title: 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 support. 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 parenteral or enteral nutrition, and had indwelling urinary catheters. We excluded patients with hepatic or renal failure. Urine samples were collected every 6 hours starting at 6:00 am and kept refrigerated until the 24-hour collection was complete. Samples were analyzed using an automated urease enzymatic reaction. Samples were multiplied by a factor of 4 (6-hour samples) or 2 (12-hour samples) to estimate 24-hour totals and then compared with actual 24-hour totals. Twenty-four patients (18 men) completed the study; 21 patients had 6-hour samples (84 samples), and 24 patients had 12-hour samples (24 samples). Estimated 24-hour UUN from 6-hour (14.7-15.7 g/d) and 12-hour (15.2 g/d) samples did not differ significantly (p > .5) from actual 24-hour totals (15.1 g/d). Shortened UUN collection times may be used to estimate 24-hour nitrogen losses in critically ill patients receiving continuous nutrition support.
authors.affiliation: Nutrition Care Service, University of Utah Hospital, 50 N. Medical Drive, Salt Lake City, UT 84132, USA. caran.graves@hsc.utah.edu
authors.forename: Caran
authors.initials: C
authors.lastname: Graves
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Saffle
authors.forename: Stephen
authors.initials: S
authors.lastname: Morris
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D003422:Critical Care; D016638:Critical Illness / Q000628:therapy; D004750:Enteral Nutrition; D005260:Female; D006801:Humans; D007362:Intensive Care Units; D007700:Kinetics; D008297:Male; D008875:Middle Aged; D009584:Nitrogen / Q000652:urine*; D010288:Parenteral Nutrition; D011446:Prospective Studies; D013997:Time Factors; D014508:Urea / Q000652:urine*
chemical_list: D014508:Urea; D009584:Nitrogen