Is parenteral phosphate replacement in the intensive care unit safe?

Area of Science:

• Critical Care Medicine
• Nephrology
• Clinical Chemistry

Background:

• Hypophosphatemia is common in intensive care units (ICUs), particularly with refeeding and continuous renal replacement therapy (CRRT).
• Optimal intravenous phosphate supplementation protocols in general ICUs remain unclear, with recent concerns about acute kidney injury.
• Auditing current practices is crucial to refine phosphate administration guidelines.

Purpose of the Study:

• To audit the practice of parenteral phosphate administration in a general ICU setting.
• To evaluate the efficacy and safety of 20 mmol phosphate infusions.
• To assess the impact on serum phosphate, renal function, and ionized calcium levels.

Main Methods:

• Prospective audit of 20 mmol parenteral phosphate infusions in 58 adult ICU patients.
• Data collected included patient demographics, infusion duration, CRRT status, and serum levels of phosphate, urea, creatinine, and electrolytes.
• Serum phosphate and ionized calcium levels were measured before and after phosphate administration.

Main Results:

• 63.8% of patients were hypophosphatemic (<0.87 mmol/L) before infusion; phosphate levels increased significantly (0.79 to 1.07 mmol/L, P < 0.001).
• Phosphate infusion corrected hypophosphatemia in 67.7% of indicated cases, with no adverse effects on renal function (urea, creatinine).
• Two patients developed hyperphosphatemia (>1.45 mmol/L), and arterial ionized calcium decreased significantly (1.15 to 1.13 mmol/L, P < 0.01).

Conclusions:

• Parenteral phosphate infusion effectively corrected hypophosphatemia in most patients without impairing renal function.
• Approximately one-third of infusions were administered to non-hypophosphatemic patients, indicating potential overuse.
• The observed decrease in ionized calcium suggests potential calcium-phosphate complex formation and soft tissue deposition risk, warranting careful monitoring.