ICP, CPP, MAP copy PDF

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With reference to normal values, explain the relationship between Intra cranial pressure (ICP), mean arterial pressure (MAP) and cerebral perfusion pressure (CPP). (5 marks) Cerebral perfusion pressure (CPP) is the pressure which drives cerebral blood flow (CBF) through the vascular beds of the brain via the circle of willis. It is the difference between arterial and venous circulation. It is influenced by mean arterial pressure (MAP) and intracranial pressure (ICP), with normal CPP being 70-80mmHg. MAP is the average pressure exerted onto arterial walls during one cardiac cycle encompassing both systole and diastole pressures and ensures tissues are well perfused. Normal MAP value ranges between 70-100mmHg and is influenced by cardiac output (CO) and total peripheral resistance (TPR): MAP=CO x TPR. TRP is dictated by 3 factors: blood viscosity, total blood vessel length and vessel diameter, with the latter being the most easily and regularly varied by the autonomic nervous system in relation to stimulus. CO is influenced by stroke volume (SV) and heart rate (HR). Due to the direct relationship, if CO increases, so will MAP and vice versa. These interactions between CO and MAP and their influencers will affect the CPP. There is evidence that early hypotension (MAP...