Impact of Acquired Hypernatremia in the ICU on Mortality in Patients with Acute Respiratory Failure: A Retrospective Analysis from the NIS Database

Introduction: Hypernatremia is a critical condition frequently present in critically ill patients. In patients with acute respiratory failure, studies have shown that it worsens patients’ condition and prolongs the time for mechanical ventilation, leading to adverse outcomes, yet in-hospital mortality is not completely acknowledged.

Methodology: Analyzing data from the National Inpatient Sample database (2018–2021), a retrospective analysis was conducted using proper ICD-10 codes to identify patients with acute respiratory failure, then dividing them into two groups: with and without hypernatremia. Primary outcome assessed in-hospital mortality, while secondary outcomes were length of stay (LOS) and demographics.

Results: Out of 153,840 hospitalized patients that met our criteria (median age 64, 56% male), 76,950 (50%) were selected for the hypernatremia group. Hypernatremic patients (median age 66, 57.5% male) had higher mortality (28.2% vs. 18.9%, OR=1.489, CI=1.432–1.548, p<0.001) and longer LOS (11 vs. 5 days). Hypernatremia increased mortality risk (OR=1.522, CI=1.480–1.564), especially with diabetes insipidus (OR=11.664), dementia (OR=2.192), and acute kidney injury (OR=1.630).

Hypernatremic patients had more illness severity (OR=1.273, CI=1.223–1.323) and fewer routine discharges (OR=0.814, CI=0.783–0.846).

Discussion: Hypernatremia increased mortality (28.2% vs. 18.9%, OR=1.522) and length of stay (11 vs. 5 days) in this population, particularly in patients with comorbidities like diabetes insipidus, dementia, and acute kidney injury. Routine ICU monitoring of blood gases facilitates the detection and the opportunity to create a proper management plan to improve the outcomes. Racial differences and different clinical courses were identified, requiring more research.

Conclusion: Hypernatremia is an independent mortality risk factor in this population; it can be worsened and altered by other subsequent factors of patients’ conditions, like comorbidities. Proper management of hypernatremia is needed to avoid the worst outcomes and should be personalized depending on each specific patient. Acknowledging patient-acquired hypernatremia in the ICU in this population is an opportunity in healthcare for prevention, and management serves to boost patients’ survival.

Keywords: Hypernatremia, acute respiratory failure, intensive care unit, in-hospital mortality, National Inpatient Sample (NIS)