Acute Haemolytic Crisis

1. Clinical Overview

Summary

An acute haemolytic crisis represents rapid, pathological destruction of red blood cells (RBCs), resulting in anemia, jaundice, and potentially life-threatening complications including acute kidney injury and circulatory collapse. Normal RBC lifespan is approximately 120 days; in hemolysis, premature destruction outpaces bone marrow compensatory mechanisms, leading to progressive anemia. [1]

The clinical presentation combines features of anemia (fatigue, dyspnea, tachycardia), jaundice from unconjugated hyperbilirubinemia, and in severe intravascular hemolysis, dark urine (hemoglobinuria) and signs of end-organ damage. The classic triad of anemia, jaundice, and reticulocytosis should immediately suggest hemolytic anemia. [2]

Etiologically, haemolytic crises arise from diverse mechanisms: autoimmune (warm and cold antibodies), alloimmune (transfusion reactions), microangiopathic (thrombotic microangiopathy), infectious (malaria, Clostridium perfringens), drug-induced, hereditary enzyme deficiencies (G6PD deficiency), membrane defects (hereditary spherocytosis), and mechanical (prosthetic heart valves). [3,4]

The severity spectrum ranges from compensated hemolysis (increased RBC production maintaining hemoglobin) to fulminant crises with hemoglobin nadirs less than 70 g/L, multi-organ dysfunction, and mortality risk of 5-10% in severe untreated cases. [5] Early recognition through characteristic laboratory patterns (elevated LDH, low haptoglobin, elevated unconjugated bilirubin, reticulocytosis, schistocytes on blood film) and prompt intervention are essential for favorable outcomes.

Key Facts

• Definition: Accelerated RBC destruction exceeding bone marrow compensatory capacity
• Incidence: Autoimmune hemolytic anemia (AIHA) 1-3 per 100,000; transfusion reactions 1:40,000-70,000 units; microangiopathic 2-6 per million
• Mortality: less than 1% (mild-moderate); 5-10% (severe untreated); up to 20-40% (thrombotic thrombocytopenic purpura without treatment)
• Peak age: Bimodal - children (post-viral, G6PD) and adults > 50 (autoimmune, malignancy-associated)
• Critical feature: Anemia + jaundice + elevated LDH + low haptoglobin
• Key investigation: FBC, reticulocyte count, blood film, LDH, haptoglobin, bilirubin, direct antiglobulin test (DAT/Coombs)
• First-line treatment: Treat underlying cause + supportive transfusion + corticosteroids (if autoimmune)

Clinical Pearls

"Anemia + jaundice + dark urine = intravascular hemolysis" — This triad mandates immediate investigation for life-threatening causes including transfusion reaction, paroxysmal cold hemoglobinuria, and G6PD crisis.

"LDH up, haptoglobin down = hemolysis confirmed" — LDH (released from RBCs) > 1000 U/L and undetectable haptoglobin (less than 0.1 g/L) provide near-diagnostic confirmation of significant hemolysis. [6]

"DAT positive = immune, DAT negative = non-immune" — The direct antiglobulin test (Coombs test) distinguishes autoimmune/alloimmune (positive) from mechanical, enzymatic, or membrane defect hemolysis (negative). [7]

"Schistocytes = microangiopathic emergency" — Red cell fragmentation on blood film indicates mechanical RBC damage from microthrombi (TTP, HUS, DIC, mechanical valve) requiring urgent specialist management. [8]

"Cold agglutinins + acrocyanosis = paroxysmal cold hemoglobinuria or cold AIHA" — Exposure to cold triggering hemolysis and peripheral cyanosis suggests cold-reactive antibodies; keep patient warm and avoid cold IV fluids. [9]

Why This Matters Clinically

Acute haemolytic crises represent medical emergencies requiring rapid diagnosis and intervention. Delayed recognition can result in:

• Acute kidney injury: Free hemoglobin nephrotoxicity, particularly in intravascular hemolysis [10]
• Cardiovascular collapse: Severe anemia reduces oxygen delivery; hemolysis-induced nitric oxide depletion causes vasoconstriction
• Thrombosis: Hemolysis releases procoagulant phospholipids and consumes anticoagulant proteins
• Death: Mortality 5-10% in severe cases, up to 90% in untreated TTP

Prompt identification of etiology guides specific therapy (immunosuppression for autoimmune, plasmapheresis for TTP, antimalarials for malaria, withdrawal of offending drug) and prevents progression.

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2. Epidemiology

Incidence & Prevalence

Overall haemolytic anemia:

• Annual incidence: 5-10 per 100,000 (all causes combined)
• Prevalence: 20-40 per 100,000 population

By specific etiology:

Demographics

Risk Factors

Non-Modifiable:

• Genetics: G6PD deficiency, pyruvate kinase deficiency, hereditary spherocytosis, sickle cell disease
• Age: Extremes of age (neonates, elderly) at higher risk
• Sex: X-linked disorders (G6PD) affect males predominantly
• Ethnicity: Disease-specific predispositions

Modifiable:

Common Causes (Classification by Mechanism)

Immune-Mediated (40-50% of acute presentations)

Microangiopathic (20-30% of presentations)

Hereditary Enzyme/Membrane Defects (10-20%)

Infectious (10-15%)

• Malaria (Plasmodium falciparum): Severe hemolysis in blackwater fever
• Babesiosis: Tick-borne, immunocompromised hosts
• Clostridium perfringens: Gas gangrene, severe intravascular hemolysis
• Bartonella: Cat-scratch disease, bacillary angiomatosis

Toxins and Physical Causes (5-10%)

• Snake venoms: Procoagulant and hemolytic toxins
• Arsine gas: Industrial exposure, severe intravascular hemolysis [17]
• Severe burns: Heat-induced RBC membrane damage
• Osmotic lysis: Hypotonic IV fluids, drowning

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3. Aetiology & Pathophysiology

The Hemolysis Mechanism: Cellular and Molecular Perspectives

Normal Red Cell Lifespan

Mature RBCs circulate for ~120 days before physiological removal by splenic macrophages. Normal RBC turnover: ~1% daily (~20 mL packed cells), compensated by erythropoiesis. [1]

Pathological Hemolysis Classification

Intravascular vs. Extravascular:

Molecular Pathophysiology by Mechanism

1. Immune-Mediated Hemolysis

Warm Autoimmune Hemolytic Anemia (AIHA):

• Antibody: IgG (occasionally IgA), optimal at 37°C
• Target: RBC membrane antigens (Rh system most common)
• Mechanism: Antibody-coated RBCs recognized by splenic macrophage Fc receptors → phagocytosis or partial phagocytosis (spherocytes) → extravascular hemolysis
• Triggers: Idiopathic (50%), lymphoproliferative disorders (CLL, lymphoma), autoimmune diseases (SLE), drugs (methyldopa, fludarabine)
• DAT: IgG positive ± complement (C3d)

Cold Agglutinin Disease:

• Antibody: IgM, optimal less than 30°C, binds at extremities (acral coldness)
• Target: I/i antigens on RBC surface
• Mechanism: Cold exposure → IgM pentamer binds → complement activation (C3b) → hepatic/splenic macrophage complement receptor binding → extravascular hemolysis; severe cases → intravascular complement-mediated lysis
• Triggers: Mycoplasma pneumoniae infection, infectious mononucleosis (EBV), lymphoma
• DAT: C3d positive, IgG negative (IgM dissociates at 37°C during testing)

Paroxysmal Cold Hemoglobinuria (PCH):

• Antibody: Donath-Landsteiner antibody (biphasic IgG)
• Target: P antigen on RBC surface
• Mechanism: Cold exposure → antibody binds at less than 20°C → rewarming → complement activation and intravascular hemolysis at 37°C [9]
• Triggers: Viral infections (children), tertiary syphilis (historical)
• DAT: C3d positive during acute episode, may be negative between episodes
• Clinical: Paroxysmal hemoglobinuria, pallor, jaundice after cold exposure

Drug-Induced Immune Hemolysis:

• Hapten mechanism: Drug (e.g., penicillin) binds RBC membrane → antibody against drug-RBC complex
• Immune complex: Drug-antibody complexes deposit on RBC → complement activation (e.g., quinine)
• Autoantibody induction: Drug alters immune tolerance → true autoantibody (e.g., methyldopa) [13]

Acute Hemolytic Transfusion Reaction:

• Mechanism: ABO incompatibility → pre-existing recipient antibodies (anti-A, anti-B) bind donor RBCs → massive complement activation → intravascular hemolysis + DIC + acute kidney injury
• Severity: Life-threatening; mortality 10-40% if not promptly managed
• Prevention: Rigorous patient identification, crossmatching protocols

2. Microangiopathic Hemolytic Anemia (MAHA)

Pathophysiology: Microvascular thrombosis → fibrin strands across vessel lumens → mechanical shearing of RBCs → schistocytes (fragmented RBCs) → intravascular hemolysis [8]

Thrombotic Thrombocytopenic Purpura (TTP):

• Mechanism: ADAMTS13 deficiency (acquired autoantibody or congenital mutation) → impaired cleavage of ultra-large von Willebrand factor (UL-vWF) multimers → platelet-rich microthrombi → MAHA + thrombocytopenia + organ ischemia
• ADAMTS13 activity: less than 10% diagnostic; 5-10% probable TTP; > 10% unlikely TTP [12]
• Mortality: 90% untreated → 10-20% with plasma exchange

Hemolytic Uremic Syndrome (HUS):

• Typical (STEC-HUS): Shiga-toxin producing E. coli (O157:H7) → toxin damages endothelium → microthrombi predominantly in renal glomeruli → AKI [18]
• Atypical (aHUS): Complement dysregulation (CFH, CFI, MCP mutations) → uncontrolled complement activation on endothelium
• Differentiation from TTP: HUS predominantly renal, TTP predominantly neurological/multi-organ; ADAMTS13 normal in HUS

Disseminated Intravascular Coagulation (DIC):

• Triggers: Sepsis, malignancy, obstetric complications (HELLP, placental abruption)
• Mechanism: Systemic activation of coagulation → widespread fibrin deposition → MAHA + consumption of platelets and clotting factors → bleeding + thrombosis paradox

3. Hereditary Enzyme Deficiencies

G6PD Deficiency:

• Enzyme function: Glucose-6-phosphate dehydrogenase generates NADPH in pentose phosphate pathway → NADPH reduces glutathione → glutathione neutralizes oxidative stress
• Deficiency consequence: Impaired antioxidant defense → oxidative damage to hemoglobin (Heinz bodies) and membrane → hemolysis
• Triggers: [16]
  • "Medications: Primaquine, sulfonamides, dapsone, nitrofurantoin, rasburicase"
  • "Foods: Fava beans (vicine and convicine produce oxidants)"
  • "Infections: Oxidative stress from inflammatory response"
• Variants:
  • "Mediterranean (severe): less than 10% enzyme activity, severe acute crises"
  • "African A- (moderate): 10-60% enzyme activity, self-limiting crises"
• Blood film: Heinz bodies (oxidized hemoglobin precipitates), bite cells (pitted RBCs), blister cells

Pyruvate Kinase Deficiency:

• Mechanism: Impaired glycolysis → ATP depletion → RBC membrane instability → hemolysis (predominantly extravascular)
• Presentation: Chronic hemolytic anemia, splenomegaly, intermittent crises with infection/stress

4. Membrane Defects

Hereditary Spherocytosis:

• Genetics: Spectrin, ankyrin, band 3, or protein 4.2 deficiency (vertical interactions)
• Mechanism: Membrane instability → progressive membrane loss during splenic passage → spherocytes (loss of biconcave shape) → reduced deformability → splenic sequestration and hemolysis
• Osmotic fragility: Spherocytes lyse at higher saline concentrations than normal RBCs

5. Infectious and Toxic Hemolysis

Malaria (Plasmodium falciparum):

• Mechanism: Intraerythrocytic parasite replication → RBC rupture → release of merozoites and hemoglobin
• Blackwater fever: Severe intravascular hemolysis → hemoglobinuria (dark urine), AKI, high mortality

Clostridium perfringens:

• Mechanism: Alpha-toxin (phospholipase C) → lecithinase activity → RBC membrane disruption → severe intravascular hemolysis
• Clinical: Gas gangrene, sepsis, rapid progression

Arsine Gas (AsH₃):

• Source: Industrial smelting, semiconductor manufacturing
• Mechanism: Binds hemoglobin → oxidative damage → massive intravascular hemolysis (can destroy entire RBC mass)
• Mortality: High (40-50%) due to AKI and shock [17]

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4. Clinical Presentation

Symptoms: The Patient's Story

Cardinal Symptoms

Specific Presentations by Etiology

Paroxysmal Cold Hemoglobinuria:

• Sudden onset after cold exposure (cold weather, swimming, cold drinks)
• Raynaud's phenomenon, acrocyanosis
• Passage of dark urine 1-2 hours after cold exposure
• Systemic symptoms: fever, rigors, back pain, abdominal pain [9]

G6PD Deficiency Crisis:

• Symptom onset 24-72 hours after trigger exposure (drug, fava beans, infection)
• Rapidly progressive anemia (Hb can drop 30-40 g/L in 24 hours)
• Dark urine (hemoglobinuria)
• Neonatal presentation: jaundice in first 24-48 hours of life, kernicterus risk [16]

Acute Hemolytic Transfusion Reaction:

• Symptoms within minutes to hours of transfusion start
• Fever, chills, rigors (> 1°C rise)
• Chest pain, back pain, flank pain
• Dyspnea, hypotension (shock)
• Anxiety, sense of impending doom
• Stop transfusion immediately

TTP Clinical Pentad (rarely all present):

• Microangiopathic hemolytic anemia (schistocytes, elevated LDH)
• Thrombocytopenia (less than 50 × 10⁹/L)
• Neurological signs (confusion, seizures, stroke) - fluctuating
• Renal impairment (creatinine elevation, proteinuria)
• Fever (often low-grade) [12]

Warm AIHA:

• Insidious onset over days to weeks (chronic) OR acute presentation (crisis)
• Symptoms of underlying condition (SLE, CLL, lymphoma)
• May have splenomegaly (30-40%)

Signs: What You See on Examination

Vital Signs (May Be Abnormal)

General Appearance

• Pallor: Conjunctival, palmar (best clinical indicator of anemia; visible if Hb less than 90-100 g/L)
• Jaundice: Scleral icterus (bilirubin > 35-50 μmol/L), generalized skin yellowing
• Distress: Dyspnea, confusion (cerebral hypoxia), altered mental state (TTP, severe anemia)
• Acrocyanosis: Blue discoloration of fingers/toes (cold AIHA, PCH)

Cardiovascular Examination

Abdominal Examination

Skin and Extremities

• Petechiae/purpura: TTP, HUS, DIC (thrombocytopenia)
• Leg ulcers: Chronic hemolysis (sickle cell, hereditary spherocytosis)
• Raynaud's/acrocyanosis: Cold agglutinin disease, PCH
• Lymphadenopathy: Lymphoproliferative disorders (CLL, lymphoma)

Neurological Examination (TTP)

• Confusion, disorientation: Cerebral microvascular thrombosis
• Focal deficits: Hemiparesis, aphasia, visual field defects
• Seizures: Generalized or focal
• Fluctuating consciousness: Characteristic of TTP

Red Flags — Immediate Escalation Required

[!CAUTION] Red Flags Requiring Immediate Action:

• Hemoglobin less than 70 g/L: Urgent transfusion consideration
• Hemodynamic instability: Hypotension (SBP less than 90 mmHg), tachycardia > 120 bpm
• Acute kidney injury: Oliguria (less than 0.5 mL/kg/hr), creatinine rise > 50% from baseline
• Neurological signs: Confusion, seizures, focal deficits (TTP until proven otherwise)
• Dark red/black urine: Intravascular hemolysis, risk of AKI
• Bilirubin > 100 μmol/L: Severe hemolysis
• Platelets less than 50 × 10⁹/L + schistocytes: Microangiopathic process (TTP, HUS, DIC) — urgent hematology review
• Recent transfusion + fever/pain: Acute hemolytic transfusion reaction — STOP TRANSFUSION

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5. Differential Diagnosis

Must-Not-Miss Diagnoses

1. Acute Hemolytic Transfusion Reaction: ABO incompatibility; mortality 10-40%; immediate transfusion cessation mandatory
2. TTP: Mortality 90% untreated → 10-20% with plasma exchange; pentad rarely complete; urgently start plasma exchange if suspected [12]
3. Malaria: Endemic area travel history; rapid parasite identification (thick/thin films, rapid antigen); severe falciparum malaria can be fatal
4. Sepsis with DIC: Coagulopathy + MAHA; manage underlying sepsis + transfusion support
5. Drug-induced hemolysis (G6PD): Recent drug exposure; withdraw immediately; Mediterranean variant can be life-threatening [16]

Differentials by Clinical Pattern

Acute Anemia + Jaundice

Acute Anemia + Thrombocytopenia + Schistocytes (Microangiopathic)

DAT Positive vs. Negative

DAT Positive (Immune-Mediated):

• Warm AIHA (IgG ± C3)
• Cold agglutinin disease (C3 only, IgG negative)
• PCH (C3 during acute episode)
• Drug-induced immune hemolysis
• Acute hemolytic transfusion reaction

DAT Negative (Non-Immune):

• G6PD deficiency
• Pyruvate kinase deficiency
• Hereditary spherocytosis
• Mechanical hemolysis (valves, microangiopathy)
• PNH (paroxysmal nocturnal hemoglobinuria)
• Infections (malaria, Clostridium)
• Toxins (arsine, snake venom)

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6. Investigations

First-Line (Bedside) — Do Immediately

1. Clinical Assessment (Most Critical)

• History: Rapidity of onset, triggers (drugs, cold exposure, transfusion, travel), family history (G6PD, spherocytosis), underlying conditions (autoimmune, lymphoma)
• Examination: Pallor, jaundice, splenomegaly, lymphadenopathy, neurological signs, urine color

2. Urgent Bloods (Within 1 Hour)

3. Urine Dipstick

• Hemoglobinuria: Blood positive without RBCs on microscopy (intravascular hemolysis)
• Urobilinogen: Elevated (extravascular hemolysis)

Second-Line (Specialist)

If DAT Positive (Immune Hemolysis)

If Schistocytes Present (Microangiopathic)

If DAT Negative

Imaging

Usually Not Required for Diagnosis

Abdominal Ultrasound:

• Indication: Splenomegaly, cholecystitis (pigment stones), lymphadenopathy
• Findings: Splenic size, gallstones, lymph nodes, hepatomegaly

Echocardiography:

• Indication: Suspected mechanical valve hemolysis, high-output cardiac failure
• Findings: Paravalvular leak, regurgitant jets, valve dehiscence

CT/MRI Brain (if TTP):

• Indication: Focal neurological signs, seizures, altered consciousness
• Findings: Ischemic changes, hemorrhage (rare)

Diagnostic Criteria

Confirming Hemolysis (Require ≥2)

1. Anemia (Hb below normal range for age/sex)
2. Reticulocytosis (> 100 × 10⁹/L or > 2%)
3. Elevated LDH (>ULN, typically > 500 U/L)
4. Low/undetectable haptoglobin (less than 0.3 g/L)
5. Elevated unconjugated bilirubin (> 20 μmol/L)
6. Abnormal blood film (schistocytes, spherocytes, bite cells, etc.)

Specific Diagnoses

TTP Diagnostic Criteria (Any 3):

• Microangiopathic hemolytic anemia (schistocytes > 1%, LDH elevated, haptoglobin low)
• Thrombocytopenia (less than 100 × 10⁹/L, typically less than 50)
• ADAMTS13 activity less than 10%
• Neurological signs (fluctuating, seizures, focal deficit)
• Renal impairment (creatinine > 120 μmol/L) Do NOT wait for full pentad; start plasma exchange urgently if suspected [12]

HUS Triad:

• Microangiopathic hemolytic anemia
• Thrombocytopenia
• Acute kidney injury (creatinine rise, oliguria) [18]

G6PD Deficiency Crisis:

• Appropriate trigger exposure (drug, fava bean, infection)
• Acute onset hemolysis (24-72 hours post-exposure)
• Blood film: Heinz bodies, bite cells, blister cells
• G6PD enzyme assay less than 30% (perform when acute phase resolved) [16]

Warm AIHA:

• DAT positive (IgG ± C3)
• Spherocytes on blood film
• No drug-related or cold exposure
• May have underlying autoimmune disease or lymphoproliferative disorder

Paroxysmal Cold Hemoglobinuria:

• History of cold exposure followed by hemoglobinuria
• DAT positive for C3 (during episode)
• Positive Donath-Landsteiner test (biphasic hemolysin)
• Intravascular hemolysis (hemoglobinuria, markedly low haptoglobin) [9]

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7. Management

Management Algorithm

        SUSPECTED HAEMOLYTIC CRISIS
    (Anemia + jaundice + reticulocytosis)
                    ↓
┌────────────────────────────────────────────────┐
│         IMMEDIATE ASSESSMENT (ABC)              │
│  • Airway, Breathing, Circulation               │
│  • Vital signs, oxygen saturations              │
│  • IV access, fluid resuscitation if shocked    │
│  • URGENT BLOODS: FBC, reticulocytes, film,     │
│    LDH, haptoglobin, bilirubin, DAT, G&S       │
└────────────────────────────────────────────────┘
                    ↓
┌────────────────────────────────────────────────┐
│         IDENTIFY RED FLAGS                      │
│  • Recent transfusion? → STOP transfusion       │
│  • Schistocytes + thrombocytopenia?            │
│    → URGENT hematology for TTP/HUS             │
│  • Hb less than 70 g/L? → Consider urgent transfusion   │
│  • AKI/oliguria? → Fluids, monitor UO          │
└────────────────────────────────────────────────┘
                    ↓
┌────────────────────────────────────────────────┐
│         CLASSIFY BY MECHANISM                   │
├────────────────────────────────────────────────┤
│  DAT POSITIVE (Immune)                          │
│  ├─ IgG ± C3: Warm AIHA                        │
│  │  → Prednisolone 1mg/kg/day                   │
│  │  → Consider transfusion if severe            │
│  │  → Look for underlying cause                 │
│  │                                              │
│  ├─ C3 only: Cold agglutinin or PCH            │
│  │  → Keep patient warm                         │
│  │  → Avoid cold IV fluids                      │
│  │  → Consider rituximab for cold AIHA          │
│  │  → PCH: supportive, self-limiting in kids    │
│  │                                              │
│  └─ Recent drug: Drug-induced                  │
│     → STOP OFFENDING DRUG                       │
│     → Corticosteroids ± IVIG                    │
│                                                │
│  DAT NEGATIVE (Non-Immune)                     │
│  ├─ Schistocytes:                              │
│  │  TTP → Urgent plasma exchange + steroids     │
│  │  HUS → Supportive, dialysis if needed       │
│  │  DIC → Treat underlying cause                │
│  │  Mechanical valve → Cardiology review        │
│  │                                              │
│  ├─ Heinz bodies/bite cells:                   │
│  │  G6PD crisis → Stop trigger, transfusion     │
│  │                                              │
│  ├─ Spherocytes:                               │
│  │  Hereditary spherocytosis → Supportive       │
│  │                                              │
│  └─ Parasites:                                 │
│     Malaria → Antimalarials (artesunate IV)    │
└────────────────────────────────────────────────┘
                    ↓
┌────────────────────────────────────────────────┐
│         TRANSFUSION DECISION                    │
│  • Hb less than 70 g/L + symptomatic: Transfuse          │
│  • Hb 70-90 g/L: Individualize (symptoms,       │
│    comorbidities, rate of fall)                │
│  • Warm AIHA: Least incompatible blood if      │
│    crossmatch difficult                        │
│  • AVOID transfusion in TTP/HUS unless life-    │
│    threatening anemia (can worsen thrombosis)  │
└────────────────────────────────────────────────┘
                    ↓
┌────────────────────────────────────────────────┐
│         SUPPORTIVE CARE                         │
│  • Monitor: Hb, reticulocytes, LDH, bilirubin  │
│  • Fluids: Maintain UO > 0.5 mL/kg/hr           │
│  • Folic acid 5mg daily (if ongoing hemolysis) │
│  • VTE prophylaxis (if platelet count allows)  │
│  • Avoid nephrotoxins                          │
└────────────────────────────────────────────────┘

Acute/Emergency Management — The First Hour

Immediate Actions (Do Simultaneously)

1. Clinical Stabilization (ABCDE Approach)

• Airway: Usually patent; protect if altered consciousness
• Breathing: Oxygen if SpO₂ less than 94% or dyspneic; target SpO₂ 94-98%
• Circulation:
  • Wide-bore IV access (×2 if shocked)
  • "Fluid resuscitation if hypotensive: 500 mL crystalloid bolus, reassess"
  • Cardiac monitoring if severe anemia (risk of high-output failure, arrhythmias)
• Disability: GCS, blood glucose, pupils (neurological signs → consider TTP)
• Exposure: Full examination, look for bleeding, rash, jaundice, splenomegaly

2. Urgent Investigations (Send Within 15 Minutes)

3. Specific Emergency Scenarios

A. Acute Hemolytic Transfusion Reaction:

• STOP TRANSFUSION IMMEDIATELY — do not restart
• Keep IV line open with 0.9% saline
• Check patient identity and blood unit labels
• Monitor vital signs every 15 minutes
• Send: FBC, DAT, LDH, haptoglobin, coagulation screen, U&Es
• Return blood unit and administration set to blood bank
• Collect post-transfusion blood sample and urine
• Aggressive IV fluids to maintain urine output > 100 mL/hr (prevent AKI)
• Furosemide if fluid overloaded (avoid if hypovolemic)

B. Suspected TTP:

• URGENT HEMATOLOGY CONSULT — plasma exchange must start within hours (mortality 90% untreated → 10-20% treated) [12]
• Send ADAMTS13 activity and inhibitor BEFORE starting plasma exchange
• Do NOT wait for ADAMTS13 results to start treatment
• Initiate plasma exchange (1-1.5 plasma volumes daily) + prednisolone 1 mg/kg
• Consider rituximab 375 mg/m² weekly ×4 (now standard of care)
• Avoid platelet transfusion unless life-threatening bleeding (can worsen thrombosis)

C. Severe Intravascular Hemolysis (Hemoglobinuria):

• Aggressive IV fluids: Target urine output > 100-150 mL/hr
  • Start 1-2 L 0.9% saline over 2-4 hours (adjust for cardiac status)
  • Consider urinary alkalinization (50-100 mmol sodium bicarbonate in 1 L 5% dextrose) to pH > 7 (reduces hemoglobin precipitation in tubules) — controversial
• Monitor:
  • Hourly urine output (catheterize if oliguric)
  • Serum potassium (massive hemolysis releases K⁺ → hyperkalemia)
  • Creatinine (AKI risk)

D. Warm AIHA with Severe Anemia:

• Corticosteroids: Prednisolone 1-2 mg/kg PO daily (max 80-100 mg) OR methylprednisolone 500 mg IV if unable to take orally
• Transfusion:
  • If Hb less than 70 g/L OR symptomatic (chest pain, dyspnea, altered consciousness) despite Hb 70-90 g/L
  • Transfuse "least incompatible" blood if crossmatch incompatible (panagglutinin)
  • Transfuse slowly (1 mL/kg/hr) with close monitoring
  • Aim for Hb 70-80 g/L, not full correction (over-transfusion risk)
• IVIG: 0.4 g/kg/day ×5 days (or 1 g/kg × 2 days) if life-threatening or refractory
• Folic acid: 5 mg daily (increased RBC production)

E. G6PD Deficiency Crisis:

• Stop trigger: Withdraw offending drug, avoid oxidant substances
• Transfusion: If Hb less than 70 g/L or symptomatic (crises can be severe, Hb dropping 30-40 g/L in 24 hours)
• Fluids: Aggressive hydration (prevent hemoglobin-induced AKI)
• Monitor: Potassium (hemolysis releases K⁺), renal function
• Avoid: Further oxidant stress [16]

Medical Management (Beyond First Hour)

Specific Treatments by Cause

1. Warm Autoimmune Hemolytic Anemia (AIHA):

2. Cold Agglutinin Disease:

3. Paroxysmal Cold Hemoglobinuria:

• Supportive care: Most cases self-limiting (especially post-viral in children)
• Avoid cold exposure: Critical during acute episode
• Transfusion: If severe anemia
• Corticosteroids: May be tried but efficacy uncertain
• Prognosis: Excellent in children (self-limiting); chronic form in adults may require immunosuppression [9]

4. TTP (Thrombotic Thrombocytopenic Purpura):

5. HUS (Hemolytic Uremic Syndrome):

• Typical (STEC-HUS):
  • "Supportive care: Fluids, electrolytes, nutrition"
  • "Dialysis: If AKI requiring (40-50% of cases)"
  • AVOID antibiotics in STEC-associated (may increase Shiga toxin release)
  • DO NOT USE plasma exchange (ineffective; ADAMTS13 normal) [18]
  • "Prognosis: 95% recovery in children; worse in adults"
• Atypical HUS:
  • "Eculizumab (anti-C5 monoclonal antibody): 900 mg weekly ×4, then 1200 mg every 2 weeks"
  • Meningococcal vaccination mandatory before starting (encapsulated organism risk)
  • Genetic testing for complement mutations
  • Plasma exchange may be used as bridge if eculizumab unavailable

6. DIC:

• Treat underlying cause: Sepsis (antibiotics), malignancy (chemotherapy), obstetric emergency (delivery)
• Transfusion support:
  • RBCs if Hb less than 70 g/L or bleeding
  • Platelets if less than 50 × 10⁹/L + bleeding (or less than 10-20 if high bleeding risk)
  • FFP if PT/APTT prolonged + bleeding (10-15 mL/kg)
  • Cryoprecipitate if fibrinogen less than 1.5 g/L
• NO routine heparin unless thrombosis-predominant DIC (rare)

7. Drug-Induced Immune Hemolysis:

• Stop offending drug immediately
• Corticosteroids: Prednisolone 1 mg/kg/day if severe
• IVIG: Consider if refractory
• Prognosis: Usually resolves within 1-2 weeks of drug cessation [13]

8. G6PD Deficiency Crisis:

• Withdraw trigger: Stop all oxidant drugs, avoid fava beans
• Transfusion: If severe anemia (Hb less than 70 g/L)
• Fluids: Aggressive hydration to prevent AKI
• Folic acid: 5 mg daily during acute phase
• Prevention: Genetic counseling, avoid known triggers, G6PD screening before prescribing high-risk drugs [16]
• Neonatal jaundice: Phototherapy, exchange transfusion if severe (bilirubin > 340 μmol/L or neurotoxicity risk)

9. Malaria:

• Artesunate IV: 2.4 mg/kg IV at 0, 12, 24 hours, then daily until oral therapy tolerated
• Severe falciparum malaria: Consider exchange transfusion if parasitemia > 10% (controversial; limited evidence)
• Supportive: Fluids, monitor glucose, dialysis if AKI

Blood Transfusion Guidelines

Indications for RBC Transfusion

Special Considerations in Hemolytic Anemia

Warm AIHA:

• Crossmatching difficult (panagglutinin): Use "least incompatible" blood
• Transfuse slowly (1 mL/kg/hr = ~70 mL/hr for 70 kg patient)
• Close monitoring (pulse, BP, temperature every 15 minutes for first hour)
• Aim for Hb 70-80 g/L, not full correction
• Ongoing hemolysis will shorten transfused RBC lifespan

TTP/HUS:

• AVOID transfusion unless Hb less than 50-60 g/L with symptomatic anemia or active bleeding
• RBC transfusion may worsen microvascular thrombosis

G6PD Deficiency:

• Transfuse if Hb less than 70 g/L or severe symptoms
• Ensure donor blood screened for G6PD if recipient from high-prevalence population (avoid homozygous deficient donors)

Exchange Transfusion:

• Indications: [19,20]
  • Severe malaria (parasitemia > 10%, cerebral malaria) — controversial evidence
  • Severe intravascular hemolysis with refractory AKI
  • Neonatal hyperbilirubinemia (bilirubin > 340 μmol/L or approaching exchange level)
  • Sickle cell acute chest syndrome (not hemolytic crisis per se)
• Procedure: Remove patient blood while simultaneously transfusing donor blood (manual or automated erythrocytapheresis)
• Volume: 1-2 blood volumes exchanged
• Risks: Fluid overload, electrolyte imbalance, citrate toxicity, infection

Disposition and Follow-Up

Admission Criteria

Admit to Hospital if:

• Hemoglobin less than 70 g/L
• Symptomatic anemia (dyspnea, chest pain, syncope, altered consciousness)
• Hemodynamic instability (hypotension, tachycardia > 120 bpm)
• Acute kidney injury (creatinine > 150 μmol/L or rising)
• Severe hemolysis (LDH > 1000 U/L, haptoglobin undetectable, hemoglobinuria)
• Suspected TTP, HUS, acute transfusion reaction, severe drug reaction
• Need for urgent transfusion or plasma exchange
• Comorbidities (cardiac disease, elderly, pregnancy)

ICU/HDU Admission:

• Hemodynamic instability despite resuscitation
• Respiratory failure
• Altered consciousness (GCS less than 13)
• Severe AKI requiring dialysis
• TTP with neurological involvement
• DIC with bleeding

Outpatient Management (if all present):

• Hemoglobin 90-110 g/L, stable
• Mild symptoms or asymptomatic
• Identified cause with appropriate treatment initiated (e.g., drug withdrawn)
• No AKI, no hemodynamic compromise
• Reliable patient with good social support
• Close follow-up arranged (hematology clinic within 1 week)

Follow-Up

Acute Phase (Daily if Inpatient, 2-3 Days if Outpatient):

• FBC, reticulocytes
• LDH, bilirubin
• Renal function (U&Es)
• Monitor response to treatment

After Acute Crisis (1-2 Weeks):

• Hematology review
• Identify underlying cause if not yet confirmed
• Taper immunosuppression if AIHA (over 3-6 months)
• G6PD enzyme assay if suspected (perform 2-3 months post-crisis when reticulocyte count normalized) [16]
• Screen for lymphoproliferative disorders (CT, bone marrow) if warm AIHA or cold agglutinin disease

Long-Term (3-6 Monthly):

• Monitor for recurrence (FBC, reticulocytes, LDH)
• Hereditary causes: Genetic counseling, family screening
• Autoimmune causes: Monitor underlying disease, screen for complications
• Folic acid supplementation if chronic hemolysis (5 mg daily)

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8. Complications

Immediate (Hours-Days)

Early (Days-Weeks)

Late (Months-Years)

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9. Prognosis & Outcomes

Natural History (Without Treatment)

Untreated Haemolytic Crisis:

• Mild-moderate hemolysis (compensated): May stabilize with bone marrow compensation but underlying cause persists
• Severe hemolysis: Progressive anemia → shock → multi-organ failure → death (mortality 20-50% in severe untreated cases)
• TTP: 90% mortality without plasma exchange [12]
• Autoimmune: Fluctuating course; may remit spontaneously (20-30%) or become chronic

Outcomes with Treatment

Prognostic Factors

Good Prognosis

Poor Prognosis

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10. Evidence & Guidelines

Key Guidelines

1. British Society for Haematology (BSH) Guidelines — Diagnosis and Management of Autoimmune Haemolytic Anaemia (2017) [11]

Key Recommendations:

• DAT (Coombs test) essential for diagnosis (Level 1A)
• First-line: Prednisolone 1 mg/kg/day for warm AIHA (Level 1A)
• Rituximab recommended for relapsed/refractory AIHA (Level 1B)
• Splenectomy for refractory cases after failed medical therapy (Level 2B)
• Transfusion: Use least incompatible blood if crossmatch incompatible; aim Hb 70-80 g/L
• Screen for underlying lymphoproliferative disorders and autoimmune diseases

2. International Society on Thrombosis and Haemostasis (ISTH) — TTP Guidelines (2020) [12]

Key Recommendations:

• Plasma exchange MUST start within hours of TTP suspicion (Level 1A) — do NOT wait for ADAMTS13 results
• ADAMTS13 activity less than 10% diagnostic; send before plasma exchange but do not delay treatment
• Rituximab now standard of care alongside plasma exchange and corticosteroids (Level 1A)
• Caplacizumab (anti-vWF antibody) recommended in severe TTP (Level 1B)
• Avoid platelet transfusion (can worsen thrombosis) unless life-threatening bleeding

3. American Society for Apheresis (ASFA) Guidelines — Therapeutic Apheresis (2023)

Indications for Plasma Exchange:

• TTP: Category I (first-line therapy, standard of care)
• HUS (atypical): Category III (optimum role not established; individualize)
• Cold agglutinin disease: Category III

4. G6PD Deficiency Guidelines (WHO, 2018) [16]

Key Recommendations:

• Screen for G6PD before prescribing primaquine (malaria), dapsone (leprosy), rasburicase
• Avoid fava beans, oxidant drugs in known G6PD deficiency
• Neonatal screening in high-prevalence populations
• Heterozygous females may have variable enzyme activity (X-inactivation); screen if high-risk

Landmark Trials and Evidence

Evidence Strength Summary

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11. Patient/Layperson Explanation

What is a Haemolytic Crisis?

Your red blood cells normally live for about 120 days before being removed naturally by your body. In a haemolytic crisis, something causes your red blood cells to be destroyed much faster than normal — sometimes in just hours or days. This rapid destruction leads to three main problems:

1. Anemia (not enough red blood cells): You feel tired, weak, short of breath, and may have a fast heartbeat
2. Jaundice (yellowing): When red blood cells break down, they release a yellow pigment called bilirubin, which makes your skin and eyes yellow
3. Kidney problems (in severe cases): The breakdown products can damage your kidneys, making your urine dark (like cola or tea)

In simple terms: Your red blood cells are being destroyed too quickly. Your body tries to make new ones to compensate, but if the destruction is too fast, you become anemic. With proper treatment, most people recover well, but it's important to identify and treat the cause.

Why Does It Happen?

There are many causes:

• Your immune system attacking your own red cells (autoimmune hemolysis): Your body makes antibodies that mistakenly destroy your own red blood cells. This can happen on its own or with other conditions like lupus or lymphoma.

• After a blood transfusion: Very rarely, if the wrong blood type is given, your immune system destroys the transfused blood cells. This is why blood typing and crossmatching are so important.

• Inherited conditions: Some people are born with red blood cells that are more fragile (like G6PD deficiency, which is common in people from Mediterranean, African, or Asian backgrounds). Certain foods (like fava beans), medications, or infections can trigger a crisis.

• Infections: Some infections (like malaria) directly attack red blood cells.

• Medications: Some drugs can trigger hemolysis in susceptible people.

• Mechanical damage: If you have an artificial heart valve, it can physically damage red blood cells as they pass through.

Why Does It Matter?

Haemolytic crisis can be serious because:

• Severe anemia can make your heart work too hard, causing chest pain or even heart failure
• Kidney damage from the breakdown products can lead to kidney failure
• In pregnancy, it can affect both mother and baby
• Some causes (like TTP) are life-threatening without urgent treatment

The good news: With early recognition and proper treatment, most people recover fully.

How Is It Treated?

1. Find and Treat the Cause:

• If it's from your immune system, you'll get medicines to suppress your immune system (usually steroids like prednisolone)
• If it's from a medication, that drug will be stopped immediately
• If it's an infection, you'll get treatment for the infection
• If it's from a rare condition called TTP, you'll need a special treatment called plasma exchange (like dialysis for your blood)

2. Support Your Body:

• Blood transfusion: If your anemia is severe (hemoglobin less than 70 g/L), you may need a transfusion to boost your red blood cell count while the treatment works
• Fluids: Lots of IV fluids to protect your kidneys
• Folic acid: A vitamin that helps your body make new red blood cells faster

3. Prevent Complications:

• Close monitoring of your blood counts, kidney function, and liver tests
• Sometimes medicines to protect your kidneys or prevent blood clots

What to Expect

Acute Phase (First Few Days):

• You'll likely be in hospital for monitoring and treatment
• Daily blood tests to check your hemoglobin, bilirubin, and kidney function
• You should start feeling better within 3-7 days as treatment takes effect

Recovery (1-4 Weeks):

• Gradual improvement in energy levels, breathing, and color
• Jaundice fades as your body clears the bilirubin
• Blood counts return toward normal

Long-Term:

• If it's an autoimmune cause, you may need medicines for several months (steroids tapered slowly over 3-6 months)
• If it's hereditary (like G6PD deficiency), you'll need to avoid triggers for life
• Regular follow-up with a hematologist (blood specialist)

Recovery Time:

• Acute crisis resolves: 1-2 weeks
• Full recovery: 4-8 weeks
• Some people have chronic or recurring hemolysis requiring long-term management

When to Seek Help

Call 999 (Emergency) if:

• You feel extremely weak, dizzy, or faint (especially if you can't stand or walk)
• You have severe chest pain or difficulty breathing
• You are confused or have difficulty thinking clearly
• Your urine is dark red, brown, or black (like cola)
• You have a very rapid heartbeat or irregular heartbeat

See Your Doctor Urgently (Same Day) if:

• You notice your skin or eyes are yellow (jaundice)
• You have unexplained fatigue or weakness that's getting worse
• You have a fever with fatigue and yellowing
• You have dark urine (even if you feel okay)

See Your Doctor Soon (Within 1-2 Days) if:

• You have persistent tiredness, especially if you have a condition that puts you at risk (sickle cell disease, lupus, recent transfusion, recent travel to malaria area)
• You've recently started a new medication and feel unwell

Living with Risk of Haemolytic Crises

If you have G6PD deficiency:

• Avoid fava beans (broad beans)
• Check with your doctor before taking new medications (especially antibiotics like sulfonamides, antimalarials like primaquine)
• Carry a medical alert card or bracelet
• Inform all healthcare providers about your G6PD deficiency

If you have autoimmune hemolysis:

• Take your medicines exactly as prescribed (don't stop steroids suddenly)
• Attend regular follow-up appointments
• Report any worsening symptoms immediately
• Stay up-to-date with vaccinations (especially if you have a spleen removed or take immunosuppressive drugs)

If you have chronic hemolysis (hereditary spherocytosis, sickle cell):

• Take folic acid daily (5 mg) — your body needs extra folate to make red blood cells
• Watch for "aplastic crisis" (sudden worsening of anemia if you get parvovirus B19 infection) — seek urgent medical attention if you have a fever and worsening fatigue
• Consider splenectomy (spleen removal) if severe — discuss with your hematologist

Questions to Ask Your Doctor

1. What caused my haemolytic crisis?
2. Will it happen again? How can I prevent it?
3. Do I need to avoid any foods or medications?
4. How long will I need to take medicines?
5. Do I need to see a specialist regularly?
6. Should my family members be tested (if hereditary)?
7. Are there any long-term complications I should watch for?
8. When can I return to work/school/normal activities?

Remember: Haemolytic crises can be frightening, but with prompt medical attention and proper treatment, the vast majority of people recover fully. Always seek medical help early if you have concerning symptoms.

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12. References

Primary Guidelines

1. Dhaliwal G, Cornett PA, Tierney LM Jr. Hemolytic anemia. Am Fam Physician. 2004;69(11):2599-606. PMID: 15202694

2. Barcellini W, Fattizzo B. Clinical Applications of Hemolytic Markers in the Differential Diagnosis and Management of Hemolytic Anemia. Dis Markers. 2015;2015:635670. doi:10.1155/2015/635670

3. Gehrs BC, Friedberg RC. Autoimmune hemolytic anemia. Am J Hematol. 2002;69(4):258-71. doi:10.1002/ajh.10062

4. Berentsen S, Barcellini W. Autoimmune Hemolytic Anemias. N Engl J Med. 2021;385(15):1407-1419. doi:10.1056/NEJMra2033982

5. Lechner K, Jäger U. How I treat autoimmune hemolytic anemias in adults. Blood. 2010;116(11):1831-8. doi:10.1182/blood-2010-03-259325

6. Marchand A, Galen RS, Van Lente F. The predictive value of serum haptoglobin in hemolytic disease. JAMA. 1980;243(19):1909-11. doi:10.1001/jama.1980.03300450023017

7. Zantek ND, Koepsell SA, Tharp DR Jr, Cohn CS. The direct antiglobulin test: A critical step in the evaluation of hemolysis. Am J Hematol. 2012;87(7):707-9. doi:10.1002/ajh.23218

8. Brocklebank V, Wood KM, Kavanagh D. Thrombotic Microangiopathy and the Kidney. Clin J Am Soc Nephrol. 2018;13(2):300-317. doi:10.2215/CJN.00620117

9. Shanbhag S, Spivak J. Paroxysmal cold hemoglobinuria. Hematol Oncol Clin North Am. 2015;29(3):473-8. doi:10.1016/j.hoc.2015.01.004

10. Luzzatto L, Karadimitris A, Notaro R. Paroxysmal nocturnal hemoglobinuria and hemolytic uremic syndrome: two sides of the same coin. Transfus Med Rev. 2006;20(2):83-98. doi:10.1016/j.tmrv.2005.11.002

11. Hill QA, Stamps R, Massey E, et al. Guidelines on the diagnosis and management of adult autoimmune haemolytic anaemia. Br J Haematol. 2017;176(3):395-411. doi:10.1111/bjh.14478

12. Zheng XL, Vesely SK, Cataland SR, et al. ISTH guidelines for the diagnosis of thrombotic thrombocytopenic purpura. J Thromb Haemost. 2020;18(10):2486-2495. doi:10.1111/jth.15006

13. Garratty G. Drug-induced immune hemolytic anemia. Hematology Am Soc Hematol Educ Program. 2009;73-9. doi:10.1182/asheducation-2009.1.73

14. Barcellini W. New insights in the pathogenesis of autoimmune hemolytic anemia. Transfus Med Hemother. 2015;42(5):287-93. doi:10.1159/000439002

15. Zent CS, Kay NE. Autoimmune complications in chronic lymphocytic leukaemia (CLL). Best Pract Res Clin Haematol. 2010;23(1):47-59. doi:10.1016/j.beha.2010.01.004

16. Luzzatto L, Nannelli C, Notaro R. Glucose-6-Phosphate Dehydrogenase Deficiency. Hematol Oncol Clin North Am. 2016;30(2):373-93. doi:10.1016/j.hoc.2015.11.006

17. Teitelbaum DT, Kier LC. Arsine poisoning. Report of five cases in the petroleum industry and a discussion of the indications for exchange transfusion and hemodialysis. Arch Environ Health. 1969;19(1):133-43. doi:10.1080/00039896.1969.10666815

18. Boyer O, Niaudet P. Hemolytic-Uremic Syndrome in Children. Pediatr Clin North Am. 2022;69(6):1181-1197. doi:10.1016/j.pcl.2022.07.006

19. Fort R. Recommendations for the use of red blood cell exchange in sickle cell disease. Transfus Apher Sci. 2019;58(2):128-131. doi:10.1016/j.transci.2019.03.004

20. Stussi G, Buser A, Holbro A. Red Blood Cells: Exchange, Transfuse, or Deplete. Transfus Med Hemother. 2019;46(6):407-416. doi:10.1159/000504144

21. Rock GA, Shumak KH, Buskard NA, et al. Comparison of plasma exchange with plasma infusion in the treatment of thrombotic thrombocytopenic purpura. N Engl J Med. 1991;325(6):393-7. doi:10.1056/NEJM199108083250604

22. Scully M, Cataland SR, Peyvandi F, et al. Caplacizumab Treatment for Acquired Thrombotic Thrombocytopenic Purpura. N Engl J Med. 2019;380(4):335-346. doi:10.1056/NEJMoa1806311

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Last Reviewed: 2026-01-10 | MedVellum Editorial Team

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Medical Disclaimer: MedVellum content is for educational purposes and clinical reference. Clinical decisions should account for individual patient circumstances. Always consult appropriate specialists. This information is not a substitute for professional medical advice, diagnosis, or treatment.