Carbon Dioxide Angiography May Be Alternative to Iodinated Contrast in High-Risk Patients

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The use of carbon dioxide (CO₂) in place of, or in addition to, contrast media in angiographic procedures may be a safe alternative in patients for whom iodinated contrast nephrotoxicity is a concern, according to a report published online August 15, 2011, in Archives of Surgery. The study documents over 20 years of experience with the technique at a single institution.

Researchers led by Fred A. Weaver, MD, of the University of Southern California, Los Angeles (Los Angeles, CA), reviewed data from 951 patients who underwent 1,007 CO₂ digital subtraction angiography procedures from 1989 to 2009 at their institution. Of these, 320 cases were performed with CO₂ alone, using a mean of 186 mL (range, 10-1,080 mL), and 502 cases involved the addition of iodinated contrast (median, 8.5 mL; range, 2-550 mL). In 185 procedures, there was no record of whether additional iodinated contrast was injected. The volume of supplemental contrast was slightly greater in venous procedures than in arterial procedures.

Procedural indications included limb ischemia, aortic aneurysm, renal or visceral occlusive disease, prophylaxis or treatment of pulmonary embolism, portal hypertension, and hepatic dysfunction.

Minor Creatinine Increases, Manageable Complications

The mean preprocedural creatinine value was 2.1 mg/dL, which remained unchanged after the procedure (P = 0.56). Of 504 patients with baseline creatinine levels greater than 1.3 mg/dL, 8% saw increases in serum creatinine of more than 0.5 mg/dL following the procedure. In 245 patients with baseline creatinine levels greater than 2 mg/dL, meanwhile, no change was seen in the postprocedure serum creatinine level, with 27 (11%) experiencing an increase of more than 0.5 mg/dL.

Complications occurred in 61 patients and primarily consisted of puncture-site hematoma (n = 16; 25%) and abdominal pain (n = 10; 16%). However, all cases of abdominal pain were recorded prior to 2005, when the center began using a newer CO₂ delivery technique. In 6 of the 10 patients with such pain, the symptom was transient and the CO₂ procedure was completed uneventfully. In the other 4 patients, the pain persisted and biochemical evidence of pancreatitis developed, which resolved with supportive care in 3 patients, while the fourth developed suppurative pancreatitis.

In all, 4 patients (0.4%) died, 2 as a direct result of the angiographic procedure.

In Use Since the 1950s

Intravascular injections of CO₂ were first used for diagnostic purposes in the 1950s to diagnose pericardial effusion, which could be visualized between the gas-filled right atrium and the adjacent lung. In 1982, CO₂ digital subtraction arteriography was first described and has been effectively used in a variety of angiographic procedures. In some cases, CO₂ may be supplemented with small doses of iodinated contrast.

CO₂ is of interest as a contrast agent because, among other reasons, it is:

• Inexpensive
• Widely available
• Highly soluble in blood and rapidly eliminated via the lungs
• Not nephrotoxic, making it desirable for evaluating patients with evidence of renal dysfunction
• Not a cause of allergic contrast reactions
• Characterized by low viscosity, allowing for smaller angiographic catheters and for enhanced filling of severely diseased stenotic vessels

 

One major problem associated with the use of CO₂ procedurally is a situation known as ‘vapor lock.’ Due to its buoyancy in blood, the gas preferentially fills nondependent vessels, but if the forces of buoyancy exceed the kinetic energy of venous flow that promotes gas clearing, CO₂ can become trapped within the vascular space. Despite being highly soluble and rapidly absorbed, large injection volumes in nondependent vessels increase risk, as does room air contamination of the gas that is being injected into the patient.

“Great care must be exercised to prevent violation of the seal of the delivery system and resultant contamination of the injected gas with room air,” the study authors write. “Multiple (at least 3) purgings of the system are important to ensure that all room air contamination is eliminated.”

Advantages Seen for Patients with Renal Dysfunction

Dr. Weaver and colleagues say their 21-year experience with the CO₂ technique provides clear evidence for an advantage in patients with renal dysfunction.

The observation that only 11% of patients with baseline serum creatinine greater than 2 mg/dL saw increases of more than 0.5 mg/dL “is in contrast to the 62% incidence of renal deterioration and increased overall mortality found in patients with preexisting renal dysfunction that was documented in a large series examining contrast-induced nephropathy at the Mayo Clinic,” they report.

“Consequently, although patient hydration, bicarbonate infusion, and N-acetylcysteine have been used in an attempt to mitigate the nephrotoxic effects of iodinated contrast, contrast nephrotoxicity remains an issue,” Dr. Weaver and colleagues stress. “Adding [CO₂ digital subtraction angiography] as a complement to the above strategies markedly reduces the iodinated contrast required and thus the nephrotoxic insult, particularly in aortic, visceral/renal, and lower-extremity arterial studies.”

The study authors add that the reduced renal dysfunction or aggravation of existing renal insufficiency with the CO₂ technique suggests it should be used for procedures in which iodinated contrast nephrotoxicity is a concern.

Significant Hazards, Poor Imaging Quality

Peter A. McCullough, MD, MPH, of the Providence Park Heart Institute (Novi, MI), told TCTMD in a telephone interview that in the early years of CO₂ angiography, there were reports of fatalities involving large boluses of gas affecting vital organs. Although the new study shows that the technique can be used relatively safely, he observed that imaging quality seems rather poor, with “streaming” of the dye that makes it difficult to clearly see blood vessels.

“I think this is, unfortunately, a relatively hazardous approach that doesn’t really accomplish the goals,” Dr. McCullough said. “But I think we are moving to safer forms of contrast that don’t have the risk to the kidneys that conventional contrast has, or we’ll move to advanced imaging procedures that from a computational perspective don’t require contrast. That’s where the field is going.”

He added that while the CO₂ technique appears to have some merit for patients with peripheral arterial disease and kidney disease, and though some centers may specialize in using it, “there are too many opportunities for misadventure for this to become commoditized in terms of standard of care.”

 

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Source:
Moos JM, Ham SW, Han SM, et al. Safety of carbon dioxide digital subtraction angiography. Arch Surg. 2011;Epub ahead of print.

 

 

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