Sustainable veterinary anaesthesia: single centre audit of oxygen and inhaled anaesthetic consumption and comparisons to a hypothetical model.

Abstract

Single centre carbon footprint audit of oxygen and inhaled anaesthetic agent consumption. Retrospective audit with hypothetical intervention. Records of 100 consecutive anaesthetics were examined. Consumption of oxygen and inhaled anaesthetic agent were estimated from oxygen flowmeter and vaporiser settings. Carbon dioxide equivalents (kg CO2 e) were calculated. Records were reassessed to identify potential reductions in oxygen flow. Animals >5kg were assigned to use circle systems set at a maintenance flow of 1L/min following a short transitional period of higher flow. Animals <5kg were assigned to Mapleson-A breathing systems at a flow of 1L/min. Potential reductions in oxygen and inhaled anaesthetic agent consumption and CO2 e were calculated. A total of 14,370 minutes of anaesthesia were audited. Median bodyweight of the animals was 12.1 (interquartile range 5 to 25.8) kg. Median anaesthetic time was 110 (interquartile range 73.8 to 205) minutes. It was estimated 43,132 L of oxygen were used to vaporise 2605 mL of liquid sevoflurane and 1654 mL of liquid isoflurane. Potential oxygen consumption was 16,798 L, lowering sevoflurane consumption to 1123 mL and isoflurane to 589 mL. Using the suggested technique, oxygen and inhaled anaesthetic agent could have been reduced in 97% of anaesthetics with a median inhaled anaesthetic agent reduction of 59% (interquartile range 43 to 71%). Carbon footprint of the inhaled anaesthetic agent used was calculated as 1.82 metric tonnes of CO2 e. This could have been lowered to 0.67 metric tonnes (63% reduction). Large reductions in oxygen and inhaled anaesthetic agent consumption and therefore greenhouse gas emission and financial expenditure can be made if we audit and adapt our practices.