Electrolytes in surgical patients: the effect of pre-operative starvation and environmental temperature

Serum sodium, potassium and chloride values were measured before and after pre-operative starvation and after premedication in healthy subjects under going routine surgery, during both temperate and hot weather. No significant change in serum electrolytes occurred during temperate weather either after starvation or after premedication. In hot weather, when the subjects were sweating, a rise in serum electrolytes occurred, indicating fluid deficit of about 1-8 litres after a mean period of starvation of 11 hours; premedication with atropine and diazepam in these subjects was followed by a significant decrease in the serum electrolytes from the previous raised level after pre-operative starvation.