title: Estimation of nitrogen excretion based on abbreviated urinary collections in patients on continuous parenteral nutrition.
abstract: The physiologic response to stress can create a net loss of nitrogen, which is indicative of a catabolic state. Nitrogen balance has been demonstrated to be a useful clinical indicator of a patient's catabolic state and the effectiveness of parenteral nutrition, but requires an estimate of total urinary nitrogen excretion. The standard method for determining total urinary nitrogen excretion is 24-hour urinary urea nitrogen excretion. Unfortunately, the 24-hour urine collection is inconvenient, cumbersome, sometimes inaccurate, and induces a lag in response time to changes in therapy. Although shorter collection times have been proposed, the validity of shorter-timed determinations remains open to question. To evaluate the estimation of 24-hour urine urea excretion from shorter-timed determinations, the urinary urea nitrogen excretion of 4-, 8-, and 12-hour durations was regressed against the 24-hour collection in 56 critically ill adult patients. The 12-hour determination provided satisfactory estimates of the 24-hour nitrogen excretion, but the 4-hour and 8-hour determinations did not. Thus, two times the 12-hour urine urea nitrogen determination can be substituted for the 24-hour determination in calculating nitrogen balance. A 12-hour determination can provide a more rapid turnaround of biochemical analysis, allow more timely nutritional intervention, decrease nursing time, and reduce the frequency of inaccurate or lost specimens.
authors.affiliation: Nutrition Support Service, Allentown Hospital-Lehigh Valley Hospital, PA 18105.
authors.forename: J A
authors.initials: JA
authors.lastname: Candio
authors.forename: M J
authors.initials: MJ
authors.lastname: Hoffman
authors.forename: J F
authors.initials: JF
authors.lastname: Lucke
mesh_terms: D006801:Humans; D009584:Nitrogen / Q000652:urine*; D010289:Parenteral Nutrition, Total; D012044:Regression Analysis; D013997:Time Factors
chemical_list: D009584:Nitrogen