Preparation of the Drager Fabius CE and Drager Zeus anaesthetic machines for patients susceptible to malignant hyperthermia.

CONTEXT

Malignant hyperthermia may follow exposure to trace quantities of inhalational anaesthetics. In susceptible patients, the complete avoidance of these triggers is advised when possible; however, failing this, it is essential to washout or purge the anaesthesia machine of residual inhalational anaesthetics.

OBJECTIVE

This study examined the washout profile of sevoflurane from the Drager Fabius CE and the Drager Zeus machines.

DESIGN

The washout profile of sevoflurane was measured from the Fabius CE and Zeus anaesthesia machines following a standard period of exposure. The disposable tubing, CO2 absorber and other components of each machine were then replaced to examine their impact on the retention of sevoflurane. The effect of autoclaving the ventilator diaphragm and non-disposable ventilator tube or substituting for a new diaphragm and ventilation tube were examined in later parts of this study.

SETTING

University teaching hospital.

MAIN OUTCOME MEASURE

Time taken to reach 5 parts per million of sevoflurane when machines underwent standard washout with fresh gas flush.

RESULTS

The concentration of sevoflurane reached 5 parts per million in the Fabius CE machines after an mean (SD) of 140 min (46) at a fresh gas flow (FGF) of 10 l min(-1). The time taken for sevoflurane to reach 5 parts per million was significantly reduced when the ventilator diaphragm and non-disposable tube were replaced with either new or autoclaved components [14 or 22 min, respectively (P = 0.017, P = 0.031)]. The concentration of sevoflurane reached 5 parts per million in the Zeus machines after an mean (SD) of 85 min (6) at a fresh gas flow of 10 l min(-1). When the fresh gas flow was increased to 18 l min(-1) (the maximum allowable), the time to reach 5 parts per million was reduced to 16 min.

CONCLUSION

When preparing the Fabius CE for the malignant hyperthermia susceptible patient, remove the vaporiser, replace the disposable tubing, the reservoir bag and the CO2 absorber. Replace the ventilator diaphragm and non-disposable ventilator tube with new or autoclaved components and flush the machine at 10 l min(-1) for at least 36 min. When preparing the Zeus, remove the vaporiser, replace the disposable tubing, the reservoir bag and CO2 absorber and flush at a fresh gas flow of 10 l min(-1) for at least 90 min. In both the Fabius and Zeus, continue at a fresh gas flow of 10 l min(-1) for the duration of the operation.