CO2 as Angiography Contrast Agent May Cut Kidney Risk

Using carbon dioxide as a main contrast agent in angiography may be a good way to avoid contrast-induced nephropathy (CIN) during peripheral endovascular procedures, a study suggested.

By 3 days, CIN -- defined as a 25% or 0.5 mg/dL increase in serum creatinine -- was rarer for carbon dioxide recipients (14% versus 29% for iodinated contrast, P=0.045). Patients imaged with carbon dioxide had received a mean of 15 mL iodinated contrast, compared with 116 mL for the control cohort (P<0.0001).

On multivariable adjustment, the threshold for predicting CIN was the use of more than 25 ml of iodinated contrast (odds ratio 6.9, 95% confidence interval 1.6-30.6).

"Adjunctive use of CO₂ contrast for peripheral endovascular procedures leads to a significant decrease in the incidence of CIN. Usage of no more than 25 mL of iodinated contrast should be aimed for in high-risk patients," Narayanan Thulasidasan, MBBS, of University Health Network Toronto General Hospital, told the audience at the Society of Interventional Radiology 2016 meeting.

Thulasidasan told MedPage Today that this finding is "increasingly important in an age where patients are older than ever before, and with multiple medical problems -- most notably diabetes. We have certainly now incorporated CO₂ into our regular practice, and we hope that our work will encourage people to do the same."

Preprocedural hydration is the "only intervention proven to work" against contrast-induced kidney dysfunction, the authors noted, as lingering doubts surround the protective effects of pharmacological agents such as N-acetylcysteine and bicarbonate.

Angiography with carbon dioxide, then, is an intriguing preventative measure, given its low cost, non-nephrotoxicity, and non-allergenic qualities.

Nonetheless, the group noted that the agent -- when compared with iodinated contrast -- produces lower image quality, such as visible artifacts of bolus fragmentation and less contrast with background. They maintained, however, that this disadvantage can be mitigated with peak-opacification function during imaging.

Other pitfalls of carbon dioxide include temporary pain or paresthesia in the lower limbs. Also, carbon dioxide can be neurotoxic, making it unsafe to use intra-arterially above the diaphragm.

The prospective study included 50 consecutive patients receiving carbon dioxide as their main contrast agent in 2014. They were matched to a historical cohort that received iodinated contrast from 2012 to 2013.

Baseline characteristics were well-matched with the exception of the carbon dioxide group having higher creatinine levels to start.

Thulasidasan and colleagues noted that their carbon dioxide cohort showed a higher CIN rate when compared with others in recent literature, citing CIN rates as low as 5% seen in other studies. This "higher incidence of CIN may be explained by the higher proportion of diabetics and complex critical limb ischemia cases in our cohort," they suggested.

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