Low-flow isoflurane-nitrous oxide anaesthesia offers substantial economic advantages over high- and medium-flow...

Isoflurane consumption was studied for three different fresh gas flows in patients scheduled for major elective abdominal, urological or gynaecological surgery under general anaesthesia with an expected duration of 2 h or more. Thirty patients were randomly assigned to either high-flow anaesthesia using a partial rebreathing system without carbon dioxide absorption (Mapleson D) or medium- or low-flow anaesthesia using a circle system with carbon dioxide absorption. Patients were anaesthetised with isoflurane in 40% oxygen and 60% nitrous oxide. The amount of isoflurane consumed was measured with a precision scale. The total consumption of liquid isoflurane (mean +/- s.d.) during the first 2 h was 40.8 +/- 12.2 ml in the high-flow group, 18.5 +/- 5.4 ml in the medium-flow group and 7.9 +/- 2.2 ml in the low-flow group. The corresponding cost of isoflurane for the three groups was 214 Danish kroner (DKK) (19.5 pounds), 97 DKK (8.8 pounds) and 42 DKK (3.8 pounds), respectively. The calculated total cost of anaesthetics was 286 DKK (26 pounds), 155 DKK (14.1 pounds) and 91 DKK (8.3 pounds), respectively. In conclusion, low-flow isoflurane-nitrous oxide anaesthesia offers substantial economic advantages over high- and medium-flow isoflurane-nitrous oxide anaesthesia.