Disseminated intravascular coagulation

Question 1

Define

Answer 1

A disorder of the clotting cascade that can complicate a serious illness

→ Widespread activation of coagulation, from release of procoagulant into the circulation with consumption of clotting factors and platelets, with ↑risk of bleeding

Fibrin strands fill small vessels, haemolysing passing RBCs Fibrinolysis is also activated

Two forms:

1. Acute overt form where there is bleeding and depletionof platelets and clotting factor
2. Chronic non-overt form where thromboembolism is accompanied by generalized activation of the coagulation system

Question 2

Causes

Answer 2

Infection - particularly GRAM-NEGATIVE sepsis

Obstetric Complications

• Missed miscarriage (when the foetus dies but the body doesn’t realise it and the placenta continues to release hormones)
• Severe pre-eclampsia
• Placental abruption (separation of the placenta from the wall of the uterus during pregnancy)
• Amniotic emboli

Malignancy

• Acute promyelocytic leukaemia - ACUTE DIC
• Lung, breast and GI malignancy - CHRONIC DIC

Severe trauma or surgery

Others: haemolytic transfusion reaction, burns, severe liver disease, aortic aneurysms, haemangiomas

Pathophysiology

Acute DIC

• Endothelial damage and the release of granulocyte/macrophage procoagulant substances (e.g. tissue factor) lead to activation of coagulation
• This leads to explosive thrombin generation, which depletes clotting factors and platelets, whilst also activating the fibrinolytic system
• This leads to bleeding in the subcutaneous tissues, skin and mucous membranes
• Occlusion of blood vessels by fibrin in the microcirculation leads to microangiopathic haemolytic anaemia and ischaemic organ damage

Chronic DIC

• IDENTICAL process to acute DI
• Happens at a slower rate with time for compensatory responses
• The compensatory responses diminish the likelihood of bleeding but give rise to hypercoagulable states and thrombosis can occur

Question 3

Epidemiology

Answer 3

can be seen in any severely ill pt

Question 4

Symptoms

Answer 4

↑bruising and ↑bleeding anywhere
Severely unwell pt, symptoms of underlying disease Confusion, dyspnoea

Question 5

Signs

Answer 5

Signs of underlying disease

Fever

Evidence of shock (hypotension, tachycardia)

Acute DIC

• Petechiae, purpura, ecchymoses
• Epistaxis
• Mucosal bleeding
• Overt haemorrhage
• Signs of end organ damage
• Respiratory distress
• Oliguria due to renal failure

Chronic DIC

• Signs of deep vein and arterial thrombosis or embolism
• Superficial venous thrombosis

Question 6

Investigations

Answer 6

Bloods

FBC

• Low platelets
• Low Hb
• High APTT/PT
• Low fibrinogen
• High fibrin degradation products
• High D-dimers

Peripheral Blood Film

• Schistocytes