Anesthesia & Clinical Research
Open Access

Abstract

Arterial to End-Tidal Carbon Dioxide Tension Differences in Infants and Children

Brigitte Ickx, Jacques-Olivier Dolomie, Mariame Benalouch, Christian Melot and Pierre Lingier

Background: Several reports have demonstrated substantial mean differences between arterial carbon dioxide
tension (PaCO2) and end-tidal carbon dioxide tension (ETCO2) in children under anesthesia.
Aim: We explored the importance of the (a-ET) PCO2 gradient in a pediatric population receiving general
anesthesia, with special attention to the relative effects of age and weight.
Methods: After induction of general anesthesia, 129 children, ASA I or II, and between 1 day and 15 years old,
had an endotracheal tube placed and mechanical ventilation initiated. After reaching a steady-state ETCO2, an
arterial blood sample was obtained and the PaCO2 measured.
Results: The mean (a-ET) PCO2 was 1.6 ± 4.3 mmHg for the entire pediatric population. There was a significant
negative correlation between (a-ET) PCO2 and age and weight (r =-0.42, P<0.0001 and -0.44, P<0.0001,
respectively). The calculated (a-ET) PCO2 varied from 6.8 ± 6.9 mmHg in neonates to 4.8 ± 4.4 mmHg in children
aged between 2 and 4 months. After 8 months, (a-ET) PCO2 was less than 2 mmHg. A negative (a-ET) PCO2 of -1.8
± 1.4 mmHg was observed in 44 (34%) patients with an age range between 4 to 8 years.
Conclusion: Our results indicate that ETCO2 gives an excellent value of the PaCO2 in children more than 8
months. However, PaCO2 cannot be extrapolated accurately from ETCO2 in babies less than 4 months or weighing
less than 5 kg who are mechanically ventilated via an endotracheal tube. Nevertheless, ETCO2 remains a key
monitoring as a trend monitor and mandatory to identify the tracheal position of the tube.