Is on-line monitoring of renal function possible?

Twenty patients who had undergone open heart surgery were studied in order to determine whether measurement of the combined urinary sodium and potassium concentration can be used to monitor renal function. The clearances of creatinine and the free water demonstrated a significant statistical correlation with the combined urinary sodium and potassium concentration. We conclude that measurement of the combined sodium and potassium concentration in the urine can be used as an indicator of renal function. Thus, measurement of the electrical conductivity in the urine might be suitable as an on-line monitor of renal function during surgery or in the intensive care unit.