Extracorporeal membrane oxygenation for overwhelming Blastomyces dermatitidis pneumonia

Abstract

is a fungus that is found primarily in endemic areas of the midwestern and southcentral USA. Blastomycosis pneumonia may develop after the inhalation of spores. While blastomycosis may lead to acute or chronic pneumonitis, it will rarely result in the development of the acute respiratory distress syndrome (ARDS). In this situation, mortality rates are 50–80%. Patients who survive, however, commonly show good recovery of pulmonary function. Extracorporeal membrane oxygenation (ECMO), a modified form of cardiopulmonary bypass that allows systemic perfusion, oxygenation, and carbon dioxide removal, may be used to support patients with cardiorespiratory failure that is refractory to conventional therapies. The use of ECMO allows the reduction of high levels of mechanical ventilatory support that may cause iatrogenic injury to the diseased lung. Fungal diseases are often contraindications for ECMO use, since systemic fungal organisms may bind to the ECMO circuit and be difficult to eradicate. It may be reasonable to utilize ECMO, however, if the fungal infection is isolated to the respiratory system. We report the case of a patient with ARDS secondary to blastomycosis pneumonia who was treated with ECMO due to the failure of conventional cardiorespiratory supports. To our knowledge, this is the first report of the use of ECMO for this condition.

Introduction

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In general, a primary fungal infection, especially when the infection is hematogenous, is a contraindication to the use of ECMO. Historically, patients with hematogenous fungal infections do poorly on ECMO, primarily because the mycosis cannot be eradicated from the synthetic surfaces of the ECMO circuit. The restriction against ECMO support for cardiorespiratory failure secondary to fungal pneumonia without hematogenous spread is less certain. In theory, this condition should not preclude the use of ECMO, but no reports about the use of ECMO in this situation are available.

We report our experience with the use of ECMO to support a previously healthy adolescent with respiratory failure secondary to blastomycosis pneumonia to raise awareness of this disease as a cause of pneumonia and better understand the use and limitation of extracorporeal support in this condition.

Postmortem findings

was noted in the bloodstream or in any other organs outside of the lungs. The final pathologic cause of death was listed as fungal pneumonia with extensive destruction of lung tissue.

Chest radiograph on day of intubation. Note consolidation of right hemithorax and left lower thorax.

Section of lung tissue from post-mortem examination. H/E stain, magnification 200 ×. Note multinucleated giant cells consistent with blastomycosis and extensive destruction of lung.

Comments

]. The typical patient with blastomycosis is male, aged 25–50 years, and habitually exposed to the outdoor environment. Children are rarely diagnosed with blastomycosis (epidemics excepted). The occurrence of blastomycosis in this patient, without living in an endemic area or with a history of prolonged outdoor activity, is extremely unusual.

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]. In our experience with pediatric respiratory failure, patients receiving mechanical ventilation for less than 7 days prior to ECMO initiation have a 67% survival rate.

In general, ECMO is not utilized during an active fungal infection, since fungal elements in the bloodstream adhere to the synthetic elements of the ECMO circuit, making it impossible to eradicate them with antifungal agents. Pulmonary blastomycosis, however, is often localized to the respiratory tract, making contamination of the ECMO circuit less likely. Since this patient was previously healthy, had single-organ disease and had failed less invasive forms of pulmonary support, ECMO was instituted to limit further iatrogenic lung injury from mechanical ventilation during completion of amphotericin B treatment. Despite ECMO support, eradication of blastomycosis and healing of diseased lung tissue did not occur and the patient did not survive.

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]. In this situation, severe lung injury may occur. Another potential problem with high levels of bypass is the potential limitation of drug delivery to the infected area; inadequate pulmonary blood flow reaching the lungs will lead to impaired fungal eradication. In this case, however, care was taken to limit the extent of cardiopulmonary bypass and to maintain pulmonary blood flow. It is possible that local blood flow was limited by tissue and vascular injury from the pneumonia, resulting in subtherapeutic tissue levels of amphotericin B. This would be consistent with the pathologic findings of heavy concentrations of fungal elements in injured lung parenchyma that was not in proximity to normal vascular structures.

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It is also possible that this case was referred for ECMO too late in the course of disease to achieve any substantial benefit with the 'lung rest' provided by ECMO.

In summary, we present the first description of the use of ECMO to support respiratory failure in an adolescent with ARDS secondary to blastomycosis pneumonia. Despite the use of adequate antifungal agents, the reduction of ventilatory settings to non-toxic ranges, and adequate oxygen delivery to other organ systems, eradication of the blastomycosis did not occur and no lung recovery took place.

Keywords

• ECMO
• fungal infection
• blastomycosis
• respiratory failure
• extracorporeal life support
• pneumonia
• ARDS