Hemolytic Anemias & Hemoglobinopathies
Comprehensive emergency evaluation and protocolized management of acute hemolytic anemias and severe hemoglobinopathies: laboratory hallmarks of hemolysis (elevated LDH, indirect hyperbilirubinemia, low haptoglobin, peripheral blood smear review); distinguishing Intravascular (hemoglobinuria, hemosiderinuria) vs. Extravascular hemolysis; Glucose-6-Phosphate Dehydrogenase (G6PD) deficiency acute oxidative flares (bite cells, Heinz bodies, fava beans, rasburicase, primaquine); Autoimmune Hemolytic Anemia (Warm AIHA [IgG/spherocytes] vs. Cold Agglutinin Disease [IgM/acrocyanosis in cold]); Coombs testing; and transfusion crossmatch pitfalls ('incompatible unit' emergency release).
Resuscitation Quick Actions • First 2 Minutes
Hemolysis Lab Tetrad
1) Elevated LDH, 2) High indirect bilirubin, 3) Undetectable haptoglobin (< 10–20 mg/dL), 4) Elevated reticulocyte index (> 2–3%)
Direct Coombs (DAT)
Direct Antiglobulin Test detects IgG/C3 bound to RBC surface; positive confirms Autoimmune Hemolytic Anemia (AIHA)
Warm AIHA Treatment
Methylprednisolone 1 to 2 mg/kg IV daily (IgG mediated, extravascular splenic clearance); warm fluids; avoid unnecessary transfusions
Cold Agglutinin Disease
IgM mediated (Mycoplasma, EBV); causes complement fixation; KEEP PATIENT AND ALL IV FLUIDS WARM (avoid steroids/splenectomy)
G6PD Oxidative Triggers
Fava beans, Rasburicase, Primaquine, Dapsone, Nitrofurantoin, Phenazopyridine, Sulfamethoxazole -> causes bite cells & Heinz bodies
All Units Incompatible
In severe AIHA, autoantibodies cross-react with all donor units: if patient is in shock, release 'LEAST INCOMPATIBLE' blood immediately
Bottom-Line Clinical Pearl
Acute hemolysis presents with the classic triad of ANEMIA, JAUNDICE, and SPLENOMEGALY. Laboratory confirmation requires four concordant biomarkers: (1) High indirect bilirubin, (2) Markedly elevated LDH, (3) Undetectable serum Haptoglobin (< 10–20 mg/dL), and (4) High Reticulocyte count (> 2–3%). Peripheral blood smear is the single most valuable diagnostic emergency test: spherocytes indicate Autoimmune Hemolytic Anemia (AIHA) or Hereditary Spherocytosis; schistocytes indicate microangiopathic hemolytic anemia (TTP/HUS/DIC); bite cells and Heinz bodies indicate G6PD deficiency under oxidative stress. For Warm AIHA (IgG mediated, 37°C), first-line therapy is high-dose IV Methylprednisolone (1–2 mg/kg); avoid transfusions unless in severe cardiovascular collapse. If transfusion is mandatory, blood banks will report 'ALL UNITS INCOMPATIBLE' due to pan-agglutinating autoantibodies: administer 'least incompatible' uncrossed PRBCs slowly with the blood bank director's approval.
Hemolysis occurs when erythrocyte lifespan is shortened below normal ($< 120\text{ days}$), overwhelming the bone marrow's regenerative capacity. Pathophysiology is strictly categorized by anatomical site of red cell destruction:
| Hemolysis Category | Mechanism & Anatomical Site | Classic Etiologies | Laboratory & Urinalysis Hallmarks |
|---|---|---|---|
| Intravascular Hemolysis | Erythrocytes are directly lysed within circulating blood vessels, releasing free hemoglobin into the plasma | ABO incompatible transfusion, G6PD severe oxidative crisis, Microangiopathic Hemolytic Anemia (TTP, HUS, DIC), Paroxysmal Nocturnal Hemoglobinuria (PNH), prosthetic heart valves | Gross hemoglobinuria (dark reddish-brown urine; urine dipstick positive for blood, but zero intact RBCs on microscopy); acute renal tubular necrosis; severe drop in haptoglobin; elevated free plasma hemoglobin. |
| Extravascular Hemolysis | Abnormal, antibody-coated, or deformed erythrocytes are phagocytosed by macrophages in the splenic red pulp and hepatic reticuloendothelial system | Warm Autoimmune Hemolytic Anemia (AIHA), Hereditary Spherocytosis, Sickle Cell Disease, Thalassemia | Splenomegaly on exam; indirect hyperbilirubinemia with jaundice; pigmented gallstones; absence of hemoglobinuria (hemoglobin is processed into bilirubin inside macrophages). |
| Diagnostic Domain | Warm Autoimmune Hemolytic Anemia (Warm AIHA) | Cold Agglutinin Disease (Cold AIHA) |
|---|---|---|
| Autoantibody Class | IgG autoantibodies (active at normal body temperature, $37^\circ\text{C}$) | IgM autoantibodies (active at colder temperatures, $< 30^\circ\text{C}$) |
| Associated Triggers | Idiopathic (50%), SLE, CLL, non-Hodgkin lymphoma, drugs (penicillins, cephalosporins) | Mycoplasma pneumoniae pneumonia, Epstein-Barr Virus (EBV/mononucleosis), lymphoproliferative disorders |
| Site of Destruction | Extravascular: splenic macrophages recognize IgG Fc portion and ingest membranes, forming SPHEROCYTES | Intravascular & Extravascular: IgM binds RBCs in cold extremities, fixes complement (C3b); hepatic Kupffer cell clearance |
| Physical Hallmarks | Acute fatigue, pallor, scleral icterus, splenomegaly | Acrocyanosis (painful bluish-purple mottled discoloration of ears, nose, fingers, toes upon cold exposure) |
| First-Line Therapy | High-dose IV Methylprednisolone (1–2 mg/kg/day); IVIG; rituximab; splenectomy for refractory disease | KEEP PATIENT AND ALL INFUSIONS WARM! Steroids and splenectomy are INEFFECTIVE; treat with Rituximab. |
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