Arterial Blood Gas Sampling

ContraindicationsTop

There are no absolute contraindications. Take special care in patients with significant coagulation abnormalities (eg, due to anticoagulant treatment), thrombocytopenia (<30×109/L), or with a diastolic blood pressure >120 mm Hg.

Potential ComplicationsTop

Bleeding, bruising, arterial spasm and arterial wall dissection, thrombosis, arterial embolism.

Patient PreparationTop

Obtain informed consent for the procedure. Place the patient in a supine position; a sitting position is optional in the case of upper extremity arterial blood sampling.

Puncture SiteTop

1. The radial artery in the palmar crease area, between the radial styloid process and the flexor carpi radialis tendon (the nondominant limb is preferred). It is recommended that the Allen test be performed before arterial puncture and particularly before arterial catheterization: Ask the patient to close their fist for 30 seconds, apply finger pressure to both forearm arteries (the ulnar artery and the radial artery; this is best done with the limb elevated), then release pressure on the ulnar artery. Repeat the test, this time releasing pressure on the radial artery. The capillary return time should be <5 seconds. The test is positive if the hand remains blanched after this time (this is a sign of impaired perfusion; see Figure: Testing for the involvement of hand arteries). Patients with positive results of the Allen test should not undergo arterial puncture on the affected limb. In emergencies it may not be possible to perform the Allen test; this should be documented in the medical chart.

2. The femoral artery distal to the inguinal ligament, most frequently in the inguinal crease (the artery is located lateral to the femoral vein and medial to the femoral nerve).

3. The brachial artery in the elbow (this site is not recommended due to the risk of hematoma causing nerve compression; if used, the nondominant limb is preferred).

EquipmentTop

1. Needle bore 0.5 to 0.6 mm (25-23 gauge) for radial artery puncture or 0.6 to 0.7 mm (23-22 gauge) for femoral or brachial artery puncture.

2. Heparinized syringe or insulin syringe flushed with heparin (optimally heparin should be drawn and then ejected via the needle that would subsequently be used for arterial puncture).

3. Stopper cap for sealing syringe (or needle) after sample collection.

4. Nonsterile disposable gloves; skin disinfectant (single-use alcohol swabs or single-use cotton swab with disinfectant solution); sharps disposal container; equipment for infiltration anesthesia if necessary (see Infiltration Anesthesia).

ProcedureTop

1. Perform hand hygiene and wear disposable gloves. Clean and disinfect skin (as for peripheral venipuncture: see Intravenous Injections) and anesthetize with 1% lidocaine.

2. Hold the artery still between your fingertips and insert the needle at a 90 degree angle (a 45 degree angle is optional for the radial artery; Figure 1).

3. After pulsatile blood outflow in the syringe is confirmed, draw ~1 mL of blood, gently pulling the syringe plunger. Take care not to aspirate air into the syringe. After sample collection, seal the syringe (or the needle) with a stopper cap and invert the syringe several times to mix the contents.

4. Apply compression to the artery until bleeding stops: for ≥5 minutes in the case of radial artery and for ≥10 to 15 minutes in the case of brachial or femoral arteries.

Blood gas analysis should be performed within 15 minutes. If this is not feasible, the blood sample can be stored in a refrigerator for ≤1 hour at ~4 degrees Celsius and transported to the laboratory on ice.

FiguresTop

Figure 21.19-1. Techniques of radial artery puncture for arterial blood gas sampling.