Target-Controlled Inhalational Anesthesia-Isoflurane Consumption with Adequacy of Anesthesia Monitoring in Conventional and Multimodal Analgesia - A Comparative Study.

Background: In a time of increased concern over the environmental impact of chlorofluorocarbons, there is an impetus to minimize inhalational anesthetic consumption. It is possible with multimodal analgesia (MMA) and the use of end-tidal controlled anesthesia (EtCA) which is a low-flow anesthesia technique with adequacy of anesthesia (AoA) monitoring. In MMA, all four elements of pain processing namely transduction, transmission, modulation, and perception are targeted with drugs having a different mechanism of action. In EtCA, anesthetic gases are automatically adjusted for the set minimal alveolar concentration by newer anesthesia work station (GE Healthcare Aisys CS2). AoA is a derived parameter of entropy and surgical pleth index which measures the depth of anesthesia and analgesia, respectively.

Aim: The aim is to assess the difference in isoflurane consumption between MMA and conventional groups for a given period of time with EtCA and AoA monitoring.

Setting and design: This was a prospective randomized controlled trial involving 60 patients undergoing laparoscopic cholecystectomy. They were divided into MMA group and conventional group.

Materials and methods: Both the groups received preemptive intravenous diclofenac sodium 75 g and 2% xyloadrenaline infiltration at entry ports. MMA group in addition received paracetamol 1 g and clonidine 0.75 μg.kg^{- 1}. Intraoperatively, patients were on EtCA with AoA monitoring.

Statistical analysis: Mean differences in isoflurane consumption between the two groups were compared using an independent t-test. Postextubation adverse effects of analgesic drugs and awareness under general anesthesia were compared using the Chi-square test and presented as numbers and percentages. P < 0.05 was considered a statistically significant.

Results: Mean isoflurane consumption in the conventional group was 12.7 ± 5.3 mL which was significantly higher than the MMA group which was 8.9 ± 4.1 mL (P = 0.002). The duration of anesthesia between the groups was not significant clinically (P = 0.931).

Conclusion: EtCA with MMA significantly reduces isoflurane consumption compared to the conventional group of anesthesia.