Disseminated Intravascular Coagulation
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Direct answer
Disseminated intravascular coagulation is a secondary, systemic activation of clotting that consumes platelets and factors and causes thrombosis and bleeding at the same time. It is a complication of an underlying illness, most often severe sepsis, acute promyelocytic leukaemia, obstetric emergencies or extensive tissue injury. Diagnosis rests on low platelets, prolonged clotting times, low fibrinogen and raised D-dimer, and treatment is removing the trigger while replacing deficient components.
What you must remember
- Mechanism: tissue factor or endothelial injury generates thrombin, so fibrin deposits in microvessels while platelets and clotting factors are consumed.
- Common triggers: Gram-negative and meningococcal sepsis, placental abruption, retained dead fetus, acute promyelocytic leukaemia, burns, heat stroke and snake envenomation.
- Laboratory profile: thrombocytopenia, prolonged prothrombin and activated partial thromboplastin times, low fibrinogen, raised D-dimer and schistocytes on smear.
- ISTH overt DIC score: points for platelet count, D-dimer, prothrombin time prolongation and fibrinogen; a total of 5 or more supports overt disease.
- Fibrinogen threshold: cryoprecipitate is considered for low fibrinogen, roughly below 1 g/L, when bleeding occurs.
- Heparin: reserved for dominant thrombosis such as purpura fulminans, and not routine in bleeding DIC.
A sequence from trigger to replacement
Management is a sequence rather than a single drug. The trigger is treated first, and components are replaced according to bleeding and laboratory thresholds.
- Treat the trigger: antibiotics and source control for sepsis, delivery for obstetric causes, and all-trans retinoic acid with chemotherapy for acute promyelocytic leukaemia.
- Score the disease: calculate the ISTH overt DIC score from platelet count, D-dimer, prothrombin time and fibrinogen, and repeat it as the picture changes.
- Assess bleeding: decide whether there is active bleeding or only laboratory change, since replacement is driven by clinical bleeding and thresholds.
- Replace platelets: transfuse for active bleeding or a low count, with higher targets before procedures, following local protocols.
- Replace fibrinogen and plasma: give cryoprecipitate for bleeding with low fibrinogen, and fresh frozen plasma for bleeding with prolonged clotting times.
- Consider anticoagulation with care: heparin is limited to thrombosis such as purpura fulminans, since it can worsen haemorrhage.
Where the exam tries to catch you
DIC vignettes test whether the candidate looks beyond the laboratory numbers.
- Trap: correcting the lab values without treating the trigger Correct: DIC persists until the cause, such as sepsis or abruption, is controlled.
- Trap: calling DIC a primary clotting disorder Correct: it is secondary, and consumption with schistocytes and rising D-dimer distinguishes it from inherited deficiencies.
- Trap: giving full-dose heparin to every bleeding child Correct: anticoagulation is reserved for dominant thrombosis, because it worsens haemorrhage.
- Trap: missing acute promyelocytic leukaemia in a child with DIC Correct: this needs all-trans retinoic acid promptly, not just blood products.
Frequently asked questions
What is the commonest trigger of DIC in children?
Severe sepsis, especially Gram-negative and meningococcal infection, is the commonest trigger of disseminated intravascular coagulation in children. Acute promyelocytic leukaemia and extensive tissue injury are other important triggers that exam vignettes often test.
What laboratory pattern confirms DIC?
Disseminated intravascular coagulation shows falling platelets, prolonged prothrombin and activated partial thromboplastin times, low fibrinogen and raised D-dimer. Schistocytes on a blood film support a microangiopathic picture.
What is the ISTH overt DIC score?
The ISTH overt DIC score adds points for platelet count, D-dimer, prothrombin time prolongation and fibrinogen, and a total of 5 or more supports overt disease. It complements the clinical picture rather than replacing it.
When is cryoprecipitate given in disseminated intravascular coagulation?
Cryoprecipitate is given to replace fibrinogen when bleeding occurs with low fibrinogen, since fibrinogen is the key substrate for clot formation. The threshold is set by local protocols and the clinical situation.