Hypophosphatemia in Chronic Obstructive Pulmonary Disease Patients Requiring Mechanical Ventilation and Its Impact on Weaning in an Intensive Care Unit of a Tertiary Care Hospital in Eastern India

TL;DR

Low phosphate levels in COPD patients on ventilators are linked to poor weaning outcomes and higher mortality in an Indian ICU.

Contribution

Identifies serum phosphate as a predictive biomarker for successful weaning in mechanically ventilated COPD patients.

Findings

25% of COPD patients on mechanical ventilation had hypophosphatemia on admission.

A serum phosphate level of ≥3.0 mg/dL before weaning predicted successful weaning with 86.4% sensitivity.

Lower phosphate levels, higher age, and longer ICU stays were associated with higher mortality.

Abstract

Background

Hypophosphatemia, defined as a serum phosphate level less than 2.5 mg/dL, is a frequent finding in patients with chronic obstructive pulmonary disease (COPD) and has been speculated to negatively affect weaning outcomes. This study aimed to determine the incidence of hypophosphatemia in COPD patients requiring mechanical ventilation and evaluate the predictive role of hypophosphatemia as an indicator of successful weaning from mechanical ventilation in such patients admitted to the intensive care unit (ICU) in a tertiary care hospital in eastern India.

Methodology

This prospective observational study included 60 adult patients aged 18 to 75 years with acute exacerbations of COPD on mechanical ventilation in the ICU who were planned to undergo a weaning trial. Serum phosphate levels were assessed at the time of admission and before each weaning attempt. Weaning outcomes at each attempt, length of ventilator and ICU stay, and mortality were recorded. Data collection was initiated after approval of the Institutional Ethics Committee. Receiver operating curve (ROC) analysis was done to identify the cut-off value of serum phosphate which predicted successful weaning.

Results

Of 60 participants, hypophosphatemia on admission was present in 15 (25%) patients. Despite the correction, 13 (21.7%) patients had hypophosphatemia before the first weaning attempt. Only 22 patients out of 60 were successfully weaned off from mechanical ventilation in the first trial, accounting for a success rate of 36.7%, of whom 20 were normophosphatemic (90.9%). In the second and third weaning trials, hypophosphatemia was significantly associated with weaning failure. Overall differences in mean serum phosphate levels among those who failed to wean in each weaning trial and the successful attempt were statistically significant (p < 0.001). On ROC analysis of serum phosphate level before the first weaning trial, a cut-off value of ≥3.0 mg/dL was identified to have 86.4% sensitivity, 55.3% specificity, 52.8% positive predictive value, 87.5% negative predictive value, and 66.7% diagnostic accuracy in predicting weaning success. Five patients died, accounting for a mortality rate of 8.3%. Lower mean serum phosphate levels before the first weaning trial, higher mean age, and longer ventilator and ICU days were significantly associated with mortality among our study participants (p < 0.05).

Conclusions

Our findings suggest that maintaining normal serum phosphate levels is critical to successfully weaning off patients with COPD from ventilator support.

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