Both nitric oxide and cytokines are considered mediators of the acute-phase response in humans, and their early postoperative period plasma levels have been found to be of prognostic value. On the other hand, it has been suggested that the fatty emulsions used in total parenteral nutrition (TPN) may induce changes in macrophage function. In the present study we investigated the postoperative evolution of tumor necrosis factor-alpha (TNF-alpha), interleukin-1 (IL-1), interleukin-6 (IL-6), and nitrate/nitrite plasma levels under three different TPN regimens. Twenty-one patients diagnosed with upper digestive tract neoplasm, without preoperative TPN, and having undergone radical surgery, were randomly assigned to three groups: Group I, all nonprotein calories supplied by hypertonic glucose solution: Group II, 55% of the nonprotein calories supplied by glucose and 45% by 20% long-chain triacylglycerides emulsion (LCT) (Intralipid 20%, Kabi-Pharmacia); Group III, same as Group II, but a 20% emulsion of a mixture of medium-chain and long-chain triacylglycerides (MCT/LCT) (Lipofundina MCT/LCT 20%, B. Braun) was used instead of LCT. Blood samples were obtained on postoperative Days 1-5 and 10, 3 h after ending the lipid infusion. In all the three groups IL-1, IL-6, and TNF-alpha levels rose after surgery, peaking at Day 2, whereas NO2/NO3 levels had their peak at Day 3. Day-to-day comparison of plasma levels of cytokines and NO2/NO3 between the investigated groups did not show any statistical significance. Differences between group means were not found when the areas under the curve over the first 5 postoperative days were compared (1.72 +/- 0.25, Group I; 1.88 +/- 0.34, Group II; and 2.52 +/- 0.50, Group III, for TNF-alpha; 1.79 +/- 0.12, Group I; 1.92 +/- 0.18, Group II; and 1.50 +/- 0.12, Group III, for NO2/NO3). We conclude that the different parenteral nutrition regimens studied do not evoke alterations in cytokine and NO2 + NO3 levels in the patient groups investigated in this study.