OXYGEN CONSUMPTION AND CARBON DIOXIDE ELIMINATION IN INFANTS AND CHILDREN DURING ANAESTHESIA AND SURGERY

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 < 5 kg) had congenital heart malformations and were studied during controlled mechanical ventilation, where-as the remainder (n = 34) who were healthy, breathed spontaneously. Anaesthesia was maintained with oxygen in air (FlO₂ 0.45) and halothane through a non-rebreathing circuit. Minute ventilation was measured by pneumo-tachography, 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×kg+19.8 (r = 0.94) and VCO₂ to body weight by the equation: VCO₂ = 4.8×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.