Nutritional Support and the Surgical Patient

Yvonne Huckleberry


Am J Health Syst Pharm. 2004;61(7) 

In This Article

Monitoring NS Adequacy

Once NS has been initiated perioperatively, clinical and biochemical monitoring can be used to help gauge that calories and protein are sufficient to improve or maintain nutritional status. Clinical monitoring includes trends in weights (with consideration of fluid balance) and wound healing. Some of the most common biochemical monitoring variables have been described previously. These include albumin, prealbumin, and transferrin. In addition to visceral proteins, one of the most clinically useful tests for adequate protein is nitrogen balance; this assesses nitrogen intake versus nitrogen loss. Nitrogen intake is calculated from protein delivered (in grams) divided by 6.25. Nitrogen loss is calculated as the urea nitrogen from a 24-hour urine collection plus 3-5 g of insensible nitrogen losses. The goal for patients receiving NS is to achieve a positive nitrogen balance. As with visceral proteins, improvement in nitrogen balance may not be possible during the acute phase of critical illness. In addition, nitrogen-balance assessments can be skewed by unquantified protein losses (e.g., drainage from large wounds, protein-losing enteropathy) and renal dysfunction. These confounding issues can make the assessment of NS adequacy difficult for some patients.


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