Medical Nutrition: RCT finds little benefit from fish oil for fistula failure
The FAVOURED study looked at the potential effectiveness of both fish oil and aspirin in preventing the failure of arteriovenous fistulas (AVF) in dialysis patients, after previous studies suggested their benefit for dialysis patients receiving grafts.
Fistulas are artificial veins, often in the arm, created to provide access for dialysis in patients with kidney disease. They are preferred over grafts, but have a longer maturation time and a significantly higher risk of early failure (20-50%), said the FAVOURED researchers - led by Dr Ashley Irish from Fiona Stanley Hospital in Australia.
“Fish oil has been shown to increase patency rates in [grafts], but it has not been assessed in AVFs,” they said.
Writing in JAMA Internal Medicine, the team initially suggested that fish oil might help fistulas mature and prevent failure by blocking platelet aggregation, as well as decreasing blood viscosity, and promoting the widening of vessels (vasodilation).
“In patients with chronic kidney disease undergoing creation of an AVF, three months’ treatment with fish oil at a dose of 4g per day did not reduce the composite primary outcome of AVF failure nor any of the individual components, which included AVF abandonment, thrombosis, and cannulation failure, assessed at 12 months," wrote he team.
Irish and her team recruited 567 patients from 35 dialysis centres in four countries (Australia, New Zealand, Malaysia and the UK) in to the RCT - with 536 patients included in the final analysis. Subjects received either 4g per day of fish oil, or 4g of olive oil as a placebo, delivered as two 1g capsules twice daily.
The fish oil supplements were Omacor capsules containing 46% eicosapentaenoic acid and 38% docosahexaenoic acid.
However, the researchers found no benefit to the supplementation. Blood tests showed subjects receiving fish oil supplements had increased omega-3 levels, confirming they were taking the capsules – but no other clinically relevant effects were apparent.
Indeed, those receiving fish oil showed the same 47% fistula failure rate as those receiving placebo.
“The trial finished before reaching the planned recruitment target but was able to show that fish oil is unlikely to reduce the risk of AVF failure by 30%; results were consistent with, at best, a 14% RR reduction,” the authors added.
The authors wrote that it was unknown whether the levels of the fish oil fatty acids were insufficient to promote the expected effects.
“However, the doses of eicosapentaenoic and docosahexaenoic acids used in the FAVOURED trial were higher than doses used in studies assessing [graft] outcomes, and studies in patients with chronic kidney disease using a comparable dose of fish oil achieved significant reductions in blood viscosity, platelet aggregation, and blood pressure consistent with biological effects,” they added.
Aspirin, too, showed a similar failure rate.
“The proportion of new AVFs that failed within 12 months of surgery was nearly 50% and was not reduced by 12 weeks of fish oil supplementation or low-dose aspirin therapy. This study suggests that neither fish oil nor aspirin can be recommended for the prevention of AVF failure,” the authors wrote in their conclusion.
Source: JAMA Internal Medicine
Published online ahead of print, doi:10.1001/jamainternmed.2016.8029
“Effect of Fish Oil Supplementation and Aspirin Use on Arteriovenous Fistula Failure in Patients Requiring Hemodialysis; A Randomized Clinical Trial”
Authors: Irish AB, Viecelli AK, Hawley CM, Hooi L, Pascoe EM, Paul-Brent P, Badve SV, Mori TA, Cass A, Kerr PG, Voss D, Ong L, Polkinghorne KR