Background: The objective of this study was to assess the relationship between admission serum potassium and the risk of respiratory failure requiring mechanical ventilation in all hospitalized patients.
Methods: All non-dialysis and non-mechanically ventilated patients who had serum potassium measurement at admission from 2011 to 2013 were studied. Serum potassium levels were stratified into five groups; ≤3.4, 3.5 to 3.9, 4.0 to 4.4, 4.5 to 4.9, 5.0 to 5.4, and ≥5.5 mEq/L. The outcome of interest was the respiratory failure requiring mechanical ventilation during hospitalization. Logistic regression analysis was performed to assess the independent risk of in-hospital respiratory failure requiring mechanical ventilation based on various admission serum potassium, using serum potassium of 4.0 to 4.4 mEq/L as the reference group.
Results: Of 67,034 eligible patients, with the mean admission serum potassium of 4.2 ± 0.5 mEq/L, 2,886 (4.3%) patients developed respiratory failure requiring mechanical ventilation during hospitalization. As demonstrated by U-shaped association, increased risk of in-hospital respiratory failure was significantly associated with low admission serum potassium ≤ 3.4 mEq/L (odds ratio 1.36, p-value <0.001) and high admission serum potassium ≥5.5 mEq/L (odds ratio 1.37, p-value = 0.01).
Conclusion: Increased risk of in-hospital respiratory failure requiring mechanical ventilation was noted when serum potassium was below 3.5 mEq/L or above 5.4 mEq/L at the time of hospital admission. Patients with either hypokalemia or hyperkalemia are at risk of respiratory failure requiring mechanical ventilation.
Keywords: Potassium; electrolytes; hyperkalemia; hypokalemia; respiratory failure.