Arterial Blood Gas Sampling - Sampling and Analysis

Sampling and Analysis

Arterial blood for blood gas analysis is usually drawn by a respiratory therapist and sometimes a phlebotomist, nurse or doctor. Blood is most commonly drawn from the radial artery because it is easily accessible, can be compressed to control bleeding, and has less risk for occlusion, the selection of which radial artery to draw from is based on the outcome of an Allen's test. The femoral artery (or less often, the brachial artery) is also used, especially during emergency situations or with children. Blood can also be taken from an arterial catheter already placed in one of these arteries.

There are plastic and glass syringes used for blood gas samples. Most syringes come pre-packaged and contain a small amount of heparin, to prevent coagulation or need to be heparinised, by drawing up a small amount of liquid heparin and squirting it out again to remove air bubbles. Once the sample is obtained, care is taken to eliminate visible gas bubbles, as these bubbles can dissolve into the sample and cause inaccurate results. The sealed syringe is taken to a blood gas analyzer. If a plastic blood gas syringe is used, the sample should be transported and kept at room temperature and analyzed within 30 min. If prolonged time delays are expected (i.e., greater than 30 min) prior to analysis, the sample should be drawn in a glass syringe and immediately placed on ice . Standard blood tests can also be performed on arterial blood, such as measuring glucose, lactate, hemoglobins, dys-haemoglobins, bilirubin and electrolytes.