Sounds like the events that surrounded the sudden death of pop artist Andy Warhol.
He was sedated--in post-op after routine gall bladder surgery----the private nurse at his bedside saw that he had turned blue. He had not gasped for breath or called out for help.
Hospital emergency rushed in---but could not get the tube down his throat....blamed it on rigor mortis.
Later its was determined, Warhol was allergic to the post-op meds--the allergy caused his throat to close up....a common occurrence with allergies.
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I read/heard that sometimes small doses of 3 different drugs are used in case a patient has an unknown problem with one medication.
The patient is fully anesthetized but not with a full dose of any one drug but rather with smaller doses of 3.