19 / 208
Introduction
17
1
Despite the improvement of neuro-endocrine, immunologic and metabolic status, clinical
parameters, such as weight and functional status (measured with the Functional Status
Scale in medical and cardiac critically ill children), are known to be worse at discharge
71,87
.
Profound muscle weakness, due to muscle wasting and critical illness myopathy as observed
with prolonged duration of the stable phase, contributes to morbidity and adverse outcome
in the ICU and PICU
88,89
and may even cause long-term functional disability beyond hospital
discharge
89
.
Nutrient administration in the stable and recovery phase
The focus of nutritional therapy during the stable and recovery phase should be aimed at
restoration of lean body mass whereas synthesis of excess fat mass is to be avoided. To prevent
muscle weakness, the duration of immobilisation should be reduced as much as possible
90
. A
combination of optimal nutritional support and physical exercise/mobilisation appears to be a
logical intervention, but no such studies have been performed in critically ill patients
91
.
A recent systematic review and a single centre study in mechanically ventilated children,
calculated a minimum intake of respectively 57 and 58 kcal/kg/day to achieve a positive
nitrogenbalance
92,93
. Inboth studies, a protein intake of 1.5 g/kg/daywas required to equilibrate
nitrogen balance, reflecting a protein-energy ratio of around 10 energy%protein. Since these
two studies made no distinction between the phases of critical illness, it remains unclear if
this minimal intake should already be provided in the acute phase or should be reserved for
subsequent phases. Because nutritional intake during the stable and recovery phase is not
only aimed at equilibrating nitrogen balance, but also at enabling recovery, growth and catch-
up growth, caloric intake during these phases needs to be inclined from the above mentioned
minimum intake
94,95
. Indeed, higher caloric and protein intake (with a sufficient protein-energy
ratio) via the enteral route are associated with higher 60-day survival
2,96
, asking for a more
aggressive feeding approach than in the acute phase.
Energy expenditure throughout the course of critical illness
Energy requirements for critically ill children vary between individuals and also between
the phases of critical illness. REE is one component of total energy expenditure (TEE), the
other components are physical activity, the thermic effect of food, and the energy cost of
growth. Currently, optimal caloric intake in critically ill children is frequently defined as 90-
110% of REE
1,97-99
, with an intake below or above this range indicating underfeeding and
overfeeding, respectively. In order to prevent the
detrimental effects associated with these
two types of malnutrition, REE is advised to guide nutritional therapy throughout the course
of illness
2,4,100-102
. Ideally, REE should be measured using indirect calorimetry (IC). With IC, a
metabolic monitor is attached to the ventilator circuit of the child to derive REE from minute-
to-minute measurements of oxygen consumption (VO
2
) and carbon dioxide production
(VCO
2
)
103
. Alternatively, a canopy mode can be used for spontaneously breathing children. The