Pathophysiology
Haemostasis does not only involve clot formation, but equally it requires dissolution of this clot (fibrinolysis). As we have discussed other aspects of the coagulation cascade in other CCCs such as in haemophilia and patient on anti-platelet therapy, let’s review the physiology of fibrinolysis briefly as this is the final component to consider in haemostasis:
Prostacyclin and nitrous oxide are constantly being released by intact endothelium to inhibit any unwanted coagulation. Endothelium also produces tissue plasminogen activator (tPA) as well as thrombomodulin which confine haemostasis to the site of injury.
tPA activates plasminogen → plasmin. Plasmin is the important proteolytic enzyme that breaks down fibrin into fibrin degradation products such as D-dimers, for example.
In DIC, there is dysregulation of fibrinolysis and clotting resulting in widespread coagulation and depletion of the clotting factors and platelets.
Tissue factor (TF) is released in response to pro-inflammatory cytokines which then promotes coagulation in inflammatory states (such as sepsis). It is also highly prevalent in the lungs, brain and placenta, hence it is readily released and activates coagulation in traumatic states as well.
⚠️ Risk factors and causes
- Sepsis
- Major trauma/burns
- Malignancies - such as AML.
- Obstetric complications - eclampsia/HELPP syndrome, abruptio placental, amniotic fluid embolism.
- Organ failure - such as severe pancreatitis or acute liver failure.
🔢 Classification
We can classify DIC as either acute or chronic
- Acute DIC - rapid-onset widespread bleeding and thrombosis → hypoperfusion, infarction and end-organ failure. It occurs with major trauma, sepsis, massive blood transfusion.
- Chronic DIC - subacute bleeding and diffuse thrombosis. More prevalent in malignancies, and less acute disorders.
😷 Presentation
- ⭐️ Excessive bleeding - such as epistaxis, gingival bleeding, haematuria, ecchymosis, or oozing.
- ⭐️ Petechiae - another sign of widespread bleeding.
- Confusion or coma - signs of microvascular/macrovascular thrombosis.
- Fever - as it often occurs due to severe infection.
- Hypotension, tachycardia, oliguria - signs of circulatory collapse, for example within the context of sepsis.
- Purpura fulminans or gangrene - rapid bleeding of the skin followed by sudden death due to microvascular thrombosis.
If there are signs of bleeding at 3 unrelated sites, this is highly suggestive of DIC. It is also vital to consider the systemic disease or trauma that could be causing the DIC of course.
🔍 Investigations
- Platelet count - thrombocytopenia.
- Prothrombin time - often prolonged.
- Fibrinogen - decreased as it is excessively used up.
- D-dimer - elevated as fibrin is continuously being broken down, producing more degradation products.
💯 Criteria and scoring
The International Society of Thrombosis and Haemostasis (ISTH) provides a scoring system to help with diagnosis of DIC.
A score of >5 is suggestive of overt DIC, while a score of <5 does not rule out DIC, but is suggestive of non-overt DIC and so tests should be repeated in the next 1-2 days.
There are 4 parameters that are considered:
- Platelet count
>100 - 0
<100 - 1
<50 - 2
- Fibrin degradation products (D-dimer)
No increase - 0
Moderate increase - 1
Strong increase - 2
- Prolonged prothrombin time
<3 seconds - 0
3-6 seconds - 1
>6 seconds - 2
- Fibrinogen level
>1 - 0
<1 - 1
🧰 Management
- Treatment of underlying disorder
- If the patient is actively bleeding or at high-risk of bleeding:
- Platelet transfusion + fresh frozen plasma (for replacement of coagulation factors) + anti-coagulants
- Treatment of underlying disorder