Carbon dioxide (CO2) gas was used as a contrast agent in the venous circulation in the 1950s and 1960s to delineate the right heart for evaluation of suspected pericardial effusion. This imaging developed from animal and clinical studies, which demonstrated that CO2 use was safe and well-tolerated with peripheral venous injections.
In the 1970s, CO2 was used as an intra-arterial contrast agent. With the advent of digital subtraction angiography (DSA) in 1980, CO2 angiography became a useful diagnostic tool, particularly in patients who were hypersensitive to iodinated contrast material or whose renal function was compromised. Now, with the availability of high-resolution DSA and a reliable gas delivery system, CO2 angiography has become widely used for vascular imaging and endovascular procedures.
Because the use of CO2 is not associated with nephrotoxicity or allergic reactions, it is increasingly being used as a contrast agent for aortography, as well as for outflow assessment, renal arteriography, and visceral angiography. The gas is the preferred contrast agent for central venography of the upper extremity; for wedged hepatic venography in order to visualize the portal venous system before transjugular intrahepatic portosystemic shunt (TIPS); and for fine-needle TIPS procedures.
CO2 is used to guide various vascular interventions, including angioplasty and stent placement, transcatheter embolization, and endovascular abdominal aortic aneurysm (AAA) repair as can be seen in the images. The first image shows an aortic aneurysm seen with CO2 and the second is an angiogram of the blood vessels of the foot.
Advantages of carbon dioxide
CO2 is less dense than iodinated contrast medium, thus requiring digital subtraction for gas imaging. The overall quality of CO2 vascular images is slightly less than that obtained with contrast medium. Usually, multiple hand injections are required, and the radiation exposure to the operator and patient may be increased. However, CO2 has several notable advantages, as compared with iodinated contrast medium.
CO2 causes no allergic reaction. Because CO2 is a natural byproduct, it cannot cause a hypersensitivity reaction. Therefore, CO2 is an ideal alternative to iodinated contrast medium for patients who have a history of allergic reactions. No steroid preparation is needed when CO2 is used.
CO2 causes no renal toxicity. Experimental and clinical findings indicate that the selective injection of CO2 into the aorta or into the renal artery is safe and causes no renal injury, even in patients with diabetes or compromised renal function. Therefore, the gas is the preferred contrast agent for renal artery angioplasty and stent placement.
CO2 causes no hepatic toxicity. The authors have personally used CO2 as a contrast agent for celiac, splenic, superior mesenteric, and hepatic arteriograms for patients with a variety of disorders. No injuries to the hepatic parenchyma have occurred after the injection of CO2.
Unlimited amounts of CO2 may be used for vascular imaging because the gas is effectively eliminated by means of respiration. However, the operator should allow sufficient time for its clearance.
CO2 is particularly useful for patients with a compromised cardiac and renal function who are undergoing complex vascular interventions.
The vascular team at Narayana routinely uses CO2 for patients who need it as we have the specialised equipment needed to deliver CO2 safely and also the high-quality cath lab and software needed to interpret the images accurately.
