minutes if the sample remains at room temperature.

Placing the specimen on ice maintains the temperature at 1° to 5°C which will stabilize the specimen and provide reliable results for one to two hours. However, it is best that analysis of the sample be performed as soon as possible.

 

EQUIPMENT AND MATERIALS:

All reagents and test materials for this test are stored at the analyzer at room temperature. Pulsator Plus arterial blood collection kits Ref # G1542 are ordered from Sims Poretx Co. as needed containing:

1. Air-tight plastic syringes
2. Sodium heparin (0.5 mL)
3. Syringe needle (23 gauge, preferably)
4. Cap
5. Alcohol prep pad
6. Sterile gauze
7. Band-aid

PROCEDURE:

Radial Puncture Procedure:

1. Check physician order; if appropriate, call the floor to verify that specified conditions in the order have been met.
2. Prepare blood gas kit at patient bedside.
3. Fill plastic bag with ice.
4. Attach needle to syringe and mix heparin in the syringe, completely coating inside.
5. Holding the syringe upright, pull the plunger back and forth to distribute the dry heparin.
6. Identify the patient and explain the procedure, including discomfort that might be expected (throbbing pain when the needle reaches the artery, possibly shooting pains to the fingers and thumb).
7. Record percent oxygen.
1. Room air
2. Oxygen via nasal canal = 21 (arm. air) + (4 x #l liters).
3. Oxygen via mask - percent O₂ set at valve on mask or near humidifier (if you can’t find it, ask the attending nurse).
8. Perform the Allen Test
1. Occlude radial and ulnar pulses at the wrist as the patient opens and closes fist until his palm blanches.
2. Release pressure on the ulnar artery only, and watch for flushing of the hand (return of color within 5 seconds indicates sufficient collateral circulation).
1. Note: For the unconscious patient - raise the hand above the heart level and squeeze until it blanches. Block radial and ulnar arteries and lower hand. Release pressure on ulnar and observe for flushing.
2. In either case, if the Allen Test fails, arterial puncture must not be performed and ordering physician notified.
9. Position the patient comfortably, with the arm fully extended and anterior surface upward. With middle and/or index finger, palpate the artery, locating the area of maximum pulsation.
10. Cleanse the area thoroughly with an alcohol sponge. Prep fingers used to palpate the artery. Cleanse the puncture site a second time.
11. Using forefinger and middle of your free hand to stabilize the artery, hold the syringe as you would a pencil at an angle between 45° and 90°, bevel up. Arterial pressure will push blood into the syringe.
12. After collecting 2-3 mL of blood, remove needle and immediately apply pressure to the puncture site. Maintain pressure a minimum of two minutes (3-5 minutes is preferable). If the patient is on anticoagulant therapy, apply pressure for 15 minutes and apply a pressure dressing.
13. Seal syringe, being sure to remove air bubbles. Rotate sealed syringe to mix blood with heparin.
14. Label syringe, put on ice, and transport to lab immediately. Recheck puncture site before leaving.

 

Radial Puncture Technique: Infants & Children

1. To minimize anxiety of other children within close proximity, perform in a treatment room.
2. Enlist the aid of sufficient personnel to provide for patient immobilization.
3. Use a heparinized tuberculin syringe. For greater maneuverability, a butterfly may be substituted for the conventional needle. REMEMBER: A plastic syringe will not provide arterial return alone; pressure must be applied.

 

Brachial Puncture Technique:

1. Consider this site only if neither radial is satisfactory.
2. Suppinate patient’s arm (palm up) with elbow straight.
3. Locate pulse above the brachial fascia at the elbow, but within one inch of the elbow.
4. Above this site, the median nerve is very close to the artery.
5. Above this site, the artery is more difficult to stabilize.
6. Cleanse site and prep fingers as for radial puncture.
7. Perform puncture at an angle of about 90°, avoiding veins that might be superimposed on the artery.
8. After collection, apply pressure. Do not leave patient until you are sure bleeding has stopped.

 

Arterialized Capillary Sample Collection Technique:

1. Warm capillary bed 5-10 minutes; vasodialation increases blood flow to near arterial rate.
2. Sites: heel pad, ear lobe, and fingertip.
3. Draw full heparinized capillary tubes, excluding air bubbles.
4. Seal both ends of tube.
5. Place on ice and transport to the lab immediately.

 

NOTES: Authorization process for all personnel is as follows:

1. To observe three (3) arterial punctures performed by an authorized technologist.
2. Perform at least three (3) arterial punctures under supervision of an authorized technologist.
3. Approval by pathologist for proficiency; competency report to be presented to pathologist after completion of orientation or annual competency.

Draw samples anaerobically, without introducing air bubbles in the syringe and cap the syringe. If bubbles develop during sample collection, remove them immediately.

Draw capillary samples in heparinized capillary tubes. Cap the tube on both ends.

LIMITATIONS: Do not use other common anticoagulants, such as EDTA, citrates, or oxalates, since they markedly alter the pH. Because of the high gas solubility of paraffin hydrocarbons, avoid the use of grease or mineral oil lubricants.

REFERENCES:

1. Anderson, James, 1983. Grant’s Atlas of Anatomy, 8th Ed., Williams and Wilkins. Baltimore. (plates 6-68, 6-74)
2. Annino, Joseph S. and Griese, Roger W., 1976. Clinical Chemistry: Principles and Procedures, 4th Ed., Little, Brown and Co., pp. 115-129.
3. Avery, Gordon, 1981. Neonatology, 2nd Ed., J.B. Lippincott Co., Philadelphia. p. 420.
4. Blood Gas Manager Model 1312; pH/Blood Gas Analyzer - Operator’s Manual, Instrumentation Laboratory, Inc., Lexington, MA.
5. Davidson, Israel and Henry, John B., 1974. Todd Sanford Clinical Diagnosis by Laboratory Methods. W.B. Saunders Co., Philadelphia. p520.
6. Droske, Susan. and Francis, Sally A., 1981. Pediatric Diagnostic Procedures, John Wiley and sons, New York. pp. 91-92.
7. Gunter, Clarence A., Ed, 1977. Pulmonary Medicine, J.B. Lippincott Co., Philadelphia. pp. 124-127.
8. Kaplan, Alex and Szabo, LaVerne. 1979. Clinical Chemistry Interpretation and Techniques. Lea and Febiger. Philadelphia. pp. 124-127.
9. Young, Pat and Stevens, June. Step by Step Through an Arterial Stick. RN, 1981, October. pp. 46-50.
10. Wong, Siew Jyu, M.D. 1983, Personal Communication. NHMH, Wilmington, NC.
    

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