Disseminated Intravascular Coagulation (DIC)

Related Subjects: |Microangiopathic Haemolytic anaemia |Haemolytic anaemia |Immune (Idiopathic) Thrombocytopenic Purpura (ITP) |Thrombotic Thrombocytopenic purpura (TTP) |Haemolytic Uraemic syndrome (HUS) |Thrombocytopenia |Disseminated Intravascular Coagulation (DIC)

⚠️ Disseminated intravascular coagulation (DIC) is a life-threatening clinicopathological syndrome. It arises from widespread activation of coagulation, generating fibrin clots that cause organ dysfunction, while consuming platelets and clotting factors → paradoxical bleeding + thrombosis. 💀 Classic teaching: “DIC = Death Is Coming”.

📖 About

• Seen in ~1% of hospital inpatients, usually in the context of severe underlying illness (e.g., ICU patients).
• Characterised by uncontrolled coagulation → consumption of clotting factors → bleeding diathesis.
• Results in massive haemorrhage, microthrombi, multi-organ failure; prognosis is poor and depends on reversing the trigger.

🦠 Important Causes

• Sepsis – most common; esp. Gram-negative, but also Gram-positive, viral (e.g., COVID-19, HIV, CMV), fungal, parasitic (malaria).
• Trauma & tissue injury – major trauma, burns, crush injuries, snake bites.
• Malignancy – acute promyelocytic leukaemia (APL/M3), solid tumours with metastases.
• Obstetric catastrophes – amniotic fluid embolism, placental abruption, severe pre-eclampsia/eclampsia, HELLP syndrome.
• Other: severe liver failure, massive transfusion/ABO incompatibility, vasculitis, aneurysms, heatstroke, recreational drugs.

🧬 Pathophysiology

• Excess thrombin generation → widespread fibrin clots in microvasculature.
• Consumption of fibrinogen, clotting factors (esp. II, V, VIII), and platelets.
• Platelet trapping → thrombocytopenia.
• Secondary hyperfibrinolysis → elevated fibrin degradation products (FDPs)/D-dimer.

🩺 Clinical Features

• Typically in critically ill patients (e.g., ICU, sepsis, trauma).
• Bleeding: oozing from IV sites/wounds, mucosal (mouth/GI), haematuria, epistaxis, intracerebral haemorrhage.
• Microvascular thrombosis → digital ischaemia, purpura fulminans, organ failure (renal, hepatic, pulmonary, CNS).
• Respiratory failure: ARDS on CXR in severe cases.

🔬 Investigations

• Platelets: usually <50–100 ×10⁹/L (often <50 in overt DIC).
• PT, APTT: prolonged.
• Fibrinogen: low (<1 g/L in overt cases; Clauss method preferred).
• Factor VIII/vWF: often reduced (consumed).
• ↑ FDPs / D-dimer (key fibrinolysis markers; very high in acute DIC).
• Blood film: schistocytes (fragmented RBCs from microangiopathic haemolysis).
• CXR: may show ARDS pattern.

📊 Scoring System (Overt DIC – ISTH)

• Platelet count: >100 = 0; 50–100 = 1; <50 = 2.
• Fibrin markers (D-dimer/FDPs): no increase = 0; moderate increase (>3× upper limit) = 2; strong increase (>7× upper limit or ≥5× in classic) = 3 (ISTH 2025 refinement uses D-dimer thresholds).
• PT prolongation: <3s = 0; 3–6s = 1; >6s = 2 (or INR equivalent).
• Fibrinogen: >1 g/L = 0; <1 g/L = 1.
• Score ≥5 = compatible with overt DIC (repeat daily). <5 = suggestive of non-overt DIC (repeat every 1–2 days, monitor clinically).

📌 Differentials

• Thrombotic thrombocytopenic purpura (TTP).
• Haemolytic uraemic syndrome (HUS).
• HELLP syndrome / severe pre-eclampsia.
• Severe malignant hypertension.
• Liver failure / vitamin K deficiency (isolated coagulopathy).

🩸 Blood Film: Schistocytes

💊 Management (always involve Haematology urgently)

• 1. Treat the underlying cause aggressively – this is the cornerstone (e.g., antibiotics for sepsis, delivery/evacuation in obstetrics, ATRA/chemotherapy in APL, source control in trauma).
• 2. Supportive measures (transfusion only if bleeding or high-risk):
  • Active bleeding or invasive procedure → platelets if <50 ×10⁹/L (target >50); FFP 15 mL/kg if PT/APTT prolonged.
  • Low fibrinogen (<1 g/L) with bleeding → cryoprecipitate (or fibrinogen concentrate) to target >1–1.5 g/L.
  • Monitor response: repeat platelets, PT/APTT, fibrinogen post-replacement.
• 3. Thrombosis-predominant DIC: consider therapeutic heparin (e.g., purpura fulminans, acral ischaemia) if no contraindications.
• 4. Non-bleeding critically ill patients: standard VTE prophylaxis with LMWH if appropriate.
• Avoid routine prophylactic transfusions based on labs alone (per BSH/ISTH). Consider Pabrinex (thiamine) in at-risk patients (e.g., alcoholics/sepsis) to prevent Wernicke's encephalopathy.

📚 Reference

• British Society for Haematology (BSH): Guidelines for diagnosis & management of DIC (2009, addendum 2012 – current UK standard)
• ISTH SSC on DIC: Overt scoring system (2001, with 2025 refinements to D-dimer thresholds)
• No specific NICE guideline for DIC; refer to related pathways (e.g., NG51 sepsis, CG144 VTE).

Cases - Disseminated Intravascular Coagulation (DIC)

• Case 1 - Obstetric Emergency: A 32-year-old woman presents with massive postpartum haemorrhage following placental abruption. She is hypotensive and oozing blood from venepuncture sites. Bloods show platelets 45 ×10⁹/L, PT and APTT prolonged, fibrinogen very low, D-dimer markedly elevated. Diagnosis: Acute DIC secondary to obstetric catastrophe.
• Case 2 - Sepsis-Associated DIC: A 70-year-old man with pneumonia becomes hypotensive and develops mottled skin and purpura fulminans. He has active bleeding from his nasogastric tube. FBC: platelets 30 ×10⁹/L, Hb 7.8 g/dL. Coagulation profile: prolonged PT/APTT, low fibrinogen, high fibrin degradation products. Diagnosis: Sepsis-induced DIC.
• Case 3 - Malignancy-Related Chronic DIC: A 65-year-old woman with known metastatic pancreatic cancer presents with bruising, mucosal bleeding, and recurrent venous thromboembolism despite anticoagulation. Platelets are 80 ×10⁹/L, fibrinogen borderline low, PT mildly prolonged, D-dimer persistently elevated. Diagnosis: Chronic DIC in the context of malignancy.

Teaching Commentary 🩸

DIC is a pathological activation of the coagulation cascade, leading to simultaneous thrombosis and bleeding. In acute settings (e.g., sepsis, trauma, obstetrics), rapid consumption causes life-threatening bleeding. In chronic forms (e.g., malignancy), thrombosis may predominate with subtler bleeding. Diagnosis combines clinical context + labs: thrombocytopenia, prolonged PT/APTT, hypofibrinogenaemia, raised D-dimer. Management prioritises treating the underlying cause, with targeted supportive transfusion for bleeding and cautious anticoagulation if thrombosis dominates (BSH/ISTH guidance).