Rosen & Barkin's 5-Minute Emergency Medicine Consult (552 page)

PCP in children is typically more severe.

DIAGNOSIS

• Subacute presentation
  
• Up to 7% of patients can be asymptomatic.
  
• Patients on inhaled pentamidine prophylaxis may have milder symptoms:
  
  • Increased incidence of pneumothorax
    
  • Increased incidence of extrapulmonary disease
    

• Fever
  
• Cough with none or minimal amount of white sputum
  
• Dyspnea on exertion or at rest:
  
  • Progressive over days (most common in non–HIV-immunocompromised hosts)
    
  • Indolent, developing over weeks to months (more common in HIV-positive hosts)
    
  • Oxygen desaturation with exercise
    
• Chills
  
• Fatigue
  
• Weight loss
  
• Chest pain
  

• Tachypnea
  
• Tachycardia
  
• Crackles and rhonchi on lung exam
  

• CBC
  
• Electrolytes
  
• Arterial blood gas (ABG)
  
• Lactate dehydrogenase (LDH)
  
• Blood cultures
  
• Chest x-ray
  

• ABG:
  
  • Obtain in all cases of PCP.
    
  • Calculate the alveolar–arterial (A–a) gradient (usually increased).
    
  • Adjunctive corticosteroid therapy for A–a gradient >35 mm Hg or PaO
    ₂
    <70 mm Hg
    
• LDH:
  
  • Elevated in HIV-positive patients with PCP compared to non-PCP pneumonia
    
  • Higher levels correlate with poorer prognosis.
    

• Chest radiograph:
  
  • Classically reveals bilateral interstitial or central alveolar infiltrates
    
  • Radiograph normal in up to 25% of patients with PCP
    
  • Early or mild infection associated with decreased sensitivity
    
  • Atypical presentations include:
    
    • Lobar infiltrates
      
    • Cysts
      
    • Pneumothoraces
      
    • Pleural effusions
      
    • Nodular infiltrates
      
  • Prophylaxis with aerosolized pentamidine is a risk factor for developing predominantly upper lobe.
    
  • Chest radiograph abnormalities can persist for months after treatment.
    
• High-resolution chest CT:
  
  • High sensitivity for PCP in HIV-positive patients.
    
  • Reveals patchy ground-glass attenuation
    

• Induced sputum:
  
  • Definitive diagnosis requires presence of
    Pneumocystis
    organisms in an appropriately stained respiratory specimen.
    
  • Specificity approaches 100%, but sensitivity depends on quality of induced sputum and lab expertise.
    
  • Less sensitive in patients on inhaled pentamidine prophylaxis and non–HIV-positive patients
    
• Bronchoalveolar lavage:
  
  • Perform if the induced sputum is nondiagnostic and the suspicion for PCP is still high.
    
  • Sensitivity 80–100%
    

Constellation of dyspnea, fever, diffuse radiographic infiltrates, minimal or nonproductive cough, and slow progressive course suggests atypical cause of the pneumonia:

• Chlamydia pneumoniae
  
• Legionella
  
• Mycoplasma
  
• Tuberculosis
  
• Viral pneumonia (especially cytomegalovirus)
  

TREATMENT

Provide supplemental oxygen for symptomatic patients.

• ABCs
  
• Provide adequate oxygenation with nasal cannula up to 100% nonrebreather.
  
• Perform endotracheal intubation in those with refractory hypoxemia despite maximal oxygenation or hypercarbic respiratory failure.
  
• At least 500–1,000 cc 0.9% normal saline IV bolus for hypotension, sepsis, dehydration
  

• Initiate antibiotics:
  
  • IV Bactrim is the first-line agent.
    
  • IV pentamidine for those who cannot tolerate Bactrim
    
  • Oral therapy is an option for well-appearing patients.
    
  • Alternative regimens include trimethoprim–dapsone, clindamycin–primaquine, and atovaquone.
    
  • Continue antibiotics for 21 days.
    
• Adjunctive corticosteroids in patients with A–a gradient >35 mm Hg or PaO
  ₂
  <70 mm Hg:
  
  • Must start within 1st 72 hr of treatment
    
• Isolate suspected PCP patients from others who are immunocompromised.
  

• Atovaquone: 750 mg (peds: Dosing not established) PO q12h
  
• Clindamycin/primaquine: Clindamycin 900 mg (peds: Dosing not established) IV q8h or 300–450 mg PO q6h and primaquine 15–30 mg (peds: Dosing not established) PO per day
  
• Pentamidine: 4 mg/kg/24h IV over 1 hr (peds: 3–4 mg/kg IM or IV once/day for 21 days)
  
• Prednisone: 40 mg (peds: Dosing not established) PO q12h for 5 days, 40 mg PO per day for 5 days, then 20 mg PO per day for 11 days (IV methylprednisolone at 75% of the prednisone dose may be substituted)
  
• Trimethoprim/dapsone: Trimethoprim 15–20 mg/kg/d IV div. q8h + dapsone 100 mg PO per day (peds: Dosing not established)
  
• Trimethoprim/sulfamethoxazole (Bactrim): Trimethoprim 15–20 mg/kg/d IV div. q6h and sulfamethoxazole 100 mg/kg/d IV div. q6h (peds: Dosing same)
  

• Treatment of choice is IV trimethoprim/sulfamethoxazole, followed by IV pentamidine.
  
• Dosing for alternative medications not yet established (consult pediatric infectious disease specialist).
  

FOLLOW-UP

• Moderate to severe disease (PaO
  ₂
  <70 mm Hg or A–a gradient >35 mm Hg)
  
• Inability to digest medications
  
• Inability to return for careful follow-up
  

• Nontoxic clinical appearance
  
• Mild disease state (no hypoxemia or A–a gradient)
  
• Ability to tolerate medications
  
• Close follow-up arranged
  
• If results of induced sputum are not available, add macrolide to empirical regimen.
  

Close follow-up must be arranged with infectious disease specialist to allow for outpatient management.

• Include PCP in differential diagnosis in any patient presenting with shortness of breath who is immunocompromised or is suspected of having undiagnosed HIV.
  
• Patients considered for PCP are also more likely to have TB or atypical bacterial pneumonia.
  
• Well-appearing patients with low oxygen saturations are at higher risk for complications.
  

• Thomas CF Jr, Limper AH. Pneumocystis pneumonia.
  N Engl J Med.
  2004;350:2487–2498.
  
• Huang L, Quartin A, Jones D, et al. Intensive care of patients with HIV infection.
  N Engl J Med.
  2006;355:173–181.
  
• Kovacs JA, Masur H. Evolving health effects of Pneumocystis: One hundred years of progress in diagnosis and treatment.
  JAMA
  2009;301:2578–2585.
  

See Also (Topic, Algorithm, Electronic Media Element)

• HIV/AIDS
  
• Pneumonia, Adult
  
• Pneumonia, Pediatric
  
• Tuberculosis
  

CODES

136.3 Pneumocystosis

BASICS