Phosphorus: The Forgotten Electrolyte in The Paediatric Intensive Care Unit

Objective To evaluate prevalence of hypophosphatemia and hyperphosphatemia and their association with outcome among critically ill children. Background Phosphorus is essential element for various biological functions but data about serum phosphorus level abnormalities among critically ill children are limited. Patients and methods Prospective observational study including children admitted into Pediatric Intensive Care Unit (PICU). Serum phosphorus was measured on admission, day4, day8, and day12. Pediatric Sequential Organ Failure Assessment (pSOFA) score was calculated on admission. Hypophosphatemia and hyperphosphatemia risk factors were determined. Results Hypophosphatemia and hyperphosphatemia were generally non-severe. Hypophosphatemic patients had higher frequency of sepsis on admission compared with normophosphatemic patients (36.2% vs. 12.5%, p=0.019). Frequency of steroid use was higher among hypophosphatemic children (27.7% vs. 6.3%, p=0.017). Hypophosphatemia was associated with longer PICU stay (p=0.028) and hospitalacquired infections (p=0.022). pSOFA and frequencies of both sepsis and elevated serum creatinine were significantly higher among hyperphosphatemic compared with normophosphatemic patients. Hyperphosphatemia was associated with higher mechanical ventilation rate (p=0.018). No significant difference in mortality rate was found between hypophosphatemic, hyperphosphatemic, and normophosphatemic patients. However, phosphorus level on day8 was lower among non-survivors [median (interquartile range): 3.2 (2.3–4.7) vs. 3.9 (3.4–5.2), p=0.046]. Conclusion Phosphorus abnormalities, particularly hypophosphatemia, are common among critically ill children. Hyperphosphatemia was more likely to be found among patients with renal dysfunction, sepsis, and higher pSOFA score. Hypophosphatemia was associated with longer PICU stay, hospital-acquired infections, higher mechanical ventilation rate and pSOFA score.