Washout of sevoflurane from the GEAvance and Amingo Carestation anesthetic machines

Abstract

Inhalational anesthetics must be removed from anesthetic machines to prevent malignant hyperthermia (MH) in susceptible patients or to treat MH occurring during inhalational general anesthesia. This study examines the sevoflurane washout from the GE Avance and Amingo Carestations™. The care stations were contaminated with sevoflurane during general anesthesia. Then, the vaporizer was removed, the CO₂ absorber was exchanged against an empty one and the breathing tubes were substituted by clean ones. In the first part, the fresh gas flow was 10 l/min. In the second part, the Advanced Breathing System™ (ABS™), the internal breathing circuit, was replaced by a laundered component. The fresh gas flow was set to 10 l/min for 10 min and to 5 l/min for the following 20 min. In the 25 measurements of the first part, the sevoflurane concentration decreased from a median of 31.60 ppm [interquartile range (IQR) 130.12 ppm] within 22 min in every case to values below 5 ppm and stayed there for the last 8 min of the measuring (P < 0.0001). In the 15 measurements of the second part, the sevoflurane concentration fell from the median of 8.56 ppm (IQR 8.99 ppm) within 5 min to values being significantly below 5 ppm and stayed there for the following 25 min (P < 0.0001). In case of sudden onset of MH, the Avance or Amingo Carestation™ can stay in place, if the fresh gas flow is increased to 10 l/min or more. To prepare these machines for MH-susceptible patients, the ABS™ should be substituted by a laundered component.