In case of Functional endoscopic sinus surgery (FESS) under General Anesthesia, after extubation uneventfully, suddenly saturation fall to 46% then to 0%. So we re-intubate it in awake condition and ventilate by bain's circuit and give Etofylline and simultaneously nebulize the patient and let situation under control. So what was d reason this happened.

How better we can handle it in ot. Please give ur precious suggestions.