Changes in body protein, body potassium, and lean body mass during total parenteral nutrition

Lean body mass by anthropometry (AMLBM), total body potassium (TBK), and total body nitrogen (TBN) by prompt gamma analysis, are reported in 38 malnourished patients during total parenteral nutrition. Over long periods (greater than 2 months) TBN increased 32% while AMLBM and TBK rose only by 9.2 and 9.5%, respectively. Changes in AMLBM and in K were significantly correlated, but changes in nitrogen were not correlated with either. From short-term studies, the same conclusions can be obtained; although there are changes in lean body mass and in potassium, there is no correlation with such changes in nitrogen. With repletion, changes in body protein are not necessarily related to changes in AMLBM or to TBK: the latter two reflecting total and intracellular water, respectively, but not protein content.