Important Pre-Procedural Step: The Modified Allen Test

This assesses collateral circulation (ulnar artery) to ensure hand viability if the radial artery is compromised.

Step-by-Step Procedure

Step 1: Preparation & Safety

• Informed Consent: Explain the procedure, its purpose, and that it is more painful than a venipuncture. Obtain verbal or written consent.
• Gather Equipment: ABG syringe (pre-heparinized), needle (typically 22-25 gauge), alcohol and chlorhexidine swabs, 2×2 gauze, adhesive bandage, ice slurry (if transport delay > 10 min), personal protective equipment (PPE): gloves, face shield.
• Patient Position: Supine or semi-Fowler’s with wrist extended. Place a small towel roll or positioning device under the wrist for hyperextension (approx. 30-45 degrees). Ask the patient to relax their hand (“like a handshake”).

Step 2: Artery Palpation & Site Selection

• Palpate the radial artery (medial to the radial styloid) for maximum pulse point.
• Avoid areas with scars, lesions, or overlying infection.
• Note the angle and depth of the artery.

Step 3: Skin Cleaning & Anesthesia (if used)

• Clean the site vigorously with alcohol, then chlorhexidine (or per facility protocol). Allow to air dry.
• Local Anesthetic (Best Practice): Using a small needle (e.g., 27-30g), inject 0.5-1.0 mL of 1% lidocaine WITHOUT epinephrine intradermally/subcutaneously over the artery. Wait 60-90 seconds for effect. This greatly reduces pain.

Step 4: Artery Puncture

1. Prepare Syringe: Hold the ABG syringe like a pencil. Remove the needle cap.
2. Anchor the Artery: Using the non-dominant hand, palpate the pulse firmly with the index and middle fingers. The fingers should straddle the intended puncture site.
3. Insert the Needle: Enter the skin at a 30-45 degree angle, bevel up, aiming directly for the point of maximum pulsation between your two anchoring fingers.
4. Advance: A flash of bright red, pulsatile blood will appear in the syringe hub. The syringe will self-fill due to arterial pressure. Do NOT pull back the plunger.
5. Collect Sample: Obtain 1-2 mL of blood (most syringes have a mark).

Step 5: Post-Puncture

1. Withdraw & Apply Pressure: Quickly withdraw the needle and immediately apply firm, direct pressure with sterile gauze for at least 5 minutes (longer if coagulopathic).
2. Expel Air & Mix: Immediately remove any tiny air bubbles, cap the syringe securely, and gently roll it between your palms to mix heparin. Do NOT shake.
3. Label & Cool: Label the syringe at the bedside with patient info. Place it in the ice slurryimmediately if there’s any delay in analysis.
4. Patient Care: Apply an adhesive bandage after ensuring bleeding has stopped. Instruct the patient to avoid using the wrist heavily for an hour.

Step 6: Sample Analysis & Documentation

• Transport to analyzer promptly (ideally within 10 minutes).
• Document: Time of collection, site used, patient’s temperature, respiratory rate, FiO2 (if on oxygen), any complications (e.g., hematoma).