Laboratory Data in nutrition assessment

25 hours625 nitrogen balance challenges urea nitrogen

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Unformatted text preview: adults gaining weight or recovering from illness or injury weight Nitrogen balance is negative during Nitrogen starvation, catabolism, PEM starvation, Nitrogen Balance Calculations • • • Nitrogen balance = nitrogen intake (g/24 Nitrogen hours) –(urinary nitrogen [g/24 hours) + 2 g/24 hours g/24 Use correction of 4 g/24 hours if urinary Use urea nitrogen is used urea Nitrogen intake = (grams protein/24 Nitrogen hours)/6.25 hours)/6.25 Nitrogen Balance Challenges • • • Urea nitrogen is highly variable as a Urea percent of total nitrogen excreted percent It is nearly impossible to capture an It accurate nitrogen intake for patients taking food po taking Most useful in evaluating the Most appropriateness of defined feedings, e.g. enteral and parenteral feedings enteral Visceral Proteins: Serum Albumin • • • • • • Reference range: 3.5-5.2 g/dl Abundant in serum, stable (half-life 3 weeks) Preserved in the presence of starvation Preserved (marasmus) (marasmus) Negative acute phase reactant (declines with the Negative inflammatory process) inflammatory Large extravascular pool (leaves and returns to Large the circulation, making levels difficult to interpret) interpret) Therefore, albumin is a mediocre indicator of Therefore, nutritional status, but a very good predictor of morbidity and mortality morbidity Visceral Proteins: Plasma Transferrin • • • • • Reference range: 200-400 mg/dl Half-life: 1 week Negative acute phase respondent Increases when iron stores are depleted Increases so affected by iron status as well as protein-energy status protein-energy Responds too slowly to be useful in an Responds acute setting acute Visceral Proteins: Transthyretin (Prealbumin) • • • • • Reference range: 19-43 mg/dl Half-life: 2 days Negative acute-phase reactant Zinc deficiency reduces levels Due to short half-life, it is useful in Due monitoring improvements in proteinmonitoring energy status if baseline value is obtained energy near the nadir as inflammatory response wanes wanes Visceral Proteins: Retinol-Binding Protein • • • • • Reference range: 2.1-6.4 mg/dl Half-life: 12 hours Negative acute-phase protein Unreliable when vitamin A (retinol) status Unreliable is compromised is Elevated in the presence of renal failure, Elevated regardless of PEM status regardless Visceral Proteins...
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