Utilization of d-methionine during total parenteral nutrition in postsurgical patients

Abstract

Utilization of intravenously administered d-methionine was measured in morbidly obese subjects fed parenterally after elective gastric bypass surgery. Five patients were infused with a 25% glucose—4.25% amino acid solution containing dl-methionine, and four were treated with a 25% glucose—3.5% amino acid solution containing only l-methionine. Mean (± SD) total daily methionine excretion was 0.06 ± 0.04 mmoles (of 28 ± 4 mmoles infused) in patients treated with the l-methionine containing solution, and was 15.2 ± 4.2 mmoles/day (of 45.2 ± 5 mmoles dl-isomer infused) in patients treated with the dl-methionine containing so.lution. In these latter patients, 90 to 98% of the excreted methionine was the d-isomer. The data indicate 64 ± 23% of infused d-methionine is excreted in the urine. Four patients excreted between 70 to 85% of infused d-methionine in the urine, but one patient excreted only 35 to 55%, suggesting better utilization. Plasma methionine levels were higher (9.9 ± 1.9 µmoles/100 ml) in patients infused with solutions containing dl-methionine than those infused with the l-methionine solution (4.5 ± 1.0 µmoles/100 ml). In the former case, 49% of plasma methionine was the d-isomer. The data indicate poor d-methionine utilization by postsurgical patients during total parenteral nutrition when given as dl-methionine in the presence of other amino acids and glucose.