Clinical Research Comparison of Urine Urea Nitrogen Collection Times in Critically Ill Patients

ABSTRACT: Twenty-four-hour urine urea nitrogen (UUN) collections are used to assess nitrogen loss in critically ill patients but are often difficult to obtain accurately. This prospective study compared 6- and 12-hour UUN collections with 24-hour UUN collections in critically ill patients receiving continuous nutrition sup-port. ICU patients admitted from September 1999 through January 2003 who had UUN collections as part of routine care were recruited into the study. Patients were not receiving oral diets, were receiving continuous paren-teral or enteral nutrition, and had indwelling urinary catheters. We excluded patients with hepatic or renal failure. Urine samples were collected every 6 hours start-ing at 6:00 AM and kept refrigerated until the 24-hour collection was complete. Samples were analyzed using a