Hypophosphatemia during postoperative glucose infusion.

The study was undertaken to elucidate if hemodilution is a cause of the fall in serum concentration of inorganic phosphate during postoperative infusion of glucose, and if the fall in serum phosphate is related to the tonicity of the solutions and/or the rate of infusion. The study comprised 48 patients in five subgroups. Hemodilution was clearly demonstrated not to be responsible for any of the fall in serum phosphate. The size of this fall was independent of whether the administered solution was isotonic or hypertonic. Reducing the infusion rate from 0.30 to 0.15 g glucose/kg/hour did not reduce the fall in serum phosphate. It was therefore concluded that whenever glucose solutions are administered in the postoperative period, a fall in serum phosphate of c. 0.25-0.35 mmol/l is to be expected.