Noninvasive, real-time monitoring of renal function during critical care.

The inadequacy of the current techniques to monitor renal function has been the most important limitation for determining the appropriateness of a particular form of therapy in acute renal failure. The objective of this study was to determine the advantage offered by a new method of accurate, noninvasive, and real-time monitoring of renal function during the critical care of patients. A radiation detector attached to a miniature data logger was used to monitor the clearance of the glomerular filtration agent 99mTc-diethylene triamine pentaacetic acid from the extracellular space in 20 patients admitted into an intensive care unit. The rate constant for this clearance was calculated online from 5-min epoch lengths of activity versus time. Changes in this constant were compared with changes in plasma creatinine and timed urine output. The results showed that the ambulatory renal monitor could accurately measure rapid changes in renal function during the critical care of patients who are at risk of acute renal failure with a resolution time of 5 to 10 min. The sensitivity and specificity of the technique are also superior to plasma creatinine and urine output because it can detect minimal and transient changes in renal function that otherwise may have gone undetected by these parameters. This unique approach should allow for the immediate institution and/or adjustment of the appropriate therapeutic procedure to preserve or improve the renal function.