Objective: To obtain objective information on the metabolic situation in critically sick children in intensive care units as a baseline for treating adverse metabolic conditions. Method: Indirect calorimetry by means of a Deltatrac II Datex/Engström apparatus in spontaneously breathing and artificially ventilated children. Department: Intensive care unit, Paediatric Clinic IPVZ, Thomayer Hospital, Prague. Patients: In the course of three years 409 examinations were made of 150 children aged 2 days to 18 years, incl. 21 with artificial pulmonary ventilation. Among these children a group of 71 children was selected regardless of age, severity of the condition and diagnosis where indirect calorimetry revealed an increased protein utilization (more than 20% ratio of REE) as energy substrate. This group was analyzed further as regards objective metabolic indicators which can be assessed by indirect calorimetry. Results: The criterion of serious catabolism is reduction of REE by more than 25% of the appropriate values and protein utilization exceeding 30% of the assessed REE. There were 31/71 (71%) such p atients in the authors’ group. In all metabolic intervention was attempted (branched amino acids as the main energy substrate in complete parenteral nutrition, temporary elimination of fats and restriction of non-protein sources of energy). In 22/31 the authors succeeded and a favourable metabolic situation was achieved. In nine patients they failed. Seven of the latter died (the mortality rate in the whole group suffering from catabolism was 8/71). Conclusion: Indirect calorimetry provides valid, non-invasive and immediate information on the metabolic situation of critically ill children under conditions of intensive care. It is important that the authors were able to define criteria of severe catabolism (REE lower than BMR by more than 25% and protein utilization exceeding

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