In patients with traumatic brain injury, we need to maintain a MAP that is higher than 70 mmHg for adequate perfusion and EtCO2 that is lower, around which range?

• A. Higher, lower
• B. Lower, higher
• C. Higher, higher
• D. Lower, lower

Answer: (A)

In traumatic brain injury, keeping cerebral perfusion adequate means ensuring the mean arterial pressure is sufficient—generally aiming for MAP above about 70 mmHg. At the same time, lowering CO2 helps reduce cerebral blood volume and intracranial pressure by causing cerebral vasoconstriction, so EtCO2 is kept in a lower range, around 30–35 mmHg. Since EtCO2 mirrors PaCO2, this combination translates to higher MAP with lower EtCO2. But use low CO2 carefully and temporarily, as too much reduction can risk cerebral ischemia.