Global Warming Impact and Clinical Effects of a Novel 'streamed-in' Nitrous Oxide Administration as a Carrier Gas During Sevoflurane General Anaesthesia: a Randomized Pilot Study

Environmental hazards of human activity are a topic of present day world, global warming being one of the leading concerns. Gases that contribute to this are greenhouse gases. Nitrous oxide (N2O) is a greenhouse gas that is commonly used in medical practice, mostly confined to provision of anaesthesia during surgical procedures in the operation theatre. N2O is not a potent anesthetic, and is used as a carrier for volatile anesthetic during general anaesthesia. This is to reduce the use of volatile anesthetics and other analgesic drugs while maintaining adequate depth of anaesthesia and analgesia. The N2O gas that is used during general anaesthesia is scavenged and released into the atmosphere without any processing. In the atmosphere it stays and produces deleterious greenhouse effect primarily owing to its long lifetime of 114 years. In addition, it also causes depletion of ozone layer. The green house effect of gases is evaluated and compared with the use of carbon-di-oxide equivalents (CDE). When the effects are considered for 20 years it is termed CDE20.The efforts to reduce these harmful effects can be directed towards reduction/cessation of N2O use, or its post anesthetic processing. The long history of its use in clinical practice and benefits such as analgesia for various procedures; makes it difficult to be completely taken out of usage in the present day anaesthesia practice. Though processing of N2O after use during GA is possible, it's impractical because of cost efficiency. We therefore, have directed our focus on further reducing its consumption while being used for GA. Low- flow anaesthesia has been in practice for the same reason (i.e. to reduce the wastage of gases). This study is aimed to reduce the N2O consumption even further by employing a novel 'streamed-in' technique of N2O administration during low-flow GA. Conventionally, N2O use is initiated during the initial high fresh gas flows (FGF) before shifting to low-flow ventilation. 'Streamed-in' N2O administration strategy employs initiation of N2O into FGF after the institution of low-flow anaesthesia. Hence, the participants are not exposed to an unconventional drug or a new route of its administration, but an alternate strategy to its conventional use. We aim to evaluate the novel technique of 'streamed-in' N2O during sevoflurane GA for its global warming effects (in terms of CDE20) and its clinical effects ( intraoperative general anaesthesia state, hemodynamic profile) and post operative effects( postoperative nausea vomiting -PONV, postoperative pain profile- numerical rating scale-NRS)