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[ Graft Patency For Hemodialysis - Fish Oil Supplements Show Mixed Results ]

Graft Patency For Hemodialysis - Fish Oil Supplements Show Mixed Results


A study in the May 2 issue of JAMA reveals that daily ingestion of fish oil did not lower the percentage of grafts with loss of patency, i.e. that remained open in patients with new synthetic arteriovenous grafts within 12 months. An arteriovenous graft is a synthetic tube that is grafted between an artery and vein in order to gain vascular access for hemodialysis.
Those who took fish oil were observed to have a longer period of time without thrombosis - their rate of thrombosis was reduced by 50% and they achieved a significant decrease in the frequency of radiological and surgical interventions compared with those who did not.
According to the article's background information:
"Optimal hemodialysis requires reliable vascular access. Current options include the arteriovenous fistula [surgical creation of a connection between an artery and vein], synthetic arteriovenous graft, and central venous catheter, which in the United States are used in 55%, 21%, and 24% of prevalent patients receiving hemodialysis, respectively. The arteriovenous graft was the predominant vascular access type in North America during the early 1990s but fell out of favor owing to its high complication rates and associated costs. For example, thrombosis occurs in more than 50% of all arteriovenous grafts within 1 year after placement, necessitating a salvage procedure in more than 75%."

Until now, none of the multiple interventions were able to reduce the rate of thrombosis convincingly or consistently. The omega-3 fatty acids in fish oils have antiproliferative, antioxidant, and vasodilatory (dilation) effects, which, in theory could prevent the narrowing of arteriovenous grafts (stenosis) and thrombosis. According to a small, single-center prospective study of fish oil prophylaxis the 12-months graft patency showed an improvement.
From November 2003 to December 2010, Charmaine E. Lok, M.D., M.Sc., of the University of Toronto and Toronto General Hospital and her team performed a randomized controlled trial in 15 North American dialysis centers to compare arteriovenous graft patency, rates of thrombosis and intervention in patients with end-stage renal disease. The study involved a total of 201 adults with stage 5 chronic kidney disease, of which 50 % were women, 63% were white and 53% had diabetes. The participants were randomly allocated to either receive four 1g fish oil capsules per day or placebo on day 7 after their arteriovenous graft was created, with a follow-up 12 months after graft creation.
The study's primary outcome was determined as the percentage of participants who experienced a graft thrombosis or radiological or surgical intervention during 12 months of follow-up.
The results demonstrated that there was no considerable difference with loss of native patency in either group, with 48% (48/99) in those in the fish oil group, compared with 62% in the placebo group (60/97).
The authors note:
"However, the rate of these events was significantly lower in the fish oil group. The frequency of thrombosis events was reduced by half in the fish oil group, and the frequency of corrective interventions was lower."

Whilst the 12-months event-free rate, i.e. no loss of native patency of arteriovenous graft in the fish oil group was 48% that of the placebo group was 32%. Both groups had similar reasons for arteriovenous graft loss. The 12-months thrombosis-free rate was significantly higher in the fish oil group with 64% compared to just 47% in the placebo group.
The authors write:
"Analysis of cardiovascular outcomes demonstrated superior cardiovascular event-free survival in the fish oil group. Compared with baseline, there were clinically significant reductions in systolic blood pressure at 6 months in the fish oil group that were sustained to 12 months. 64% (63/99) of patients in the fish oil group compared with 42% (41/97) in the placebo group had at least 1 reduction in the dose or frequency of their antihypertensive medications. Although the risk of the primary end point 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."

According to the researchers, the use of arteriovenous grafts has dropped over the last decade, which was mainly due to higher use of fistulas.
They conclude:
"Arteriovenous grafts may be suitable for patients receiving hemodialysis whose veins are unsuitable for fistula creation or who have experienced prior problems with fistula nonmaturation. However, compared with functioning fistulas, arteriovenous grafts may require a 3- to 4-fold higher frequency of interventions to maintain equivalent long-term patency. 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."

In response to the question whether clinicians should consider raising the use of hemodialysis grafts together with administrating fish oil and an antiplatelet agent to prolong graft patency based on these findings, Bradley S. Dixon, M.D., of the University of Iowa, Iowa City, replies in an accompanying editorial: "
Thus far, the available data do not support this approach. 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. 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."

Written By Petra Rattue
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