ABG Sampling: Complications and How to Avoid

August 15, 2009

Note:

If needle comes out of the artery during specimen aspiration, withdraw needle, hold pressure, and start over.
If no blood is returned, slowly and carefully withdraw needle to re-enter artery.
If no blood return after first attempt, withdraw needle to point just below skin surface, change direction and descend needle again.
And finally, if unsuccessful after two attempts, withdraw needle completely and carry out post-puncture care.

Most series who have prospectively evaluated complications of arterial puncture have come to the same conclusion. The procedure is safe, the occurrence of severe complications are rare and most of the complications are minor and temporary.

Pain

Generally, arterial punctures are painful and the patient will feel some discomfort or pain sometime after the procedure even if a local anesthetic was used. Pain during and following the procedure is a frequent complaint and is reported to occur in 10% of the patient population. When systemically looked for, tenderness at the puncture site was observed in 15% of patients. You can minimize the pain by using thin needles and by the use of local anesthetic. However, the local anesthetic is ineffective in preventing late symptoms. Sometimes the pain is felt proximal or distal to the puncture site and this type of pain could be secondary to arterial spasm. In most cases the discomfort following an arterial puncture is temporary and minor.

Hematoma (Bruising)

Leakage of blood into tissue due to lack of sufficient elastic tissue to seal puncture site, especially in elderly. Because the blood is under considerable pressure in the arteries, blood is initially more apt to leak from an arterial puncture than from a venipuncture site. However, arterial puncture sites tend be close more rapidly due to the elastic nature of the arterial wall. This elasticity tends to decrease with age; therefore, the probability of a hematoma formation is greater in older patient or in patients receiving anticoagulants. Bruising is the most frequently observed complication occurring at 30% of puncture sites. In most, it is mild but in some you could encounter large bruises. The bruising is more common at the radial site. The brachial and femoral arteries lie deep, and this may account for less frequently observed bruising at these sites. A hematoma can occur at the puncture site in patients on anticoagulation. Serious retro peritoneal hemorrhage has been reported. The hematoma formation in anticubital fossa is tolerated poorly and can result in median nerve compression and ischemic changes secondary to compression of the artery. Ensure using small diameter needle. Ensure proper technique in holding site X5 minutes post-puncture.

Hemorrhage

Occurs when patient receiving anticoagulant therapy or patients with known blood coagulation disorders. Two minutes after pressure is released inspect site for bleeding oozing or seepage of blood; continue pressure until bleeding ceases. Sometimes a longer compression time is necessary.

Compression Neuropathy

Compression neuropathy secondary to hematoma occurs at the cubitalfossa and the inguinal region. The fascia that holds the neurovascular bundle is tight and any extravasation of blood is
tolerated poorly. In the anticubital fossa the brachial artery and the median nerve pass underneath the bicepital aponeurosis. This fascia is unyielding and any hematoma formation results in compression of the median nerve and brachial artery. If the fasciotomy is not performed, it could eventuate into Volkmann’s contracture. On radial artery puncture it is very rare, but some cases with temporary numbness of the hand were noticed.

Aneurysm

Aneurysm of the punctured vessel has been reported. This occurs with repeated punctures. Fortunately this complication is rare.

Arteriospasm

May occur secondary to pain or anxiety. Spasms can temporarily decrease the pulse and cause pain. Occasionally the vessel can occlude secondary to thrombosis. Rarely has perivascular fibrosis and occlusion of the vessel been noted. The collateral arch with ulnar artery fortunately prevents any serious ischemic changes.

A.V. Fistula

Iatrogenic arteriovenous fistula has been reported rarely in patients who have hand multiple arterial punctures. This complication is rare.

Mercury Embolism

Mercury embolism has been reported in the days when mercury was used as an aerobic seal and mixing agent. This complication does not occur any more.

Infection of Health Care Provider

Occurs when health care provider contacts with infections contained in blood of infected patients. Universal blood & body fluid precautions should be implemented. All blood samples from all patients must be treated with full precautions.

Infection/inflammation adjacent to puncture site

Can caused when inadequate cleansing prior to puncture. Ensure appropriate cleansing technique. Avoid sites indicating presence of infection or inflammation.

Thrombus formation

Injury to the intima of the artery can lead to clot (thrombus) formation. A large thrombus can obstruct the flow of blood and impair circulation.
Problems with the integrity of the ABG
The following are problems that can cause erroneous result in ABG analysis.

Air bubbles

If not removed immediately, oxygen from the bubbles can diffuse into the sample and CO2 can escape, changing the results.

Delay in cooling

Blood cells continue to consume oxygen and nutrients and produce acids and carbon dioxide at room temperature. If the specimen remains at room temperature for more then 5 to 10 minutes, the pH, blood gases, and glucose values will change. Cooling to between 1ºC to 5ºC slows the metabolism and helps stabilize the specimen. Processing the specimen as soon as possible after collection will ensure the most accurate results.

Venous blood mixed in ABG sample

Normal arterial blood is brighter, whereas venous blood is slightly darker in color. Sometimes it is difficult to distinguish between arterial and venous blood in patients with poor oxygen content. This will make their arterial blood appear as dark as venous blood. The best way to be certain that a specimen is arterial is if the blood pulses into the syringe. In some cases, such as with low cardiac output, a specimen may need to be aspirated. In such instances, it is hard to be certain that the specimen is really arterial.

Improper anticoagulant

Heparin is the accepted anticoagulant for ABGs. Oxalates, EDTA and citrates may alter results, especially pH. Too much heparin can cause erroneous results due to acidosis and too little can result in clotting.