What are the lower and upper limits of cerebral blood flow autoregulation in mean arterial pressure?

What are the lower and upper limits of cerebral blood flow autoregulation in mean arterial pressure?

• A. 25 and 125 mm Hg
• B. 25 and 200 mm Hg
• C. 40 and 250 mm Hg
• D. 60 and 160 mm Hg

Answer: (D)

Cerebral blood flow autoregulation keeps brain blood flow constant over a range of mean arterial pressures by adjusting the diameter of cerebral vessels. In adults with normal CO2, this range is roughly a MAP of 60 mm Hg up to about 160 mm Hg. Within this window, vessels dilate or constrict to maintain steady blood flow despite changes in pressure. When MAP falls below about 60, vessels are maximally dilated and CBF becomes pressure-dependent, so further drops can lead to ischemia. When MAP rises above about 160, vessels are maximally constricted and CBF starts to rise with pressure, increasing the risk of hyperperfusion, edema, or hemorrhage. CO2 levels, age, and chronic hypertension can shift this range, but 60–160 mm Hg is the classic teaching range.

Cerebral blood flow autoregulation keeps brain blood flow constant over a range of mean arterial pressures by adjusting the diameter of cerebral vessels. In adults with normal CO2, this range is roughly a MAP of 60 mm Hg up to about 160 mm Hg. Within this window, vessels dilate or constrict to maintain steady blood flow despite changes in pressure. When MAP falls below about 60, vessels are maximally dilated and CBF becomes pressure-dependent, so further drops can lead to ischemia. When MAP rises above about 160, vessels are maximally constricted and CBF starts to rise with pressure, increasing the risk of hyperperfusion, edema, or hemorrhage. CO2 levels, age, and chronic hypertension can shift this range, but 60–160 mm Hg is the classic teaching range.