[Minimal flow anesthesia in newborn infants--advantages and risks].

The long predominance of the semi-open anaesthetic system in paediatric anaesthesia has been ended by the introduction of circle systems by Altemeyer. Narcoses in newborn infants, however, are usually performed with a circle system and a fresh gas flow (FGF) that greatly exceeds the ventilation volume per minute required. This prevents a desirable degree of gas climatisation. A reduction of fresh gas flow for anaesthesia in neonates makes high demands on the anaesthesia ventilators. The safety and precision of present anaesthesia ventilators with different principles of function and construction were studied by means of a lung model reducing the FGF from 4.0 l/min to 0.5 l/min. In order to clarify the importance of a reduction of the FGF for the climatisation of anaesthetic gases and heat regulation in neonates we measured the temperatures of the respiratory gas at the tip of the tube and the body temperatures with a temperature sound. We compared 42 newborn patients anaesthetized with either high gas flow (3.0 l/min) or minimal gas flow. Our results showed that ventilators suitable for safely reducing FGF in neonates are available. Not every ventilator, however, offers the degree of precision required. Depending on FGF heat regulation in newborn infants differed significantly. Using high flow ventilation respiratory gas and rectal temperatures declined continuously. When FGF was reduced there was a significant increase of temperature parameters after 25 min (gas) and 35 min (body). Body temperature came back to normal values or stayed normal. Artificial ventilation of neonates in anaesthesia lasting more than 50 minutes should routinely be performed with minimal FGF in order to ensure normothermia.