Fish Oil Benefit for Dialysis Grafts Unclear - MedPage Today PDF Print

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By Todd Neale, Senior Staff Writer, MedPage Today

Published: May 01, 2012

Reviewed by Dori F. Zaleznik, MD; Associate Clinical Professor of Medicine, Harvard Medical School, Boston.

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For patients with a new synthetic arteriovenous graft for hemodialysis vascular access, taking fish oil every day led to a mix of negative and positive results, a randomized trial showed.

The percentage of patients who had a loss of native graft patency through 1 year -- the primary outcome -- was lower with fish oil than with placebo, although the difference was not significant (48% versus 62%, P=0.06), according to Charmaine Lok, MD, of Toronto General Hospital, and colleagues.

When looking at the rate of the loss of native patency, however, the difference favored fish oil recipients and was statistically significant (3.43 versus 5.95 per 1,000 access-days, P<0.001), the researchers reported in the May 2 issue of the Journal of the American Medical Association.

The findings, which were originally reported at the American Society of Nephrology meeting last year, also showed advantages for fish oil on some secondary endpoints, including cardiovascular events and blood pressure.

"Although the risk of the primary endpoint was not significantly lower among fish oil recipients, this should be considered in the context of the apparent consistent clinical benefits observed for the secondary outcomes," Lok and colleagues wrote.

Agreeing in an accompanying editorial was Bradley Dixon, MD, of the University of Iowa in Iowa City, who noted that interpreting the results is not as straightforward as looking at the failed primary outcome.

"The secondary outcomes measuring the rate of loss of graft patency are important and relevant, and deserve the attention of physicians caring for patients receiving a new graft," he wrote.

Lok and colleagues noted that grafts have become increasingly less popular since the study was started, with most patients now receiving arteriovenous fistulas. Currently, only about 21% of patients receive a synthetic graft.

The declining appeal of synthetic arteriovenous grafts is related to the risk of recurrent stenosis and thrombosis. The omega-3 fatty acids in fish oil have been proposed as a solution to those problems.

"Identification of safe and inexpensive agents that prolong arteriovenous graft patency and reduce the frequency of interventions to salvage graft complications might encourage increased use of grafts," the researchers wrote.

Their study, the Fish Oil Inhibition of Stenosis in Hemodialysis Grafts (FISH) trial, was a randomized, double-blind, placebo-controlled trial performed at 15 North American dialysis centers from November 2003 to December 2010. It included 201 adults with end-stage renal disease.

For 1 year, the patients were randomized to either four fish oil capsules per day or matching placebo. The fish oil capsules contained 400 mg eicosapentaenoic acid (EPA) and 200 mg docosahexaenoic acid (DHA).

The primary outcome was the percentage of patients who developed graft thrombosis or required radiological or surgical intervention during follow-up.

Although the between-group difference in that outcome was not statistically significant, fish oil significantly reduced the rate of thrombosis (1.71 versus 3.41 per 1,000 access-days, P<0.001) and of corrective interventions (2.89 versus 4.92 per 1,000 access-days, P<0.001).

In addition, daily fish oil was associated with the following:

  • Improved cardiovascular event-free survival: HR 0.43, 95% CI 0.19 to 0.96, P=0.04
  • An improvement in mean systolic blood pressure: -3.61 versus +4.49 mm Hg, P=0.01
  • An increase in the percentage of patients who had at least one reduction in the dose or frequency of antihypertensives: 64% versus 42%, P=0.004

Lok and colleagues noted that the potential cardiovascular benefits of fish oil should be confirmed in future studies because of the small number of patients and events, which limited statistical power. The study was also limited by failure to achieve the target enrollment numbers.

In his editorial, Dixon said that available data do not support an increase in the use of hemodialysis grafts combined with fish oil capsules and antiplatelet therapy.

"Despite the reduction in the rate of graft thrombosis and angioplasty procedures with fish oil, the rate of these events is still lower with arteriovenous fistulas, and fistulas remain the preferred means of hemodialysis access," he wrote. "However, if a patient cannot obtain a fistula and requires a graft, use of fish oil and an antiplatelet agent appears reasonable, pending the results of further studies."

The study was supported by peer-reviewed grant funding from the Physician's Services Incorporated Foundation and the Canadian Institutes of Health Research (CIHR). During the study, Lok and two of her co-authors were supported by CIHR New Investigator Awards. Lok was also supported by the CIHR Randomized Clinical Trials Mentoring Program. The other authors reported support from Alberta Heritage Foundation for Medical Research Population Scholar Awards, a Government of Canada Research Chair, and the National Institute of Diabetes and Digestive and Kidney Diseases.

Lok reported that she had no conflicts of interest. Her co-authors reported relationships with Amgen, Leo, Roche, Merck, Baxter, Novartis, UpToDate, Oliver Medical Management, the University of Alabama at Birmingham, and the Center for Biostatistics and AIDS Research at Harvard School of Public Health.

Dixon reported receiving consulting fees from Proteon Therapeutics, Pervasis Therapeutics, Novita Therapeutics, and Shire Pharmaceuticals; receiving grants or grants pending from Proteon Therapeutics, Novartis Pharmaceuticals, Cardiokine, and Reata Pharmaceuticals; and receiving payment for lectures from the Cincinnati Hemodialysis Vascular Access Symposium and VEITHsymposium.

Primary source:Journal of the American Medical Association
Source reference:
Lok C, et al "Effect of fish oil supplementation on graft patency and cardiovascular events among patients with new synthetic arteriovenous hemodialysis grafts: a randomized controlled trial" JAMA 2012; 307: 1809-1816; DOI: 10.1001/jama.2012.3473.

Additional source: Journal of the American Medical Association
Source reference:
Dixon B "Fish oil and hemodialysis graft patency: does time matter?" JAMA 2012; 307: 1859-1860; DOI: 10.1001/jama.2012.4101.

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