The brain bit Kid flow is about 50 nil / 100 gin / min. and its 02 consumption 3.5 ml / 100 gin / ruin. - about twice as much oxygen 13 supplied compared to what is utilized, howeVer, brain tissue has almost no tolerance fbr 02 deprivation, Cerebral Ischaemia results when the blood and / supply to the brain is diminished, and usually, treatment can only he attempied idler the ischaemic insult has already occurred, exceptions are ex—the ,t temporary occlusion of a major vessel during in tracranial aneurysm clipping or coronary artery by pass surgery, where sonic prophylaxis may be possible, t hifortunately, there is no "magic bullet" available clinically which will compete!), prevent neuronal damage in any of these, situations, there is .evidence, however, abut animal as well as-human studies that ischacniic neuronal damage may be ameliorated even if theropy is started alter ischaemic, but the time "window" for starlingirealincal is probably brief . We can encounter cerebral *lumina in cardiac surgery, neurosurgery carotid endartarectomy, or use of deliberate hpotension, other situations seen typically in the ICU may include post-cardiec arrest or post-diowning, head trauma, Or Woke patients . When CEP falls below' 20 ml / 109 gin / min., noticeable changes —occur on the EEG, between CI317 ranges.(20 nil - 10 ml / I00 gin / min.), brain reeove:ry is possible without permanent damage if flow is restored, within a "windoW" period, this phenomenon has been called the Ischemic penumbra", if blood and 02 deprivation perSist long enough, a series of events is initiatel which ultinletely leads to cell death