Coagulation and Transfusion Medicine Flashcards

A 78-year-old male on long-term apixaban for atrial fibrillation presents to the emergency department with a life-threatening gastrointestinal bleed. He requires urgent endoscopy. Which of the following is the most appropriate agent for the immediate reversal of apixaban's anticoagulant effect?

Answer: Andexanet alfa

Andexanet alfa is a recombinant modified factor Xa protein that acts as a decoy, binding to and sequestering factor Xa inhibitors like apixaban and rivaroxaban. [2, 3] This action rapidly neutralizes their anticoagulant effect. [1, 12] PCC contains factors II, VII, IX, and X, and can be used off-label, but it is not a specific antidote. Vitamin K is used to reverse warfarin and has no effect on DOACs. FFP contains all clotting factors but is not concentrated, requires large volumes, and is not a first-line reversal agent for factor Xa inhibitors. [9, 22]

A massively bleeding trauma patient has a critically low fibrinogen level of 0.7 g/L. Which blood product is the most concentrated source of fibrinogen and therefore the most appropriate choice to specifically correct this deficiency?

Answer: Cryoprecipitate

Cryoprecipitate is a plasma-derived product that is a concentrated source of fibrinogen, Factor VIII, von Willebrand factor, and Factor XIII. [5, 8, 15] It is the treatment of choice for significant hypofibrinogenemia (<1.0-1.5 g/L) as it provides a large amount of fibrinogen in a small volume. [7, 8, 14] While FFP contains fibrinogen, it is much less concentrated, requiring a larger volume to achieve the same effect. [4, 9] Platelets and PRBCs do not contain significant amounts of fibrinogen.

Within two hours of receiving a transfusion of packed red blood cells, a 65-year-old ICU patient develops acute respiratory distress, hypoxemia (SpO2 85% on 60% O2), and bilateral infiltrates on chest X-ray. Her blood pressure is 90/50 mmHg, and there are no signs of fluid overload such as jugular venous distension or peripheral edema. Which of the following is the most likely diagnosis?

Answer: Transfusion-Related Acute Lung Injury (TRALI)

The clinical picture of acute hypoxemia and bilateral pulmonary edema occurring within 6 hours of transfusion, in the absence of signs of circulatory overload (e.g., hypotension rather than hypertension), is characteristic of Transfusion-Related Acute Lung Injury (TRALI). [11, 23, 34] TRALI is a form of non-cardiogenic pulmonary edema. [10, 34] In contrast, Transfusion-Associated Circulatory Overload (TACO) is a cardiogenic or hydrostatic pulmonary edema, typically associated with signs of fluid overload like hypertension and elevated central venous pressure. [36, 42] Anaphylaxis often involves bronchospasm and urticaria, and an acute hemolytic reaction typically presents with fever, chills, hemoglobinuria, and flank pain.

A bleeding patient's ROTEM analysis shows a normal EXTEM Clotting Time (CT), but the Maximum Clot Firmness (MCF) is severely reduced. The FIBTEM analysis also shows a severely reduced MCF. What is the most likely deficiency that needs to be addressed?

Answer: Fibrinogen deficiency

In ROTEM, the Maximum Clot Firmness (MCF) reflects the overall strength of the clot, which is dependent on platelets and fibrinogen. The FIBTEM test uses cytochalasin D to inhibit platelets, thereby isolating the contribution of fibrinogen to clot strength. [31, 47] A severely reduced MCF on both the EXTEM and FIBTEM tests indicates that the primary problem is a deficiency in fibrinogen quantity or quality. [30, 46] A normal Clotting Time (CT) suggests that the initiation of coagulation (i.e., coagulation factor activity) is adequate.

A 52-year-old patient with end-stage liver disease is actively bleeding. Laboratory results show INR 3.0, platelets 50 x 10^9/L, and fibrinogen 0.8 g/L. To establish a functional clot, which of the following should be prioritized for replacement?

Answer: Cryoprecipitate or Fibrinogen Concentrate

In patients with end-stage liver disease, coagulopathy is complex, involving deficiencies in both pro- and anti-coagulants. [27, 43] However, fibrinogen is the essential substrate for clot formation. A level below 1.0-1.2 g/L is critically low and severely impairs the ability to form a stable clot, regardless of other factor levels. [18, 32] Therefore, correcting the severe hypofibrinogenemia with a concentrated source like cryoprecipitate or fibrinogen concentrate is the first priority. [20, 44] While platelets, FFP, and PCC may also be required, they cannot be effective without sufficient fibrinogen substrate.

Which of the following statements best describes the primary mechanism of action of tranexamic acid (TXA) in a trauma patient with massive hemorrhage?

Answer: It prevents the breakdown of existing clots by inhibiting plasminogen activation.

Tranexamic acid is a synthetic lysine analog. Its primary mechanism is antifibrinolytic. It competitively inhibits the activation of plasminogen to plasmin, the enzyme responsible for clot degradation (fibrinolysis). [28, 29] By preventing plasmin from binding to fibrin, it stabilizes formed clots and reduces bleeding, particularly in the context of trauma-induced coagulopathy where hyperfibrinolysis is common. [25, 33] It does not directly activate platelets, provide clotting factors, or inhibit fibrin formation.