Drawing ABG’s

Phlebotomists that have received additional training may perform a specific type of blood collection called an Arterial Puncture. This test is usually performed to obtain arterial blood gases, or ABG’s. Typically, ABG’s are performed by Registered Nurses, Respiratory Therapists, as well as EMT (Emergency Medical Technicians), Medical Technologists and Technicians.

A Level II Phlebotomist, one that has received additional training, that has been certified by their healthcare facility would perform ABG procedures in addition to their regular Phlebotomy duties. The training needed to perform this procedure includes theory, observation of the ABG procedure itself, as well as successful demonstration of the procedure under supervision.

Performing an arterial blood gas test (ABG’s) involves puncturing an artery and collecting arterial blood. This test can be more painful for the patient and is not, therefore, used for routine blood tests. In addition, performing an arterial puncture can be more difficult to perform and carries additional risks. Venous blood, blood from the vein, varies in composition depending on the area of the body it is taken from, for what area it serves. Arterial blood, however, remains consistent throughout the body.

Collecting Capillary Blood – Capillary blood is the smallest of the veins and arteries that form capillary beds. Used for infants and children, burn victims, as well as those elderly patients with poor veins, capillary blood can be obtained with a dermal puncture on the patient’s heel or fingertip. The blood collected is a mix of both venous and arterial blood.

Collecting Venous Blood – This is the most common type of blood collection, and most laboratory reference ranges are for venous blood. Collected from the vein, venous blood is blood that is deoxygenated, meaning it no longer is carrying blood. It flows from capillary blood vessels (tiny, hair like vessels) into larger veins to the right side of the heart. Venous blood is typically collected by directly accessing a vein, through a needle stick, in the antecubital area of the arm (bend) or the top of the hand (opposite the palm).

Collecting Arterial Blood – Deoxygenated blood is pumped from the right side of the heart. The blood then travels to the lungs where it becomes oxygenated. The oxygen- rich blood is then pumped through the left side of the heart through arteries. Obtained directly from the artery, ABG’s are performed to evaluate the arterial blood gases. Arteries used for this testing include the radial artery or the femoral artery (in the groin). Arterial catheters can also be used to obtain arterial blood.

The usual site for performing an arterial puncture is the radial artery. This is on the thumb side of the wrist. When choosing a site for an arterial puncture, the Phlebotomist must determine there is more than one artery supplying blood to the area. This ensures the patients’ circulation will not be compromised if there is an obstruction or any damage. The radial artery is ideal because both the radial and the ulnar artery, on the opposite side of the wrist, supply the hand’s blood supply.

The Phlebotomist also evaluates the tissue and surrounding structures that surround the artery. The surrounding tissue keeps the artery from rolling, and the site must be chosen to cause as little damage to the surrounding area as possible. The Phlebotomist must examine the surrounding area to make sure there are no rashes, inflamed areas, bruising (hematoma) and that there are no wounds near the chosen site.

Physicians and Respiratory Therapists use the valuable information provided by ABG’s in the diagnosis and treatment of critically ill patients or those with respiratory issues. The Phlebotomist may be ordered to obtain ABG’s on patients who suffer from asthma, heart conditions, cystic fibrosis or COPD (chronic obstructive pulmonary disease). Burn victims as well as those suspected of carbon monoxide poisoning can also need this test performed. A patient on mechanical ventilation, a machine that breathes for them, has ABG’s performed on a regular basis to ensure proper ventilation. This test is used for people who are in heart failure, kidney failure, who are suffering severe infection as well as those patients who have overdosed. This makes ABG’s one of the most common tests that are performed on critically ill patients.

When a person breathes in oxygen, it is not simply exhaled. A complicated oxygen exchange is done throughout the body in the process. The information provided by performing an arterial blood gas allows both the Physician as well as Respiratory Therapist to better understand the patient’s oxygenation levels – how well their body utilizes the oxygen they breathe. The arterial blood gas results can show how well a patient’s lungs are able to provide oxygen to the blood (our inhale), as well as how well the patient is able to rid itself of carbon dioxide (our exhale).

Additionally, this test shows a patient’s PH levels, which can be a good indicator of a critical process in the patient’s body. The test also shows the Respiratory Therapist the effectiveness of ventilation or oxygen that is being provided to the patient. Bicarbonate levels provided by the blood gas can show kidney function. The arterial blood gas also indicates the patients’ oxygen saturation level. Frequently seen in hospitals as a fingertip device, external devices such as a fingertip o2 device can be affected by a patient’s circulation. (i.e. if the patient has cold hands, the fingertip O2 saturation measure may inaccurately measure lower). The oxygen saturation level obtained by arterial blood gas testing is accurate. Oxygen saturation shows the percentage of oxygen breathed that actually goes to the tissues.

Those interested in pursuing Phlebotomy may notice a variance in duties from one facility to the next. While working at one hospital, the Phlebotomist may never perform an arterial puncture due to a large Respiratory Therapy department. However, at another facility, after additional training the Phlebotomist may regularly perform this test in addition to their regular blood draws. A recent online survey shows 58% indicated that at their facility all ABG’s were drawn by Respiratory Therapy, while 11% indicated at their facility the Phlebotomists performed over 90% of ABG’s.




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