Treatment of hypophosphataemia in critically ill patients with a two day dosing regimen

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Introduction

Standard phosphate replacement regimens [1,2] are only 21–30% effective at correcting serum concentrations in severely hypophosphataemic critically ill patients, with 60–85% of patients redeveloping hypophosphataemia. We evaluated a two day regimen employing a rapid infusion rate.

Method

Fifty-two intensive care patients developing hypophosphataemia (<0.8 mmol/l) were evaluated. Intravenous phosphate doses on days 1 and 2 were based on the morning serum phosphate concentration: 0.8–0.6 mmol/l: 20 mmol and 20 mmol, 0.6–0.4 mmol/l: 40 mmol and 20 mmol, <0.4 mmol/l: 50 mmol and 20 mmol. Sodium phosphate (0.1 mmol/ml) was infused at 10 mmol/h. Serum phosphate and ionised calcium concentrations and calcium phosphate product were determined pre-infusion, immediately post-infusion and 6 h post-infusion for each dose and after 24 h. Twenty-two patients were receiving CRRT.

Results

See Table 1.

Only seven calcium phosphate product values were slightly raised (range: 4.9–5.7 mmol²/l²). Twenty-two patients had ionised calcium concentrations of ≤ 1.05 mmol/l on occasions during the regimen but the extent of the hypocalcaemia was mild (mean [SD] ionised Ca: 0.99 (0.07) range: 0.68-1.05 mmol/l [n=50]) and usually transient. Furthermore the degree of change in ionised calcium concentrations from pre-treatment values for all patients was not significant (see Table 1). No clinical evidence of hypocalcaemia was noted.

Conclusion

The two day intravenous phosphate regimen described is safe and highly effective at correcting hypophosphataemia in critically ill patients.

Table 1