🩸 Hemolysis — What It Is, Why It Happens, and How to Spot It

Hemolysis is the premature destruction of red blood cells (RBCs). Free hemoglobin is released, which can circulate, bind haptoglobin, get filtered into urine, or be processed to indirect bilirubin → jaundice and pigment gallstones.

🔀 Two main pathways

• Intravascular hemolysis – RBCs rupture in the bloodstream

  • Clues: ↓ haptoglobin, ↑ LDH, hemoglobinuria/hemosiderinuria, schistocytes

• Extravascular hemolysis – RBCs destroyed by macrophages (spleen/liver)

  • Clues: Spherocytes, splenomegaly, ↑ indirect bilirubin, jaundice

🧪 High-yield lab patterns (table)

Feature	Intravascular	Extravascular
Haptoglobin	Low	Normal / slightly low
LDH	High	High
Bilirubin	↑ Indirect (mild–mod)	↑ Indirect (often higher)
Urine findings	Hemoglobinuria, hemosiderinuria	Usually absent
Peripheral smear	Schistocytes	Spherocytes, bite cells (G6PD)

🧬 Common causes to recognize

• Immune

  • Warm AIHA (IgG): SLE, CLL, methyldopa; + direct Coombs.

  • Cold agglutinin (IgM): Mycoplasma, EBV; acrocyanosis.

• Hereditary membrane/enzyme

  • Hereditary spherocytosis (spectrin/ankyrin; ↑ MCHC; splenomegaly).

  • G6PD deficiency (oxidative stress: sulfa drugs, fava beans, primaquine → Heinz bodies/bite cells).

  • Sickle cell disease (vaso-occlusion + hemolysis).

• Mechanical/microangiopathic

  • TTP/HUS, DIC, malignant HTN, prosthetic valves → schistocytes.

• Complement

  • Paroxysmal nocturnal hemoglobinuria (PNH): CD55/59 deficiency; dark morning urine, thrombosis.

• Infectious/toxic

  • Malaria, clostridial sepsis, snake venom; severe burns.

🎯 MCAT focus points

• Distinguish intravascular vs extravascular patterns from labs.

• Direct vs indirect Coombs in immune hemolysis.

• Associate buzzwords: bite cells/Heinz (G6PD), spherocytes (HS), schistocytes (MAHA), and low haptoglobin (intravascular).

🩺 NCLEX nursing pearls

• Transfusion reaction: fever, flank pain, hypotension, chest tightness → STOP transfusion, keep IV open with normal saline, notify provider/blood bank, send tubing + blood, collect urine/Coombs labs, monitor urine output and vital signs.

• Manage complications: hyperkalemia, AKI, jaundice; patient teaching about dark cola-colored urine.

🧩 Rapid practice (answers below)

1. Dark morning urine, pancytopenia, thrombosis. Likely dx?

2. Child with jaundice, splenomegaly, ↑MCHC, spherocytes. Best definitive treatment?

3. Febrile patient with schistocytes, thrombocytopenia, neuro signs. Diagnosis to prioritize?

Keys: 1) PNH. 2) Splenectomy (after vaccines). 3) TTP (ADAMTS13 deficiency)—start plasma exchange urgently.

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