Hello, My father was recently in a car accident (85 years old). The air bag hit him, cracking his sternum and 3 ribs. He spent a few days in IMCU then was discharged home...he was only home for 2 days, when he suffered a pulmonary embolism. Now, he is in ICU (day 8)..on a ventilator, he has mild renal insufficiency, some cardiac disease ... they have taken away the IV heparin drip and placed him on baby aspirin, he is getting his metoprolol, amiodarone for his occasional a-fib and tachycardia. My father is a very thin man (142 lbs), previously he was getting sedation since he is on a ventilator (Precedex). My question is; they have taken my father off the Precedex..it has been over 20 hours...but he is not waking up. He responds to pain by shaking his head and opening his eyes slightly..his pupils are stil reactive. Why is my father not waking up?