Hemostasis and Coagulation Practice Questions

25 multiple-choice questions on Hemostasis and coagulation for paramedic and EMT students, from Chapter 25 (Hematologic Emergencies). Read each question, pick your answer, then tap Show answer to check it and read the explanation.

25 practice questions

1. The coagulation cascade in a wound is triggered mainly when blood contacts:

   1. A. Oxygen in the outside air
   2. B. Red cells that have been crushed
   3. C. Plasmin released by the vessel
   4. D. Tissue factor from damaged cells
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   Answer: D. Tissue factor from damaged cells

   Damaged tissue exposes tissue factor, which activates factor VII and starts the cascade. Air exposure does not cause clotting, crushed red cells do not start it, and plasmin breaks clots down rather than forming them.

2. The correct order of hemostasis is:

   1. A. Fibrin clot, vessel spasm, platelet plug
   2. B. Platelet plug, fibrin clot, vessel spasm
   3. C. Vessel spasm, platelet plug, fibrin clot
   4. D. Fibrinolysis, platelet plug, vessel spasm
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   Answer: C. Vessel spasm, platelet plug, fibrin clot

   Vascular spasm comes first, then platelets stick and aggregate, and then the coagulation cascade forms a stable fibrin mesh.

3. Platelets stick to injured vessel walls with the help of:

   1. A. Factor VIII alone
   2. B. Von Willebrand factor
   3. C. Plasminogen activator
   4. D. Antithrombin III
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   Answer: B. Von Willebrand factor

   Von Willebrand factor bridges exposed collagen and platelets. A deficiency causes von Willebrand disease.

4. Newborns routinely receive a vitamin K injection because they:

   1. A. Have too few platelets at birth
   2. B. Have little vitamin K and no gut bacteria
   3. C. Lack fibrinogen until about 6 months of age
   4. D. Need it to make red blood cells
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   Answer: B. Have little vitamin K and no gut bacteria

   Little vitamin K crosses the placenta, breast milk holds little, and the newborn gut has not yet been colonized by the bacteria that make it. Without the shot, vitamin K deficiency bleeding can cause brain hemorrhage in the first months. Newborn platelet counts and fibrinogen are normal.

5. Thrombin is formed from:

   1. A. Prothrombin
   2. B. Fibrinogen
   3. C. Plasminogen
   4. D. Albumin
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   Answer: A. Prothrombin

   Prothrombin (factor II) is converted to thrombin by the prothrombinase complex, which includes factor Xa.

6. The D-dimer blood test, used when a clot is suspected, measures:

   1. A. The number of circulating platelets
   2. B. The amount of vitamin K in plasma
   3. C. Fragments of broken-down fibrin
   4. D. How long plasma takes to clot
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   Answer: C. Fragments of broken-down fibrin

   When the body breaks down a fibrin clot, D-dimer fragments are released. A normal D-dimer helps rule out DVT or PE in low-risk patients, but surgery, pregnancy, cancer, and infection also raise it, so a high value is not specific. Clotting time is measured by the INR and aPTT.

7. The enzyme that breaks down fibrin is:

   1. A. Thrombin
   2. B. Factor X
   3. C. Heparin
   4. D. Plasmin
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   Answer: D. Plasmin

   Plasminogen is converted to plasmin. Fibrinolytic drugs such as alteplase work by speeding up this step.

8. A patient on warfarin has an intracranial bleed and an INR of 4.5. Along with IV vitamin K, the hospital will most likely give:

   1. A. Protamine sulfate by slow IV push
   2. B. Desmopressin to release stored factors
   3. C. Pooled platelets from several donors
   4. D. Prothrombin complex concentrate
   Show answer

   Answer: D. Prothrombin complex concentrate

   Four-factor prothrombin complex concentrate (4F-PCC) supplies concentrated vitamin K-dependent factors and corrects the INR within minutes, while IV vitamin K gives a lasting effect. Protamine neutralizes heparin, desmopressin does not replace the factors warfarin has depleted, and platelets do not either.

9. Compared with aspirin, ibuprofen's effect on platelet function:

   1. A. Lasts the full life of each platelet
   2. B. Wears off as the drug is cleared
   3. C. Is stronger and permanent
   4. D. Activates platelets instead of blocking them
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   Answer: B. Wears off as the drug is cleared

   Ibuprofen blocks platelet COX reversibly, so platelet function returns within about a day after the last dose. Aspirin blocks COX permanently, so its effect lasts until new platelets are made, about 7 to 10 days. Both still add bleeding risk while active.

10. The INR is mainly used to monitor:

    1. A. Heparin therapy
    2. B. Aspirin therapy
    3. C. Warfarin therapy
    4. D. Platelet transfusion
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    Answer: C. Warfarin therapy

    The INR standardizes the prothrombin time. A typical target on warfarin is 2 to 3, while a normal INR is about 1.

11. The aPTT is classically used to monitor:

    1. A. Unfractionated heparin
    2. B. Warfarin (Coumadin)
    3. C. Clopidogrel (Plavix) therapy
    4. D. Low-dose aspirin
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    Answer: A. Unfractionated heparin

    Unfractionated heparin prolongs the aPTT, so hospitals adjust heparin drips by it. Clopidogrel and aspirin act on platelets, which the aPTT does not measure.

12. A man with hemophilia A who has not had recent factor replacement would most likely have:

    1. A. A long INR with a normal aPTT
    2. B. A low platelet count with a normal aPTT
    3. C. A long aPTT with a normal INR
    4. D. A normal aPTT and a normal INR
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    Answer: C. A long aPTT with a normal INR

    Factor VIII works in the intrinsic pathway, which the aPTT measures. The INR reflects factors such as VII and stays normal, and the platelet count is normal in hemophilia. A normal INR therefore does not rule out a serious bleeding disorder.

13. A patient who had a coronary stent placed 2 months ago asks whether he can stop his clopidogrel because he bruises easily. The best advice is:

    1. A. Do not stop it without his cardiologist
    2. B. Stop it for a week to see if bruising eases
    3. C. Switch to taking aspirin twice daily
    4. D. Cut the dose in half on his own
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    Answer: A. Do not stop it without his cardiologist

    Stopping antiplatelet therapy soon after a stent can cause sudden stent thrombosis and a STEMI. Easy bruising is an expected effect; heavy or uncontrolled bleeding needs evaluation, and any change must be made by the prescriber.

14. Heparin works mainly by:

    1. A. Blocking vitamin K
    2. B. Boosting antithrombin
    3. C. Dissolving fibrin clots
    4. D. Blocking platelet receptors
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    Answer: B. Boosting antithrombin

    Heparin greatly increases antithrombin activity, which inactivates thrombin and factor Xa.

15. The reversal agent for unfractionated heparin is:

    1. A. Vitamin K (phytonadione)
    2. B. Idarucizumab
    3. C. Naloxone
    4. D. Protamine sulfate
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    Answer: D. Protamine sulfate

    Protamine binds heparin and neutralizes it. It only partly reverses low-molecular-weight heparin such as enoxaparin.

16. Which patient taking dabigatran is most likely to have a higher-than-expected drug level?

    1. A. One with worsening kidney function
    2. B. One who eats many leafy green vegetables
    3. C. One who recently quit smoking cigarettes
    4. D. One taking a daily multivitamin tablet
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    Answer: A. One with worsening kidney function

    About 80% of dabigatran is cleared by the kidneys, so dehydration or kidney injury lets it build up and raises bleeding risk. Vitamin K in leafy greens affects warfarin, not dabigatran.

17. Andexanet alfa is used to reverse:

    1. A. Vitamin K antagonists
    2. B. Low-molecular heparin
    3. C. P2Y12 platelet blockers
    4. D. Factor Xa inhibitors
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    Answer: D. Factor Xa inhibitors

    It binds and neutralizes factor Xa inhibitors such as apixaban and rivaroxaban. Availability varies, and many hospitals use four-factor prothrombin complex concentrate instead. Vitamin K and PCC, not andexanet, reverse warfarin.

18. A patient stable on warfarin begins eating large spinach salads every day. You would expect his INR to:

    1. A. Rise, raising bleeding risk
    2. B. Stay the same with any diet
    3. C. Fall, raising clot risk
    4. D. Fall, raising bleeding risk
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    Answer: C. Fall, raising clot risk

    Spinach and other leafy greens are rich in vitamin K, which counteracts warfarin, so the INR falls and protection against stroke or clots drops. Patients should keep vitamin K intake steady rather than avoid greens entirely.

19. A patient with a mechanical heart valve is most likely taking which anticoagulant?

    1. A. Apixaban
    2. B. Warfarin
    3. C. Rivaroxaban
    4. D. Dabigatran
    Show answer

    Answer: B. Warfarin

    Direct oral anticoagulants are not used with mechanical valves; dabigatran caused more clots and bleeding than warfarin in that group. These patients stay on warfarin with a higher INR target.

20. A man who used synthetic cannabinoids has bleeding gums, blood in his urine, and a very high INR. Several others in his area have the same problem. The likely cause is:

    1. A. Acute leukemia from the drug
    2. B. Undiagnosed hemophilia A
    3. C. A long-acting rat-poison anticoagulant
    4. D. Thrombocytopenia caused by the smoke itself
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    Answer: C. A long-acting rat-poison anticoagulant

    In 2018, synthetic cannabinoids laced with brodifacoum, a long-acting rodenticide, caused clusters of severe bleeding with very high INRs. These 'superwarfarins' block vitamin K recycling for weeks, so patients need vitamin K for months. Hemophilia does not raise the INR.

21. Hypothermia worsens bleeding in trauma because it:

    1. A. Raises the platelet count
    2. B. Slows clotting enzymes
    3. C. Speeds up clot formation
    4. D. Increases fibrinogen production
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    Answer: B. Slows clotting enzymes

    Clotting enzymes and platelets work poorly when cold, even when lab tests run at normal body temperature look fine. Prevent heat loss in every bleeding patient. Cold does not raise platelet counts or fibrinogen.

22. The lethal triad of trauma consists of:

    1. A. Hypoxia, hypercarbia, and hypotension
    2. B. Tachycardia, fever, hypotension
    3. C. Bradycardia, hypertension, apnea
    4. D. Hypothermia, acidosis, coagulopathy
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    Answer: D. Hypothermia, acidosis, coagulopathy

    Each element worsens the others. Prevent heat loss, control bleeding, and limit crystalloids.

23. Why do large volumes of crystalloid worsen trauma coagulopathy?

    1. A. They dilute clotting factors
    2. B. They activate too many platelets
    3. C. They break down fibrinogen
    4. D. They bind free calcium
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    Answer: A. They dilute clotting factors

    Crystalloids carry no clotting factors. They also cool the patient and can worsen acidosis. They do not activate platelets or break down fibrinogen, and saline does not bind calcium the way the citrate in stored blood does; the problem is simply that they replace lost blood with fluid that has no clotting proteins.

24. Fresh frozen plasma is given to replace:

    1. A. Red blood cells
    2. B. Clotting factors
    3. C. Platelets
    4. D. White blood cells
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    Answer: B. Clotting factors

    Plasma contains all the coagulation factors. It is used in massive transfusion and to reverse warfarin.

25. Cryoprecipitate is rich in:

    1. A. Albumin
    2. B. Red blood cells
    3. C. Platelets
    4. D. Fibrinogen
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    Answer: D. Fibrinogen

    Cryoprecipitate contains fibrinogen, factor VIII, von Willebrand factor, and factor XIII.