By Dr. David Chong

An arterial blood gas (ABG) will help in the assessment of oxygenation, ventilation, and acid-base homeostasis. It can also aid in the determination of poisonings (carboxyhemaglobinemia or methemaoglobinemia) and in the measurement of lactate concentration. Arterial puncture is a relatively straight forward technique that is easily performed at the bedside. Pulse oximetry will give a reasonable estimate of the adequacy of oxygenation in many circumstances but does not assess acid-base status or ventilation and should not be used alone in cases where these measurements are important.

Percutaneous puncture of the artery should be performed using standard precautions. The radial artery is the most common and best site for arterial puncture. The radial artery is easily compressible, superficial and has good collateral circulation. Except under unusual circumstances (i.e. severe peripheral vascular disease), it is not necessary to routinely perform an Allen’s test prior to arterial puncture. In patients that are hypotensive, the axillary and femoral arteries are potential alternate sites. Contraindications to these alternate sites include severe coagulaopathy and bypass grafting of that limb. Complications include pain, vasovagal episodes, hematomas, bleeding, and rarely aneurysyms.

1. Wear gloves.
2. Consider the use eye protection.
3. Place the patient’s palm upward and gently extend the wrist 10-20 degrees.
4. Clean the site with alcohol.
5. Consider 1-2% lidocaine with a 25 gauge needle to make a wheal over the puncture site for patient comfort.
6. Enter the skin at a 30-45% angle with a heparinized abg syringe.
7. Withdraw the needle from the skin and compress the site for 5 minutes.
8. Do not recap the needle (except for specially designed hinged caps) and remove the needle from the syringe and secure a syringe cap.
9. Place in an ice water slurry and transport to the lab expeditiously or
10. Place a drop of blood in an abg analysis cassette and insert into a bedside testing device.