emDOCs Revamp – Acute Chest Syndrome

Author: Kyle Smiley, MD (EM Resident Physician / San Antonio, TX); Jonathan Henderson, MD (PEM Attending, Washington, DC) Rachel Bridwell, MD (EM Attending Physician, Charlotte, NC) // Reviewed by: Alex Koyfman, MD (@EMHighAK, EM Attending Physician, UTSW / Parkland Memorial Hospital); Brit Long, MD (@long_brit, EM Attending Physician, San Antonio, TX)

Welcome to emDOCs revamp! This series provides evidence-based updates to previous posts so you can stay current with what you need to know.

An 8-year old male with a history of sickle cell anemia presents to the ED for evaluation of fever for 2 days and “feeling like I can’t get a full breath”. His immunizations are current and has received all pneumococcal vaccinations. His medical history is significant for three prior admissions for vaso-occlusive crises that have responded well to appropriate therapy, including pain control with NSAIDs and opioids, blood transfusions, antibiotics, and intravenous (IV) crystalloids. He has met all his developmental milestones and has no other chronic medical conditions.

Triage vital signs include BP 127/81, HR 119, T 102.9 F temporal, RR 25, SpO2 89% on room air.

Physical examination:

General: Uncomfortable, tired

Neuro: Acting appropriately for age, crying in pain, uncomfortable appearing, moving all 4 extremities with equal and reactive pupils

HEENT: PERRLA, bilateral scleral icterus, TMs clear bilaterally, nasal mucosa unremarkable, oropharynx clear and moist, no lymphadenopathy

CV: Sinus tachycardia, cap refill <2 secs

Pulm: Tachypneic without mild accessory muscle use. Left lower lung field end demonstrates expiratory wheezing on auscultation. Other lung fields unremarkable.

Abdomen: ND, NT, no guarding or rebound

MSK: Tenderness to palpation over L ribs 7-9

Derm: No rashes

Imaging:

Image 1: Case courtesy of Miriam Leiderer, Radiopaedia.org, rID: 81468

Chest radiograph (CXR) shows new left lower lobe opacity

What’s most likely diagnosis?

Answer: Acute Chest Syndrome^1-26

Epidemiology:

• Approximately 300,000 infants born annually worldwide with Sickle Cell Disease (SCD)¹
  • Most commonly in sub-Saharan Africa, India, Middle East, Mediterranean populations
  • Approximately 100,000 live in the US
  • 50% of SCD patients will have >1 episode of Acute Chest Syndrome in their lifetime with approximately 150,000 ED visits for pain crises and acute chest annually, and the second most common reason for hospitalization in those with SCD^2,3
• Most common in pediatrics within SCD population
• Causes ~25% of SCD deaths
  • Mortality rate of 4-9% in adults per episode
  • Risk factors for severe acute chest syndrome⁴
• Fever, O₂ saturation <95%, asplenia, history of reactive airway disease, anemia, leukocytosis, adult age

Pathophysiology:

• beta-chain mutation produces hemoglobin S⁵
  • HbS polymerization triggered by hypoxemia, acidosis, dehydration, pain and fever causing hemolysis and vaso-occlusive events
  • Treatment with opioids and pain induce hypoventilation and local tissue hypoxia, further exacerbating sickling process
• Triggers identified in ~40% of cases^2,6,7
  • Infection
  • Fat embolism
  • Pain crisis
  • Environmental toxins (e.g.-smoke, high ozone levels, smog)
  • Asthma/reactive airway disease (RAD)
• Diagnostic criteria^7,8
  • Respiratory symptoms +/- fever (at least 38.0 C or 100.4 F)
  • New radiodensity on CXR
  • Although uncommon, can occur in sickle cell trait⁸

Presentation:

• Most commonly:
  • Fever (80%), cough (62%), chest pain (44%), dyspnea (40%), and occasionally hemoptysis, reactive airway disease (13%)^10,11
  • Presentation may be sudden in onset or be preceded by prodromal pain in extremities (40%) or thorax as well neurologic complaints of confusion or altered mental status
    • Adult presentation: chest pain, dyspnea, pain prior to ACS, neurologic findings
    • Pediatric presentation: fever, wheezing, and less commonly present with pain
  • Based on the wide variety presentation, ACS should be considered in anyone presenting with respiratory symptoms, neurologic complaints, extremity complaints, or concern for pain crisis
    • Rapidly progressive acute chest syndrome¹²
      • Progresses to respiratory failure within 24hrs of symptom onset
      • Associated with multi-organ failure and death
    • Consider in rapid drop in hemoglobin, low platelets, altered mental status, high fever
    • Pulmonary hypertension may contribute to presentation¹³
  • Hypercoagulability, endothelial injury, chronic inflammation, chronic hemolysis, altered nitric oxide levels increase risk
    • Up to 40% have increased pulmonary arterial pressure on echocardiogram

Evaluation:

• Assess ABCs and begin resuscitation
  • Wheezing often present and ~25% will be hypoxic, rales may also be present⁸
    • Pulse oximetry often overestimates true SpO2
      • Hypothermia, hypotension, vasoconstriction limit accuracy
      • Only measures hemoglobin A, not hemoglobin S
    • Up to 3x less accurate in black patients
  • Tachycardia multifactorial: pain, hypoxia, anemia
  • Often pale or jaundiced
  • Consideration of pulmonary hypertension¹³
    • Symptoms are fatigue, SOB, CP, lightheadedness, syncope, palpitations
      • Think about when patient has these and is fluid overloaded
      • Look like acute chest but refractive to standard therapy
        • SCD patients should receive echo every 1-3yrs as adult¹⁴
          • Tricuspid regurgitant jet velocity >2.5 m/s is associated with increased mortality
  • Laboratory evaluation¹⁵
    • Complete blood count (CBC) for hemoglobin/hematocrit
    • Reticulocyte count
    • Complete metabolic panel
      • Increased liver associated enzymes (LAEs), increased creatinine from acute kidney injury, increased bilirubin from intravascular hemolysis
    • Electrocardiogram
    • Type and screen
      • Consideration for potential red blood cell transfusion
    • Blood cultures empirically due to high risk for sepsis
    • Respiratory viral panel
      • Source detection
    • Consider ABG if worsening respiratory status despite non-invasive oxygenation or concern for respiratory failure
  • Imaging:
    • Chest plain radiograph must demonstrate new infiltrate^1,2,6-11
      • 2-view if possible
      • Sensitivity >85%, specificity <60%
      • Lung US has better sensitivity
    • CT not routinely recommended given sensitivity of CXR¹⁶
      • Can be used with negative CXR and high clinical suspicion
      • CT pulmonary angiography if concern for PE or clinical suspicion high despite negative CXR
        • Most patients with PE present with chest pain and SOB, complicating diagnosis
        • SCD patients are hypercoagulable with 60% lifetime risk¹⁷
          • 17% of acute chest patients have concomitant PE
            • Lab findings suspicious for PE
              • Baseline Hgb >8.2 g/dL, PLT >440,000 cells/uL, PaCO2 <38 mmHg
            • Consider when rapid deterioration despite conventional therapy, cardiogenic dysfunction, concern for DVT on exam, unclear etiology for acute chest syndrome
              • SCD patients have elevated D-dimer at baseline, decreasing utility of this test¹⁷

Treatment:

• ABCs—Allow patient to assume position of comfort:
  • Hypoxia common and often multi-factorial secondary to respiratory splinting, pulmonary microvascular occlusion, anemia
    • Therapeutic oxygen decreases RBC sickling
      • Goal oxygen saturation >/=95%^2,15
    • Bronchodilators administered only in patients with RAD and wheezing on auscultation
    • Steroids should be avoided unless concomitant reactive airway disease or COVID positive
      • Associated with increased risk of fat embolism and rebound vaso-occlusive crises¹⁵
    • Incentive spirometry reduces atelectasis and chest splinting, and should be encouraged in this population
  • Transfusion for hemolytic anemia^1,2,7,15
  • Consider for Hgb <7 g/dL or 10-20% below baseline with target Hgb of 10-11 g/dL
    • Reserve exchange transfusion for hematology
  • Empiric IV fluids have fallen out of favor and treatment focuses on maintaining euvolemia^11,19,20
    • Unless clinically dehydrated or unable to tolerate PO, these patients should be placed on maintenance fluids only given concern for fluid overload
      • Goal is euvolemia
    • May increase hospital length-of-stay if aggressively fluid resuscitated due to significant pulmonary edema risk
  • Pulmonary hypertension
    • When refractory to above supportive measures:
      • PDE-5 inhibitors, endothelin receptor antagonists, prostanoids
      • Early vasopressors/inotropes, addressing volume overload with diuretic, avoiding intubation
    • Pain control
      • Multi-modal
        • Intranasal fentanyl (1.5-2 mcg/kg, max 100 mcg) while obtaining IV access²⁰
        • IV/IM ketorolac (1 mg/kg, max 15 mg)
        • Morphine (05-0.1 mg/kg, max 4 mg per dose q20-30min) or hydromorphone (0.01-0.02 mg/kg, max 0.4 mg q20-30 min per dose)
          • PRN naloxone in case of respiratory depression
        • Some patients have SCD crises pain plan for reference
      • Antimicrobials¹¹
        • Ceftriaxone + azithromycin if penicillin allergy for both children and adults. May substitute levofloxacin if allergic to cephalosporin
        • Anti-viral medications if indicated
          • Oseltamivir for influenza
            • Patients >14 days old
          • Remdesivir for COVID
            • Patients >28 days old and at least 7lbs (3.2 kg)
          • Consult hematology after initial stabilization for clinical recommendations
          • Transfer to tertiary center if you do not have appropriate consult services in house
            • Early hematology consult is necessary as they often follow these patients closely
            • Patients may require ICU care when requiring significant respiratory support e.g. NIPPV/intubation or when concerned for refractory shock^23-26
              • Risk factors for ICU requirements due to disease severity
                • ARDS from pulmonary sequestration/infarction
                • O2 saturation <85% on room air or <90% on maximum supplemental O2
                • Segmental or lobar infiltrates in >2 lobes
                • Hgb S level >30% and requiring transfusion
                • Rapid platelet decline or platelets <200 cells/uL
              • Rapidly progressive acute chest syndrome or high concern for this diagnosis should prompt ICU admission
            • ECMO has been used successfully in patients whose cardiopulmonary support requirements cannot be met with above measures²²

Disposition

• Acute chest patients require admission to hospital for monitoring given high risk for decompensation
  • Most will require ICU admission^22-26
  • If PICU unavailable at your hospital, transfer to nearest appropriate center
• Consultation to pulmonary and cardiology involvement for transthoracic echocardiogram and management recommendations if concern for pulmonary hypertension

Pearls

• Diagnostic criteria: any respiratory infection symptoms plus new pulmonary consolidation on radiograph or CT in patient with any sickle phenotype
• Early and aggressive pain control with intranasal fentanyl improves patient centered outcomes
• Seek out patient’s pain crisis plan if they have one as this can guide analgesic therapy
• Consult hematology expediently for pain control, infection, and transfusion recommendations

Additional FOAM Resources:

1. https://litfl.com/sickle-cell-crisis/
2. https://emergencymedicinecases.com/sickle-cell-acute-chest-syndrome/
3. https://aliemcards.com/cards/acute-chest-syndrome/
4. https://www.emdocs.net/acute-chest-syndrome/
5. https://www.paediatricfoam.com/2020/11/sickle-cell-chest-crisis/
6. https://emcrit.org/pulmcrit/sickle-chest/

References:

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