Transfusion Reactions: Mechanism, Symptoms, and Prevention

Incompatible blood transfusion triggers a potentially fatal immune-mediated hemolytic reaction.

Pathophysiology (ABO Incompatibility)

1. Antibody binding: Recipient's preformed anti-A/anti-B IgM binds donor RBC antigens.
2. Complement activation: Classical pathway → C5b-9 (MAC) formation → intravascular hemolysis.
3. Cytokine storm: TNF-α, IL-1, IL-6, bradykinin → fever, hypotension, DIC.
4. Hemoglobinemia/hemoglobinuria: Free Hb binds haptoglobin → renal tubular toxicity → acute kidney injury.

Clinical Presentation

• Acute (during/within 4h): fever, chills, flank pain, dark urine, hypotension, DIC, renal failure, shock.
• Delayed (3–10 days): falling Hb, jaundice, reticulocytosis (extravascular hemolysis).

Other Reaction Types

• Febrile non-hemolytic (FNHTR): anti-HLA/HNA antibodies.
• Allergic/urticarial: anti-IgA, plasma proteins.
• Anaphylactic: anti-IgA in IgA-deficient.
• TRALI: anti-HLA/HNA in donor plasma → pulmonary edema.
• TACO: volume overload.
• Bacterial sepsis: contaminated unit.

Prevention

• ABO/Rh typing and antibody screen (recipient).
• Crossmatch (electronic or serologic).
• Patient identification (wristband, two identifiers).
• Leukoreduction, irradiation (for at-risk).

Immediate Management

• STOP transfusion.
• IV access, fluids, vasopressors if hypotensive.
• Send blood bag, post-transfusion samples for workup.
• Supportive care (renal, respiratory, DIC management).