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عمومی::
ایسکیمیک مغزی، ایسکمی مغزی
However, this may result not only from a reduction in viscosity but also as a compensa- tory response to reduced oxygen delivery.15 Although arte- rial oxygen content can be reduced by both hypoxia and by hemodilution, the increase in CBF that accompanies hypoxia is of a greater magnitude than that by hemodilu- tion induced reduction in oxygen delivery.11 The effect of a reduction in viscosity on CBF is more important with focal cerebral ischemia, a condition in which vasodilation in response to impaired oxygen delivery is probably already maximal.
In patients with focal cerebral ischemia, a hematocrit of 30% to 34% will result in optimal delivery of oxygen.
There- fore, viscosity is not a target of manipulation in patients at risk as a result of cerebral ischemia, with the possible excep- tion of those with hematocrit values higher than 55%.
Thus the effects of dexmedeto- midine on CBF were primarily mediated by its ability to suppress the CMR; the reduction in CBF is commensurate with the reduction in CMR, and there is no evidence that dexmedetomidine causes cerebral ischemia.
It also augments the function of the normal cardiovascular system when an increase in the MAP is desired as an adjunct to the treat- ment of focal cerebral ischemia, especially in the setting of vasospasm.
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