Accuracy of inhaled agent usage displays of automated target control anesthesia machines

Abstract

Automated low flow anesthesia machines report how much inhaled anesthetic agent has been used for each anesthetic. We compared these reported values with the amount of agent that had disappeared by weighing the vaporizer/injectors before and after each anesthetic. The vaporizers/injectors of the Aisys, Zeus and FLOW-i were weighed with a high precision weighing scale before and after anesthesia with either desflurane in O2/air or sevoflurane in O2/N2O. These values were compared with the values reported by the cumulative agent use display tools of the respective anesthesia machines using a linear curve fit. Twenty-five measurements were performed in each group, except for the sevoflurane data with the Aisys that were available from another study (87 pairs). We also determined the amount lost by inserting and removing the vaporizers/injectors or by performing a machine checkout, corrected the measured amounts for these artifacts and repeated the linear fits. The average amount of sevoflurane and desflurane wasted by inserting and removing the cassette for the Aisys, Zeus, and FLOW-i were 0.21, 0.12, and 0.04 mL and 0.12, 0.61, and 1.13 mL liquid agent, respectively. The average amount of sevoflurane and desflurane wasted by the machine checkout with the Aisys, Zeus, and FLOW-i were 1.78, 0.21, and 1.67 mL and 2.39, 0.67, and 4.19 mL, respectively. Performance error of the displayed amount of agent use remained within 10 % of the weighed amount, expect for amounts less than 3 mL sevofurane with the FLOW-i and less than 20 mL desflurane with the Aisys and FLOW-i. Cumulative agent usage displayed by the Aisys, Zeus, and FLOW-i is within 10 % of the measured consumption, except for low consumption cases (<3 mL sevoflurane, <20 mL desflurane). The differences may be due to either measurement error or cumulative agent display error. The current results can help the researchers decide whether the displayed amounts are accurate enough for their study purposes. The extent to which these discrepancies differ between different units of the same machine remains unstudied.

Environmental And Economic Impact of Using A Higher Efficiency Ventilator And Vaporizer During Surgery Under General Anesthesia: A Randomized Controlled Prospective Cohort

“…We also recognize that our protocol speaks to only one facet of environmental impacts as it relates to volatile agent delivery and not a full life cycle assessment of carbon footprint in the larger context. However, our results resonate with the growing support that anesthesia providers should avoid unnecessarily high fresh gas ow rates for all inhaled drugs (1,14) and employ technologies that are more e cient.…”

Observational audit of sevoflurane consumption during paediatric anaesthesia

“…These machine logs have been shown to be accurate within 10% of the weighed amount of the volatile agent. 6 The GE Aisys CS 2 machines were equipped with Et Control providing automated target control for the volatile agent. Breathing systems used were Limb-O TM circuits (CareFusion, San Diego, CA, USA) and Ayres T-pieces (Intersurgical Ltd, Wokingham, UK).…”

The financial and environmental impact of purchased anaesthetic agents in an Australian tertiary hospital

“…15,16 Machine testing costs and environmental impact Using the volumes of agents used per machine test as determined by Dehouwer et al for Dr€ ager Zeus V R (Dr€ agerwerk AG & Co. Lu¨beck, Germany) (n ¼ 11), GE Aisys TM (General Electric healthcare, Chicago, USA) (n ¼ 5) and Getinge Flow-I (Getinge, Gottenburg, Sweden) (n ¼ 2) machines, the costs and GHG emissions from the testing of these machines at Austin Health are displayed in Table 1. 17 Removing desflurane from these machines to avoid unnecessary testing (i.e. when desflurane is not planned to be used) would save A$14,630 per year and 36,909 kgCO 2 e. This assumed 260 checks per year (daily check, five days per week over 52 weeks).…”