Prediction of total urinary nitrogen from urea nitrogen for burned patients

Although many of the current nutrition assessment techniques are inappropriate for burned patients, we have found nitrogen balance to be a helpful measure of the effectiveness of nutrition therapy if it is used in conjunction with other measures of nutritional status. Many clinicians suggest that a 24-hour urinary urea nitrogen (UUN) measurement, in addition to a correction term of 2 to 4 gm nitrogen, will accurately represent all nitrogen losses (urinary non-urea nitrogen, fecal, integumental). However, since no burned patients were used in the development of that method, its use may not be appropriate for burned patients. As an alternative to total urinary nitrogen (TUN), which is costly and time consuming, we have developed a simple way to predict TUN from UUN, percent initial total body surface area burn, and age for pediatric and adult burned patients. We propose that nitrogen balance may then be determined from the predicted TUN by an equation showing that nitrogen balance equals daily nitrogen intake minus predicted TUN plus fecal and normal nitrogen loss.