If you've ever been scheduled for surgery, you might have been surprised when your doctor mentioned blood thinners, especially if you thought bleeding was already a concern during operations. It may seem counterintuitive, but blood thinners play a crucial role in making surgeries safer, Mostly for patients at risk of deep vein thrombosis (DVT) or pulmonary embolism (PE).

In this blog, we'll explain why blood thinners are given before surgery, what they actually do in the body, and what Indian patients should know before undergoing a procedure.

Why are blood thinners given before surgery?

Blood thinners are prescribed before surgery to prevent the formation of blood clots during and after the procedure. While clotting is a natural process to stop bleeding, surgery increases the risk of forming abnormal clots inside blood vessels, especially in the legs and lungs.

Some of the main reasons include:

• Prolonged immobility: Patients undergoing long surgeries or recovery periods often stay in bed for hours or days, slowing blood flow and raising clot risks.
• Tissue damage: Surgery causes tissue injury, which activates the body’s natural clotting response.
• Underlying conditions: People with heart disease, obesity, cancer, or a history of clots are at higher risk and benefit from blood thinners.

What do blood thinners do in your body before surgery?

Blood thinners don’t literally “thin” the blood. Instead, they act on specific parts of the clotting process to lower the risk of abnormal clots. This is particularly important in major surgeries involving the abdomen, pelvis, or bones.

Here’s how they help:

• Block clotting proteins: Medications like Evaparin 40, which contains Enoxaparin (a low molecular weight heparin), reduce the activity of proteins that cause clots to form.
• Prevent growth of small clots: If small clots form during surgery, these medicines stop them from becoming larger and potentially dangerous.
• Reduce post-operative complications: These medications are especially useful in preventing pulmonary embolism and strokes in surgeries with a higher clotting risk, like orthopedic or cancer operations.

Using these medications correctly improves outcomes and keeps patients safer through recovery.

When exactly are blood thinners given before surgery?

Timing is crucial when using blood thinners for surgery. Doctors decide when to give them based on your health status, the type of surgery, and the specific medication used.

Here's what the schedule typically looks like:

• Before surgery: Blood thinners may be started 12–24 hours before the procedure, depending on the risk of clotting and bleeding.
• After surgery: In many cases, especially orthopedic surgeries, doctors restart blood thinners 6–12 hours after surgery to maintain clot prevention without causing excess bleeding.

Are there risks to using blood thinners before surgery?

Yes, like any medication, blood thinners come with risks, especially when used around surgery. However, these risks are carefully balanced with the benefits.

Potential concerns include:

• Increased bleeding: This is the most common side effect. Surgeons manage this by carefully timing the dose and monitoring your condition.
• Bruising or hematomas: Since the blood doesn’t clot as easily, you may notice more bruising at injection sites or around the surgical area.
• Allergic reactions: Rarely, patients may develop skin reactions or allergies to heparin-based products.

Doctors weigh all these risks before starting any blood thinner and adjust the plan as needed to avoid complications.

Who needs blood thinners the most before surgery?

Not all patients are given blood thinners, but some groups are more likely to receive them due to a higher risk of clotting. You might be prescribed these medications if you:

• Are undergoing joint replacement or major abdominal surgery
• Have a history of DVT, PE, or clotting disorders
• Are immobile or bedbound for extended periods
• Are being treated for cancer
• Have obesity, diabetes, or heart disease

In these cases, blood thinners are a proactive measure to prevent serious health events after surgery.

What precautions should be taken while on blood thinners?

While blood thinners are beneficial, you must take some precautions to ensure your safety:

• Follow dosing instructions exactly: Do not skip or double up on doses.
• Inform all your doctors: Always let your healthcare providers know you're taking a blood thinner.
• Avoid certain medications: Over-the-counter pain relievers like ibuprofen or aspirin may increase bleeding risk.
• Watch for unusual symptoms: Report any unexpected bruising, bleeding, or dizziness to your doctor immediately.
• Be cautious with sharp objects: Even a small cut could bleed more than usual, so take extra care when shaving or cooking.

Do blood thinners affect anesthesia?

Yes, blood thinners can affect anesthesia, especially when regional or spinal anesthesia is planned. These medications increase the risk of bleeding in and around the spinal cord, which can lead to serious complications such as spinal hematoma—a rare but potentially permanent cause of nerve damage. That’s why anesthesiologists always review your blood thinner history before surgery. They may recommend stopping certain medications temporarily or switching to alternatives based on your clotting risk. The timing of stopping and restarting blood thinners is carefully managed to ensure both anesthesia safety and continued protection against harmful clots during your hospital stay.

Conclusion

A proactive safety precaution that helps avoid potentially deadly blood clots is the use of blood thinners prior to surgery. Surgeons and anesthesiologists minimize complications and enhance recovery outcomes by carefully assessing your risk and precisely timing the medication. Although taking a "blood thinner" prior to surgery may seem dangerous, you can be sure that this is a well-researched and widely recognized method of providing safer surgical care.

If you're scheduled for a long surgery or caring for someone who is, ask the doctor about DVT prevention. The right questions and the right precautions can make all the difference in recovery.