title: The estimation of 24-hour urine urea nitrogen excretion from urine collections of shorter duration in continuously alimented patients.
abstract: Urine urea nitrogen excreted in 24 hr is used to estimate nitrogen balance in patients. Normal diurnal variation of urea excretion may be less pronounced in patients alimented continuously, and a urine collection of shorter duration may be representative of the 24-hr excretion. Five stabilized trauma center patients on continuous enteral or parenteral alimentation were studied with six consecutive 4-hr urine collections analyzed for urine urea nitrogen content. Excretion rates for various lengths of urine collection were compared with the 24-hr excretion rate. Urine collections spanning 4 or 8 hr frequently exceeded an error of 10% in predicting 24-hr urea nitrogen excretion, while collections of 12 hr or more had small errors. A comparison of three consecutive 8-hr collections was suggestive of diurnal variation existing under these conditions.
mesh_terms: D001806:Blood Urea Nitrogen; D002940:Circadian Rhythm; D004750:Enteral Nutrition; D006801:Humans; D010288:Parenteral Nutrition; D010289:Parenteral Nutrition, Total; D013048:Specimen Handling