[Blood pressure and the brain]

During acute cerebral infarction, autoregulation is abolished. Brain perfusion therefore directly depends on perfusion pressure and cardiac output. For this reason, in the early state of stroke, elevated blood pressure improves cerebral blood flow and only values of 210 mmHg systolic or above should be lowered. With the development of a vasogenic brain edema or a dysfunctional blood-brain barrier (usually on day 2 to 4 after infarction), blood pressure must be normalized in order to avoid hemorrhage and to minimize edema. In the presence of space occupying edema or intracranial hemorrhage, only those antihypertensive substances may be used which do not cause a dilatation of brain vessels. Direct vasodilators and calcium antagonists are not suitable in this situation. Furthermore, antihypertensive medication which causes bradycardia (e.g. beta blockers) should be avoided, because in acute stroke, brain perfusion also depends on the cardiac output. For primary and secondary stroke prevention normalization of blood pressure is essential. Efficacy is basically independent of the kind of antihypertensive medication used. Effective normalization of blood pressure probably helps to prevent vascular dementias of all kinds. Convincing studies however are still lacking for most sorts of antihypertensive medication.