A septic patient develops DIC with active bleeding from IV sites. The physician administers platelet transfusions and fresh frozen plasma. Which outcome is most consistent with the pathophysiology of DIC?
ASustained improvement — replacing consumed factors stops the coagulopathy
BTemporary improvement followed by resumed consumption, because the underlying trigger has not been addressed
CWorsening — platelet transfusions accelerate thrombin generation and worsen thrombosis
DNo effect — in late DIC, laboratory values no longer respond to factor replacement
The key therapeutic insight is that DIC is a secondary syndrome — the consumption continues as long as the underlying source of tissue factor exposure persists. Platelet transfusions and FFP temporarily replenish substrates but do not stop the pathological process driving their consumption. The infection must be treated; only then will the TF exposure stop and the coagulopathy resolve. Treating the coagulopathy in isolation is a fundamental error that the mechanism predicts will fail.
Question 2 Multiple Choice
In DIC, elevated D-dimer most directly reflects which part of the pathophysiological sequence?
AActive thrombin generation converting fibrinogen to fibrin
BPlatelet activation and consumption by systemic thrombin
CCompensatory fibrinolysis breaking down fibrin clots to produce degradation products
D-dimer is a specific fibrin degradation product released when plasmin degrades cross-linked fibrin. Its elevation in DIC reflects the compensatory fibrinolytic response to massive fibrin deposition — plasmin is generated in response to the clots being formed throughout the microcirculation. D-dimer does not directly measure thrombin generation (that's reflected in fibrinogen consumption and PT/aPTT prolongation) nor platelet loss.
Question 3 True / False
A patient in early DIC is more likely to present with bleeding than with organ dysfunction due to microvascular thrombosis.
TTrue
FFalse
Answer: False
This reverses the clinical timeline. Early DIC manifests as thrombosis — microthrombi in capillaries causing organ dysfunction (renal failure, respiratory distress, altered consciousness). Bleeding is a late manifestation, occurring after coagulation factors and platelets have been exhausted by the thrombotic process. The sequence is: thrombosis first, then consumption, then bleeding. Thinking that DIC always presents primarily with bleeding misses the early thrombotic phase where intervention can be most effective.
Question 4 True / False
The presence of schistocytes on peripheral blood smear in DIC reflects mechanical injury to red blood cells by fibrin strands deposited in small vessels.
TTrue
FFalse
Answer: True
Schistocytes (fragmented erythrocytes) form when red blood cells are sheared by fibrin strands deposited across the lumen of small vessels — a direct consequence of microvascular thrombosis. Their presence is a morphological hallmark of microangiopathic hemolytic anemia and confirms that fibrin deposition in the microvasculature is occurring. This connects the laboratory finding directly to the pathophysiological mechanism of DIC.
Question 5 Short Answer
Explain why DIC presents with both clotting and bleeding simultaneously — what is the pathophysiological mechanism that creates this apparent paradox?
Think about your answer, then reveal below.
Model answer: Systemic tissue factor exposure triggers thrombin generation throughout the entire vascular tree, causing widespread fibrin deposition and platelet activation (thrombosis). This massive activation consumes platelets and clotting factors faster than they can be replenished, depleting the raw materials needed for hemostasis (consumption coagulopathy). The clotting and the bleeding are not two separate processes but one process viewed at different time points: early DIC manifests as thrombosis; late DIC manifests as hemorrhage from exhausted substrates.
The paradox resolves when you follow the timeline. Both thrombosis and bleeding are driven by the same root cause — systemic TF-driven thrombin generation — just observed at different stages. This is why treating only the bleeding (with factor replacement) without addressing the trigger is insufficient: the consumption continues as long as the source of TF exposure persists.