Arterial Blood Gas Analysis and the Elderly

Vol. 16 •Issue 5 • Page 58
Arterial Blood Gas Analysis and the Elderly

As our population ages, RTs must be particularly skilled in caring for geriatric patients.

The respiratory therapist groans as you hand out her assignment. The patient is a 76-year-old curmudgeon with chronic obstructive pulmonary disease whose lengthy lectures about what’s wrong with hospitals today are well-known to the respiratory care department.

It’s easy to let negative attitudes and stereotypes interfere with successful care of elderly patients. They require a bit more time, energy, and empathy from health care personnel. As respiratory managers, it’s important to show your staff how these challenges also can bring great rewards.

The unique issues RTs encounter when obtaining arterial blood gas samples are a case in point. Your team not only must be aware of the patient’s condition, but also be able to modify physical examination and specimen collection accordingly. All the while, they must maintain good interpersonal skills and compassion.

Changes due to aging

The normal aging process and the effects of acute and chronic illness have implications in obtaining a ABG sample from both well and frail geriatric patients. For example, musculoskeletal system changes include loss of skeletal mass, diminished flexion and extension in the lower back and arms, and decreased muscle strength.

Muscular weakness and painful joints increase patient discomfort. RTs should keep these factors in mind when assisting the patient into the correct position to obtain the safest arterial puncture.

As the integument system ages, the skin wrinkles, and it becomes thin, fragile, and easily bruised. Subcutaneous fat is lost, and sweat glands atrophy. Hair loss on the scalp and other body areas often occurs.

Due to these factors, it’s important to be gentle with the patient when prepping and palpating the puncture site. Apply pressure only as needed to ensure a clean aseptic area and identify the track of the artery.

After completing the blood draw, raise the patient’s arm above the heart, while holding pressure to the site for at least three to five minutes and longer for patients on blood thinning therapy. Hematoma, the bleeding from the artery into the surrounding tissue, can occur if insufficient time or pressure is applied to the puncture site.

The aging process also influences the vascular system. Many studies have revealed that aging is associated with marked structural and functional changes of the blood vessel wall.

The vessel wall endothelium takes part in the local regulation of vascular tone by releasing relaxing and contracting factors such as neurotransmitters and circulating hormones. These normal changes may offer an explanation for the various vascular symptoms, including pain, cramps, swelling, and skin changes observed in the older person.

Arterial wall stiffness increases, and arterial compliance decreases with age. Aging blood vessels have greater lumen diameter and wall thickness. These factors may undermine the RT’s ability to obtain a rapid ABG specimen.

Anchoring of the artery may be needed in the elderly patient because many will have vessels that move out of their alignment, but be careful not to obliterate the pulse. Also, remember the radial and brachial nerves run adjacent to the artery, and passing a needle through them can do permanent damage.

Reducing risks

Obtaining an ABG analysis is one of the basic tests in determining pulmonary function in patients, but obviously it’s not without risks. Well-trained and prepared RTs help minimize the opportunity for complications to occur.

For example, before performing an ABG, the RT always should ask the patient if he or she has bleeding or clotting problems or is taking anticoagulant medication such as aspirin, warfarin, or heparin. Patients who are no longer receiving anti-coagulation dosages of the following drugs still will be susceptible to hematoma for the listed length of time:


  • aspirin: eight days
  • heparin: four hours
  • warfarin: two to five days.Be prepared to administer fresh-frozen plasma or other coagulation factors such as vitamin K injections to help restore clotting ability.

    When an artery is punctured, there’s always a danger of a thrombus forming and blocking the arterial blood flow. For this reason, it’s necessary to check for collateral circulation (Allen test) before the puncture and check for a pulse distal to the site of the puncture following the procedure.

    At the wrist, the radial artery is the site of choice for obtaining an arterial sample. The radial is near the surface, relatively easy to palpate and stabilize, and usually has good collateral supply from the ulnar arteries.

    Perform the modified Allen test on the hand with the best radial pulse. Many times, RTs observe geriatric patients who have cold hands and wrists in a very low perfusion state. If the patient’s pulse isn’t felt at the radial site on either hand, inform the physician. He or she may choose another site to administer the ABG.

    Acing the Allen test

    Here’s a refresher on how to perform the modified Allen test: Compress both ulnar and radial arteries at the wrist to obliterate pulses. Next, have the patient clench and release a fist until blanching of the hand occurs. Then, with the radial artery still compressed, release pressure on the ulnar artery and watch for the return of pinkness to the hand.

    However, not all geriatric patients will be able to squeeze their hands hard enough and some not at all to give a proper reading. If a patient is unable to cooperate, compress both ulnar and radial arteries at the wrist to obliterate pulses.

    Next, elevate the patient’s hand above the level of the patient’s heart. The idea is to drain the blood from the hand and have some blanching occur to compare with the return of blood. With the radial artery still compressed, lower the patient’s hand below the level of his heart, and release the pressure on the ulnar artery.

    If pinkness fails to appear using either technique, assume the patient’s collateral circulation is inadequate. Inform the ordering physician that you may be unable to obtain the ABG at the radial site.

    Interpersonal skills

    When asking geriatric patients to cooperate with maneuvers such as the Allen test, RTs must humanize their approach to patient care. This will help to reduce patients’ anxiety and confusion. Practice the following communication techniques:


  • Provide active listening and observation by recognizing the patient’s cues and letting him do most of the talking.
  • Provide reinforcement by encouraging a flow of conversation with small words, nodding your head, touching the patient’s hand, and maintaining steady eye contact.
  • Provide reflection by thinking about what it would be like to step into the patient’s shoes.
  • Use open questions prefixed by who, what, when, where, why, and how.It’s also essential to establish a relaxed atmosphere. Patients often feel vulnerable because of their lack of expert medical knowledge. Help level the playing field by providing instruction to the patient.

    Explain why an ABG is done. Relate it to the injury or disease state the patient is suffering from and how the information will help them get well. Tell the patient the procedure may be uncomfortable but that everything will be done to alleviate his discomfort. Emphasize the importance of normal breathing to prevent altering the analysis.

    Ensure that time at the bedside is all about patient comfort by spending a few minutes getting organized prior to performing the arterial puncture. Make sure all paperwork is obtained, the body temperature of the patient is known, and the ABG kit is prepared. Be certain the needle is attached firmly to the syringe, the patient name label is filled out, a needle stopper is ready, and the plastic bag has ice in it for sample protection. Following this simple checklist can expedite obtaining the sample and transporting it to the lab for analysis.

    In summary

    Geriatric patients have special needs in all aspects of care at the bedside. Acute and chronic illness often takes a sociological and psychological toll on these patients, so RTs must relate to them with compassion.

    With all these factors in mind, dealing with an elderly patient can be personally rewarding, and the results from ABG analysis will benefit the treatment plans of all the disciplines involved in the care of your patient.


    1. AARC clinical practice guidelines; sampling for arterial blood gas analysis. Respiratory Care. 1992;37:913-7.

    2.Giner J, Casan P, Belda J, et al. Pain during arterial puncture. Chest. 1996;110:1443-5.

    3.Hicks G. Blood gas and acid-base measurement. In: Dantzker D, MacIntyre N, Bakow E, editors. Comprehensive respiratory care. Philadelphia: WB Saunders; 1995.

    4.Shapiro BA, Peruzzi WT, Kozelowski-Templin R. Clinical application of blood gases, 5th ed. St Louis: Mosby-Year Book Inc; 1994.

    5.Vanhoutte P. Aging and vascular responsiveness. J Cardiovasc Pharmacol. 1988;12(suppl 8):S11-8.

    6.Luscher T, et al. Endothelium dependent control of vascular tone: Effects of age, hypertension and lipids. Basic Res Cardiol. 1991;86:143-58.

    7.Noll G, et al. Endothelial function of resistance arteries in aging and hypertension. J Appl Cardiol. 1991;6:185-93.

    8.Luscher T, Tanner F, Dohi Y. Age, hypertension and hypercholesterolemia alter endothelium-dependent vascular regulation. Pharmacol Toxicol. 1992;70(suppl 11)(6 Pt 2):S32- 9.

    Gene Gill, RRT, is a staff therapist practicing geriatrics, EENT, oncology, and critical care in the respiratory care services department at the University of Texas Medical Branch, Galveston.

    ABCs of ABGs

    The procedure for obtaining the ABG specimen is common for most health care facilities. Undesirable side effects can include infection so sterile technique must be used to ensure no pathogens will be passed directly into the patient’s blood stream.

    1. Verify the physician’s order.

    2. Check the patient’s record for precautions to be taken such as in anticoagulant therapy.

    3. Make positive identification: Check identification bracelet and/or bed label and ask for verbal identification.

    4. Introduce yourself to patient and explain what you’re about to do.

    5. Palpate right and left radial pulses. Select the vessel with the most prominent pulse for puncture.

    6. Perform the modified Allen test on hand with best radial pulse to ensure adequate collateral circulation.

    7. Open the ABG collection set, remove the pre-heparinized syringe, needles, and syringe cap; and fill plastic bag about half full with crushed ice.

    8. Assemble the syringe, keeping the chamber and tip sterile.

    9. Attach the needle to the syringe, keeping needle in sterile protective cap.

    10. Palpate the chosen radial artery as before, noting the point of maximal pulse. This will be the puncture site.

    11. Stabilize the wrist in the position that presents the maximal pulse.

    12. Rub the puncture site with a Betadine® prep pad, let the site dry, and then wipe the site with an alcohol prep pad.

    13. Remove the needle cap, and at a 35- to 40-degree angle, pierce the skin at the puncture site, and slowly advance the needle in one plane. When the artery is punctured, blood will enter the syringe. If the needle goes through the artery, slowly withdraw the needle until blood again appears in the syringe.

    14.After enough blood has filled the syringe, withdraw the needle and immediately apply pressure directly on the puncture site with sterile gauze. At the same time, insert the needle into the cork or rubber stopper provided in most ABG kits.

    15.After applying a pressure pad at the puncture site for a sufficient period of time, remove the pressure pad and again palpate a pulse distal to puncture site. Apply a clean adhesive bandage on the puncture site.

    16.Hold the syringe vertically, gently tap the barrel to dislodge any air bubbles, and advance the plunger until it forces any air out of the syringe. The cellular constituents of blood remain metabolically active while in the syringe. Air bubbles can cause a gas equilibration between the air and the arterial blood. This will lower the PaCO2 and increase the PaO2.

    If a large bubble is present, arterial gas tensions in the sample will change over time. If the sample can’t be analyzed quickly, it should be cooled immediately to 2ºC to 5ºC (simple ice slush). The sample can then be stored for up to one hour with little or no clinically significant effect on the result.

    17. Remove the needle and cap the syringe. Gently roll the syringe between the palms of your hands to mix the heparin and totally immerse the barrel of syringe in the bag of ice.

    18.On the lab slip, indicate the FIO2 and patient’s temperature, and check off the tests requested by the physician.

    19. Record any ventilator parameters on the appropriate clinical sheet, if applicable.

    20. Analyze the arterial blood and post the results; call the results to the physician if it’s appropriate.

    21. Document on the patient flow sheet, date and time of stick, results of Allen test, and which radial artery was used to perform puncture. Also document any undesirable side effects that may occur.

    –Gene Gill, RRT



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