<s>[INST] context: Closed head injuries may result in cerebral concussion from depression of the reticular formation of the brainstem. This type of injury is usually reversible. Local bleeding and swelling (intracranial or extracranial) produce an increase in the intracranial pressure. A characteristic symptom pattern occurs initiated by progressive depression of mental status. Increasing intracranial pressure tends to displace brain tissue away from the source of the pressure; if the pressure is sufficient, herniation of the uncal process through the tentorium cerebri occurs. Pupillary dilation is caused by compression of the ipsilateral oculomotor nerve and its parasympathetic fibers. If the pressure is not relieved, the contralateral oculomotor nerve will become involved and, ultimately, the brainstem will herniate through the foramen magnum and cause death. Hypeension and bradycardia are preterminal events. Emergency measures to reduce intracranial pressure while preparing for localization of the clot or for a craniotomy or both include hyperventilation, dexamethasone (Decadron), and mannitol infusion. Of these, hyperventilation produces the most rapid decrease in brain swelling. [/INST] question: Initial emergency reduction of intracranial pressure is most rapidly accomplished by | options: A: Saline-furosemide (Lasix) infusion B: Urea infusion C: Hyperventilation D: Intravenous dexamethasone (Decadron) | answer: C </s>