Pneumocystis Pneumonia, Emergency Medicine

Basics

Description

Originally called Pneumocystis carinii pneumonia, then renamed Pneumocystis jirovecii but still referred to as PCP
Most common opportunistic infection in patients with HIV, even with PCP prophylaxis and antiretroviral therapy
Believed to be transmitted by respiratory-aerosol route:
- Cysts colonize respiratory tract.
- Cysts rupture and multiple trophozoites release and form foamy exudate in alveoli.
Most cases are believed to represent reactivation of latent disease, although person-to-person transmission suggested.
Actual mode of transmission is unclear.

Etiology

Pneumocystis is classified as a fungus.
Pneumocystis occurs in hosts with altered cellular immunity:
- HIV infection (most common, especially when CD4 count <200 cells/mm3)
- Cancer
- Corticosteroid treatment
- Organ transplantation
- Malnutrition

PCP in children is typically more severe. ‚

Diagnosis

Signs and Symptoms

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

History

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

Physical Exam

Tachypnea
Tachycardia
Crackles and rhonchi on lung exam

Essential Workup

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

Diagnosis Tests & Interpretation

Lab

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 PaO2 <70 mm Hg
LDH:
- Elevated in HIV-positive patients with PCP compared to non-PCP pneumonia
- Higher levels correlate with poorer prognosis.

Imaging

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

Diagnostic Procedures/Surgery

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%

Differential Diagnosis

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

Pre-Hospital

Provide supplemental oxygen for symptomatic patients. ‚

Initial Stabilization/Therapy

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

Ed Treatment/Procedures

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 PaO2 <70 mm Hg:
- Must start within 1st 72 hr of treatment
Isolate suspected PCP patients from others who are immunocompromised.

Medication

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

Disposition

Admission Criteria

Moderate to severe disease (PaO2 <70 mm Hg or A " “a gradient >35 mm Hg)
Inability to digest medications
Inability to return for careful follow-up

Discharge Criteria

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.

Followup Recommendations

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

Pearls and Pitfalls

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.

Additional Reading

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.

Codes

ICD9

136.3 Pneumocystosis ‚

ICD10

B59 Pneumocystosis ‚

SNOMED

415125002 Pneumocystosis jiroveci pneumonia (disorder)

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