When a adolescent head injury victim wakes up from a coma what is the first course of action the doctor will take? how is the situation handled?

Assess and treat: Assuming the adolesccent is metabolically and otherwise stable it depends on the clinical presentation. Thus, the first steps are assessment of mood, combatitiveness, orientation, and other neurological functions, motor, speech, etc. Assisting with establishing and maintaining orientation, educating the patient about their status, and arranging for pt, ot, speech/language and/or neuropsych evals.

No one thing: There is not one "first thing" a doctor would do since decisions are related to the specific illness or injury causing the coma & associated problems. In general as someone improves from critical illness, physicians will began to withdraw therapies no longer needed such as a ventilator, or an intracranial pressure monitor, continue to treat ongoing problems like infection, start rehab and monitor.