Association of phosphate decline after nutritional support with extubation failure in critically ill patients

While hypophosphatemia is known to complicate weaning, the impact of early phosphate dynamics following nutritional support remains unclear. This study aimed to determine the association between the relative rate of phosphate decline after initiation of nutritional support and extubation outcomes in critically ill patients.

This retrospective cohort study was conducted in the medical intensive care unit of a tertiary academic hospital. Adult patients receiving invasive mechanical ventilation who underwent planned extubation after initiation of enteral and/or parenteral nutrition between 2022 and 2025 were included. The primary exposure was the phosphate drop rate, defined as the percent decline in serum phosphate from baseline to nadir within 72 h after initiation of nutritional support. The primary outcome was extubation failure, defined as reintubation or death within 7 days after planned extubation.

Among 287 patients included in the final analysis, 55 (19.2%) experienced extubation failure. The extubation failure group showed a greater decline in serum phosphate than the success group (35.6 ± 19.6% vs. 27.3 ± 19.0%; p = 0.004), while baseline phosphate levels were similar between groups. In multivariable analysis, each 10% increase in phosphate drop rate was independently associated with extubation failure (adjusted odds ratio 1.22; 95% CI, 1.06-1.42). Restricted cubic spline analysis demonstrated that phosphate drop rate was associated with extubation failure (P for overall = 0.025) without evidence of a nonlinear relationship (P for nonlinearity = 0.692). In receiver operating characteristic analysis, the phosphate drop rate showed modest discrimination for extubation failure (area under the curve 0.612; 95% CI, 0.530-0.694).

A greater decline in serum phosphate after initiation of nutritional support was independently associated with extubation failure in patients receiving invasive mechanical ventilation. Monitoring early phosphate trajectories during nutritional support may help identify patients at increased risk of extubation failure.