injured brain, there may be varying degrees of regional or global compromise of cerebral autoregulation, with the worst case being where CBF varies directly as blood pressure-the 'pressure-passive' state. These are important concepts that must be kept in mind when choosing sedation medications, all of which will have some effect on CBF, CMRO 2 and MAP and ICP. GENERAL PRINCIPLES OF SEDATION Definition of sedation Within the context of neurocritical care, sedation is defined as incremental reduction in level of consciousness to maintain a state of amnesia, hypnosis and analgesia, from which patients can be readily recruited to participate in a comprehensive neurological examination. There are two fundamental sedation pathways in the Intensive Care Unit (ICU): • Use of sedative medications with primary aim to relieve pain, agitation and distress, with concomitant reduction in level of consciousness [1] • To relieve distress refractory to standard palliative treatment. Consideration of the second option is outside the scope of this study. PAD are commonly observed in neurologically injured patients, just as seen in patients on general medical and surgical ICU. All patients therefore require screening for symptoms. Various sedation strategies can be employed to reduce PAD. [2] Goal-directed sedation is a commonly practiced REVIEW OF BASIC CEREBRAL PHYSIOLOGY No review of sedation practice in neurocritical care is complete without reviewing basic cerebral physiology. The brain is a highly metabolically active organ and utilises around 3-3.5 ml O 2 /100 g/min, which is termed as cerebral metabolic demand for O 2 (CMRO 2). This takes approximately 15% of the cardiac output. Of the energy utilised by the brain, majority (60%) is used for generating electrical activity while the rest (40%) is used for cellular homeostasis. CPP measured as the difference between mean arterial pressure (MAP) and ICP, for the most part influences cerebral blood flow (CBF). In a normal brain, autoregulation of cardiac output to the brain provides a reasonably constant CBF over an MAP range of approximately 65-150 mmHg. However, in an Departments of 1 Anesthesiology and Pain Medicine and