Hypophosphatemia on the intensive care unit: individualized phosphate replacement based on serum levels and distribution volume

Abstract

Background: Hypophosphatemia occurs in about 25% of patients admitted to the intensive care unit. To date, a safe and validated phosphate replacement protocol is not available.

Objective: To evaluate an individualized phosphate replacement regimen.

Design: Fifty consecutive intensive care unit patients with a serum phosphate level<0.6 mmol/L were treated with sodium-potassium-phosphate intravenously at a rate of 10 mmol/h. The dose was calculated according to the following equation: Phosphate dose in mmol=0.5×Body Weight×(1.25-[serum Phosphate]). Phosphate levels were measured immediately upon completion of the infusion, as well as the next morning at 8 am.

Results: Post-infusion phosphate levels were >0.6 mmol/L in 98% of the patients. Hyperphosphatemia, hyperkalemia or a decrease in serum calcium were not observed. In about a third of patients serum phosphate decreased to <0.6 mmol/L within the next 24 hours after infusion. The phosphate distribution volume calculated from the results of infusion and corrected for renal phosphate loss during the infusion period was 0.51 L/kg (95% CI 0.42-0.61 L/kg).

Conclusion: This study shows that phosphate replacement with dose calculation based on serum phosphate levels and a Vd of 0.5 L/kg is effective and safe.

Keywords: Hypophosphatemia; ICU; Phosphate replacement.