Now for a word on blood pressure, which will sound simplistic because this topic is complex. Systemic blood pressure is the result of the cardiac output working against the systemic resistance (SVR). SVR is fundamentally the aggregate of local arteriolar resistances which in turn are set by the perfusion needs of the tissues supplied by each arteriole. Unless there is a reasonable level of blood pressure achieved against this resistance, the kidneys will not be adequately perfused, they will retain salt and increase the blood pressure by increasing output.
This sounds a slow process, and it is. There is therefore another mechanism, the baroreceptors of the aorta, which exercises a more rapid control of blood pressure by increasing SVR at times of acute hypotension. They do so by forcing certain arterioles to constrict even if local perfusion is not optimal, typically those of the gut and skin. Hence the pale, sweaty, "shut down" appearances of acute shock and the tendency to bowel ischaemia in prolonged hypotension. They work by activating the adrenergic sympathetic system. This mechanism works well, but if uncorrected the arterioles will eventually re-establish their local dominance, the periphery will warm up and the blood pressure will fall precipitously.
To illustrate this, the figure below shows the result of acute, severe blood loss in a series of experimental cats. Note the initial reaction to maintain blood pressure and its eventual failure.