Autoregulation is abolished by which of the following?

Autoregulation is abolished by which of the following?

• A. Hyperbaric oxygen
• B. Cardiopulmonary bypass with core temperature 27° C
• C. Chronic hypertension
• D. 3% isoflurane

Answer: (D)

Cerebral autoregulation can be abolished by volatile anesthetics, especially when used at higher concentrations. Isoflurane causes cerebral vasodilation and increases cerebral blood flow while blunting the vessels’ ability to constrict or dilate appropriately in response to changes in perfusion pressure. When autoregulation is abolished, cerebral blood flow becomes pressure-passive and follows the mean arterial pressure rather than staying constant. A 3% concentration of isoflurane is deep enough to markedly impair autoregulation, making it the best choice. Other options don’t typically abolish autoregulation in the same way: hyperbaric oxygen tends to cause vasoconstriction and can reduce flow without eliminating the regulatory mechanism; deep hypothermia with CPB reduces metabolic demand and can alter flow dynamics but doesn’t universally abolish autoregulation; chronic hypertension shifts the autoregulation curve but does not remove the ability to regulate blood flow within its adapted range.

Cerebral autoregulation can be abolished by volatile anesthetics, especially when used at higher concentrations. Isoflurane causes cerebral vasodilation and increases cerebral blood flow while blunting the vessels’ ability to constrict or dilate appropriately in response to changes in perfusion pressure. When autoregulation is abolished, cerebral blood flow becomes pressure-passive and follows the mean arterial pressure rather than staying constant. A 3% concentration of isoflurane is deep enough to markedly impair autoregulation, making it the best choice.

Other options don’t typically abolish autoregulation in the same way: hyperbaric oxygen tends to cause vasoconstriction and can reduce flow without eliminating the regulatory mechanism; deep hypothermia with CPB reduces metabolic demand and can alter flow dynamics but doesn’t universally abolish autoregulation; chronic hypertension shifts the autoregulation curve but does not remove the ability to regulate blood flow within its adapted range.