Cerebral blood flow is related to the cerebral perfusion pressure (CPP), which equals the mean arterial blood pressure (MAP) minus the ICP: CPP = MAP - ICP. For this reason, ICP management is devoted in part to providing blood supply to cerebral tissue that is adequate to meet metabolic demands and thereby avoid secondary ischemic injury.
Most centers use 20 cm H20 or 15 mm Hg as the threshold for diagnostic and therapeutic intervention in severe head injury. Lower levels of ICP (<15 cm H20, 10 mm Hg) may be more appropriate for infants and young children. Recently, many experts have advocated using adequate CPP (>70 in adults), rather than controlled ICP, as an endpoint for severe-head-injury management. This recommendation is controversial, particularly in the pediatric population. Because very young patients normally have a much lower MAP than adults, appropriate CPP levels are difficult to determine. Nevertheless, the recent emphasis on CPP has reinforced the importance of maintaining systemic blood pressure and therefore cerebral perfusion. Ino-tropic agents, such as dopamine, are helpful in the maintenance of normotension in head-injured patients.
According to the Monro-Kellie hypothesis, ICP is determined by changes in the volume of intracranial contents within a rigid, closed space (the skull). ICP management strategies may be conveniently categorized by the component of intracranial contents they are intended to modify: (i) brain parenchyma, (ii) cerebral blood volume, and (iii) CSF. Naturally, any mass lesions may directly contribute to intracranial hypertension and should be removed surgically.
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Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...