What are the diagnostic and management steps for a sickle cell crisis?

Diagnosis of Sickle Cell Crisis

Sickle cell crisis is diagnosed clinically based on acute severe pain in a patient with known sickle cell disease, supported by laboratory evidence of worsening hemolysis and exclusion of life-threatening complications. 1

Clinical Presentation

The diagnosis begins with recognizing the characteristic features of acute vaso-occlusive crisis:

• Acute severe pain in bones, joints, chest, or abdomen that is more severe than the patient's baseline chronic pain 1
• Fever may be present and requires immediate evaluation for infection, as infections are a leading cause of morbidity and mortality in sickle cell disease 1
• Respiratory symptoms including chest pain, dyspnea, or hypoxia should raise concern for acute chest syndrome 1
• Neurologic symptoms beyond transient mild headache require urgent stroke evaluation 1

Essential Laboratory Evaluation

A comprehensive laboratory panel is mandatory and should include complete blood count, markers of hemolysis, renal and liver function tests, and coagulation studies to assess crisis severity and detect organ damage. 2

Core Laboratory Tests

• Hemoglobin level must be compared to the patient's baseline (typically 6-9 g/dL in HbSS patients), as acute drops indicate hemolysis or sequestration 2
• Reticulocyte count assesses bone marrow response to hemolysis and helps differentiate hyperhemolytic crisis from aplastic crisis 2, 3
• White blood cell count may be elevated in acute crisis and can indicate infection or inflammation; higher WBC counts are associated with admission decisions 2, 4
• Bilirubin (total and direct) levels increase due to red cell breakdown 2
• Blood urea nitrogen and creatinine evaluate for acute kidney injury from vaso-occlusion 2
• Liver enzymes (AST, ALT, alkaline phosphatase) may be elevated with hepatobiliary involvement 2
• Coagulation studies (PT, PTT) assess for coagulopathy 2

Important Diagnostic Considerations

Baseline laboratory values must be known for comparison, as many patients have chronic abnormalities. 2 A hemoglobin of 7 g/dL may represent a significant acute drop for one patient but baseline for another. 2

The complete blood count and reticulocyte count alone do not determine admission decisions in uncomplicated vaso-occlusive crisis, though elevations in WBC count appear associated with admission. 4

Specialized Testing Based on Complications

For Suspected Acute Chest Syndrome

• Arterial blood gas to evaluate oxygenation and acid-base status 2
• Blood cultures if infection is suspected as a trigger 2
• Chest radiograph to identify new segmental infiltrates 1

For Suspected Stroke

• Review previous transcranial Doppler results (within 12 months for HbSS, 24 months for HbSC/HbSβ+ thalassemia) 2
• Neuroimaging for any acute neurologic symptom beyond transient mild headache 1
• CBC, reticulocyte count, blood type and crossmatch for potential exchange transfusion 1

For Suspected Priapism

• Corporal blood gas to differentiate ischemic from non-ischemic priapism 2

For Suspected Splenic Sequestration

• Serial hemoglobin measurements looking for drops >2 g/dL below baseline 1
• Physical examination for rapidly enlarging spleen 1

Critical Diagnostic Pitfalls to Avoid

Do not rely solely on hemoglobin levels to determine transfusion need—consider the patient's baseline hemoglobin and clinical status. 2

Screen all patients with hemoglobinopathies for recent transfusion at presentation, as hyperhemolysis syndrome can occur after transfusion and presents with precipitous hemoglobin drops despite ongoing reticulocytosis. 5 This life-threatening complication requires early steroid initiation and can be missed if transfusion history is not obtained. 5

In acute anemia with ongoing reticulocytosis and infection, consider hyperhemolytic crisis even without preceding transfusion, along with aplastic crisis, immune hemolytic anemia, and sequestration crises. 3

Obtain baseline oxygen saturation for comparison and monitor continuously until saturation is maintained at baseline in room air. 1

Blood cultures must be obtained if temperature reaches ≥38.0°C or signs of sepsis are present, with prompt antibiotic initiation. 1

Diagnostic Algorithm

1. Confirm sickle cell disease diagnosis (should be known from newborn screening or previous hemoglobin electrophoresis) 6
2. Assess pain severity and location using validated pain scales 1
3. Measure vital signs including temperature, oxygen saturation, blood pressure, and respiratory rate 1
4. Obtain comprehensive laboratory panel as outlined above 2
5. Compare current values to patient's baseline (especially hemoglobin, which varies by genotype: HbSS typically 6-9 g/dL, HbSC higher) 7, 2
6. Screen for life-threatening complications: acute chest syndrome (chest pain, respiratory symptoms, fever), stroke (neurologic symptoms), splenic sequestration (rapidly enlarging spleen, acute hemoglobin drop >2 g/dL), priapism (>4 hours duration) 1
7. Obtain blood cultures if febrile and initiate antibiotics promptly 1
8. Document recent transfusion history to assess hyperhemolysis risk 5