Adult human brain represents about 2% of the total body weight however it receives 12-15% of the cardiac output this high flow rate is a reflection of the brain high metabolic rate. Brain ischaemia is a serious complication following surgical and non-surgical events. During reperfusion window (which is the time between onset of focal ischaemia and resumption of perfusion) pharmacological and physiological intervention may limit the volume of the infract. In the penumbral zone pharmacological agents may reduce the infract volume without reperfusion, so the ischaemic penumbra has become target for new treatment strategies, and cerebral protective agents have developed to prevent brain injury at points along the ischaemic cascade. There are many monitoring techniques to identify and prevent damage caused by cerebral ischaemia these includ e: EEG, somatosensory evoked potentials, brain stem auditory evoked potentials, visual evoked potentials and electromyography has also been used recently in neurosurgical procedures. The new trials to reduce ischaemic brain injury : include NMDA receptor antagonists, antioxidants and studying the role of nitric oxide in cerebral ischaemia with evaluation of its protective especially in acute phase of focal insult as it enhance reperfusion in the ischaemic tissue. Thus, brain protection regimens are most effective prior to the onset of ischaemia, certain therapies initiated after beginning of insult to minimize it may be effective after head trauma and in the ICU.