Safety and efficacy of semi‐closed circle ventilation in small infants

The purpose of this clinical trial was to investigate the safety and efficacy of semi-closed circle ventilation of the Drager anaesthesia ventilators (Cicero, Cato), using a fresh gas flow (FGF) of 600ml.min -1 . Twenty infants, weighing less than 6000g, without cardiorespiratory abnormalities who required general anaesthesia of at least 30 min were included. The FGF was reduced to 600ml.min -1 after 10 min of denitrogenation with a FGF of 4 to 6 l.min -1 . The composition of the FGF (600ml.min -1 ) was calculated as follows: oxygen necessary for consumption (60ml.min -1 ) plus the remaining FGF in a 1:2 relationship for oxygen. The inspiratory nitrogen fraction was calculated to exclude accumulation. Inspiratory fractions of 02 and N 2 O plus inspiratory and endtidal CO 2 partial pressures and noninvasive oxygen saturation were the control parameters. The gas concentrations (02 and N 2 O) remained within safe limits. Hypoxic gas concentrations were not observed. Neither nitrogen nor CO 2 accumulated in the circle system. In conclusion, low flow anaesthesia can be performed safely in infants under 6000 grams with the Drager Cicero and Cato anaesthesia ventilators.