Carbon Dioxide Angiography Safe, Preserves Renal Function in EVAR

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Using carbon dioxide (CO₂) instead of conventional iodinated contrast for angiography is a safe, effective way of preserving renal function during endovascular aortic aneurysm repair (EVAR), according to results published online February 16, 2012, ahead of print in the Journal of Vascular Surgery.

Researchers led by Enrique Criado, MD, of the University of Michigan Medical School (Ann Arbor, MI), performed EVAR under CO₂ angiographic guidance in 114 patients, comparing them with a cohort of 22 EVAR patients in whom iodinated contrast alone was used for angiography.

In the CO₂ patients, all cases were technically successful without any conversions to open repair. In 42 of the CO₂ patients, some iodinated contrast (mean 37 mL per case) was used at the operator’s discretion to visualize renal arteries or other branches not well seen with CO₂ alone, or to confirm suspected endoleak noticed on CO₂ angiography.

Accurate Endoleak Detection

At the end of the procedure, CO₂ angiography identified 20 endoleaks (2 type 1, 16 type 2, and 2 type 4). No additional endoleaks were detected with intraoperative iodinated contrast, and at 1-month follow-up, no additional type 1 or type 3 endoleaks were detected by CT or ultrasound.

Operative time, fluoroscopy time, and volume of iodinated contrast were all lower in the CO₂ group compared with EVAR patients in whom angiographic guidance was performed with iodinated contrast alone (table 1).

Table 1. Procedural Outcomes

Postoperatively, there were 2 deaths (1.7% mortality at 30 days), 2 instances of renal failure requiring dialysis, and no complications related to CO₂ use. Among patients with moderate to severely decreased eGFR, patients undergoing EVAR with iodinated contrast had a 12.7% greater decrease in eGFR compared with the CO₂ EVAR group (P = 0.004). At 1, 6, and 12 months, CT angiography showed well-positioned endografts with the expected patent renal and hypogastric arteries in all patients and no difference in endoleak detection between the CO₂ and iodinated contrast groups. Overall, 8 transluminal interventions and 1 open conversion were required, and no aneurysm-related deaths occurred.

“CO₂-guided EVAR is technically feasible and safe,” the researchers conclude. “It eliminates or reduces the need for [iodinated contrast] use, may expedite the procedure, and avoids deterioration in renal function in patients with pre-existing renal insufficiency.”

Iodinated Contrast to Be Avoided

The authors note that renal failure following EVAR remains a source of postoperative morbidity and mortality related to multiple factors, one of which is iodinated contrast use. “The administration of [iodinated contrast] is perhaps the only factor contributing to renal dysfunction that could be completely avoided, simply by avoiding its use,” they note, adding that CO₂, when used as a contrast agent, provides all the information available with iodinated contrast but with no known renal toxicity plus extremely low cost.

However, relatively few vascular surgeons are familiar with the use of CO₂ or other alternative contrast agents. “This is most likely the reason for the notable paucity of publications in which CO₂ angiography was used for EVAR guidance,” the authors explain.

However, in a telephone interview with TCTMD, Peter A. McCullough, MD, MPH, of the Providence Park Hospital (Novi, MI), did not view CO₂ angiography in as positive a light.

“Off the bat, in 42 of the patients, the doctors felt the carbon dioxide imaging wasn’t good enough,” he said. “They couldn’t see if there was leaking around the stent graft or if it was well positioned, and those are pretty serious concerns.”

Potential for Ischemic Injury?

Also, he noted that based on baseline eGFR, the patients’ risk of renal injury was not especially high. “That’s not the level where we start to do really extreme things, like preemptive hemofiltration,” Dr. McCullough said. “Having said that, though, they still had a couple patients who needed to go on dialysis.”

Overall, Dr. McCullough expressed 2 main concerns: that the use of CO₂ cannot universally spare patients from the need for iodinated contrast, as shown in the study, and that CO₂ may actually be provoking some ischemic injury. “If you fill the arteries with CO₂, there’s not oxygen in that location to deliver to the red blood cells for at least some period of time,” he said. “I think there’s a little concern about actually causing ischemic kidney damage with CO₂.”

Previous concerns, though, regarding correct endograft positioning and the potential for an embolus traveling to the heart or lungs appear to have been adequately dealt with, he added.

Dr. McCullough observed that solely focusing on the type of contrast to reduce kidney injury is the wrong approach. “That’s just flawed thinking,” he said. “It’s more than the contrast that causes acute kidney injury. We have to get into a different paradigm. The million dollar question is, is there a preventive approach? Are there medicinal or other ways? Can we cool the kidneys, can we hyperoxygenate them? What other ways are there that we can provide kidney protection?”

In terms of better evaluating the clinical utility of CO₂ angiography, Dr. McCullough recommended a small randomized, prospective trial using sensitive bioindicators of kidney injury. “That biochemical pattern would probably tell us if we’re on the right track,” he said. “But it’s not like we can say, ‘Wow, this paper really makes us feel that this is safer.’”

Study Details

Mean preoperative eGFR was 65 mL/min. Levels were normal (≥ 90 mL/min) in 16 patients, mildly decreased (60-89 mL/min) in 52, moderately to severely decreased (15-59 mL/min) in 44, and 2 patients were on dialysis.

 

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Source:
Criado E, Upchurch GR, Young K, et al. Endovascular aortic aneurysm repair with carbon dioxide-guided angiography in patients with renal insufficiency. J Vasc Surg. 2012;Epub ahead of print.

 

 

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

 

 

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