- What test should be performed to evaluate for infectious causes of pneumonia?
Role of Flexible Fiberoptic Bronchoscopy
The utility of flexible fiberoptic bronchoscopy (FOB) in immune-compromised patients for the evaluation of pulmonary infiltrates is a frequently debated topic. Current studies suggest a diagnosis can be made in approximately 80% of cases in the immune-compromised population.32,53 Noninvasive testing such as urine and serum antigens, sputum cultures, Aspergillus galactomannan assays, viral nasal swabs, and PCR studies often lead to a diagnosis in appropriate clinical scenarios. Conservative management would dictate the use of noninvasive testing whenever possible, and randomized controlled trials have shown noninvasive testing to be noninferior to FOB in preventing need for mechanical ventilation, with no difference in overall mortality.54 FOB has been shown to be most useful in establishing a diagnosis when an infectious etiology is suspected.55 In multivariate analysis, a delay in the identification of the etiology of pulmonary infiltrate was associated with increased mortality.56 Additionally, early FOB was found to be superior to late FOB in revealing a diagnosis. 32,57 Despite its ability to detect the cause of pulmonary disease, direct antibiotic therapy, and possibly change therapy, FOB with diagnostic maneuvers has not been shown to affect mortality.58 In a large case series, FOB with bronchoalveolar lavage (BAL) revealed a diagnosis in approximately 30% to 50% of cases. The addition of transbronchial biopsy did not improve diagnostic utility.58 More recent studies have confirmed that the addition of transbronchial biopsy does not add to diagnostic yield and is associated with increased adverse events.59 The appropriate use of advanced techniques such as endobronchial ultrasound–guided transbronchial needle aspirations, endobronchial biopsy, and CT-guided navigational bronchoscopy has not been established and should be considered on a case-by-case basis. In summary, routine early BAL is the diagnostic test of choice, especially when infectious pulmonary complications are suspected.
Contraindications for FOB in this population mirror those in the general population. These include acute severe hypoxemic respiratory failure, myocardial ischemia or acute coronary syndrome within 2 weeks of procedure, severe thrombocytopenia, and inability to provide or obtain informed consent from patient or health care power of attorney. Coagulopathy and thrombocytopenia are common comorbid conditions in the HSCT population. A platelet count of < 20 × 103/µL has generally been used as a cut-off for routine FOB with BAL.60 Risks of the procedures should be discussed clearly with the patient, but simple FOB for airway evaluation and BAL is generally well tolerated even under these conditions.
Early Nonifectious Pulmonary Complications
Case Patient 2 Continued
Bronchoscopy with BAL performed the day after admission is unremarkable and stains and cultures are negative for viral, bacterial, and fungal organisms. The patient is initially started on broad-spectrum antibiotics, but his oxygenation continues to worsen to the point that he is placed on noninvasive positive pressure ventilation. He is started empirically on amphotericin B and eventually is intubated. VATS lung biopsy is ultimately performed and pathology is consistent with diffuse alveolar damage.
- Based on these biopsy findings, what is the diagnosis?
Based on the pathology consistent with diffuse alveolar damage, a diagnosis of idiopathic pneumonia syndrome (IPS) is made.
- What noninfectious pulmonary complications occur in the early post-transplant period?
The overall incidence of noninfectious pulmonary complications after HSCT is generally estimated at 20% to 30%.32 Acute pulmonary edema is a common very early noninfectious pulmonary complication and clinically the most straightforward to treat. Three distinct clinical syndromes—peri-engraftment respiratory distress syndrome (PERDS), diffuse alveolar hemorrhage (DAH), and IPS—comprise the remainder of the pertinent early noninfectious complications. Clinical presentation differs based upon the disease entity. Recent studies have evaluated the role of angiotensin-converting enzyme polymorphisms as a predictive marker for risk of developing early noninfectious pulmonary complications.61
Peri-Engraftment Respiratory Distress Syndrome
PERDS is a clinical syndrome comprising the cardinal features of erythematous rash and fever along with noncardiogenic pulmonary infiltrates and hypoxemia that occur in the peri-engraftment period, defined as recovery of absolute neutrophil count to > 500/μL on 2 consecutive days.62 PERDS occurs in the autologous HSCT population and may be a clinical correlate to early GVHD in the allogeneic HSCT population. It is hypothesized that the pathophysiology underlying PERDS is an autoimmune-related capillary leak caused by pro-inflammatory cytokine release.63 Treatment remains anecdotal and currently consists of supportive care and high-dose corticosteroids. Some have favored limiting the use of gCSF given its role in stimulating rapid white blood cell recovery.33 Prognosis is favorable, but progression to fulminant respiratory failure requiring mechanical ventilation portends a poor prognosis.