For suspected elevated intracranial pressure, what PaCO2 target range is commonly used?

• A. PaCO2 25-30
• B. PaCO2 30-34
• C. PaCO2 40-50
• D. PaCO2 35-45

Answer: (D)

Maintaining normocapnia is essential because PaCO2 directly influences cerebral blood flow and intracranial pressure. CO2 is a potent vasodilator in the brain; rising CO2 levels cause cerebral vessels to dilate, increasing cerebral blood volume and elevating intracranial pressure. Conversely, lowering CO2 causes vasoconstriction and reduces cerebral blood flow, which can risk brain tissue ischemia if sustained. For suspected elevated intracranial pressure, you want to keep ventilation within the normal PaCO2 range to avoid these harmful effects and maintain stable cerebral perfusion. The commonly used target is 35 to 45 mmHg. (Note: in acute crises, brief hyperventilation to the lower end of this range may be used temporarily to reduce ICP, but it’s not a long-term goal due to ischemia risk.)