Urea and electrolyte measurement in pre-operative surgical patients.

In a prospective study of 1062 patients who presented for routine and emergency surgical procedures, the frequency of urea and electrolyte measurement was determined. In addition, the incidence of abnormal urea and electrolyte measurements were recorded. It was found that these abnormal values were most frequent in the paediatric population (though they they had the fewest urea and electrolyte measurements performed) and in the over 60s. The American Society of Anesthesiologists' grade was found to be a useful predictor as to whether the urea and electrolyte measurement could be expected to be abnormal. It is suggested that American Society of Anesthesiologists' Grade I patients do not require routine urea and electrolyte measurements whilst those in grades 3, 4 and 5 and those on diuretics do.