Lowering temperature of patient does not reduce contrast-induced nephropathy

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WASHINGTON, D.C.—In patients at high risk for radiocontrast nephropathy (RCN) undergoing invasive cardiology procedures, cooling may be safely achieved and is well-tolerated, but those results do not point to a significant reduction in RCN, according to a late-breaking clinical trial presented Tuesday at the 20th annual Transcatheter Cardiovascular Therapeutics (TCT) scientific symposium.

The prospective, randomized, multicenter clinical COOL RCN [COOLing to Prevent Radio Contrast Nephropathy in Patients Undergoing Diagnostic or Interventional Catheterization] trial was presented by principal investigator, Gregg W. Stone, MD, who is also the co-director of TCT and professor of medicine and the director and education at the Center of Interventional Vascular Therapy at New York-Presbyterian Hospital/Columbia University Medical Center in New York.

According to Stone, patients with pre-existing renal insufficiency, heart disease or diabetes are at particularly high risk of developing RCN after cardiac cath. Mild hypothermia to protect the kidneys of high-risk patients while they are undergoing cardiac cath is one potential therapy.

Stone said that this “is a novel approach to preventing a common but serious side effect of radiographic contrast agents. The body is cooled from the inside out by approximately 7 degrees Fahrenheit.”

The Reprieve System from Radiant Medical was used in the trial, which was initially intended to enroll 400 patients at up to 35 sites. The Reprieve uses a heparin/hydrogel coated PET balloon that pumps in cool blood and pumps out warm blood.

Stone said that the study terminated early due to financial insolvency of Radiant, but Radiant’s assets were purchased by ZOLL Circulation, who funded completion of the study. The researchers enrolled 136 randomized patients between March 2006 and August 2007.

The researchers examined 128 evaluable patients, 70 of whom were maintained at normal temperature levels, and 58 of whom were brought to a hypothermic level.

In the pilot study, Stone reported that 32 patients (with a median age of 71, 50 percent of whom were diabetic) were hydrated and cooled to 33 to 34 degrees Celsius less than 90 minutes prior to and for three hours after contrast were administered. Cooling had to be achieved before the first administration of contrast agent, but the target core temperature in patients was 33 degrees Celsius; no contrast was administered before 34 degrees Celsius.

The observed rate of RCN in the control arm—18.6 percent—was lower than had been anticipated, which was 35 percent. This fact, coupled with the enrollment of only 34 percent of planned resulted in a wide point estimate for the treatment effect of systemic hypothermia.

Stone concluded that in patients at high risk for RCN undergoing invasive cardiology procedures hydrated with NS + NaHCO3, systemic hypothermia using the Reprieve system may be safely achieved and is well tolerated, and does not result in a significant reduction in RCN.

“The most exciting new application that people might pursue [due to the safety of this technology] is the reduction in infarct size through systemic hypothermia. Zoll is actively pursuing this,” Stone said.

He noted that several vendors on the TCT showroom floor with various cooling systems also are pursuing trials in the MI space, although he noted that some studies are also looking into stroke as well.