Critical CBF in patients anesthetized with isoflurane is

Critical CBF in patients anesthetized with isoflurane is

• A. 5 mL/100 g/min
• B. 10 mL/100 g/min
• C. 18 mL/100 g/min
• D. 25 mL/100 g/min

Answer: (B)

Critical cerebral blood flow is the minimum blood flow needed to keep brain tissue alive and prevent ischemia. Isoflurane, a volatile anesthetic, dilates cerebral vessels and raises overall CBF while lowering cerebral metabolic rate. This combination means the brain tolerates hypoperfusion less well during anesthesia, so the threshold for ischemia drops. The level at which ischemia becomes likely under isoflurane is about 10 mL of blood per 100 g of brain tissue per minute. Normal awake CBF is much higher, around 50–60 mL/100 g/min, but under these anesthetic conditions the brain’s critical limit is closer to 10. Thus the best answer is the value around 10 mL/100 g/min.

Critical cerebral blood flow is the minimum blood flow needed to keep brain tissue alive and prevent ischemia. Isoflurane, a volatile anesthetic, dilates cerebral vessels and raises overall CBF while lowering cerebral metabolic rate. This combination means the brain tolerates hypoperfusion less well during anesthesia, so the threshold for ischemia drops. The level at which ischemia becomes likely under isoflurane is about 10 mL of blood per 100 g of brain tissue per minute. Normal awake CBF is much higher, around 50–60 mL/100 g/min, but under these anesthetic conditions the brain’s critical limit is closer to 10. Thus the best answer is the value around 10 mL/100 g/min.