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🩸 DIC & Thrombotic Microangiopathies

ISTH Score Treat the Trigger TTP · ADAMTS13 HUS / aHUS Schistocytes
Consumptive Coagulopathy · MAHA ISTH DIC Score TTP · HUS · HELLP ISTH/BSH DIC guidance · TTP & complement TMA · Marino 5th Ed (2025) · Washington Manual
📅 Last reviewed July 2026 · Next review January 2027 · Compiled by Dr. Anmol Srivastava Anaesthesia, Emergency Medicine & Critical Care Medicine · Reviewed by Dr. Tanya Chawla Anaesthesia & Critical Care
📘 1 · Washington Manual of Critical Care

Two Families of Microvascular Clotting

The critically ill patient with a falling platelet count, red-cell fragments on the film and either bleeding or organ ischaemia has a microvascular clotting disorder until proven otherwise. These fall into two families: disseminated intravascular coagulation (DIC), a consumptive coagulopathy driven by an underlying illness that activates coagulation system-wide; and the thrombotic microangiopathies (TMAs) — TTP, the haemolytic uraemic syndromes and their relatives — driven by a defect in vWF handling or complement regulation. The single most useful test to tell them apart is the humble coagulation screen: it is deranged in DIC and normal in the TMAs.

Summarised from the Washington Manual of Critical Care — DIC & Thrombotic Microangiopathies.

The shared signature — MAHA + thrombocytopenia

  • Microangiopathic haemolytic anaemia (MAHA) — schistocytes on the film, ↑ LDH, ↓ haptoglobin, ↑ indirect bilirubin, negative direct Coombs.
  • Thrombocytopenia from platelet consumption in microthrombi.
  • Organ injury from microvascular occlusion — brain (TTP), kidney (HUS), or multi-organ (DIC).
📗 2 · Marino's The ICU Book, 5th Edition (2025)

DIC — Simultaneous Clotting and Bleeding

DIC is not a disease but a response: a trigger — sepsis, trauma, obstetric catastrophe, malignancy — unleashes systemic thrombin generation. Microthrombi form throughout the circulation and consume platelets and clotting factors faster than the marrow and liver can replace them. The patient therefore clots and bleeds at the same time, and the only treatment that reverses the process is elimination of the trigger. Products and anticoagulants are supportive; they do not cure DIC.

Summarised from Marino PL. The ICU Book, 5th Ed — Disseminated Intravascular Coagulation.
🔬 The DIC cascade
TriggerSepsis · trauma/burns · obstetric (abruption, AFE, retained products) · malignancy (esp. APML) · snakebite
Massive tissue factor / thrombin generation → systemic microvascular fibrin thrombi
Consumption of platelets & factors → bleeding
Microthrombi → ischaemic organ injury
Secondary fibrinolysis → ↑ D-dimer, ↓ fibrinogen
Result↓ platelets · ↑ PT/APTT · ↓ fibrinogen · ↑↑ D-dimer · schistocytes — simultaneous bleeding & clotting
📗 Marino — TMA is a different mechanism entirely
  • TTP — severe ADAMTS13 deficiency (usually autoantibody) → ultralarge vWF multimers → platelet-rich microthrombi; predominantly neurological. Coagulation screen is normal.
  • Typical HUS — Shiga-toxin (E. coli O157, Shigella) after bloody diarrhoea; predominantly renal, mostly children — supportive care, no routine antibiotics.
  • Atypical HUS — dysregulated alternative complement pathway → treat with eculizumab.
  • Secondary / obstetric TMA — HELLP, pre-eclampsia, drug-induced, transplant — overlap; delivery is definitive for HELLP.
📋 3 · Scoring DIC & Working Up the TMA

Evidence-Based Management

Diagnose DIC with the ISTH score, trended ISTH
In a patient with a disorder known to cause DIC, score: platelets (<100 = 1, <50 = 2), D-dimer/FDP (moderate ↑ = 2, strong ↑ = 3), PT prolongation (3–6 s = 1, >6 s = 2), fibrinogen (<1 g/L = 1). ≥5 = overt DIC; <5 = repeat and trend. No single test makes the diagnosis — it is the pattern and its trajectory that matter.
Treat the trigger — everything else is supportive STRONG
The cornerstone is prompt, aggressive treatment of the underlying cause (source control + antibiotics for sepsis; deliver/evacuate the uterus in obstetric DIC; ATRA for APML). Give blood products only if bleeding or before a procedure, not to "correct numbers": platelets for <50 with bleeding (<20 without), FFP for prolonged PT/APTT with bleeding, cryoprecipitate/fibrinogen if fibrinogen <1.5 g/L. See Transfusion & Coagulopathy.
Anticoagulation in DIC — selective, not routine individualise
In the thrombotic-predominant phenotype (e.g. purpura fulminans, arterial/venous thrombosis, or as VTE prophylaxis once not actively bleeding), therapeutic or prophylactic heparin may be used. It is contraindicated when bleeding dominates. Antifibrinolytics (TXA) are generally avoided in DIC except in the hyperfibrinolytic states (APML, some obstetric/trauma DIC) where they are used with caution.
TMA — plasma exchange first, ask questions later EMERGENCY
If MAHA + thrombocytopenia with a normal coagulation screen, treat as TTP: start urgent plasma exchange + corticosteroids (add caplacizumab and rituximab per local protocol), and send ADAMTS13 before the first plasma — but do not wait for it. Consider atypical HUS → eculizumab if renal-predominant and ADAMTS13 not severely low; consider HELLP in pregnancy → deliver. Withhold platelet transfusion in TTP unless life-threatening bleeding.
🇮🇳 Indian Context

The commonest DIC triggers in Indian ICUs are sepsis, obstetric emergencies (abruption, amniotic fluid embolism, sepsis, retained products), severe falciparum malaria, and viper snakebite — Russell's viper venom is a potent procoagulant and causes a venom-induced consumption coagulopathy where the priority is adequate antivenom, not FFP (see Snakebite). In obstetric DIC, source control (delivery/evacuation) plus balanced products and fibrinogen replacement is life-saving. Access to plasma exchange and eculizumab is limited to larger centres — recognise TTP early and refer for apheresis; eculizumab for atypical HUS is expensive and may require special access.

💊 4 · Drug & Product Doses

Products, Anticoagulants & TMA Therapy

AgentIndicationDoseNotes
PlateletsDIC with bleeding (<50) or <201 adult dose ≈ ↑ 20–40 ×10⁹/LWithhold in TTP unless life-threatening bleeding
Fresh frozen plasmaBleeding with prolonged PT/APTT~15 mL/kgReplaces all factors; not to "normalise numbers" without bleeding
Cryoprecipitate / fibrinogen concentrateFibrinogen <1.5 g/L (bleeding/obstetric)Cryo ~2 pools, or fibrinogen 2–4 gObstetric target fibrinogen >2 g/L
Heparin (prophylactic/therapeutic)Thrombotic-predominant DIC / VTE prophylaxisStandard dosingContraindicated when bleeding dominates
Plasma exchangeTTP (definitive)1–1.5 plasma volumes daily until remissionStart on suspicion; send ADAMTS13 first
CorticosteroidsTTP (immune)Methylprednisolone 1 mg/kg/day (higher in severe)Adjunct to PEX
CaplacizumabAcquired TTP (anti-vWF nanobody)Per protocol with PEXFaster platelet recovery; monitor bleeding
EculizumabAtypical (complement-mediated) HUSPer protocolMeningococcal vaccination/prophylaxis needed
🗺 5 · Clinical Flowchart

Approach to MAHA + Thrombocytopenia

1

Recognise the pattern

  • Falling platelets + schistocytes + ↑LDH/↓haptoglobin (MAHA) ± bleeding or organ ischaemia
  • Send coagulation screen, fibrinogen, D-dimer, film, LDH, haptoglobin, bilirubin, creatinine, ADAMTS13, pregnancy test
2

Read the coagulation screen — the fork in the road

  • Deranged (↑PT/APTT, ↓fibrinogen, ↑↑D-dimer) → DIC — apply the ISTH score
  • Normal screen → thrombotic microangiopathy (TTP/HUS) — treat as TTP until excluded
3a

If DIC → treat the trigger

  • Source control + antibiotics; deliver/evacuate uterus; ATRA for APML; antivenom for snakebite
  • Products only if bleeding/pre-procedure; heparin only if thrombotic-predominant & not bleeding
3b

If TMA → plasma exchange

  • Urgent PEX + steroids (+ caplacizumab/rituximab) for TTP; ADAMTS13 sent before first plasma
  • Consider aHUS → eculizumab (renal-predominant); HELLP in pregnancy → deliver
4

Support & monitor organs

  • Renal replacement for AKI; neuro-obs in TTP; serial platelets, LDH, fibrinogen, D-dimer
  • Avoid unnecessary platelet transfusion in the TMAs
5

Reassess trajectory

  • DIC resolves as the trigger is controlled; persistent DIC = uncontrolled source
  • TTP relapses — continue PEX until platelet & LDH normalise, then taper immunosuppression
⚠️ 6 · Common Mistakes

Common Mistakes in DIC & TMA

❌ Mistake 1 — Treating DIC with products instead of the trigger

Transfusing to normalise the coagulation screen without controlling the source (sepsis, retained products, snakebite) fuels ongoing consumption. Eliminating the trigger is the only cure; products are supportive and reserved for bleeding.

❌ Mistake 2 — Missing TTP because the screen is normal

A normal PT/APTT/fibrinogen with MAHA + thrombocytopenia is TTP, not "mild coagulopathy". Missing it forfeits the window for plasma exchange, which is life-saving.

❌ Mistake 3 — Transfusing platelets in TTP

Adding platelets to a platelet-consuming microthrombotic process can worsen organ ischaemia. Withhold unless there is life-threatening bleeding.

❌ Mistake 4 — Giving FFP instead of antivenom in viper-bite coagulopathy

Russell's viper venom keeps consuming factors until neutralised. Adequate antivenom is the priority; FFP alone is poured into a leaking bucket.

❌ Mistake 5 — Antibiotics for Shiga-toxin (typical) HUS

Antibiotics in E. coli O157 gastroenteritis may increase toxin release and HUS risk. Typical HUS is largely supportive.

❌ Mistake 6 — Forgetting pregnancy

In a pregnant/peripartum woman, HELLP and obstetric DIC are common and delivery is often the definitive treatment — always send a pregnancy test and involve obstetrics.

🎓 7 · Exam Pearls — DrNB / PDCC / IFCCM / EDIC

Exam Pearls

Q: How do you score DIC?
ISTH score: platelets, D-dimer/FDP, PT prolongation, fibrinogen — ≥5 in a patient with a known trigger = overt DIC. Trend it.

Q: What is the single best treatment of DIC?
Prompt treatment of the underlying cause. Products are supportive and given only for bleeding or pre-procedure.

Q: How do you separate DIC from TTP?
DIC has a deranged coagulation screen (↑PT/APTT, ↓fibrinogen, ↑↑D-dimer); TTP has a normal screen with MAHA + thrombocytopenia.

Q: What causes TTP and how is it treated?
Severe ADAMTS13 deficiency (usually autoantibody) → urgent plasma exchange + steroids ± caplacizumab/rituximab.

Q: Typical vs atypical HUS?
Typical = Shiga-toxin after bloody diarrhoea, renal, supportive care. Atypical = complement dysregulation → eculizumab.

Q: Which snake causes DIC in India, and how is it managed?
Russell's viper (procoagulant venom) → venom-induced consumption coagulopathy; adequate antivenom, not FFP alone, is the treatment.

Q: When is heparin used in DIC?
In the thrombotic-predominant phenotype (e.g. purpura fulminans) or for VTE prophylaxis once not actively bleeding — not routinely.

📚 8 · References

References

  1. Wada H, Thachil J, Di Nisio M, et al. (ISTH SSC). Guidance for diagnosis and treatment of DIC. J Thromb Haemost. 2013;11:761–767.
  2. Levi M, Toh CH, Thachil J, Watson HG (BSH). Guidelines for the diagnosis and management of disseminated intravascular coagulation. Br J Haematol. 2009;145:24–33.
  3. Zheng XL, Vesely SK, Cataland SR, et al. (ISTH). ISTH guidelines for diagnosis & treatment of thrombotic thrombocytopenic purpura. J Thromb Haemost. 2020;18:2486–2521.
  4. George JN, Nester CM. Syndromes of Thrombotic Microangiopathy. N Engl J Med. 2014;371:654–666.
  5. Scully M, Cataland SR, Peyvandi F, et al. (HERCULES). Caplacizumab Treatment for Acquired TTP. N Engl J Med. 2019;380:335–346.
  6. Marino PL. The ICU Book, 5th Edition. Disseminated Intravascular Coagulation. Wolters Kluwer; 2025.
  7. Washington Manual of Critical Care, 4th Edition. Kollef MH, Witt CA (eds). DIC & Thrombotic Microangiopathies. Wolters Kluwer; 2023.