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)