<prompt> Cerebral Ischemia occurs when cerebral blood flow is less than:10 m1100g minute20 m1100g minute40 ml 100gminute50 m1100gminute  <response>: Answer is B 20 m1100g minute: Cerebral blood flow 20 ml 100g tissue per minute causes cerebral ischemia without infarction Harrison s 18 th 3271 Critical Cerebral Blood Flow Effects 5 20 mU100 gmminute Cerebral Ischemia without infarction Reversible unless prolongedfOr several hours or days Clinical syndrome of TIA Consciousness is usually lost as the brain tissue loses the capacity to make neurotransmitter substances and coma ensues Damage is Reversible 16-18 ml 100 gm minute Cerebral Infarction within one hour 10 ml 100 gm minute Cerebral Infarction within several minutes Membrane integrity is lost Biochemical cascade of neuronal destruction becomes irreversible Zero ml 100 gm minute Death of Brain tissue within 4 - 6 minutes 