LONGITUDINAL CHANGES OF BIOCHEMICAL PARAMETERS IN MUSCLE DURING CRITICAL ILLNESS

The study was undertaken to characterize the time course of biochemica l parameters in skeletal muscle during critical illness to gain inform ation for the design of a suitable protocol for interventional studies using metabolic or nutritional manipulation. Critically ill patients in our intensive care unit ([ICU] N = 9) were investigated on two sepa rate sampling occasions with percutaneous muscle biopsies for determin ation of protein, nucleic acids, free amino acids, energy-rich phospha tes, fat, water, and electrolytes. The first biopsy specimen was taken 3 to 11 days after admission and the second biopsy specimen 3 to 7 da ys later. Protein concentration, expressed as alkali-soluble protein ( ASP)/DNA, decreased by 12% (P <.02) between the two biopsies. The tota l free amino acid content was only 50% of normal, but remained unalter ed over time. In particular, the concentration of glutamine remained l ow, approximately 25% of normal, In contrast, branched chain amino aci d (BCAA) increased by 25% (P <.05) and phenylalanine by 55% (P <.05) b etween biopsies. The fat content related to fat-free solid (FFS) incre ased by 130% (P <.001) between the two biopsies. Muscle water did not change during the study period, The extracellular portion was double t he normal value when related to FFS. Intracellular water, on the other hand, was outside the 95% confidence interval for normal values in th e second biopsy. The concentrations of adenosine triphosphate (ATP), c reatine, phosphocreatine, and the phosphorylated fraction of total cre atine remained at the same level between the two biopsies. We conclude that in critically ill patients, there is a decrease in protein conte nt over time and increases in BCAA, phenylalanine, and fat content, wh ile the low glutamine level and high extracellular water content remai n unaltered. The temporal alterations were well characterized after a 5-day study period. Copyright (C) 1997 by W.B. Saunders Company.