Phosphate replacement in the critically ill: potential implications for military patients

Severe hypophosphataemia in the intensive care unit (ICU) setting has been widely associated with adverse clinical outcomes across multiple organ systems, as well as increased mortality. However, the clinical significance of mild or moderate hypophosphataemia remains uncertain. This can lead to heterogeneous phosphate replacement protocols across different institutions. The aim of this study was to assess the significance of mild and moderate hypophosphataemia on clinical outcomes across several organ systems.

All patients over a 3-week period in our ICU were retrospectively analysed with admission serum phosphate compared with subsequent clinical outcomes after admission. Low serum phosphate (0.3-1.0 mmol/L), according to local protocol, was compared with normal serum phosphate (>1.0 mmol/L).

Of the 72 patients admitted to intensive therapy unit during this period, 14/72 (19%) had phosphate levels deemed low (<1.0 mmol/L) and received phosphate supplementation. No significant difference was found between groups in terms of cardiac arrhythmias (p=0.55), capillary blood glucose (p=0.08) and serum lactate (p=0.32). Low phosphate (0.3-1.0 mmol/L) was not associated with increased likelihood of requiring ventilation. Platelet count was significantly lower in the low phosphate group (p=0.008).

In our study, mild and moderate hypophosphataemia was not associated with adverse clinical outcome across most organ systems analysed. Given the current evidence and results of this study, we would suggest that there is a trend towards over-replacement of phosphate, representing a potential clinical safety issue as well as clear financial implications.