Which MAP range supports effective autoregulation of cerebral blood flow?

Which MAP range supports effective autoregulation of cerebral blood flow?

• A. 40-60 mm Hg
• B. 60-90 mm Hg
• C. 70-150 mm Hg
• D. 100-180 mm Hg

Answer: (C)

Cerebral autoregulation keeps blood flow to the brain constant by changing the diameter of cerebral vessels in response to fluctuations in mean arterial pressure. Within roughly 70 to 150 mmHg of MAP, the brain can compensate so that cerebral blood flow remains steady. This is why that range is the best match for effective autoregulation. If MAP falls below about 70, the vessels can’t dilate enough, and cerebral blood flow decreases, risking ischemia. If MAP rises above about 150, the vessels can’t constrict further, and blood flow increases, which can raise intracranial pressure and lead to edema. Outside this window, cerebral blood flow becomes more pressure-dependent and less well regulated. Note that factors like CO2 levels can shift this autoregulatory range, and injured brains may have a narrowed or shifted window, affecting target MAP in practice.

Cerebral autoregulation keeps blood flow to the brain constant by changing the diameter of cerebral vessels in response to fluctuations in mean arterial pressure. Within roughly 70 to 150 mmHg of MAP, the brain can compensate so that cerebral blood flow remains steady. This is why that range is the best match for effective autoregulation. If MAP falls below about 70, the vessels can’t dilate enough, and cerebral blood flow decreases, risking ischemia. If MAP rises above about 150, the vessels can’t constrict further, and blood flow increases, which can raise intracranial pressure and lead to edema. Outside this window, cerebral blood flow becomes more pressure-dependent and less well regulated. Note that factors like CO2 levels can shift this autoregulatory range, and injured brains may have a narrowed or shifted window, affecting target MAP in practice.