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Abstract
Background: Hyponatremia (serum sodium <135 mmol/L) is a common electrolyte disturbance in community-acquired pneumonia (CAP) and has been associated with adverse outcomes. However, robust data from Pakistan and other low- and middle-income countries remain limited. This study aimed to determine the frequency of admission hyponatremia and evaluate its independent association with hospital outcomes in Pakistani patients hospitalized with CAP.
Methods: This retrospective cohort study included 400 adult patients admitted to a tertiary care hospital with community-acquired pneumonia. Patients were categorized as hyponatremic or normonatremic based on admission serum sodium levels. Clinical outcomes assessed included in-hospital mortality, ICU admission, need for invasive mechanical ventilation, and length of hospital stay. Multivariable logistic regression was used to evaluate the independent association between hyponatremia and in-hospital mortality after adjusting for age, sex, CURB-65 score, comorbidities, and serum creatinine.
Results: Hyponatremia was present in 126 of 400 patients (31.5%). Compared with normonatremic patients, hyponatremic patients had significantly higher in-hospital mortality (10.3% vs. 2.2%; p < 0.001), greater ICU admission rates (20.6% vs. 10.9%; p = 0.010), and longer hospital stays (median 10 vs. 7 days; p < 0.001). Mechanical ventilation was more frequent among hyponatremic patients but did not reach statistical significance (11.1% vs. 6.2%; p = 0.088). After multivariable adjustment, hyponatremia remained independently associated with in-hospital mortality (adjusted OR 5.71, 95% CI 2.02–16.13; p = 0.001).
Conclusion: Admission hyponatremia is common in hospitalized CAP patients and independently predicts higher mortality, ICU admission, and prolonged hospitalization. To our knowledge, this study provides the first evidence from Pakistan demonstrating the independent prognostic value of hyponatremia in CAP after adjusting for established severity indices, supporting its use as a simple, low-cost risk stratification tool in resource-limited settings