# Impact of serum phosphate levels during CRRT on extubation failure and hospital mortality in mechanically ventilated ICU patients—A study based on the MIMIC-IV database

## TL;DR

This study shows that high serum phosphate levels during CRRT in ICU patients are linked to higher risks of extubation failure and hospital mortality.

## Contribution

The study identifies serum phosphate levels as an independent risk factor for extubation failure and hospital mortality in CRRT patients.

## Key findings

- High phosphate levels (Phosphate_min > 4.5 mg/dL) are a moderate predictor of extubation failure and hospital mortality.
- A J-shaped relationship exists between phosphate levels and both outcomes, with lowest risk at 1.60–1.98 mg/dL.
- Maintaining phosphate within a therapeutic range may reduce ICU complications.

## Abstract

Electrolyte imbalances, particularly phosphate depletion, are prevalent yet often underestimated complications in the Intensive Care Unit (ICU), notably among patients undergoing Continuous Renal Replacement Therapy (CRRT). Therefore, this study aims to examine the impact of serum phosphate levels during CRRT on the incidence of extubation failure and hospital mortality in mechanically ventilated patients.

Patients subjected to both CRRT and mechanical ventilation were extracted from the MIMIC-IV database. Cox regression analysis was employed to identify the potential risk factors for the extubation failure and hospital mortality rates. Patients were categorized into three groups based on their minimum serum phosphate level (Phosphate_min) during CRRT. Kaplan-Meier survival analysis and Receiver Operating Characteristic (ROC) curves were employed to assess differences in the primary outcomes among these groups. Additionally, a restricted cubic spline curve was utilized to explore potential nonlinear relationships between Phosphate_min and the primary outcomes.

The analysis included 816 ICU patients undergoing CRRT and mechanical ventilation. Cox regression analysis identified Phosphate_min as a significant risk factor for both extubation failure (HR 1.29; 95% CI 1.22–1.36, p < 0.001) and hospital mortality (HR 1.48; 95% CI 1.37–1.60, p < 0.001). ROC curve analysis indicated that a Phosphate_min > 4.5 mg/dL was a moderate predictor for both extubation failure and hospital mortality. Kaplan-Meier analysis revealed significantly higher risks of the primary outcomes in the group with Phosphate_min > 4.5 mg/dL compared to the lower phosphate groups (log-rank p < 0.001). Additionally, restricted cubic spline analysis showed a J-shaped relationship between Phosphate_min and both primary outcomes, with nadirs at approximately 1.60 mg/dL for extubation failure and 1.98 mg/dL for hospital mortality.

Phosphate_min emerges as an independent risk factor for both extubation failure and hospital mortality. Maintaining serum phosphate levels within a therapeutic range may potentially mitigate these risks.