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Oxygen consumption and carbon dioxide elimination in infants and children during anaesthesia and surgery
1Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota 55905.
Insights
Oxygen consumption and carbon dioxide elimination in infants and children are closely related to body weight. Halothane anesthesia may affect carbon dioxide elimination in younger children, potentially impacting metabolic assessments.
Area of Science:
- Pediatric Anesthesiology
- Respiratory Physiology
- Metabolic Studies
Background:
- Accurate measurement of metabolic gas exchange is crucial for assessing physiological status in pediatric patients.
- Understanding factors influencing oxygen consumption (VO2) and carbon dioxide elimination (VCO2) is vital, especially during anesthesia.
- Congenital heart malformations can alter metabolic and respiratory parameters in infants and children.
Purpose of the Study:
- To quantify oxygen consumption (VO2) and carbon dioxide elimination (VCO2) in a cohort of infants and children.
- To investigate the relationship between VO2, VCO2, and body weight in this pediatric population.
- To explore potential influences of congenital heart disease and halothane anesthesia on gas exchange.
Main Methods:
- Measured VO2, VCO2, minute ventilation (VE), tidal volume (VT), respiratory rate (f), and end-tidal carbon dioxide (E'CO2) in 38 infants and children (3.6-25 kg).
- Included 4 children with congenital heart malformations under mechanical ventilation and 34 healthy children breathing spontaneously.
- Utilized pneumotachography, an infrared capnograph, and mass spectrometry for gas analysis under halothane anesthesia.
Main Results:
- Established strong linear relationships between VO2 and body weight (VO2 = 5.0 x kg + 19.8) and VCO2 and body weight (VCO2 = 4.8 x kg + 6.4).
- Found no significant differences in VO2 or VCO2 between children with and without heart disease, nor before and after surgery.
- Observed reduced VCO2 (respiratory quotient < 0.7) in 11 of 21 patients < 10 kg, suggesting potential halothane-induced inhibition of lipolysis in brown adipose tissue.
Conclusions:
- Pediatric oxygen consumption and carbon dioxide elimination are reliably predicted by body weight.
- Congenital heart disease did not significantly alter measured gas exchange parameters in this study.
- Halothane anesthesia may transiently reduce carbon dioxide elimination in younger, smaller children, possibly related to suppressed brown adipose tissue metabolism.
Abstract:
Oxygen consumption (VO2, ml min-1) and carbon dioxide elimination (VCO2, ml min-1), minute ventilation (VE), tidal volume (VT), rate of ventilation (f) and end-tidal carbon dioxide concentration (E'CO2%) were measured in 38 infants and children (body weights 3.6-25 kg). Four children (body weight less than 5 kg) had congenital heart malformations and were studied during controlled mechanical ventilation, whereas the remainder (n = 34) who were healthy, breathed spontaneously. Anaesthesia was maintained with oxygen in air (FIO2 0.45) and halothane through a non-rebreathing circuit. Minute ventilation was measured by pneumotachography, E'CO2 with an in-line infra-red carbon dioxide meter and gas concentrations with a mass spectrometer. There were no differences in VO2 and VCO2 between children with and without heart disease. VO2 was related to body weight by the equation: VO2 = 5.0 x kg + 19.8 (r = 0.94) and VCO2 to body weight by the equation: VCO2 = 4.8 x kg + 6.4 (r = 0.94). There were no differences between VO2 or VCO2 before and after the start of surgery. In 11 of 21 patients weighing less than 10 kg, a reduced VCO2 was noted, giving respiratory quotients of less than 0.7. It is speculated that this age-dependent variation of VCO2 may result from partial inhibition of lipolysis in brown adipose tissue produced by halothane.