Definition of shock and its impact on outcome (my ideas)

A usual way to define shock is MAP <= 65 or SBP <= 70, but why? What about the other parameters?

It is said that when the MAP requires to keep adequate perfusion to brain and heart is MAP >=70. I have seen the number >= 60, too. The MAP should probably be from invasive intra-arterial BP. We are talking about brain and heart, so a good clinical sign to monitor is consciousness. This would correlate with cerebral perfusion pressure (CPP) and cerebral blood flow (CBF).

What about the other end-organ damages as a result of shock? The most important one would probably be the kidney. To prevent "acute kidney injury," we need adequate "renal blood flow." To get enough blood flow, we need both adequate cardiac output and allocation of blood to the kidneys. When there is inadequate blood pressure to brain and heart, peripheral vasoconstriction occurs, and it does not spare the kidneys, resulting in inadequate renal blood flow. To reallocate blood to the kidneys, peripheral vasoconstriction needs to resolve, by giving adequate fluid volume. People sometimes talk about vasodilators too, but I won't be talking about that now.

Other end-organs, such as GI tract are less important, so we are not talking about that now.

SBP is another parameter. There is a goal in septic shock saying we should keep MAP >= 90, but I am not sure about that.

DBP is a less talked-about in shock. However, SBP minus by DBP, or the pulse pressure, correlates with stroke volume.

However, I have heard that in acute hypertension, keeping DBP < 110, does prevent end-organ damage.

Pulse, or heart rate, is another thing to monitor. It does tell you about decrease in blood pressure to carotid sinuses and aortic arch, and the resultant reflex tachycardia, therefore implying the physiology.

Some other interesting parameters are, CVP, PCWP, and cardiac index. I will probably be talking about that later.