Saline Bests Bicarbonate for Preventing Contrast Nephropathy

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A strategy of hydration with sodium chloride (saline) is more effective than bicarbonate for preventing contrast-induced nephropathy (CIN) in patients with renal dysfunction undergoing intravascular contrast procedures, according to a study published online January 19, 2012, ahead of print in the European Heart Journal. Furthermore, the researchers say their findings may suggest a way to initiate maximal protection when needed.

Christian Mueller, MD, of University Hospital Basel (Basel, Switzerland), and colleagues randomized 258 consecutive patients with renal insufficiency undergoing intra-arterial or intravenous vascular contrast procedures to 1 of 3 regimens:

• 24-hour saline (0.9% 1 mL/kg/h for at least 12 hours pre- and postprocedure; n = 89)
• 7-hour sodium bicarbonate (3 mL/kg bolus for 1 hour before and 1 mL/kg/h during contrast exposure and for 6 hours after the procedure; n = 87)
• Short-term sodium bicarbonate (3 mL/kg bolus over 20 minutes before the procedure plus oral sodium bicarbonate [500 mg per 10 kg]; n = 82)

Less Change in eGFR with Saline

Overall, the 3 regimens were well tolerated with no serious adverse events related to infusion. In addition, none of the patients required IV diuretics or nitrates due to pulmonary congestion.

At 48 hours, the maximum change in eGFR was similar between the 2 bicarbonate groups, but greater with the 7-hour sodium bicarbonate regimen compared with saline. Likewise, the maximum change in serum cystatin C also was greater in the 7-hour bicarbonate group compared with saline but similar between the 2 bicarbonate groups (table 1).

Table 1. eGFR and Serum Cystatin C Changes at 48 Hours

Similarly, the incidence of CIN (increase of ≥ 25% or of ≥ 44 µmol/L in baseline SCr within 48 hours) was lower with saline compared with 7-hour bicarbonate (1% vs. 9%; P = 0.02) and similar between the 2 bicarbonate groups (10% for both; P = 0.9).

There were no differences between the 3 groups in in-hospital morbidity and mortality, time to hospital discharge, or 90-day mortality or need for renal replacement therapy.

According to the authors, the findings expand on previous evidence and suggest that 24-hour saline “seems … to be the regimen of choice whenever maximal protection is desired and logistics permits. The short-term sodium bicarbonate regimen seems to be an attractive alternative for all other patients, including those undergoing outpatient procedures,” they add.

Issues of Confounding, Practicality

In a telephone interview with TCTMD, Richard J. Solomon, MD, of the University of Vermont (Burlington, VT), questioned some key aspects of the study.

“They obviously didn’t give similar amounts of salt and they also took patients who were on lots of diuretics, which made up about 80% of [the saline group], and gave them a lot of saline. The creatinine looks better because what they actually did was correct volume depletion. It has nothing to do with prevention of renal injury,” he said. “That probably explains the huge difference [in CIN] between the groups.”

Dr. Solomon also questioned the inclusion of patients who were undergoing computed tomography (CT). Cardiac catheterization was performed in 23%, PCI in 21%, and CT in 45% of the study population.

“No one has looked, quite frankly, at the efficacy of bicarbonate in CT patients. Maybe it does or does not work in that population, but we have no data to use for comparison,” he said.

Overall, Dr. Solomon said he does not believe the study has valid clinical implications because of all the confounding. Most importantly, however, he said the biggest issue that is not addressed by the researchers is the impracticability of the 24-hour saline method.

“Nobody, at least in the [United States] or Canada, is going to give this therapy because insurance isn’t going to pay for it,” he said. “So, who knows what the implications are of these findings when you are talking about a therapy that isn’t even practical?”

Peter A. McCullough, MD, MPH, of the Providence Park Heart Institute (Novi, MI), told TCTMD in an email communication that although the trial is small, it does confirm previous data showing that with adequate volume supplementation with either saline or sodium bicarbonate, rates of CIN are low. 

But he took issue with the authors’ assertion that their findings do not refute a controversial hypothesis that alkalization using bicarbonate might provide additional kidney protection in at-risk patients because they did not use equal volumes in the 2 bicarbonate arms.

“There is no preferential benefit attributable to sodium bicarbonate despite the theoretical evidence that alkalization of the urine should reduce oxidative stress and tubular injury,” Dr. McCullough noted.

Study Details

Baseline characteristics were well matched among the groups. The mean age of the study population was 77 years and 64% were male. Mean eGFR at baseline was 43.6 ± 11.6 mL/min/1.73 m². The cause of kidney dysfunction was primarily vascular nephropathy (48%) followed by the combination of vascular and diabetic nephropathy (23%).

All patients received a nonionic contrast agent, primarily low osmolar (88%). Six different types of contrast media were used. These included: iopromide, iomeprol, iopentol, iohexol, iobitridol and iodixanol.

 

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Source:
Klima T, Christ A, Marana I, et al. Sodium chloride vs. sodium bicarbonate for the prevention of contrast medium-induced nephropathy: A randomized controlled trial. Eur Heart J. 2012;Epub ahead of print.

 

 

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