Oxygen consumption in critically ill children

Measurement of oxygen consumption (VO₂) in the critically ill patient has become an important tool because of its prognostic value and therapeutic implications. If oxygen delivery does not match VO₂, tissue hypoxia ensues followed by organ failure. It is well known that critically ill patients have increased VO₂, however what has not been fully explored is whether different disease categories have varying degrees of VO₂. The purpose of this study was to determine if VO₂ differs between subgroups of critically ill children.

Methods

Ninety patients between the ages of 5 weeks and 16 years who were mechanically ventilated were included in this study. Patients were excluded if: air leak around the endotracheal tube was > 5%, FiO₂ was > 0.6, or catecholamine infusion was required. VO₂ was measured within the first 24 hours of admission to the pediatric intensive care unit. A Deltatrac metabolic monitor, which uses a paramagnetic oxygen analyzer, was used to measure VO₂. Measurements were obtained over 20 min and standardized to body surface area. Patients were categorized into medical, surgical, trauma, sepsis or cardiac surgery subgroups. Mean VO₂ in the medical subgroup was compared to the other subgroups.

Data was analyzed using one-way ANOVA and Bonferroni Multiple Comparisons test.

Results

There was a statistically significant difference in the mean VO₂ between patients in the medical subgroup and patients in sepsis subgroup (P < 0.001), surgery subgroup (P < 0.01), and cardiac surgery subgroup (P < 0.001). There was no significant difference in the mean VO₂ between patients in the medical subgroup and trauma subgroup.

Discussion

We have demonstrated that VO₂ varies based on the category of critical illness. This finding is significant given the importance of optimizing and matching oxygen delivery to a patients' VO₂.

Table 1