Proefschrift Kerklaan

Chapter 8

In children with tube leak and children on HFO and ECMO, measurement of expiratory VCO 2 is inherently meaningless. In children with a supplied oxygen level of more than 60%, validation is restricted by the limitations of IC, so other validation techniques (e.g. double-labelled water) can be used to study this method in these children. Although limited to a selected group of patients, clinical implementation of the ventilator- derived method will provide a more reliable determination of REE. Continuous provision of values will help to visualise the course of REE values during PICU stay and thereby allow early detection of changes in REE, as can be expected in septic neonates, children with fever and neonates after surgery (Chapter 1). In order to do so, VCO 2 values from the ventilator need to be automatically registered by the patient data management system and recalculated into REE based on the previously validated metabolic equation 13 . Measurements with more than 10% fluctuation in VCO 2 will need to be discarded automatically. Based on the remaining steady- state VCO 2 measurements, mean REE values can be provided to the attending clinicians to guide nutritional therapy. Although repeated measurements of REE improved outcome in geriatric patients following surgery 14 and showed a trend towards improved hospital mortality inmechanically ventilated adults 15 , a single determination of REE is sufficient to guide nutrition in the majority of critically ill children. Repeated measurements may be useful only in children with suspected metabolic alterations or malnutrition 16 . Use of REE to guide nutritional support In contrast with the paediatric guidelines, results from recent large RCTs in the adult ICU question the need for matching REE by the enteral route during the acute phase of critical illness. No differences in mortality or other clinical outcome measures were found between permissive underfeeding and planned delivery of a full amount of nonprotein calories in critically ill adults 17,18 . Moreover, no faster recovery was observed in critically ill adults receiving more than 30% of the caloric goal by the enteral route compared to adults receiving less than 30% during the first week of the adult version of the PEPaNIC trial (EPaNIC trial) 19 . Finally, endogenous energy production during the acute phase of critical illness limits the use of exogenous provided energy. The optimal amount of required energy to supplement this endogenous production cannot be measured by IC. Therefore, emphasis on measurement of REE to guide nutritional therapy is likely to shift to subsequent phases of critical illness, aimed at restoration of lean body mass while synthesis of excess fat mass should be avoided. This is already practiced in the NICU, where longitudinal IC measurements are mainly used to guarantee appropriate growth for this population 20,21 . However, these phases are characterised by weaning or even absence of ventilatory support (Chapter 1), limiting the use of IC or ventilator-derived values. Moreover, independently of the phase, application of IC in preterm infants is extremely challenging and therefore hardly practiced outside research settings. In absence of REE measurements, early initiation of nutrition is aspired in all preterm infants (Chapter 5), irrespective of severity of illness 22 .

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