STABLE ISOTOPIC QUANTITATION OF PROTEIN-METABOLISM AND ENERGY-EXPENDITURE IN NEONATES ON-EXTRACORPOREAL AND POST-EXTRACORPOREAL LIFE-SUPPORT

It is generally assumed that extracarporeal life support (ECLS) provid es a metabolic ''rest state'' by replacing approximately 80% of cardio pulmonary work. The aim of this study was to precisely quantify neonat al energy expenditure (EE) and whole-body protein metabolism on (durin g) and post (after) venoarterial ECLS using stable isotope tracer tech niques. Nine parenterally fed neonates on-ECLS were studied at 7.8 +/- 1.0 days of life (mean +/- SE), five of which were studied post-ECLS on 27.0 +/- 5.4 days of life, EE and whole-body protein metabolism wer e quantified using a primed, continuous infusion of L-[1-C-13]leucine and (NaHCO3)-C-13. The neonates studied on- and post-ECLS had similar rates of endogenous leucine flux (370 +/- 46 mu mol/kg/h v 339 +/- 76 mu mol/kg/h), leucine oxidation (161 +/- 22 mu mol/kg/h v 121 +/- 25 m u mol/kg/h), nonoxidative disposal rates of leucine (313 +/- 37 mu mol /kg/h v 331 +/- 75 mu mol/kg/h), net protein balance (-2.31 +/- 0.8 g/ kg/d v -0.33 +/- 1.1 g/kg/d), and EE (88.6 +/- 7.7 kcal/kg/d v 84.3 +/ - 9.2 kcal/kg/d). These results demonstrate that neonates on-ECLS are in hypermetabolic and protein catabolic states that continue in the po st-ECLS phase. The authors conclude that ECLS does not provide a metab olic ''rest state.'' Copyright (C) 1997 by W.B. Saunders Company.