Comparison of anaesthetic gas consumption and stability of anaesthesia using automatic and manual control over the course of anaesthesia

BACKGROUND: The automatic control module of end-tidal volatile agents (EtC) was designed to reduce the consumption of anaesthetic gases, increase the stability of general anaesthesia and reduce the need for adjustments in the settings of the anaesthesia machine. The aim of this study was to verify these hypotheses.

METHODS: The course of general anaesthesia with the use of the EtC module was analysed for haemodynamic stability, depth of anaesthesia, end-expiratory concentration of anaesthetic, number of ventilator key presses, fentanyl supply, consumption of volatile agents and anaesthesia and operation times. These data were compared with the data obtained during general anaesthesia controlled manually and were processed with statistical tests.

RESULTS: Seventy-four patients underwent general anaesthesia for scheduled operations. Group AUTO-ET (n = 35) was anaesthetized with EtC, and group MANUAL-ET (n = 39) was controlled manually. Both populations presented similar anaesthesia stability. No differences were noted in the time of anaesthesia, saturation up to MAC 1.0 or awakening. Data revealed no differences in mean EtAA or the fentanyl dose. The AUTO-ET group exhibited fewer key presses per minute, 0.0603 min^-1, whereas the MANUAL-ET exhibited a value of 0.0842 min^-1; P = 0.001. The automatic group consumed more anaesthetic and oxygen per minute (sevoflurane 0.1171 mL min^-1; IQR: 0.0503; oxygen 1.8286 mL min^-1, IQR: 1,3751) than MANUAL-ET (sevoflurane 0.0824 mL min^-1, IQR: 0.0305; oxygen 1,288 mL min^-1, IQR: 0,6517) (P = 0.0028 and P = 0.0171, respectively).

CONCLUSION: Both methods are equally stable and safe for patients. The consumption of volatile agents was significantly increased in the AUTO-ET group. EtC considerably reduces the number of key presses.

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