<prompt> Primary mechanism responsible for cerebral protection effect of thiopentone isGABA action, calcium channel block and free radicle removalIncreased cerebral blood flowDecreased lowered cerebn metabolismReduces cerebral 02 demand by limiting CBF  <response>: C i.e. Decreased lowered cerebn metabolism Barbiturates thiopental, primarily decreases cerebral metabolismQ resulting in a dose related depression of cevebral metabolic oxygen consumption CMR02.Reduced CMRO2 causes progressive slowing of EEG, a reduction in rate of ATP consumption, cerebral vasoconstriction reducing cerebral blood flow and intracranial tension and protection from incomplete cerebral ischemiaQ. Thiopentone Sodium Thiopentone is a yellow coloured powder used as 2.5 solution at 5 mgkg dose for smooth induction. It is ultrasho actingQ due to rapid redistributionQ. It is contraindicated in porphyria.Q. 