Medical Air-Oxygen versus Nitrous Oxide-Oxygen: A comparative study in Patients Undergoing Laparoscopic Cholecystectomy under General Anaesthesia

Abstract

Background: Laparoscopic procedures are gaining more popularity over conventional open abdominal surgeries.Nitrous oxide is still a popular anaesthetic carrier gas as it is cheap and reliable, provides powerful analgesia, decreases the need for maintenance anaesthetics, etc. However one of the most notable side effects of nitrous oxide is its ability to expand air-filled cavities such as the bowel. Medical air is an inert gas, environment friendly and does not have greenhouse effect as seen with nitrous oxide. However, it can cause awareness and increase requirement of anaesthestic agents to maintain depth of anaesthesia.Objective: To compare Propofol doses used for maintaining the depth of anaesthesia and to observe clinical signs of awareness in patients receiving oxygen-air and oxygen-nitrous oxide in undergoing laparoscopic cholecystectomy. Methods:80 adult patients of ASA grade I and II scheduled for elective laparoscopic cholecystectomy surgeries under GA were randomly divided into two groups of 40 each. Group A received oxygen and air (FiO2 0.4) and Group B received oxygen and nitrous oxide (FiO2 0.4). Dose of IV propofol infusions to maintain depth of anaesthesia, clinical signs of awareness and post op hypoxaemia were assessed. Data obtained was analyzed with suitable statistical tests.Results: Propofol requirements in both the groups were comparable. The total mean dose of Propofol required in Group A was 424.20±14.37 mg whereas in Group B, it was 402.20±14.56 mg (p=0.001) to maintain the depth of anaesthesia. There was no incidence of awareness or post op hypoxaemia in both the groups.Conclusion: Air can be used as a carrier gas instead of nitrous oxide with a significant increase in requirement of anaesthetic agentbut no increased incidence of hypoxaemia or signs of awareness.