NITROGEN-BALANCE DURING EXTRACORPOREAL MEMBRANE-OXYGENATION

Extracorporeal membrane oxygenation (ECMO) has been used as a support system for neonates with pulmonary failure since 1975. During ECMO, th ermal regulation, pulmonary gas exchange, and cardiac output can be pa rtially or nearly completely provided by the circuit. The presumed res ultant decrease in energy requirement has prompted the question of whe ther infants are in a catabolic or anabolic state of metaboblism while on ECMO. Directly measuring the metabolic rate in babies on ECMO is d ifficult. However, studying the nitrogen balance in these infants may suggest an answer. Nitrogen balance was studied in 21 neonates spannin g a single ECMO team's experience at two institutions. Children were s tudied at the Ochsner Clinic from 1986 to 1990 and at the University o f Chicago Wyler Children's Hospital from 1990 to the present. The infa nts received total parenteral nutrition (TPN) as their only nutritiona l source during the entire ECMO course. During this time, 24-h urine c ollections were analyzed for urine urea nitrogen (UUN). The daily nitr ogen balance was calculated by subtracting nitrogen output (estimated as the UUN) from nitrogen input (the measured amino acid content of th e intravenous feeding). Fecal losses were not included in the nitrogen output since the infants were not enterally fed and rarely had stools while on ECMO. The kilojoules (1 kilocalorie = 4.2 kilojoules) and pr otein provided by the parenteral nutrition varied. Nitrogen intake exc eeded nitrogen output by ECMO day 2 (the initial nitrogen balance dete rmination). Infants receiving as little as 0.4 g/kg protein and 168 kJ /kg daily remained in positive nitrogen balance.