PLEURAL FLUID IN A PNEUMOTHORAX: DON'T ANCHOR IN SHALLOW WATER

Abstract

TOPIC: Chest Infections TYPE: Fellow Case Reports INTRODUCTION: During the 1980's Pneumocystis pneumonia (PCP) was the leading cause of HIV-AIDS related death. The diagnostic standard is by PCR. While pneumocystis is now an incorporated differential in HIV-AIDS patients with respiratory failure, sputum or bronchoalveolar lavage, samples can be difficult to obtain in non-intubated patients. We present a patient being presumptively treated for COVID in the midst of the pandemic, with spontaneous bilateral pneumothoraces and newly diagnosed HIV, for whom analysis of scant pleural fluid led to key diagnostic and treatment implications. CASE PRESENTATION: A 36-year-old, male with no medical history was admitted to an outside hospital for progressive hypoxemic respiratory failure requiring high-flow nasal cannula, secondary to presumptive COVID-19 pneumonia despite several negative PCR and antibody tests. He developed a secondary spontaneous pneumothorax on hospital day 10, for which a pigtail catheter was placed, and he subsequently was transferred to our institution for severe ARDS treatment. Prior to transfer, he received Tocilizumab, dexamethasone, and convalescent plasma per institutional COVID-19 guidelines. Due to persistently low WBC counts and failure to respond to therapy, an HIV test on hospital day 10 resulted positive, as well as a CD-4 count <50 cells/mm3. Due to the new diagnosis of HIV-AIDS, Pneumocystis pneumonia was suspected, and treatment was initiated despite pending diagnostic confirmation. On arrival, existing pigtail chest tube showed intermittent leak with enlarging pneumothorax thus a second tube was placed. After insertion, pleural fluid was sent for cell-count and microbiologic studies resulting in positive PCP. Treatment continued with Trimethoprim-Sulfamethoxazole. The patient ultimately developed bilateral pneumothoraces, required intubation, and subsequent ECMO. DISCUSSION: This case highlights two pertinent clinical points: the under-appreciated diagnostic utility of pleural-fluid sampling, and the importance of recognizing anchoring bias.While PCP is typically diagnosed from sputum or BAL samples, pleural fluid sampling has only been done anecdotally in the context of known PCP infections after prior treatment with Pentamidine. The positive PCP result on pleural fluid analysis confirmed the diagnosis despite the patient being unable to produce sputum and too unstable for BAL. While treatment was initiated empirically, the importance of diagnostic confirmation cannot be understated in a patient being subjected to immunosuppressive therapy and a worsening clinical course. Therefore, the under-appreciated and under-utilized analysis of the scant pleural fluid obtained after pneumothorax decompression, as well as the consequences of anchoring bias are exemplified in this case. CONCLUSIONS: Pneumothrax is a common complication of PCP, and minimal pleural fluid expelled after decompression is an important diagnostic source. REFERENCE #1: Thomas CF, Limper AH. Pneumocystis Pneumonia. N Engl J Med. 2004;350: 2487–2498. doi:10.1056/NEJMra032588 REFERENCE #2: Schaumberg TH, Schnapp LM, Taylor KG, Golden JA. Diagnosis of pneumocystis carinii infection in HIV-seropositive patients by identification of P carinii in pleural fluid. Chest. 1993;103: 1890–1891. REFERENCE #3: Horowitz ML, Schiff M, Samuels J, Russo R, Schnader J. Pneumocystis carinii Pleural Effusion: Pathogenesis and Pleural Fluid Analysis. Am Rev Respir Dis. 1993;148: 232–234. DISCLOSURES: No relevant relationships by Saad Ahmad, source=Web Response No relevant relationships by Alfredo Astua, source=Web Response No relevant relationships by Richard Durrance, source=Web Response No relevant relationships by Jonathan Vincent Reyes, source=Web Response