The Predicting Ability of Serum Phosphorus to Assess the Duration of Mechanical Ventilation in Critically Ill Patients

Abstract

Background: No previous study exists to evaluate serum phosphorus (Ph) level as a predictor of the need to mechanical ventilation (MV). This study was designed to determine the predictive ability of admission serum Ph level on MV in patients admitted in Intensive Care Unit (ICU).

Materials and methods: This prospective study was conducted on 100 patients (>16 years old), admitted to our ICU over 1-year. Patients were classified into two groups according to the days of the need to MV. Group A: Patients who required equal or <5 days MV, and Group B: Patients who required more than 5 days of MV. We measured total serum Ph concentrations at the times of ICU admission, connecting to the ventilator and weaning from the ventilator.

Results: There were significant differences between serum Ph concentration on admission to ICU (Group A: 3.39 ± 0.39 mg/dl, Group B: 2.89 ± 0.31 mg/dl, P < 0.001), at the time of connecting to ventilator (Group A: 2.49 ± 0.38 mg/dl, Group B: 2.25 ± 0.26 mg/dl, P = 0.004) and weaning from ventilator (Group A: 3.42 ± 0.33 mg/dl, Group B: 2.98 ± 0.34 mg/dl, P < 0.001) between two groups. Duration of ICU stay in Group A was 6.08 ± 1.48 days and in Group B was 15.35 ± 6.45, this difference was significant (P < 0.001). We found the best cut-off point of 3.07 for serum Ph concentration to predict the longer duration of MV.

Conclusion: According to the results of our study, hypophosphatemia may increase the need to MV. Therefore, monitoring serum Ph level is a good prognostic factor to predict the need to ventilation.

Keywords: Critically ill patient; hypophosphatemia; mechanical ventilation; phosphorus; sequential organ failure assessment score.

Figure 1

Receiver operating characteristics curves for need to longer mechanical ventilation drawn of serum phosphorus concentration on admission (curve a). Sequential organ failure assessment score on admission (curve b)