Metabolic and thermogenic response to continuous and cyclic total parenteral nutrition in traumatised and infected patients

16 traumatised or infected patients on mechanical ventilation were randomised to continuous TPN or to cyclic TPN after a 24-h period of glucose infusion (1.25 kJ x kg BW(-1) x h(-1)). Energy supply was equivalent to 1.3 x baseline energy expenditure. Glucose, fat and amino acids were administered at a constant rate over 24 h in the continuous TPN group and over 12 h, followed by glucose (1.25 kJ x kg BW(-1) x h(-1)), in the cyclic TPN group. Nutrient-induced thermogenesis was lower during continuous than during cyclic TPN (5 +/- 4 vs. 12 +/- 7%, mean +/- SD, p < 0.05), as was the increase in CO(2) elimination (13 +/- 11 vs. 30 +/- 7%, respectively, p < 0.01). Energy balance was more positive during continuous TPN. In both groups, energy expenditure reached a plateau during the first 12 h of TPN infusion. The lower nutrient-induced thermogenesis and more positive energy balance, indicates a more efficient utilisation of nutrients during continuous than during cyclic TPN. The lower CO(2) production during continuous TPN, may be advantageous when respiratory function is compromised. The plateau in energy expenditure in response to TPN infusion may be useful as a guideline for nutritional therapy.