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Pharmacology · chapter 20 · Anticoagulant, Antiplatelet, and Thrombolytic Drugs

Anticoagulants

The 14 things this section of the textbook says that you are most likely to be asked about — quoted word for word, not retold. Then 6 practice questions with the reasoning.

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Key points

  1. Anticoagulants do not dissolve clots

    One important note is that anticoagulants do not dissolve existing clots. Instead, they prevent further clot formation and allow the body to naturally dissolve any existing clots over time.

  2. Why they are high-alert medications

    Many anticoagulants have a narrow therapeutic index, meaning that the dose must be individualized, monitored, and controlled to ensure that clients do not experience therapeutic failure (e.g., a clotting complication from their disease) or adverse events. Because of this, anticoagulants are classified as high-alert medications (Institute for Safe Medication Practices, 2018).

  3. Higher INR means more bleeding risk

    A higher INR indicates that the blood is thinner and less likely to form a clot, and the client is more prone to bleeding.

  4. Heparin infusion is titrated to labs

    For treatment of a thromboembolism, it is typically given as a weight-based continuous infusion that is titrated based on client response. Response is measured using either the PTT or anti-Xa level, depending on the institutional protocol.

  5. Warfarin needs overlap with heparin

    For example, warfarin takes several days to achieve therapeutic anticoagulation, so overlap with a parenteral agent (e.g., continuation of heparin or initiation of enoxaparin) is warranted until then.

  6. HIT: stop heparin immediately

    Although the platelets are decreased, the client is in a highly hypercoagulable state. Heparin must be discontinued immediately, and alternative anticoagulation with a non-heparin-based anticoagulant is required.

  7. When to suspect HIT

    The diagnosis of HIT is more likely and should be considered when the platelet count drops by 50% or more.

  8. Enoxaparin and the kidneys

    A major disadvantage of enoxaparin is that it is eliminated by the kidneys and therefore the dose must be adjusted or the drug must be avoided in those with kidney dysfunction.

  9. How warfarin works

    Warfarin inhibits the production of vitamin K in the body. Vitamin K is needed for production of clotting factors II, VII, IX, and X.

  10. Warfarin's usual INR goal

    The therapeutic goal INR varies per indication but is usually 2–3. Some clients with mechanical heart valves have an INR goal of 2.5–3.5.

  11. Keep vitamin K intake consistent

    Since warfarin decreases vitamin K production, dietary intake of vitamin K opposes the anticoagulant effect and can decrease warfarin’s effect. Conversely, if a client regularly consumes vitamin K foods but abruptly stops, their blood can quickly become over-anticoagulated.

  12. Dabigatran capsules must stay whole

    The capsules must be swallowed whole and cannot be crushed, opened, or chewed. It also must be stored in the original packaging and discarded four months after opening.

  13. Giving protamine safely

    Safety Alert Protamine Protamine is administered by slow IV push, no faster than 50 mg per 10 minutes, because faster infusion causes hypotension. It also can cause severe hypersensitivity reactions, so the nurse should have resuscitation equipment and epinephrine available during administration for potential emergency response.

  14. Signs of bleeding

    Some symptoms of bleeding are blood in the stool; dark, tarry-appearing stools; blood in the urine; epistaxis (nosebleed); gingival bleeding; very severe headache; coffee-ground emesis; and hemoptysis.

Terms to know

Anticoagulants
Anticoagulants Used as Blood Thinners Anticoagulants are commonly referred to as blood thinners.
Heparin-induced thrombocytopenia (HIT)
Heparin-induced thrombocytopenia (HIT) is a rare although major complication of heparin therapy.
Enoxaparin
Enoxaparin Enoxaparin is a derivative of heparin and is referred to as a low molecular weight heparin.
Protamine
Protamine Protamine is a protein that neutralizes heparin.
Vitamin K
Vitamin K (Phytonadione) Vitamin K is also known as phytonadione.

Practice questions

Stuck on select-all-that-apply? How to take them one option at a time.

The graded version needs JavaScript. Every question is below anyway, with the answer and why.

Every question here, with the answer

  1. A client on a continuous heparin infusion has a platelet count that has dropped by more than half since the infusion started. What should the nurse anticipate?

    1. Continue heparin and give a platelet transfusion.
    2. Stop heparin and start a non-heparin anticoagulant.
    3. Switch the client to enoxaparin.
    4. Increase the heparin rate because the client is now at risk of clotting.

    Answer: Stop heparin and start a non-heparin anticoagulant.

    A drop in platelets of 50% or more points to HIT, a hypercoagulable state in which heparin must be stopped immediately and a non-heparin anticoagulant started. Continuing or increasing heparin worsens HIT, and enoxaparin is a heparin derivative that can also cause HIT.

  2. A client who takes warfarin tells the nurse, "I've decided to stop eating kale and broccoli completely." What is the best response?

    1. Diet has no effect on warfarin.
    2. Keep the amount of vitamin K foods you eat consistent rather than stopping them suddenly.
    3. That is a good idea; vitamin K foods must be avoided.
    4. Eat more of these foods on days you feel you are bruising.

    Answer: Keep the amount of vitamin K foods you eat consistent rather than stopping them suddenly.

    Vitamin K opposes warfarin, so intake should be consistent; it does not need to be avoided altogether. Suddenly stopping regular vitamin K foods can quickly over-anticoagulate the blood. Adjusting intake by symptoms or ignoring diet is unsafe.

  3. A nurse is teaching a client who will inject enoxaparin at home. Which instructions should the nurse include? Select all that apply.

    1. Do not expel the air bubble from the pre-filled syringe.
    2. Avoid injecting into bruised or scarred skin.
    3. Rub the site afterward to help absorption.
    4. Inject through thin clothing if needed.
    5. Inject into a skin fold of the abdomen.

    Answer: Do not expel the air bubble from the pre-filled syringe., Avoid injecting into bruised or scarred skin., Inject into a skin fold of the abdomen.

    Enoxaparin is injected into a held skin fold of the abdomen, without ejecting the air bubble, and not into bruised or scarred skin. The client should avoid rubbing the site and avoid injecting through clothing.

  4. A client with an intracranial hemorrhage is receiving protamine to reverse heparin. Which action by the nurse is most important?

    1. Give it with vitamin K to improve its effect.
    2. Give it slowly and keep resuscitation equipment and epinephrine available.
    3. Stop monitoring the PTT once protamine is given.
    4. Give it as a rapid IV push to reverse heparin quickly.

    Answer: Give it slowly and keep resuscitation equipment and epinephrine available.

    Protamine is given by slow IV push because fast infusion causes hypotension, and it can cause severe hypersensitivity reactions, so emergency equipment and epinephrine must be ready. Vitamin K reverses warfarin, not heparin, and PTT should still be monitored for heparin rebound.

  5. Which findings in a client taking an anticoagulant should the nurse recognise as possible signs of bleeding? Select all that apply.

    1. Very severe headache
    2. Coffee-ground emesis
    3. Dark, tarry stools
    4. Nosebleed
    5. Increased appetite

    Answer: Very severe headache, Coffee-ground emesis, Dark, tarry stools, Nosebleed

    Tarry stools, coffee-ground emesis, very severe headache and epistaxis are all listed signs of bleeding from anticoagulants. Increased appetite is not a sign of bleeding.

  6. A client is being prescribed dabigatran and asks if the capsules can be opened and mixed with applesauce. What should the nurse say?

    1. Yes, but only after the first four months.
    2. No, the capsules must be swallowed whole.
    3. Only if you take it with food.
    4. Yes, opening the capsule is fine.

    Answer: No, the capsules must be swallowed whole.

    Dabigatran capsules must be swallowed whole and cannot be crushed, opened, or chewed. None of the other options is supported by the section.

Where every quote comes from

Section 20.2 Anticoagulants of Pharmacology for Nurses by Tina Barbour-Taylor, Leah Mueller (Sabato), Donna Paris, Dorie Weaver, OpenStax, 2024. Read the whole section free at openstax.org.

The textbook is licensed under CC BY-NC-SA 4.0. This page quotes it word for word and adds the headings, the order and the practice questions; references to the book's figures and stray spaces left by its formatting are removed. The page is shared under the same licence. Nothing here is sold.