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The Effect of Fish Oil on Hemostasis and Coagulations During Cardiac Surgery

Ischal Erez, MD, Anna Kowalczyk, MD and Hong Liu, MD
University of California Davis Health System, Sacramento, CA 95817

The effects of polyunsaturated omega-3 fatty acids (n-3 PUFAs), typically consumed in a form of fish oil, have been studied for years. It is widely known that PUFAs exert an anti-inflammatory effect, reduce triglyceride levels and impair platelet aggregation (1). More recent literature points to the of ability of n-3 PUFAs to modulate myocardial calcium channels, decrease fatty acid synthesis and up-regulate gene expression for fatty acid oxidation (4). Additionally, changes in vascular endothelium have been discovered in response to n-3 PUFA supplementation, including increased prostacyclin production (3). The purported cardiovascular benefits may include secondary prevention of cardiovascular disease, prevention of post angioplasty restenosis, graft re-stenosis after CABG and even post surgical dysrhythmias (3,4). However, the potential anticoagulant effect of fish oil has caused many centers - including ours – to recommend cessation of n-3 PUFAs at least 2 weeks prior to elective surgery. The question arises - is this an evidence-based practice?

The proposed mechanism of platelet inhibition by n-3 PUFAs is fatty acid insertion into the platelet membrane, resulting in change of its surface charge (1). Measured bleeding time in patients taking n-3 PUFA supplements has been shown to increase up to 1.5 times in laboratory conditions. Despite this, many clinical studies show that bleeding does not increase in these patients, even during hospitalizations for myocardial infarction when potent anticoagulants are used (2). Multiple other studies evaluating fish oil in percutaneous coronary angioplasty confirmed that bleeding does not increase in patients consuming n-3 PUFAs (5). These studies show lack of added bleeding risk in non-surgical patients and those undergoing minimally invasive procedures, but what about surgical patients?

Two studies have demonstrated that in spinal decompression and spinal arthrodesis there is no difference in surgical bleeding when patients take fish oil (6,7). Another study revealed that n-3 PUFA supplementation added to TPN after major abdominal surgery did not increase bleeding risk (8). In a review of 19 clinical trials of either vascular surgery or procedures involving femoral artery punctures, no increase in bleeding events was observed (5). Lastly, in a recent large randomized blinded placebo controlled trial examining the effect of fish oil on preventing post-cardiac surgery atrial fibrillation (OPERA trial), no difference in clinically significant bleeding was found between the two groups. In fact, fewer blood products were administered perioperatively in the n-3 PUFA group (9).

It stands to reason that decreasing platelet aggregation and increasing the bypass graft endothelial prostacyclin levels might actually benefit CABG patients. Additionally, if fish oil reduces the incidence of atrial fibrillation following heart surgery, perhaps we should routinely treat these patients with n-3 PUFAs. Indeed, in an animal study, cod liver oil alone was superior to aspirin and dipyridamole in reducing post CABG graft intimal hyperplasia (10). However, several studies evaluating restenosis after percutaneous coronary angioplasty have shown mixed results. Two meta-analyses suggested only a modest improvement in restenosis rates (11,12). Moreover, the OPERA trial failed to demonstrate a decrease in atrial fibrillation post heart surgery (9). At this time there is insufficient evidence to support routine prescription of omega-3 fatty acids pre-operatively for heart surgery.

When confronted with the decision to postpone an operation based on recent fish oil intake, it is tempting to focus on the previously described impairment in platelet function. However, the available literature fails to demonstrate any clinically significant increase in bleeding - both in medical and surgical patients, including those undergoing cardiac surgery. Furthermore, although the data conflict, there may be a benefit to n-3 PUFA intake in the form of decreased intimal thickness and reduced graft restenosis post CABG.

In summary, despite the known inhibition of platelet aggregation, clinically significant bleeding does not increase with the use of n-3 PUFAs. Since there is no evidence of harm, and given the implications of cancelling a major operation for both patients and health care systems, it seems prudent to proceed with an elective CABG in a patient taking fish oil supplements.


  1. Cohen M, Rossi J, et al: Insights into the inhibition of platelet activation by omega-3 polyunsaturated fatty acids: beyond aspirin and clopidogrel. Thromb Res. 2011;128:335-40
  2. Salisbury A, Harris W, et al: Relation between red blood cell omega-3 fatty acid index and bleeding during acute myocardial infarction. Am J Cardiol.2012;109:13-8
  3. DeCaterina R, Giannessi D, et al: Vascular prostacyclin is increased in patients ingesting omega-3 polyunsaturated fatty acids before coronary artery bypass graft surgery. Circulation.1990;82:428-38
  4. Adkins Y, Kelley D: Mechanisms underlying the cardioprotective effects of omega-3 polyunsaturated fatty acids. JNutBio 2010;781-92
  5. Bays H, Safety considerations with omega-3 fatty acid therapy. Am J Cardiol. 2007;99:35-43
  6. Meredith D, Kepler C, et al: The effect of omega-3 fatty-acid supplements on perioperative bleeding following posterior spinal arthrodesis. Eur Spine. 2012;21:2659-63
  7. Kepler C, Huang R, et al: Omega-3 and fish oil supplements do not cause increased bleeding during spinal decompression surgery. J Spinal Discord Tech. 2012;25:129-32
  8. Heller A, Fischer S, et al: Impact of omega-3 fatty acid supplemented parenteral nutrition on haemostasis patterns after major abdominal surgery. Br J Nutr. 2002;87:95-101
  9. Mozaffarian D, Marchioli R, et al: Fish oil and postoperative atrial fibrillation, the omega-3 fatty acids for prevention of post-operative atrial fibrillation (OPERA) randomized trial. JAMA 2012;308: 2001
  10. Landymore R, MacAulay M, et al: Comparison of cod-liver oil and aspirin-dipyridamole for the prevention of intimal hyperplasia in autologous vein grafts. Ann Thorac Surg.1986;41:54-7
  11. O’Connor G, Malenka D, et al: A meta-analysis of randomized trials of fish oil in prevention of restenosis following coronary angioplasty. Am J Prev Med. 1992;8:186-92
  12. Gapinski J, VanRuiswyk J, et al: Preventing restenosis with fish oils following coronary angioplasty. A meta-analysis. Arch Intern Med. 1993;153:1595-601

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