Chronic management
Goals
The goals for long-term management of patients with a
UCD are to achieve normal growth and development,
to normalize plasma concentrations of ammonia, to
prevent protein deficiency by administering essential and conditionally EAAs, and to prevent other nutrient
deficiencies, including mineral and vitamin deficiencies.
It is not uncommon to observe families failing to
feed all the protein prescribed, because they are
concerned about elevated ammonia concentrations.
This is another reason why regular monitoring of the
patient_s nutritional status is important.
A detailed record of the diet of each patient is
critical to ensure that nutrient intake recommendations,
especially for protein, are achieved. If the
recommended protein intake is not reached or if
blood ammonia and amino acid concentrations are
abnormal, the dose of N-scavenging drug may need to
be titrated up to the maximum age-appropriate dose
for the patient. Such titration will allow maximum
protein tolerance for attaining the recommended
intake of protein for proper growth and development
while avoiding hyperammonaemia. Because of the
complexity of the combined dietary and drug treatment,
clear coordination between the physician prescribing
the drug and the dietitian calculating the diet
prescription is necessary. Titration of the drug
requires tandem monitoring of plasma ammonia and
amino acid concentrations with dietary protein and
energy intake.
Nutrient intakes from three-day diet diaries can be
calculated using appropriate software (e.g. Amino Acid
Analyzer) prior to each blood test. A nutrition diary
may reveal unbalanced protein intake during the day;
for example, 15 g of protein may have been consumed at
a single meal, while the remaining 10 g was given
between the other two meals. Because N-scavenging
drugs are typically prescribed in three to four equal
doses throughout the day, we try to discourage large
protein loads. It may be possible, however, to balance
the doses of N-scavenging drug with the patient_s eating
pattern to avoid fluctuation in nitrogen loads and
ultimately to prevent hyperammonaemia.
Nutritional adequacy
While few data are available on the growth of infants
and children with a UCD, what is known is that
historically not enough protein was prescribed to these
children to support normal growth. With the proper
incorporation of EAA mixtures, however, achievement
of adequate dietary protein intake is possible.
Acosta and colleagues (2005) recently described a
6-month, uncontrolled outpatient study of 17 infants
and toddlers with a UCD who were fed Cyclinex-1.
Length and weight z-scores rose significantly, and
protein status improved; further, three patients were
stunted and two were wasted at the beginning of the study, whereas only one patient remained stunted and
wasted by the completion of the study. In addition,
clinical data from our patients reveal that it is possible
to give the recommended amount of protein when
titrated appropriately with N-scavenging drugs. Recommended
daily intakes of protein, energy, and fluids
for infants, children, and adults with a UCD, along
with clinical data, are given in Table 2.