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Carbon dioxide (CO2) angiography is an alternative to conventionial iodinated contrast angiography, particularly in situations where there are contraindications to iodinated contrast or where a less viscous or cheaper imaging contrast can be used to the operator's advantage. This activity educates the participant on indications, contraindications, and techniques for performing CO2 angiography. Objectives: Identify indications and contraindications for CO2 angiography. Recognize complications of CO2 angiography. Describe techniques for performing CO2 angiography. Explain advantages and disadvantages of CO2 angiography compared to iodinated contrast angiography and how an interprofessional team can use CO2 angiography to provide better patient care. Access free multiple choice questions on this topic.

Room air was used as a radiographic contrast (Rotenberg 1914) prior to the use of carbon dioxide (CO2) (Rosenstein 1921).  The first intravascular contrast to be used in humans in 1924 was a liquid (Brooks 1924). Decades later, CO2 was studied in the arteries and veins of human patients, first via needle injection (Barrera 1956) and then via catheter delivery.[1] With the development of digital subtraction angiography (DSA) and FDA-approved CO2 delivery systems, CO2 angiography has became a useful alternative to more commonly used iodinated contrast, particularly in situations where the patient is hypersensitive to iodinated contrast or has compromised renal function. CO2 angiography does have limitations and risks that must be understood prior to its use by novice angiographers.

The most feared complication for intravascular use is air embolism, which can result in stroke, myocardial infarction, paralysis, amputation, or death, although this risk across all patients when managed by experienced physicians is less than 1%. A large amount of CO2 trapped in the pulmonary artery or right side of the heart (only of concern during venography) obstructs venous return resulting in bradycardia and hypotension. The patient suffering this phenomenon should be rotated into a left lateral decubitus position in an attempt to separate the CO2 into a gas layer floating "on top of" and no longer interfering with the flow of the liquid and solid components of blood.  Large gas bubbles full of CO2 can be allowed to remain "trapped" in the heart and/or a relatively reduced distribution of right pulmonary arterial tree.  Within a relatively short time depending on the size of the bubbles, the gas molecules will entirely dissolve into the bloodstream. Some people experience side effects of paresthesia, tenesmus, or nausea. Normally, nausea is only encountered when high flow rates are used for angiography. Abdominal pain during mesenteric arteriography usually can be handled by rotating the patient from side to side and massaging the abdomen.  However, persistent abdominal pain may signal the presence of a vapor lock. This phenomenon is when gas, which may also include endogenous nitrogen and oxygen, becomes trapped intraarterially due to having a diffusion constant the prevents the gas dissolving in blood while simultaneously having a high enough partial pressure relative to blood that no blood can be pumped through the gas into the capillaries. The result if not treated is mesenteric infarction. This event is reported most commonly in the scenario of a large amount of CO2 collecting in an abdominal aortic aneurysm sac and then migrating into a mesenteric branch. First-line treatment involves attempting to dislodge the gas bubble mechanically via massage, patient rotation, and/or catheter aspiration. Additional management strategies for CO2 adverse events are discussed elsewhere.[6] There have been no reports of CO2 poisoning; CO2 poisoining from non-angiographic sources presents as hypotension and hypoventilation.[7]

CO2 angiography is used by a minority of angiographers and at a minority of institutions, even though it can offer advantages in diagnostic accuracy and patient outcomes in some settings. Improving health care practitioners understanding of advantages of CO2 angiography can enable practitioners to select CO2 contrast over conventional contrast in appropriate situations that may lead to better patient outcomes. [Level V]