Acute Vaso-Occlusive Episode in Sickle Cell Anemia

Aka: Acute Vaso-Occlusive Episode in Sickle Cell Anemia, Sickle Cell Crisis, Vaso-Occlusive Pain Crisis, Sickle Cell Pain Crisis

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II. Epidemiology

  1. Affects almost all Sickle Cell Anemia patients
  2. May occur as early as age 6 months

III. Pathophysiology

  1. See Sickle Cell Anemia
  2. Deoxygenated Hemoglobin polymerizes in triple helix chains
  3. Results in Red Blood Cells assuming sickled shape
  4. Results in Occlusion of small vessels and capillaries with secondary small tissue ischemia and infarctions
    1. Repeat pain crises to the same region is a risk for avascular necrosis
    2. Bone Marrow ischemia and hyperplasia is responsible for long bone and spine pain

IV. Risk Factors: Precipitating Triggers

  1. Most episodes of Vaso-Occlusive Pain Crisis are spontaneous without identified trigger
  2. Preceded by infection 25% of the time
    1. Human Parvovirus B19 is a common viral cause
  3. Weather changes
    1. Cold Weather due to reflex vasospasm
    2. Dehydration in warm weather
  4. Physical exertion
  5. Menstruation
  6. Hypoxia
  7. Anxiety or depression

V. Findings

  1. Recurrent painful crises
    1. Typically occurs in children under age 18 years
    2. Often follows a distribution pattern specific to the patient
    3. Sudden onset deep ache pain in Abdomen, chest, back and extremities (esp. joints)
    4. Episodes typically last 4 to 6 days (but may persist weeks in some cases)
    5. Dactylitis (infants)
  2. Preverbal Children presentations may be more subtle
    1. General
      1. VOC may occur as early as age 6 months
      2. Hemoglobin F (Hb F, fetal Hemoglobin) is protective against sickling
      3. Hemoglobin F wanes at age 6 months
    2. Inconsolable Crying
    3. Irritability
    4. Altered sleep
    5. Poor feeding

VI. Labs

  1. No lab abnormality defines VOC (clinical diagnosis)
  2. Profound Anemia
  3. Reticulocyte Count <1%
  4. Consider additional labs in case of suspected infection
    1. Complete Blood Count
    2. Reticulocyte Count
    3. Blood Culture

VII. Differential Diagnosis

  1. VOC-related Chest Pain, Abdominal Pain or back pain may present in similar fashion to other serious conditions
    1. Acute Chest Syndrome
    2. Acute Abdomen
    3. Pulmonary Embolism
    4. Ureterolithiasis
  2. Bone Pain
    1. Avascular Necrosis
      1. Avascular Necrosis of the Femoral Head
      2. Avascular Necrosis of the Humeral Head
    2. Osteomyelitis
      1. Infection of infarcted bone, especially long bones
      2. Salmonella is most common organism in Sickle Cell Anemia (S. Aureus represents <25% of cases)

VIII. Precautions

  1. Sickle Cell Crisis is NOT typically a drug seeking mission
    1. Patients who present with symptoms of Sickle Cell Crisis typically have crisis
    2. Emergency departments see only 10-20% of Pain Crisis when severe
      1. Less severe episodes are treated with home management
    3. Vital Signs (Heart Rate, Blood Pressure) and labs do not differentiate a Sickle Cell Crisis
      1. Chronic severe pain leads to blunted physiologic response
    4. Believe patients presenting with Sickle Cell Anemia and effectively treat their pain
    5. Rarely, patients without Sickle Cell Anemia present with factitous crisis
      1. However these patients may be identified from the medical record
      2. Review with prescribing providers and consider behavioral health referral
    6. Address Drug Seeking Behavior after the acute pain crisis (treat pain adequately during crisis)
      1. Consider VOC therapy plan (on file in ED or patient carries with them)
  2. Evaluate for other concurrent sickle cell complications (esp. if pain pattern is not typical for specific patient)
    1. Transient Red Cell Aplasia
    2. Cerebrovascular Accident in Sickle Cell Anemia
    3. Sickle Cell Hemolytic Crisis
    4. Acute Chest Syndrome
    5. Sepsis
    6. Septic Joint or Osteomyelitis

IX. Management: Pain control for acute crisis

  1. Requires aggressive Opioid analgesia
    1. Avoid delays in management
      1. Triage patient urgently to a management bed within 30-60 minutes of presentation
      2. Start at outset by titrating to high dose Opioids in first 10 minutes of management
    2. Pain management is based on patient's reported level of pain
    3. Higher Opioid doses are frequently required
      1. Many Sickle Cell Anemia patients have developed tolerance due to Chronic Opioid use
    4. Avoid allowing Analgesics to wear off prior to re-dosing
    5. Re-evaluate pain level and sedation every 15-30 minutes
      1. Increase dose by 25% if inadequate pain control
      2. Monitor closely for respiratory depression
    6. Consider Patient Controlled Analgesia (PCA Pump)
    7. Morphine
      1. Initial: 0.1 to 0.15 mg/kg/dose IV (up to 10-15 mg in wt>50 kg)
        1. Re-evaluate and repeat as needed every 20-30 minutes initially
        2. Consider hospital admission for more than 2 doses required in 1-2 hours
      2. Later
        1. ORAL: 0.15 to 0.3 mg/kg/dose (up to 10 to 20 mg in wt>50 kg) PO every 3 to 4 hours OR
        2. IV: 0.05 to 0.1 mg/kg/dose (up to 2 to 5 mg in wt>50kg) IV every 2 to 4 hours
    8. Hydromorphone (Dilaudid)
      1. Initial: 0.01 mg/kg up to 1 mg IM or IV
        1. Adults may require 1 to 4 mg per hour
      2. Later
        1. ORAL: 0.03 to 0.08 mg/kg/dose (up to 1 to 4 mg in wt>50kg) PO every 3 to 4 hours OR
        2. IV: 0.015 mg/kg/dose (up to 0.2 to 0.6 mg) IV every 3 to 6 hours
    9. Fentanyl Intranasal
      1. Dose: 1-2 mcg/kg up to 100 mcg/dose every 15 minutes for up to 2 doses
      2. Consider if IV Access is delayed
  2. Non-Opioid Analgesics
    1. Acetaminophen
      1. Adjuct in mild to moderate pain
    2. NSAIDS
      1. High Incidence of occult renal dysfunction in Sickle Cell Anemia (Exercise caution)
      2. Serum Creatinine typically underestimates renal dysfunction in Sickle Cell Anemia
      3. NSAIDS may be used for mild to moderate pain, or adjunctive relief if no contraindications
        1. Ketorolac (Toradol) 0.5 mg/kg/dose (up to 15 mg IV and 30 mg IM)
        2. Ibuprofen
  3. Avoid agents with adverse effects
    1. Avoid Meperidine (Demerol)
      1. Meperidine metabolite normeperidine is neurotoxic and associated with increased Seizure risk
      2. Meperidine is associated with euphoria and less effective Analgesic effect
      3. Morphine or Dilaudid are preferred over Meperidine (Demerol)
    2. Avoid parenteral Antihistamines
      1. Associated with euphora
      2. Pruritus may be less common with Dilaudid than Morphine
      3. Pruritus may be treated with Benadryl
  4. Avoid agents not shown to offer benefit
    1. Blood Transfusions are not indicated for routine management of vaso-occlusive crisis
      1. However, Blood Transfusion is indicated in specific circumstances
        1. Hemoglobin <6 g/dl or significant drop from baseline (e.g. >2 g/dl)
        2. Consider in severe Tachycardia or Hypotension
    2. Magnesium does not appear to reduce pain, reduce Opioid use or reduce lengths of ED stays
      1. Brousseau (2015) Blood 126(14): 1651-7 [PubMed]
    3. Antiplatelet agents (e.g. Prasugrel) does not appear to prevent vaso-occlusive crisis
      1. Heeney (2016) N Engl J Med 374(7): 625-35 [PubMed]

X. Management: Other Measures

  1. Intravenous Fluids
    1. Avoid Fluid Overload (risk of Atelectasis and Acute Chest Syndrome)
    2. Limit total fluid to <1.5x maintenance requirements
    3. On achieving euvolemia, consider maintenance with Hypotonic Saline (D5 1/2NS) which may enter the RBC
  2. Oxygen
    1. Only indicated in Hypoxia (Oxygen Saturation <93%) or in cardiopulmonary compromise
    2. Oxygen may be associated with a higher risk of Bone Marrow suppression and secondary need for Blood Transfusions
  3. Incentive Spirometry
    1. Decreases Atelectasis risk and risk of Acute Chest Syndrome
  4. Adjunctive measures
    1. Local heat (warm compresses) applied to painful area

XI. Management: Disposition

  1. Admission criteria after 3 Opioid doses is likely to be too restrictive and result in over-admitting
  2. Consider longer emergency department course (up to 6 hours) for pain stabilization to determine if admission indicated
  3. Hospitalization Indications
    1. Complicated presentations
    2. Acute infections not meeting discharge indications below
    3. Serious complications (e.g. Acute Chest Syndrome, Sepsis, sequestration crisis, Osteomyelitis)
    4. Abnormal Vital Signs
    5. Pregnancy
    6. Lack of reliable outpatient follow-up
    7. Opioid diversion
  4. Observation Unit Indications
    1. Hospitalization indications NOT met
    2. Uncomplicated VOC with failed home and 6 hour emergency department stay
    3. Anticipated discharge within 48 hours
  5. Discharge indications when acute infection complicates Vaso-Occlusive Pain Crisis
    1. Nontoxic appearance
    2. Patient able to take oral fluids and medications
    3. Able to maintain therapy compliance
    4. Close medical follow-up is available
  6. Close follow-up is needed in all patients after Vaso-Occlusive Pain Crisis (VOC)
    1. Increased risk of associated complications (e.g. Acute Chest Syndrome)

XII. Course

  1. Acute Crisis usually resolves spontaneously 7-10 days

XIII. References

  1. Claudius, Behar and Sadowitz in Herbert (2018) EM:Rap 18(4): 10-2
  2. Dwyer, Kleinmann, Goswami and Lopez (2025) Crit Dec Emerg Med 39(1): 26-35
  3. Glassberg and Weingart in Herbert (2012) EM: Rap 12(8): 5-6
  4. Lopez, Kleinmann, Chandra and Lopez (2025) Crit Dec Emerg Med 30(3): 4-12
  5. Lowe and Wang (2018) Crit Dec Emerg Med 32(11): 17-25
  6. Welsh and Welsh (2016) Crit Dec Emerg Med 30(11): 15-23
  7. Preboth (2000) Am Fam Physician 61 [PubMed]
  8. Yawn (2015) Am Fam Physician 92(12): 1069-76 [PubMed]

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