Fish Oil Before Surgery: Safe for Your Heart?

randomized-controlled-trial PMID: 30571332

Quick Summary: A recent study found that taking fish oil before heart surgery doesn't increase the risk of bleeding. In fact, it might even reduce the need for blood transfusions!

Does Fish Oil Cause Bleeding? What the Research Says

For years, some doctors have told patients to stop taking fish oil before surgery, fearing it could increase bleeding. This new research challenges that idea. The study looked at over 1,500 people undergoing heart surgery and found:

No Increased Bleeding Risk: Patients taking fish oil did not have a higher risk of major bleeding compared to those who didn't.

Fewer Blood Transfusions: People taking fish oil needed fewer blood transfusions during and after surgery.

Higher Omega-3 Levels, Lower Risk: Patients with higher levels of omega-3 fatty acids in their blood (from the fish oil) had a lower chance of bleeding.

Study Details

Who was studied: 1,516 adults, average age 63, undergoing heart surgery (like bypass or valve replacement).

How long: Patients took fish oil or a placebo (dummy pill) for 2-5 days before surgery and then continued after surgery.

What they took: Fish oil containing EPA and DHA (the good stuff!) at a high dose before surgery, then a lower dose after.

What This Means For You

If you take fish oil and are having heart surgery: This study suggests you may not need to stop taking your fish oil. Talk to your doctor, but this research supports the idea that it's safe.

Fish oil might help: It could potentially reduce the need for blood transfusions, which is a good thing.

Consistency matters: The study suggests that having enough omega-3s in your system is important, so sticking to your fish oil routine could be beneficial.

Study Limitations

Heart Surgery Focus: This study only looked at people having heart surgery. We don't know if the results apply to other types of surgery.

Short-Term Use: The fish oil was only taken for a few days before surgery. We don't know if long-term fish oil use has different effects.

More Research Needed: While promising, more studies are needed to confirm these findings and understand the full picture.

Important Note: Always talk to your doctor about your medications and supplements before any surgery. They can give you personalized advice based on your health and the specific procedure you're having.

Key Findings

This 2018 randomized controlled trial found that perioperative fish oil supplementation (containing EPA+DHA) did not increase major bleeding risk in patients undergoing cardiac surgery. Compared to placebo:
- Major bleeding (Bleeding Academic Research Consortium criteria): 6.1% overall, with no significant difference between groups (OR: 0.81; 95% CI: 0.53–1.24; absolute risk difference: -1.1%).
- Blood transfusions: Fish oil group required significantly fewer units (mean: 1.61 vs. 1.92 in placebo; P<0.001).
- Plasma omega-3 levels: Higher achieved levels on the morning of surgery correlated with reduced bleeding risk, with the top quartiles showing 70% (OR: 0.30) and 64% (OR: 0.36) lower odds of major bleeding versus the lowest quartile.

Study Design

A multinational, placebo-controlled RCT involving 1,516 adults (mean age: 63±13 years) scheduled for cardiac surgery (52% coronary artery bypass graft, 50% valve surgery). Participants were randomized to fish oil or placebo 2–5 days preoperatively, continuing at 2g/day postoperatively. Bleeding outcomes were assessed using standardized definitions (BARC, TIMI, ISTH).

Dosage & Administration

Preoperative: 8–10g/day of fish oil (EPA+DHA) orally for 2–5 days before surgery.
Postoperative: 2g/day orally after surgery.
Placebo group received identical capsules without omega-3 fatty acids.

Results & Efficacy

Primary outcome: No statistically significant difference in major bleeding between fish oil and placebo (OR: 0.81; 95% CI: 0.53–1.24).
Secondary outcomes: Consistent null findings for increased bleeding risk across alternative definitions.
Transfusion efficacy: Fish oil reduced total blood transfusions by 0.31 units on average (P<0.001).
Omega-3 plasma levels: Patients in the highest quartiles for EPA+DHA had substantially lower bleeding risk (third quartile: OR: 0.30; 95% CI: 0.11–0.78; fourth quartile: OR: 0.36; 95% CI: 0.15–0.87).

Limitations

Population specificity: Results apply to cardiac surgery patients; generalizability to other procedures or populations is unclear.
Dosing duration: Short preoperative supplementation window (2–5 days) may not reflect chronic use effects.
Statistical power: Wide confidence intervals in primary bleeding outcomes suggest potential underpowering to detect small differences.
Observational association: The link between plasma omega-3 levels and reduced bleeding is hypothesis-generating, not causal.

Clinical Relevance

These findings challenge prior recommendations for discontinuing fish oil before surgery. For cardiac surgery patients:
- Continuing fish oil preoperatively does not increase bleeding risk.
- Supplementation may reduce transfusion needs, a clinically meaningful benefit.
- Achieved omega-3 levels correlate with bleeding protection, suggesting consistent adherence matters.
Healthcare providers should reconsider withholding fish oil in patients at risk of cardiovascular events, though further research is needed for non-cardiac surgeries.

Source: PubMed | Trial Registration: NCT00970489