By what percentage does cerebral blood flow change for each mm Hg increase in PaCO2?

By what percentage does cerebral blood flow change for each mm Hg increase in PaCO2?

• A. 1%
• B. 2%
• C. 7%
• D. 10%

Answer: (B)

Cerebral blood flow is highly sensitive to arterial CO2 levels. When PaCO2 rises, cerebral vessels dilate, increasing blood flow. The commonly taught value is that for each 1 mm Hg increase in PaCO2, cerebral blood flow rises by about 2%. So a small rise in CO2 leads to a proportional, modest increase in flow, which is why PaCO2 management is used to influence cerebral perfusion and intracranial pressure during anesthesia. The other options represent too large or too small an change per mm Hg, given the typical cerebrovascular CO2 reactivity.

Cerebral blood flow is highly sensitive to arterial CO2 levels. When PaCO2 rises, cerebral vessels dilate, increasing blood flow. The commonly taught value is that for each 1 mm Hg increase in PaCO2, cerebral blood flow rises by about 2%. So a small rise in CO2 leads to a proportional, modest increase in flow, which is why PaCO2 management is used to influence cerebral perfusion and intracranial pressure during anesthesia. The other options represent too large or too small an change per mm Hg, given the typical cerebrovascular CO2 reactivity.