Impact of admission hypophosphatemia and hypokalemia on invasive mechanical ventilation in sepsis patients

Abstract

Aims: Electrolyte disturbances are common in patients with sepsis and may impair respiratory muscle function, increasing the need for invasive mechanical ventilation (IMV). However, the impact of admission hypophosphatemia and hypokalemia on early IMV need in patients with sepsis remains incompletely understood. This study aimed to investigate the association between admission hypophosphatemia, hypokalemia, and the need for IMV within the first 24 hours of intensive care unit (ICU) admission. Methods: This retrospective cohort study included adult patients with sepsis admitted to the ICU from January 2020 to March 2026. Hypophosphatemia was defined as a serum phosphate level <2.5 mg/dl, and hypokalemia as a serum potassium level <3.5 mmol/L. The primary outcome was the association of admission hypophosphatemia and hypokalemia with the need for IMV within the first 24 hours of ICU admission. Secondary outcomes included associations of these electrolyte disturbances with in-hospital mortality, vasopressor requirement, continuous renal replacement therapy (CRRT) requirement, and ICU length of stay. Logistic regression analyses were conducted to identify factors associated with the need for IMV. Results: A total of 922 patients were included, of whom 124 (13.4%) required IMV within the first 24 hours. Hypophosphatemia was present in 91 patients (9.9%), hypokalemia in 165 patients (17.9%), and both in 36 patients (3.9%). Patients requiring IMV had significantly lower serum phosphate levels and a higher prevalence of hypophosphatemia (16.1% vs. 8.9%, p=0.012) and of combined electrolyte abnormalities (8.9% vs. 3.1%, p=0.002). In univariate logistic regression, hypophosphatemia was associated with an increased risk of IMV (OR: 1.969, 95% CI: 1.151-3.369, p=0.013), whereas combined hypophosphatemia and hypokalemia were associated with a threefold higher risk of IMV (OR: 3.010, 95% CI: 1.442-6.284, p=0.003). However, these associations were not independently significant after adjustment for potential confounders. Lower pH, higher PaCO₂, and higher SOFA scores were independently associated with the requirement for IMV. Conclusion: Admission hypophosphatemia and combined hypophosphatemia and hypokalemia were associated with a greater need for IMV in patients with sepsis. However, these associations were not independent after adjustment for disease severity and respiratory parameters. Early identification of electrolyte disturbances may help identify patients at increased risk of respiratory deterioration, although further prospective studies are needed to clarify their independent clinical significance.