B73-27 Beyond the Lungs: SIADH as a Complication of Invasive Pneumonoccal Disease

Introduction Syndrome of Inappropriate Antidiuretic Hormone (SIADH) can cause hyponatremia in hospitalized patients. Hyponatremia during an infectious process is something underdiagnosed to be a metabolic complication with etiology in many cases that could be due to SIADH. Streptococcus pneumoniae is the most common bacterial pathogen associated with CAP and can lead to life threatening complications, including sepsis, bacteremia, respiratory failure, and pleural empyema. We present a case of a 64-year-old patient with multidrug resistant Invasive pneumococcal Disease (IPD) complicated by SIADH. Case Description A 64-year-old man presented to the emergency department with two days of chest pain and productive cough. He was afebrile, tachypneic, slightly hypotensive, and borderline hypoxemic with nasal cannula at 4 liters. Laboratory evaluation revealed marked leukocytosis, lactatemia, and arterial blood gases demonstrated hypoxemia. Chest radiograph (CXR) showed dense consolidation of the left lower lobe. The patient was admitted to the intensive care unit with severe sepsis and Acute Hypoxemic Respiratory Failure. Intravenous Ceftriaxone and Azithromycin were initiated, pending culture results. Blood cultures grew Streptococcus pneumoniae resistant to Trimethoprim/Sulfamethoxazole, Ceftriaxone and Fluoroquinolones; patient was then started on Vancomycin. Despite antibiotic therapy, he developed persistent shortness of breath with CRP >300 mg/L with persistent leukocytosis. Follow up Chest Computer Tomography (CT) revealed a large partially loculated left sided pleural effusion with signs concerning for empyema. Ultrasound-guided-thoracentesis confirmed empyema with purulent fluid, pH 7.15, LDH > 2500 Patient suddenly developed hyponatremia (Na+ 125 mmol/L) with calculated serum osmolality 257 mOsm/kg with inappropriately high urine osmolality, consistent with SIADH-related hyponatremia. Patient started on urea and fluid restrictions for hyponatremia management. The patient gradually improved with resolution of sepsis and stabilization of sodium levels. He was successfully weaned from oxygen supplementation and discharged to complete antibiotics for 42 days. Discussion This case demonstrates the potential for Streptococcus pneumoniae to cause severe systemic and local complications in older adults. Hyponatremia due to SIADH is an underrecognized complication of bacteremia especially with the development of concurrent empyema. Overall, the case underscores the importance of early recognition of IPD complications and a multidisciplinary approach that includes antimicrobial therapy, ventilatory support, pleural intervention, and electrolyte management. References 1. Cherazard R, Epstein M, Doan TL, Salim T, Bharti S, Smith MA. Antimicrobial Resistant Streptococcus pneumoniae: Prevalence, Mechanisms, and Clinical Implications. Am J Ther. 2017 May;24(3):e361-e369. doi: 10.1097/MJT.0000000000000551. PMID: 28430673.2. Seidman JC. Putrid pulmonary abscess and empyema with inappropriate secretion of antidiuretic hormone. Chest. 1977 Dec;72(6):796-8. doi: 10.1378/chest.72.6.796. PMID: 923323.