Lowering contrast dose before enhanced CT reduces risk of acute kidney injury

Lowering the amount of iodinated contrast medium (ICM) administered intravenously to high-risk patients before a CT scan to less than 90 ml reduces the risk of contrast-induced acute kidney injury (CI-AKI), according to a study published in the October edition of Clinical Radiology.

Researchers found that one in ten elderly patients with aortic stenosis experienced CI-AKI after undergoing a contrast-enhanced multidetector-row CT (MDCT) before having a transcatheter aortic valve implantation (TAVI).

Author D. Jochheim, MD, of the cardiology department at Munich University Clinic, and colleagues wrote that lowering the quantity of ICM to less than 90 ml reduces this risk in patients whether or not they have pre-existing impaired renal function. The majority of patients’ renal function recovers before the TAVI procedure, they noted.

The retrospective, single-center study included 450 patients undergoing MDCT for planning TAVI procedures via transfemoral access route at Munich University Clinic between September 2009 and April 2013.

Three patients were excluded from the study because of prior kidney transplantation, 48 patients were excluded because of ICM within two weeks prior to MDCT, and 38 had incomplete data regarding laboratory values.

Only those patients with serial creatinine and estimated glomerular filtration rate (eGFR) evaluation prior to and after MDCT up to the TAVI procedure date were included in the study.

Researchers analyzed 361 patients who had undergone MDCT prior to TAVI. The researchers said they defined CI-AKI by measuring the increase in serum creatinine (SCr) of patients before and after they underwent the MDCT. There was a significant interaction between baseline eGFR and the amount of intravenous ICM administered, the study found.

Thirty-eight (10.5 percent) of the 361 patients included in the study experienced CI-AKI after MDCT. The mean age of the patients was 81.2 years and 43.2 percent were male.

After the TAVI procedure, only one patient died, and the creatinine level returned to its initial value in 30 patients. After TAVI, 59 patients experienced AKI, and of them, eight patients also experienced the same complications after MDCT. A total of 21 patients (5.8 percent) died in the hospital. Four of them were in the CI-AKI group and 17 in the group without CI-AKI , the authors wrote.

Researchers measured the mean EuroSCORE II and the mean eGFR of patients and found that patients with CI-AKI tended to have a higher EuroSCORE II.

“The main finding of the present study is that in elderly patients with symptomatic aortic stenosis undergoing MDCT for TAVI procedure planning, intravenous administration of ICM is associated with increased risk of CI-AKI only in patients with impaired baseline renal function who received ICM volumes greater than 90 ml,” the authors wrote.

Although the study focused on intravenous administration of ICM, the authors noted that “there is a large body of evidence showing a causal association between intra-arterial ICM administration and acute kidney injury.”

However, few studies have investigated the role of arterial ICM administration and acute kidney injury, they said.

Advanced age, presence of chronic renal failure, diabetes mellitus, or congestive heart failure are features that are common in patients with symptomatic aortic stenosis undergoing TAVI, and have been identified as predictors of ICM-induced AKI after intra-arterial ICM administration, they noted.