For head trauma with cerebral edema, hyperventilation should be used cautiously for limited periods to

• A. Increase cerebral perfusion
• B. Decrease elevated intracranial pressure
• C. Reduce blood pressure
• D. Improve oxygen saturation

Answer: (B)

Hyperventilation lowers intracranial pressure by reducing arterial CO2, which causes cerebral vasoconstriction and a fall in cerebral blood volume. This temporary reduction in ICP can help when there are signs of impending herniation or when ICP is critically elevated. However, because vasoconstriction can also decrease cerebral blood flow and cerebral perfusion pressure, prolonged or excessive hyperventilation risks brain ischemia, especially in edematous or hypotensive patients. So it’s used cautiously and briefly as a temporizing measure to lower ICP, not as a routine long-term therapy.