Acute Hemolytic Transfusion Reaction: ABO Incompatibility Emergency

Receiving ABO-incompatible blood triggers a Type II hypersensitivity reaction—a medical emergency with high mortality if not recognized immediately.

Pathophysiology

• Recipient's preformed anti-A/anti-B IgM antibodies bind donor RBC antigens.
• Complement activation (classical pathway) → membrane attack complex (C5b-9) → intravascular hemolysis.
• Free hemoglobin → hemoglobinuria, renal tubular toxicity, DIC, shock.
• Cytokine storm (TNF-α, IL-6, IL-8) → SIRS, multiorgan failure.

Clinical Presentation (During/Shortly After Transfusion)

• Fever, chills, rigors (often first sign)
• Flank/lumbar pain (renal capsule stretch)
• Dark/red urine (hemoglobinuria)
• Hypotension, tachycardia, dyspnea
• Oozing, DIC (schistocytes on smear)
• Anxiety, sense of doom

Immediate Management

1. STOP TRANSFUSION – keep IV open with normal saline.
2. Notify blood bank – send remaining unit + fresh patient blood for repeat typing/crossmatch/DAT.
3. Supportive: Aggressive IV hydration (target UOP >100 mL/hr), vasopressors for shock, consider mannitol/furosemide for renal protection.
4. DIC management: FFP, cryo, platelets per labs.
5. Monitor: Hb, haptoglobin, LDH, bilirubin, creatinine, coagulation, urine hemoglobin.

Delayed Hemolytic Transfusion Reaction (DHTR)

• Occurs 3–14 days post-transfusion.
• Anamnestic antibody response (IgG) to minor antigens (Kidd, Duffy, Kell).
• Extravascular hemolysis (spleen); less acute but causes anemia, jaundice.

Prevention (Zero-Tolerance Systems)

• Two-sample verification (separate draws) for type & screen.
• Electronic barcode patient ID at bedside.
• Two-person verification of unit vs. patient wristband.
• ABO compatibility check on unit label vs. patient type.

Mortality: ~10–20% for acute intravascular hemolysis; leading cause of transfusion-related death.