Use of nitrous oxide is contraindicated in all of the following surgeries except?

Ans. is 'd' i.e., Exenteration operation Filtered room air, Sulfur hexafluoride and perfluoropropane are the most commonly used gases.By varying the concentration volume and type of gas used, bubbles can be produced that will last upto 70 days before being completely absorbed.If nitrous oxide is administered during this time the bubble will rapidly expand with the risk of retinal and optic nerve ischemia.Nitrous oxide and middle ear surgeriesMiddle ear cavity is connected to eustachian tube.When nitrous oxide is inhaled in large quantities N2O replaces the N2 in the middle air cavity thereby increasing the pressure in the cavity.After discontinuation of N2O the gas is rapidly reabsorbed from the cavity thus creating negative pressure in the cavity this may cause: -Serous otitis mediaDisarticulation of stapesImpaired hearingN2O anaesthesia is hazardous to hearing in patients who have previously undergone reconstructive middle ear surgery.Micro laryngeal surgeryCO2 and (Nd : YAG) lasers are frequently used for microsurgery on the upper airway and trachea.Lasers can ignite materials used in anaesthesia. The CO2 laser can penetrate an endotracheal tube and ignite a fire. Nitrous oxide supports combustion just like O2 and may ignite fire.