Plasma ammonia
concentrations are controlled by dialysis and/or the use
of the intravenous N-scavenging drug Ammonul (sodium
phenylacetate and sodium benzoate, 10%/10%)
in the USA. In Europe, intravenous preparations are
not licensed, but they are available.
In the next phase, oral nutrition is restarted with the
addition of a module of high-quality protein. Plasma
ammonia concentrations are controlled using the oral
N-scavenging medication. Depending on the plasma
concentrations of ammonia and amino acids and the
activity of the gastrointestinal tract, the feeds may be
started at a 25–50% concentration of full protein
requirements (e.g. if the full protein requirement for
an infant is 1.4 g protein/kg body weight/day, then the
starting feeds could range between 0.35 and 0.70 g
protein/kg body weight/day), since it is important not
to wait more than 48–72 h before reintroducing the
feeds. Supplementation with the conditionally EAAs,
as well as with L-arginine and/or L-citrulline, becomes
essential at this time. Oral L-arginine and L-citrulline
are both available, whereas only L-arginine is available
in intravenous form. If an older patient becomes
nauseated, the use of ondansetron (Zofran) and other
antinausea medications may help improve the tolerance
of enteral feeds. Adequate energy intake must be
ensured throughout this phase.