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Closed-loop hydration system curbs contrast-induced nephropathy

Reuters Health • The Doctor's Channel Daily Newscast

NEW YORK (Reuters Health) – A closed-loop hydration and fluid balancing system protects against contrast-induced acute kidney injury in high-risk patients, according to results of a study published online August 15 in Circulation.

In this multicenter, investigator-driven trial, the RenalGuard system (PLC Medical Systems, Inc, Franklin, MA) proved more effective in protecting against contrast-induced acute kidney injury than sodium bicarbonate solution and N-acetylcysteine (NAC), the current standard of care for the prevention of contrast-induced nephropathy.

The study enrolled 294 patients with severe chronic kidney disease scheduled for coronary and/or peripheral angiography and/or angioplasty. The contrast agent used in all procedures was iodixanol (Visipaque; GE).

Eligible patients had an estimated glomerular filtration rate (eGFR) less than or equal to 30 mL/min/1.73 m² and/or a risk score of 11 or greater.

Fluid management was by random assignment to either sodium bicarbonate solution and NAC at a high dose (control group) or hydration with saline and NAC at a high dose controlled by the RenalGuard system, plus a low dose (0.25 mg/kg) of furosemide to induce diuresis (the RenalGuard group).

“The RenalGuard System, with its matched fluid replacement capability, enables the physician to achieve high urine output safely with a low furosemide dose by maintaining the intravascular volume and minimizing the risk of overhydration or underhydration,” Dr. Carlo Briguori from Clinica Mediterranea, Naples, Italy and colleagues explain in their paper.

With this system, “no clinically significant changes in electrolyte balance were documented and the highly accurate, temporally matched fluid replacement observed reduced the risk of hypovolemia.”

The primary outcome measure in the study was the development of contrast-induced acute kidney injury, defined as an increase in the serum creatinine concentration of 0.3 mg/dL or more over baseline at 48 hours after administration of contrast media or the need for dialysis.

According to the investigators, fewer patients in the RenalGuard group than the control group developed contrast-induced acute kidney injury (16 of 146 [11%] vs. 30 of 146 [20.5%]).

“In the RenalGuard group, we observed a 53% relative risk reduction rate compared with the control group,” Dr. Briguori and colleagues say.

With RenalGuard, they also noted a lower severity of kidney damage, a lower rate of in-hospital renal failure requiring dialysis (0.71% vs. 4.1%), and a smaller increase in cystatin C (a marker of renal function).

“The present study supports that concept that increasing the urine flow rate reduces the toxic effect of contrast media,” reads a Clinical Perspective published with the study. “The RenalGuard system is helpful in guiding the physician in achieving high urine output (?300 mL/h) while simultaneously balancing urine output and venous fluid infusion to prevent hypovolemia.”

Pulmonary edema occurred in 3 patients (2.1%) in the RenalGuard group versus 1 patient (0.7%) in the control group (P = 0.62). In all instances, pulmonary edema occurred after the coronary procedure.

The authors note that while the current study included patients with severe kidney impairment (eGFR ? 30), preliminary results from another trial support its renoprotective benefits in patients with less severe kidney impairment (eGFR < 60).

In the Matched Hydration Compared to Standard Hydration for Contrast-Induced Nephropathy Prevention, or MYTHOS trial, the rate of contrast-induced acute kidney injury was 16% in the standard hydration group versus 5% in the RenalGuard group.

“Additional studies are warranted to define the role of RenalGuard therapy in preventing contrast-induced acute kidney injury, taking into account both safety and effectiveness,” Dr. Briguori and colleagues conclude.

Renal Insufficiency After Contrast Media Administration Trial II (REMEDIAL II)
Circulation 2011;124.