Burge J C, Choban P, McKnight T, Kyler M K, Flancbaum L
School of Allied Medical Professions, Ohio State University, Columbus.
JPEN J Parenter Enteral Nutr. 1993 Nov-Dec;17(6):529-31. doi: 10.1177/0148607193017006529.
Nitrogen balance has historically been estimated by using urinary urea nitrogen (UUN) multiplied by a factor of 1.25 to account for nonurea nitrogen present in the urine. Recently, the reliability of UUN as an estimate of nitrogen losses has been questioned and the use of total urinary nitrogen (TUN) has been proposed as a more accurate measure of urinary nitrogen losses. However, analysis of TUN losses is not readily available in many hospital laboratories. Because ammonia is the major fluctuating component of urinary nonurea nitrogen and equipment to measure urinary ammonia is available in most hospitals, this study was undertaken to determine whether urinary ammonia plus UUN provides a clinically useful approximation of TUN. Twenty-four-hour urine samples acidified with boric acid during collection from 20 patients (a total of 42 samples) receiving total parenteral nutrition were analyzed for UUN, ammonia, and TUN. The UUN values ranged from 4.9 to 42.4 g/24 h. The mean difference between TUN and UUN was 1.99 +/- 0.27 g/24 h. The mean difference between TUN and UUN plus ammonia was 0.78 +/- 0.27 g/24 h. Thus, UUN alone accounted for 90% and the combination of UUN plus urinary ammonia accounted for 96% of TUN. These data suggest that UUN plus ammonia does provide a greater level of reliability as an estimate of TUN than UUN alone.
传统上，氮平衡是通过将尿尿素氮（UUN）乘以1.25来估算的，以计入尿液中存在的非尿素氮。最近，UUN作为氮损失估算指标的可靠性受到质疑，有人提出使用总尿氮（TUN）作为更准确的尿氮损失测量指标。然而，许多医院实验室无法轻易进行TUN损失分析。由于氨是尿中非尿素氮的主要波动成分，且大多数医院都有测量尿氨的设备，因此本研究旨在确定尿氨加UUN是否能在临床上有效近似TUN。对20名接受全胃肠外营养患者（共42份样本）收集的用硼酸酸化的24小时尿样进行UUN、氨和TUN分析。UUN值范围为4.9至42.4 g/24小时。TUN与UUN之间的平均差值为1.99±0.27 g/24小时。TUN与UUN加氨之间的平均差值为0.78±0.27 g/24小时。因此，单独的UUN占TUN的90%，UUN加尿氨的组合占TUN的96%。这些数据表明，与单独的UUN相比，UUN加氨作为TUN的估算指标确实具有更高的可靠性。
