Skill 18-11

Obtaining an Arterial Blood Specimen for Blood Gas Analysis

Arterial blood gases (ABGs) are obtained to determine the adequacy of oxygenation and ventilation, to assess acid-base status, and to monitor the effectiveness of treatment (Fischbach et al., 2022). The most common site for sampling arterial blood is the radial artery (Hess et al., 2021). Other arteries may be used, but it may be a prescribed intervention to obtain the sample from another artery, based on facility policy.

Analysis of ABGs evaluates ventilation by measuring blood pH and the partial pressure of arterial oxygen (Pao₂) and partial pressure of arterial carbon dioxide (Paco₂). Blood pH measurement reveals the blood's acid-base balance. Pao₂ indicates the amount of oxygen that the lungs deliver to the blood, and Paco₂ indicates the lungs' capacity to eliminate carbon dioxide. ABG samples can also be analyzed for oxygen content and saturation and for bicarbonate values. Table 18-1 highlights the normal values for ABG. A respiratory technician or specially trained nurse can collect most ABG samples, but an advanced practice professional usually performs collection from the femoral artery, depending on facility policy. An Allen test should always be performed before using the radial artery to determine whether the ulnar artery delivers sufficient blood to the hand and fingers, in case there is damage to the radial artery during the blood sampling. A negative Allen test indicates the circulation from the ulnar artery is inadequate and a site other than the radial artery must be used (the opposite arm or another site) (Hess et al., 2021). Refer to the guidelines in this skill for performing an Allen test.

A blood sample for ABG testing may also be drawn from an arterial line. Refer to Skill 18-13.

Delegation Considerations

Obtaining an arterial blood specimen for blood gas analysis is not delegated to assistive personnel (AP). Depending on the state's nurse practice act and the organization's policies and procedures, obtaining an arterial blood specimen for blood gas analysis may be delegated to licensed practical/vocational nurses (LPN/LVNs). The decision to delegate must be based on careful analysis of the patient's needs and circumstances as well as the qualifications of the person to whom the task is being delegated. Refer to the Delegation Guidelines in Appendix A.

Equipment

ABG kit, or heparinized (100 to 200 IU) self-filling 10-mL syringe with 22- to 23-gauge, 1-inch needle attached
Airtight cap for hub of syringe
2 × 2 gauze pad
Adhesive bandage
Antimicrobial swab, such as chlorhexidine or alcohol, per facility policy
Waterproof protective pad
Prescribed local anesthetic cream, as indicated
Biohazard bag
Appropriate label for specimen, based on facility policy and procedure
Cup or bag of ice and water
Gloves
Goggles or face shield
Additional PPE, as indicated
Rolled towel

Assessment

Review the patient's health record for information about the need for an ABG specimen. Ensure that the necessary computerized laboratory request has been completed. Assess the patient for any allergies, especially to the topical antimicrobial to be used for skin cleansing. Investigate for the presence of any conditions or use of medications that may prolong bleeding time, necessitating additional application of pressure to the puncture site. Assess the patient's cardiac status, including heart rate, blood pressure, and auscultation of heart sounds. Also assess the patient's respiratory status, including respiratory rate, excursion, lung sounds, and use of oxygen, including the amount being used, if prescribed. Ask the patient about any previous laboratory testing they may have had, including any problems, such as difficulty with venipuncture; fainting; or reports of dizziness, lightheadedness, or nausea. Assess the patient's anxiety level and understanding of the reasons for the blood test. Assess the need/patient preference for use of a prescribed local anesthetic (Fischbach et al., 2022).

Determine the adequacy of peripheral blood flow to the extremity to be used by performing the Allen test (detailed below). If the Allen test reveals little or no collateral circulation to the hand, do not perform an arterial stick to that artery. Assess the patient's radial pulse. If unable to palpate the radial pulse, consider using the other wrist. Assess the patient's understanding about the need for specimen collection.

Actual or Potential Health Problems and Needs

Many actual or potential health problems or issues may require the use of this skill as part of related interventions. An appropriate health problem or issue may include:

Impaired gas exchange
Injury risk
Acute pain

Outcome Identification and Planning

The expected outcome to achieve is that an uncontaminated specimen will be obtained without injury to the patient or damage to the artery and sent to the laboratory promptly. In addition, the patient demonstrates an understanding of the need and process for specimen collection.

Implementation

Action	Rationale
1. Gather the necessary supplies. Check product expiration dates. Check the patient's health record to identify the prescribed ABG analysis. Check the health record to make sure the patient has not been suctioned within the past 20 to 30 minutes. Check facility policy and/or procedure for guidelines on administering local anesthesia for arterial punctures. Administer the anesthetic and allow sufficient time for the full effect before beginning procedure.	Organization facilitates efficient performance of the procedure. Use of products that have not expired ensures proper functioning of the equipment. Checking the prescribed intervention and policy ensures that the proper procedure is initiated. Suctioning may change the oxygen saturation and is a temporary change not to be confused with baseline for the patient. Arterial puncture is a source of pain and discomfort. Intradermal injection of lidocaine around the puncture site has been shown to decrease the incidence and severity of localized pain when used before arterial puncture (American Association of Critical-Care Nurses [AACN], 2017; Hess et al., 2021).
2. Perform hand hygiene and put on PPE, if indicated.	Hand hygiene and PPE prevent the transmission of microorganisms. PPE is required based on transmission precautions.
3. Identify the patient.	Identifying the patient ensures the right patient receives the intervention and helps prevent errors.
4. Explain the procedure to the patient. Tell the patient you need to collect an arterial blood sample and the needlestick will cause some discomfort, but that they must remain still during the procedure.	Explanation facilitates engagement and provides reassurance for the patient.
5. Check the specimen label with the patient's identification bracelet. The label should include the patient's name and identification number, the time the specimen was collected, the route of collection, identification of the person obtaining the sample, the amount of oxygen the patient is receiving, the type of oxygen administration device, the patient's body temperature, and any other information required by facility policy. Depending on facility policy, specimen labels may be verified after obtaining blood samples, prior to application to blood sample tubes.	Verifying the patient's identity validates that the correct procedure is being done on the correct patient, and the specimen is accurately labeled. Oxygen information and the patient's body temperature are required for accurate analysis.
6. Assemble equipment on the overbed table or other surface within reach.	Arranging items nearby is convenient, saves time, and avoids unnecessary stretching and twisting of muscles on the part of the nurse.
7. Close the curtains around the bed, and close the door to the room, if possible.	Closing the door or curtain provides for patient privacy.
8. Provide for good light. Artificial light is recommended. Place a trash receptacle within easy reach.	Good lighting is necessary to perform the procedure properly. Having the trash receptacle in easy reach allows for safe disposal of contaminated materials.
9. If the patient is on bed rest, ask them to lie in a supine position, with their head slightly elevated and their arms at their sides. Ask an ambulatory patient to sit in a chair and support their arm securely on an armrest or a table. Place a waterproof pad under the site and a rolled towel under their wrist.	Positioning the patient comfortably helps minimize anxiety. Using a rolled towel under their wrist provides for easy access to the insertion site.
10. Perform the Allen test (Figure 1) before obtaining a specimen from the radial artery.	Allen testing assesses patency of the ulnar and radial arteries (Hess et al., 2021).
a. Have the patient clench their fist to minimize blood flow into the hand.
b. Using your index and middle fingers, press on the radial and ulnar arteries (Figure 1A). Hold this position for a few seconds.
c. Without removing your fingers from the arteries, ask the patient to unclench their fist and hold their hand in a relaxed position (Figure 1B). The palm will be blanched because pressure from your fingers has impaired the normal blood flow.
d. Release pressure on the ulnar artery (Figure 1C). If the hand becomes flushed, which indicates that blood is filling the vessels, it is safe to proceed with the radial artery puncture. This is considered a positive test. If the hand does not flush, perform the test on the other arm.
11. Put on gloves and goggles or a face shield. Locate the radial artery and lightly palpate it for a strong pulse.	Gloves and goggles (or face shield) prevent contact with blood and body fluids. If you push too hard during palpation, the radial artery will be obliterated and hard to palpate.
12. Use a single-use sterile applicator containing sterile antiseptic solution to cleanse the patient's skin at the selected puncture site with the antiseptic solution identified in facility policy. Follow the manufacturer's directions for use to determine the product application process and dry times (Gorski et al., 2021). Allow the antiseptic to dry naturally; do not wipe, fan, or blow on the skin (Gorski et al., 2021). After disinfection, do not palpate the venipuncture site. If repeated palpation is necessary, the antiseptic solution must be reapplied before venipuncture (Gorski et al., 2021).	Cleaning the patient's skin reduces the risk for transmission of microorganisms. Allowing the skin to dry maximizes antimicrobial action and prevents contact of the substance with the needle on insertion, thereby reducing the sting associated with insertion. Allowing the area to thoroughly dry avoids the possibility of the solution causing hemolysis (Gorski et al., 2021). Palpation after cleansing contaminates the area.
13. Stabilize the patient's hand with their wrist extended over the rolled towel, palm up. Palpate the artery above the puncture site with the index and middle fingers of your nondominant hand while holding the syringe over the puncture site with your dominant hand. Do not directly touch the area to be punctured.	Stabilizing the patient's hand and palpating the artery with one hand while holding the syringe in the other provides better access to the artery. Palpating the area to be punctured would contaminate the clean area.
14. Hold the needle bevel up at a 45-degree angle (Hess et al., 2021) at the site of maximal pulse impulse, with the shaft parallel to the path of the artery.	The proper angle of insertion ensures correct access to the artery. The artery is shallow and does not require a deeper angle to penetrate.
15. If local anesthetic was not used, inform the patient that they are going to feel a pinch. Puncture the skin and arterial wall in one motion. Watch for blood backflow in the syringe (Figure 2). Pulsating blood will flow into the syringe. Do not pull back on the plunger. Collect 2 to 3 mL (Hess et al., 2021).	Warning the patient prevents a reaction related to surprise. Positioning the needle at the proper angle reduces the risk of puncturing through the artery. The blood should enter the syringe automatically due to arterial pressure.
16. After collecting the sample, withdraw the syringe while your nondominant hand is beginning to place pressure proximal to the insertion site with the 2 × 2 gauze. Press a gauze pad firmly over the puncture site until the bleeding stops—at least 5 minutes (Hess et al., 2021). If the patient is receiving anticoagulant therapy or has a blood dyscrasia, apply pressure for 10 to 15 minutes; if necessary, ask a coworker to hold the gauze pad in place while you prepare the sample for transport to the laboratory, but do not ask the patient to hold the pad.	If insufficient pressure is applied, a large, painful hematoma may form, hindering future arterial puncture at the site.
17. When the bleeding stops and the appropriate time has lapsed, apply a small adhesive bandage or small pressure dressing (fold a 2 × 2 gauze into fourths and firmly apply tape, stretching the skin tight).	Applying a dressing also prevents arterial hemorrhage and extravasation into the surrounding tissue, which can cause a hematoma.
18. Once the sample is obtained, check the syringe for air bubbles; remove excess air in the syringe by holding it upright and gently tapping it, allowing any air bubbles to reach the top of the syringe, and then expel the air (Hess et al., 2021).	Air bubbles can affect the laboratory values.
19. Engage the needle guard and remove the needle. Place the airtight cap on the syringe. Gently rotate the syringe. Do not shake it. Discard the needle in a sharps container. Remove your goggles and gloves and perform hand hygiene.	Engaging the needle guard prevents accidental needlestick injury. Using an airtight cap prevents the sample from leaking and keeps air out of the syringe, because blood will continue to absorb oxygen and will give a false reading if allowed to have contact with air. Rotating the syringe ensures proper mixing of heparin in the syringe with the sample; heparin prevents blood from clotting. Vigorous shaking may cause hemolysis. Removing goggles and gloves and performing hand hygiene reduce transmission of microorganisms.
20. Record date and time the sample was obtained on the label as well as the required information to identify the person obtaining the samples. Compare the specimen label with the patient identification bracelet, as required by facility policy. Depending on facility policy, the specimen label may be verified prior to obtaining blood samples (refer to Step 5). Apply labels to the specimens, according to facility policy. Place them in a biohazard bag. Insert the syringe into a cup or bag of ice water.	Labeling ensures the specimen is the correct one for the right patient. Packaging the specimen in a biohazard bag prevents the person transporting the samples from coming in contact with blood. Ice prevents the blood from degrading.
21. Remove equipment and return the patient to a position of comfort. Raise the side rail and lower the bed.	Repositioning promotes patient comfort. Raising the rails promotes safety.
22. Put on gloves. Check the puncture site for bleeding and to see if a hematoma has developed.	Gloves prevent contact with blood and body fluids. Continued bleeding or development of a hematoma requires further intervention.
23. Remove gloves and other PPE, if used. Perform hand hygiene.	Proper removal of PPE reduces the risk for infection transmission and contamination of other items. Hand hygiene reduces the transmission of microorganisms.
24. Transport the specimen to the laboratory immediately.	Timely transport ensures accurate results.

Evaluation

The expected outcomes have been met when an uncontaminated specimen has been obtained without injury to the patient and sent to the laboratory promptly, and the patient has demonstrated an understanding of the need and process for specimen collection.

Documentation

Guidelines

Document results of the Allen test, the time the sample was drawn, the arterial puncture site, the amount of time pressure was applied to the site to control bleeding, the type and amount of oxygen therapy the patient was receiving, pulse oximetry values, the respiratory rate and effort, the patient's other vital signs, and any other significant assessments or patient reactions.

Sample Documentation

Developing Clinical Reasoning and Clinical Judgment

Unexpected Situations and Associated Interventions

While you are attempting to puncture the artery, the patient reports severe pain: Using too much force may cause the needle to touch bone, causing the patient pain. Too much force may also result in advancing the needle through the opposite wall of the artery. If this happens, slowly pull the needle back a short distance and check to see if blood returns. If blood still fails to enter the syringe, withdraw the needle completely and restart the procedure.
You cannot obtain a specimen from the same site after two attempts: Stop. Do not make more than two attempts from the same site. Probing the artery may injure it and the radial nerve.
After inserting the needle, you note that the syringe is filling sluggishly with dark red-purple blood: If the patient is in critical condition, this may be arterial blood. But if the patient is awake and alert with a pulse oximeter reading within normal parameters, you have most likely obtained a venous sample. Discard the sample and redraw.
Patient is on anticoagulant therapy: Expect to hold pressure on the puncture site for at least 10 minutes. If pressure is not held sufficiently long, a hematoma may form, place pressure on the artery, and decrease the flow of blood.
Blood was drawn without incident, but now, 2 hours later, the patient is reporting tingling in the fingers, and their hand is cool and pale: Notify the health care team. An arterial thrombosis may have formed. If not treated, the thrombosis can lead to tissue necrosis on the extremity.
Puncture site continues to ooze: If the site is not actively bleeding, consider placing a small pressure bandage on the insertion site. This will prevent the artery from continuing to ooze. Continually check the site for bleeding and assess the extremity to ensure that blood flow is adequate. The site should be monitored for several hours for bleeding (Fischbach et al., 2022).
Allen test is negative: Try the other extremity. If the other extremity has a positive result (collateral circulation), use that extremity. If the Allen test is negative in both extremities, notify the health care team.

Special Considerations

General Considerations

Be aware that use of a particular arterial site is contraindicated for the following reasons: absence of a palpable radial artery pulse, a negative Allen test indicating obstruction in the ulnar artery, cellulitis or infection in the area of the site, presence of an arteriovenous fistula or shunt, severe thrombocytopenia (platelet count 20,000/mm³ or less, or based on facility policy), a prolonged prothrombin time or partial thromboplastin time, or an elevated international normalized ratio (Fischbach et al., 2022).
Anticipate possible adverse reaction and appropriate interventions: Some patients experience lightheadedness, nausea, or vasovagal syncope during arterial puncture (Fischbach et al., 2022).
If the patient is receiving oxygen, wait 15 minutes after a change in type or mode of oxygen delivery or rate for specimen collection for ABG analysis (Fischbach et al., 2022). Indicate the amount and type of oxygen therapy the patient is receiving on the laboratory request. Also note the patient's current temperature, most recent hemoglobin level, and current respiratory rate. If the patient is receiving mechanical ventilation, note the fraction of inspired oxygen and tidal volume.
If the patient is not receiving oxygen, indicate that they are breathing room air on the laboratory request for an ABG analysis.
Specimens collected within 20 to 30 minutes of respiratory passage suctioning or other respiratory therapy will not be accurate (Van Leeuwen & Bladh, 2017).
Consider obtaining an order for the use of a local anesthetic solution (1% lidocaine solution), gel, or cream to minimize discomfort and pain for the patient, based on facility policy (AACN, 2017; Fischbach et al., 2022). The use of 1% lidocaine without epinephrine injected intradermally around the artery puncture site has been shown to decrease the incidence of localized pain (AACN, 2017). Be familiar with the requirements and specifications for particular products available for use. Application needs to occur sufficiently far in advance to allow enough time to become effective, which may be contraindicated by the patient's condition. Consider such use of lidocaine carefully because it can delay the procedure. The patient may be allergic to the drug, or the resulting vasoconstriction may prevent successful puncture.
Consider the use of topical anesthetic creams to minimize discomfort and pain for the patient, based on facility policy. Allow 60 seconds after application for patients with light skin tones and 120 seconds for patients with dark skin tones before performing the venipuncture (Fischbach et al., 2022). Be familiar with the requirements and specifications for a particular product available for use. Application needs to occur sufficiently in advance to allow enough time to become effective.
If the femoral site is used for the procedure, apply pressure for a minimum of 10 minutes.
Arterial lines may be used to obtain blood samples (refer to Skill 18-13). When sampling from arterial lines, record the amount of blood drawn for each sampling. Frequent sampling can result in a significant amount of blood being removed.
Capillary blood gas samples may be used to estimate pH and PCO₂ in infants or other people when ABG analysis is indicated but arterial access is difficult (Hess et al., 2021).

Infant and Child Considerations

Consider a combination of techniques including swaddling, breastfeeding, pacifiers, rocking, and/or administration of oral sucrose (24%) beginning 1 to 2 minutes before the venipuncture procedure for young infants to decrease the incidence of procedure-related pain (De Bernardo et al., 2018; Gorski et al., 2021).
Consider using topical anesthetic creams or gels, refrigerant spray, or iontophoresis (application of electric current to carry ionized lidocaine through the skin) with infants and children, to decrease the incidence of procedure-related pain (Kyle & Carman, 2021). Apply the product for sufficient time to reach maximal effectiveness.
Consider the use of distraction to reduce anxiety and procedure-related pain (Erdogan & Ozdemir, 2021; Gorski et al., 2021; Kuo et al., 2018).

EVIDENCE FOR PRACTICE

Relief of Pain During Blood Specimen Collection

Needle insertion for venipuncture is painful. What interventions can assist nurses to reduce the pain associated with venipuncture and arterial puncture?

Related Research

Erdogan, B., & Ozdemir, A. A. (2021). The effect of three different methods on venipuncture pain and anxiety in children: Distraction cards, virtual reality, and Buzzy^® (randomized controlled trial). Journal of Pediatric Nursing, 58, e54-e62. https://doi.org/10.1016/j.pedn.2021.01.001

Refer to the details in the Evidence for Practice in Skills 18-9.

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Skill 18-11

EVIDENCE FOR PRACTICE