Acute Respiratory Distress Syndrome Meets Methemoglobinemia: Hypoxemic Challenges in Pneumocystis

Document Type

Conference Proceeding

Publication Date

3-2026

Publication Title

Critical Care Medicine

Abstract

INTRODUCTION: The pathophysiology of acute respiratory distress syndrome (ARDS) involves alveolar capillary barrier injury, diffuse alveolar filling, and microvascular thrombosis, resulting in widespread inflammation. The management of ARDS in patients with Acquired Immune Deficiency Syndrome (AIDS) and Pneumocystis Jirovecii Pneumonia (PJP) is challenging, and the first-line treatment is Trimethoprim-sulfamethoxazole (TMP-SMX). In cases of severe sulfa allergy, Clindamycin-Primaquine is a recommended alternative, but carries the risk of inducing methemoglobinemia. DESCRIPTION: A 34-year-old female, who was receiving treatment for ARDS and PJP at outside hospital, had CT angiography of the chest showing extensive bilateral ground-glass opacities with scattered sub-centimeter nodules. HIV test was positive with a CD4 count of 16 cells per cubic milliliter and a viral load of 660,000 copies/milliliter. Due to TMP-SMX allergy, the patient was given Clindamycin-Primaquine with prednisone. She was intubated and transferred to our extracorporeal membrane oxygenation (ECMO) center for refractory hypoxemia, with a Po2/ FiO2 ratio of 59. Her methemoglobin level was 21.4%, so Clindamycin-Primaquine was transitioned to Atovaquone, and she was given methylene blue after ruling out glucose6-phosphate dehydrogenase (G6PD) deficiency. Given no history of anaphylaxis from TMP-SMX, a One-step full dose challenge was given, which she tolerated. Despite lung protective ventilation with daily proning and inhaled pulmonary vasodilators, the patient required venovenous ECMO. DISCUSSION: Clinicians may find themselves walking a hypoxemic tightrope in managing patients with ARDS who have AIDS and PJP. In patients without a history of anaphylaxis, a One-step full-dose TMP-SMX challenge should be individualized and may prevent complications, such as primaquine-induced methemoglobinemia. In methemoglobinemia, the conformational change in the quadrivalent hemoglobin unit causes impaired oxygen offloading capacity, shifting the oxygen-dissociation curve to the left and worsening hypoxemia.

Volume

54

Issue

3S

Comments

Society for Critical Care Medicine 55th Critical Care Congress, March 22-24, 2026, Chicago, IL

DOI

10.1097/01.ccm.0001184756.43881.d9

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