Approach to Thrombocytopenia in ICU

1️⃣ Why Thrombocytopenia in ICU is Important?

Thrombocytopenia (platelet count <150,000/µL) is extremely common in critically ill patients.

• Occurs in 20–50% of ICU patients
• Associated with:
• ↑ Mortality
• ↑ Bleeding risk
• ↑ Organ failure
• ↑ Length of ICU stay

⚠ In ICU, thrombocytopenia is usually multifactorial, not isolated.

2️⃣ Platelet Physiology – Quick Revision

Normal platelet count: 150,000–450,000/µL

• Produced in bone marrow (megakaryocytes)
• Lifespan: ~7–10 days
• 1/3rd sequestered in spleen
• Normal daily turnover: ~10%

3️⃣ ICU-Specific Definition & Severity Classification

⚠ In ICU, trend matters more than absolute count.

A drop >50% from baseline is clinically significant even if >150k.

4️⃣ Stepwise ICU Approach 

🔴 STEP 1: Confirm It Is Real

Exclude Pseudothrombocytopenia

Causes:

• EDTA-induced platelet clumping
• Platelet satellitism(Platelet satellitism is an in vitro laboratory artifact in which platelets adhere to the surface of neutrophils, forming a “rosette-like” pattern on peripheral smear.)

📌 Action:

• Repeat count in citrate tube
• Examine peripheral smear

🔴 STEP 2: Acute vs Chronic?

🔴 STEP 3: Determine Mechanism 

All ICU thrombocytopenia falls into 4 mechanisms:

1️⃣ Decreased Production

• Bone marrow suppression
• Chemotherapy
• Viral infections
• Severe sepsis
• Aplastic anemia

2️⃣ Increased Destruction

• Immune (ITP, HIT)
• TTP
• DIC
• Drug-induced

3️⃣ Sequestration

• Hypersplenism
• Cirrhosis

4️⃣ Dilutional

• Massive transfusion
• Aggressive fluid resuscitation

5️⃣ ICU-Specific Major Causes 

1️⃣ Sepsis-Associated Thrombocytopenia

Most common cause in ICU.

Mechanisms:

• Cytokine-mediated suppression
• Platelet consumption
• DIC
• Hemophagocytosis
• Endothelial activation

Features:

• Gradual decline
• Multiorgan dysfunction
• Elevated D-dimer

Platelet recovery = marker of sepsis resolution.

2️⃣ Disseminated Intravascular Coagulation (DIC)

Think DIC when:

• Sepsis
• Trauma
• Malignancy
• Obstetric catastrophe

Labs:

• ↓ Platelets
• ↑ PT/INR
• ↑ aPTT
• ↓ Fibrinogen
• ↑ D-dimer
• Schistocytes

🔴 Exam pearl: DIC = both bleeding + thrombosis.

3️⃣ Heparin-Induced Thrombocytopenia (HIT)

Immune-mediated thrombocytopenia due to anti-PF4 antibodies.

Occurs:

• 5–10 days after heparin
• Or earlier if prior exposure

Key Features:

• 50% platelet fall
• Thrombosis (arterial/venous)
• No bleeding
• Normal PT/aPTT

4T Score

Management:

• Stop all heparin
• Start non-heparin anticoagulant (argatroban)

⚠ Never give platelets in HIT unless life-threatening bleed.

4️⃣ Thrombotic Thrombocytopenic Purpura (TTP)

Due to severe ADAMTS13 deficiency.

Pentad (rarely complete):

• Thrombocytopenia
• MAHA
• Neurologic signs
• Renal dysfunction
• Fever

Lab clues:

• Normal PT/aPTT
• Schistocytes
• ↑ LDH
• ↓ haptoglobin

🔴 Treatment = Immediate plasma exchange
Delay increases mortality.

5️⃣ Drug-Induced Thrombocytopenia

Common ICU drugs:

• Linezolid
• Vancomycin
• Piperacillin
• Quinine
• Valproate

Typically:

• Sudden drop
• Recovery after withdrawal

6️⃣ Dilutional Thrombocytopenia

Seen in:

• Massive transfusion protocol
• ECMO
• Major trauma

Mechanism:

• Platelet dilution
• Consumption
• Shear stress destruction

6️⃣ Laboratory Approach 

Always order:

• CBC with smear
• PT/INR
• aPTT
• Fibrinogen
• D-dimer
• LDH
• Bilirubin
• Haptoglobin
• Renal function
• HIT antibodies (if suspected)

 When to Transfuse Platelets? (Guideline-Based)

⚠ Exceptions:

• TTP → NO prophylactic platelets
• HIT → Avoid platelets

9️⃣ Thrombocytopenia in Special ICU Situations

🔹 ECMO

• Mechanical destruction
• Consumption
• Heparin exposure

🔹 CRRT

• Platelet activation
• Filter loss

🔹 Liver Failure

• ↓ Thrombopoietin
• Hypersplenism
• DIC

🔹 Post-Cardiac Surgery

• CPB-related consumption
• Dilution
• HIT risk

🔟 Prognostic Implications

• Persistent thrombocytopenia = poor prognosis
• Failure of recovery by day 5 = high mortality
• Platelet recovery predicts survival in sepsis