Assessing the efficacy of intravenous nutrition in general surgical patients: dynamic nutritional assessment with plasma proteins.

We have compared the direction of changes in four plasma transport proteins measured weekly with the direction of nitrogen balance in general surgical patients receiving intravenous nutrition (IVN). Fifty four patients had IVN for 2 weeks, and 15 had IVN for 3 or 4 weeks. Change in plasma prealbumin followed the direction of nitrogen balance in both weeks of IVN in 39 of 54 of the former group, whereas none of the other plasma proteins achieved 50% accuracy. A weekly rise in plasma prealbumin had a sensitivity of 88%, specificity of 70%, positive predictive value of 93%, and negative predictive value of 56% in detecting positive nitrogen balance. Results in the patients who received 3 or 4 weeks of IVN showed an improvement in negative predictive value to 79%. None of the other plasma proteins performed as well. Twelve patients suffered a major complication of their disease or died, following their course of IVN. Nitrogen balance was the best prognostic indicator of these patients, whereas a fall in prealbumin was the best of the plasma proteins, with a sensitivity of 67%, specificity of 79%, positive predictive value of 40%, and negative predictive value of 92% in determining the incidence of complications. Prealbumin was the most suitable plasma protein for use as a dynamic index of nutritional progress in the type of patient seen in this study.