Changes in extracellular sodium content after elective abdominal vascular surgery.

ABSTRACT

To investigate the possible occurrence of extra- to intracellular sodium shift in elective surgery, whole-body extracellular sodium mass/1.73 m2 was determined as the product of plasma sodium concentration and the volume of distribution of polyfructosan-S/1.73 m2 in 53 patients before abdominal aortic surgery and on the first and fourth postoperative days. The patients were divided into four groups, receiving stepwise increasing amounts of sodium. After surgery the extracellular sodium mass was lower than expected from the sum of preoperative value and cumulative sodium balance/1.73 m2. This deficit in extracellular sodium mass showed linear correlation with the sodium balance on postoperative day 1. On day 4 the mean deficits in extracellular sodium mass ranged from 227 to 291 mmol/1.73 m2 in the four groups, and the corresponding cumulative sodium balances from 179 to 528 mmol/1.73 m2. Net shift of sodium into the cells may explain the extracellular sodium deficit.