This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General anaesthesia, Subject name: Anaesthesia
Thiopentone has cerebroprotective effect because of- 
Select and explain. 
A. Decrease cerebral metabolism, B. Reduction of vasospasm, C. Calcium channel blockage, D. Free redical removal l
A: Decrease cerebral metabolism
Answer: A: Decrease cerebral metabolism 
Explanation: Barbiturate-induced reductions in oxygen requirements and cerebral metabolic activity are mirrored by changes in the electroencephalogram (EEG), which progress from low-voltage fast activity with small doses to high-voltage slow activity, burst suppression, and electrical silence with larger doses. Barbiturates may protect the brain from transient episodes of focal ischemia (eg, cerebral embolism) but probably do not protect from global ischemia (eg, cardiac arrest). With the reduction in CMRO2, a parallel reduction in cerebral perfusion occurs, as seen in decreased cerebral blood flow (CBF) and ICP. Ref: Miller's anesthesia 8th edition Ref: Morgan & Mikhail's clinical anesthesiology 6e.