Hypophosphataemia and its consequences in patients following open heart surgery

Plasma phosphate concentration (Pi), red cell 2,3-diphosphoglycerate (2,3-DPG) and adenosine triphosphate (ATP) concentrations were measured pre-operatively and at intervals after operation for 30 h in twelve patients (nine males and three females, 44--61 years of age), who underwent open heart surgery. All patients received intravenous injections of glucose, insulin and potassium at regular intervals. In all patients studied Pi decreased within hours following operation, remained low for about 6 h and pre-operative values were reached by 18 h. Pi decreased from 1.04 +/- 0.6 mmol/litre (mean +/- s.e. mean) to 0.32 +/- 0.06 mmol/litre. This fall in Pi was accompanied by a small but significant fall in 2,3-DPG (from 14.8 +/- 0.60 mumol/g Hb to 11.2 +/- 0.60 mumol/g Hb). ATP concentration did not change significantly. The calculated P50 (partial pressure of oxygen at which there was 50% saturation of haemoglobin) decreased by 1.2 mmHg. The regular fall in Pi which is probably due to the glucose-insulin-potassium injections was of short duration and had very little effect on red cell 2,3-DPG and ATP.