Cardiac Output, Vasospasm, and Cerebral Blood Flow

Here's an interesting article showing that enhancing the cardiac output can increase cerebral blood flow in people with vasospasm (localized vasoconstriction that produces ischemia following subarachnoid hemorrhages):

http://www.ncbi.nlm.nih.gov/pubmed/14580270

It's supposed to be a safer approach, to increase the cardiac output, than induced hypertension, to maintain cerebral blood flow to the parts of the brain that can't maintain autoregulation. The article mentions the "triple-H" therapy [hypertension, hemodilution, and hypervolemia (or hyperhydration)] that some doctors use to treat vasospasm following hemorrhages. During vasospasm, the idea is that the cerebral blood flow becomes dependent on the mean arterial pressure, when this normally, supposedly, is not the case. I'm sure the cerebral blood flow in most people is more or less independent of blood pressure, across a fairly wide range of blood pressure values. In this article, for example, researchers found that cerebral blood flow was independent of cardiac output, and this is consistent with the traditional view that cerebral blood flow is indpendent of variations in blood pressure or cardiac output or apparently anything else (it's strictly regulated and maintained in a "pristine" manner of some kind):

http://www.ncbi.nlm.nih.gov/pubmed/11762541

I just don't think it's possible to really draw conclusions based on a study like this, because the relatively up-to-date information on the regulation of cerebral blood flow, by sympathetic nerve fibers and by other types of direct, neuronal influences, shows the true complexity of the situation. Here's a good article that talks about the nervous regulation of cerebral blood flow, and it's bizarre that some of this information is still controversial and viewed as being relevant only under unusual circumstances. One of the overall ideas is that noradrenergic neurons in the locus ceruleus and serotonergic neurons in the dorsal raphe nuclei are, among other groups of neurons, able to "override" cerebral blood flow regulation, under various conditions (a lot of drugs and factors could create these conditions), and either increase or decrease it locally or in a more widespread fashion:

http://www.ncbi.nlm.nih.gov/pubmed/10458655