The study, conducted by a team of researchers including Dr William S. Harris, PhD, of the Sanford School of Medicine at the University of South Dakota, was a secondary analysis of data from a previous large scale study, the Omega-3 fatty acids for the PrEvention of post-opeRative Atrial fibrillation (OPERA) study.
Risk assessment based on anecdotal reports
For many years, the belief was that fish oils thinned the blood and so presented a risk to cardiac surgery patients, where uncontrolled, fatal bleeding is one of the dangers. While EPA specifically has been shown to be an anticoagulant factor, Harris said there was little hard data on its effects in surgery. Most of the recommendations around the safe use of omega-3 supplements for these patients was based on anecdotal information, he said.
“There has been a question since the very early work done with native Greenlanders about whether EPA was an anticoagulation factor. It was found to inhibit clotting, but no more than an aspirin would do,” Harris said.
“There were some anecdotal reports of Greenlanders getting nosebleeds and bleeding to death. This has been shown to be something of a modern urban myth, but that filtered down into recommendations for surgery. The reality is that there was no real evidence for clinically significant bleeding associated with the use of these products,” he said.
Original study looked at atrial fibrillation
The OPERA study included 1,516 patients scheduled for cardiac surgery. The patients were randomized to omega-3s or placebo. The treatment group was given large, acute doses of EPA and DHA (6.5 grams to 8 grams total) for two to five days prior to surgery, and then were administered 1.7 grams of omega-3s on the morning of the surgery. That maintenance dosage was continued until the patients were discharged.
The primary outcome for the OPERA study was to see if these acute dosages of EPA and DHA lessened the risk of postoperative atrial fibrillation, an uncomfortable and potentially dangerous complication from surgery. The study found no effect.
“It’s nice to have a big study like this to look at this question. They found no effect all. This study was well done and so doesn’t need to be done again. You can say this question has been answered,” Harris said.
“But in the original paper, they had a whole bunch of supplementary data tables [that didn’t bear on the primary outcome] and one of those outcomes was this bleeding outcome,” Harris said.
Higher omega-3s = less bleeding
Harris’s team combed through that data and applied the criteria for bleeding as put forth by the Bleeding Academic Research Consortium (BARC). They also looked for the number of units of blood needed for transfusion as a secondary target.
They found that the higher the blood EPA+DHA level on the morning of surgery, the lower the risk for bleeding according to the BARC criteria. They also found that significant reduction in the number of units of blood used for transfusions for patients in this group.
Effect not well understood
This is a surprising finding, and Harris said more work would need to be done to figure out exactly what’s going on, though he said the anti inflammatory activity of omega-3s might be playing a role.
“The standard measures of bleeding used to be done with a small razor blade cut in the arm. And then you see how long it would take for that to stop bleeding,” Harris said.
“But that doesn’t correlate well to the complexity of cardiac surgery. The cuts there are huge, and the role of inflammation is not well understood,” he said.
“So we don’t really understand why we saw this effect. But what we can say is, look, surgeons, there is no need to take patients off of omega-3s. And there are a lot of good reasons for these patients to continue to take these products,” Harris concluded.
Harris is co-inventor of the Omega-3 Index and is the founder of OmegaQuant, a firm based in Sioux Falls, SD that provides testing services to assess these levels. In addition to doing a great deal of original omega-3s research of his own, Harris has also provided blood testing services for many omega-3s studies.
The Omega-3 index is expressed as a percent of total red blood cell (RBC) fatty acids and is a long-term, stable marker of omega-3 status that accurately reflects tissue levels of EPA and DHA. An Omega-3 Index between 8% and 12% is considered the optimal range, which correlates to a sharply lower risk of fatal cardiovascular disease. Most Americans are at a 3% to 4% level, and consumers in many other countries where a Westernized diet is the norm are at a similarly low level.
Fish Oil and Perioperative Bleeding: Insights From the OPERA Randomized Trial
Circulation: Cardiovascular Quality and Outcomes. 2018;11:e004584
Authors: Akintoye E, et al.