C is for Circulation
The irreversible neurologic deficits of a stroke result when blood flow to an area of the brain is reduced to approximately 25% of the normal value.[20] This loss of perfusion leads to a lack of oxygen and glucose to the cells, resulting in cell death.[2] Cells in the central area of infarction (core infarct), where blood flow is lowest, or completely halted, typically are not salvageable. Cells in the surrounding penumbra may still be viable.[5] Because blood flow in the penumbra is also decreased, perfusion to this ischemic area needs to be reestablished quickly. A lack of adequate oxygenation and nutrients leads to the release of several toxic chemicals in the brain, including oxygen free radicals, and can result ultimately in cellular death.[13] Action taken during this critical early phase of a stroke can improve or maintain circulation, which allows sufficient oxygen and glucose to reach the neurons in this vulnerable area.
In acute stroke, circulation can be hindered by the increasing mass (eg, from edema, arterial dilation, or blood from hemorrhage) within the skull.[21] A normal response to the lack of oxygen within the brain is a rise in blood pressure. Although rising blood pressure can increase perfusion to the brain for a short time, it may lead to edema, increased intracranial pressure, and an increase in the size of brain mass and potential herniation.