Comparative quantification of carbon dioxide emissions associated with propofol and sevoflurane based anaesthesia

Healthcare significantly contributes to climate change, with anaesthesia alone accounting for 3 percent of healthcare-related greenhouse gas emissions. Volatile anaesthetics like desflurane, isoflurane, and sevoflurane have high global warming potential, with desflurane being the most harmful. Nitrous oxide also contributes to ozone depletion. Total intravenous anaesthesia, particularly with propofol, offers lower environmental impact, though concerns exist regarding propofol’s ecotoxicity, persistence, and improper disposal. Studies show TIVA emits fewer carbon equivalents compared to inhalational techniques, especially in short surgeries and paediatric cases. However, propofol waste can be high, though manageable by using smaller syringes. Some studies highlight cost-effectiveness of low-flow inhalational techniques and suggest that both environmental and economic burdens can be reduced by avoiding desflurane or nitrous oxide, minimizing fresh gas flows, and managing drug waste efficiently. Despite studies evaluating patient safety, cost, and efficacy across anaesthetic techniques, few have thoroughly assessed the environmental or economic differences between TIVA and inhalational agents like sevoflurane.AIM is to compare and quantify carbon dioxide emissions associated with propofol and sevoflurane-based anaesthesia when both are titrated to maintain depth of anaesthesia using BIS or Entropy.

OBJECTIVE is to measure and compare total carbon dioxide emissions produced during administration of propofol and sevoflurane

METHODOLOGY This study involves random allocation of patients into two groups: Group A is Sevoflurane maintenance and Group B is Propofol maintenance, following a standardized anaesthetic induction protocol using fentanyl, propofol, and vecuronium. Demographic and routine preoperative data will be collected. After induction, anaesthesia will be maintained with either sevoflurane or continuous propofol infusion, both using 60 percent nitrous oxide and 40 percent oxygen at a fresh gas flow of 2 litres per min. Depth of anaesthesia will be monitored using BIS or entropy, targeting a range of 40–60. Data on drug usage like quantities, vials used, and duration of surgery will be collected for environmental analysis. Carbon dioxide emissions from both induction and maintenance phases will be calculated using standardized formulas. For Group A, calculations will include fresh gas flow, vaporizer settings, and volume of liquid sevoflurane used. For Group B, total administered and wasted propofol volume will be noted. Nitrous oxide emissions will be calculated in both groups. It also includes assessing propofol wastage by measuring the difference between drawn and administered volume, accounting for losses in syringes and needle hubs and differences in cost in both the groups. The study will also evaluate post-operative complications/side effects of the drugs administered.

PRIMARY OUTCOME will be the mean carbon dioxide equivalent emissions calculated from use of propofol, sevoflurane and nitrous oxide. These emissions will be calculated based on standardised emission conversion factors for each anaesthetic techniques like propofol and sevoflurane during elective laparoscopic cholecystectomy surgeries.

SECONDARY OUTCOMES include

Total volume of propofol, sevoflurane, and nitrous oxide consumed per case will be estimated and compared between two anaesthesia techniques.

The volume of propofol wasted, drawn but unused,or residual, during the procedure will be quantified for the propofol group.

The direct cost of anaesthetic agents like propofol, sevoflurane, and nitrous oxide used per case will be estimated and compared between two groups.