A Ten-Year Audit of Fresh Gas Flows in a New Zealand Hospital: The Influence of the Introduction of Automated Agent Delivery and Comparisons with Other Hospitals

Abstract

Reducing fresh gas flow (FGF) rates with volatile anaesthetics reduces waste, with positive financial and environmental consequences. We have audited FGF since 2001 by analysis of data collected from anaesthetic machines. We recently introduced Aisys® (GE Healthcare, Madison, WI, USA) machines that allow automated control of end-tidal levels of volatile anaesthetics. In 2009 the mean FGF was 1.27 1/minute, which was lower than 2001 (2.05 1/minute) and 2006 (1.43 1/minute) and similar to two other New Zealand hospitals. Following introduction of the Aisys®, mean FGF initially increased to 1.5 1/minute, but fell to 1.09 1/minute over the following 12 months. Median FGF showed a similar pattern and is now <600 ml/minute. Since introduction of the Aisys® workstation the proportion of time with flow rates >41/minute has increased. The proportion of time spent in automated delivery mode has increased from 35% to 63%. Users valued the workload reduction with end-tidal control. Our findings suggest that in daily practice, with a wide range of practitioners at different levels of training and a broad patient mix, mean flow rates of around 1.3 1/minute with median flows in the range 0.5 to 1.0 1/minute are achievable targets.

Target-controlled inhalation anaesthesia: A cost-benefit analysis based on the cost per minute of anaesthesia by inhalation

“…Before TCIA, only a strict control of fresh gas flow and exclusion from clinical use of the more expensive drugs were the main saving measures to reduce the cost of the halogenated agent [10,11]. Before implementing TCIA in our hospitals, several attempts were made to reduce fresh gas flow rates in the operating rooms but failed as already published [9].…”

“…Others observed smaller reductions [7]. Few clinical studies have been conducted in current clinical practice [8,9]. However, halogenated agent cost is the main expense of an anaesthesia department, following that of neuromuscular blockers [10] and current clinical studies are probably more relevant than strictly controlled randomized studies.…”

Time to stop the go slow on the low flow

“…The reduction in volatile use while using these modes is well-described. 3 The more time spent in an automated target control mode, the more volatile agent is saved. Modern anesthesia in many parts of the world has now evolved to embrace low-flow anesthesia and automated target control volatile delivery.…”

“…That is, for cases with a similar duration we use approximately half of the sevoflurane. Our institute has a track record of adopting low-flow anesthesia and end tidal target control for adult anesthesia 3. Given that we manage children and adults under one roof, perhaps we have more readily evolved our pediatric practice to embrace low FGFs and automated target control systems.…”

Automated gas control with the Maquet FLOW-i

“…This will eliminate the above mentioned disadvantages associated with the use of low FGFs, and it will help reduce the incidence of under-dosing: in a large prospective study designed to maintain MAC above 0.7 MAC, anesthesia providers failed to do so in more than 15 % of the time when they were controlling FGF and vaporizer settings themselves [3]. Automated target control helps the clinician to use low flows more consistently [4,5].…”