This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Anaesthesia
Use of nitrous oxide is contraindicated in all of the following surgeries except: 
Select and explain. 
A. Cochlear implant, B. Microlaryngeal surgery, C. Vitrioretinal surgery, D. Exentration operation
D: Exentration operation
Answer: D: Exentration operation 
Explanation: D.i.e. Excentration operation Diffusion hypoxia is seen during recovery phase after discontinuation of prolonged N20 anesthesia. It can be prevented by continuing 100% 02 inhalation for a few minutes after discontinuing N20Q. Second gas effect occurs in initial pa of induction of N20 anesthesia. N20 also shows bone marrow suppressionQ. Excentration is enucleation + wide dissection of periorbital tissue. In it there is no closed space formation so N20 can be used. In microlaryngeal lesser surgery, N20 is contraindicated d/t risk of airway fireQ