I'm hoping someone here might be able to help me understand things better.
What I've Learned
* I've found lots of different estimates. But the popular/average seems to be that a human body contains about 6 quarts of blood. (It's actually based on your body weight, and I now have a handy-dandy spreadsheet to calculate the blood volume of potential victims.)
* The 4 Stages of Hypovolemic Shock nicely summarizes how much blood loss will require what degree of intervention.
* Possible complications of major blood loss include heart attack, kidney damage/failure, liver failure, stroke/brain damage, sepsis, gangrene of an extremity, adult respiratory distress syndrome, multiple organ dysfunction syndrome, disseminated intravascular coagulation, and from there the jargon got to be too much for me.
What I Still Don't Understand
* Referring to the Stages of Hypovolemic Shock above, it doesn't appear that someone is likely to lose consciousness until they're into Stage 4. That seems to contradict popular media portrayals of people passing out from blood loss but recovering without complication. So I guess my question here is whether that's just typical hollywood inaccuracy, or is there more variation per individual case? Basically, how likely is someone to pass out from blood loss but still be okay if they receive medical treatment in time.
* Correlating to the above, how timely would medical treatment need to be in order for it to be "in time"?
* Regarding the possible complications of blood loss, my understanding is that most of the organ failure/damage issues would be brought on by those organs not receiving adequate oxygen supply (with the exception perhaps that heart attack could be due to the heart overworking itself trying to pump the decreased volume faster to maintain oxygen supply). Is this correct?
* If organs are damaged, is this the kind of thing that could heal, or would it be permanent? For example, maybe kidney function is impaired for a while, but with rest and temporary dialysis to assist, it will eventually recover?
* Is there a typical progression of which organs will become damaged first, or in what order? Or does it vary by person? For example, might one person suffer kidney damage but have their liver be fine, and another go the other way? Or will liver damage always follow after kidney damage (or whatever order)?
* For sepsis and gangrene, are those actually caused by blood loss directly? Or are they just commonly associated with blood loss because blood loss would commonly be caused by injury, which would also commonly be a vehicle for contamination (stabbed with a dirty knife, etc.)
What I Need For My Plot
I need an assortment of victims to suffer varying degrees of blood loss (vampire attack), with varying degrees of severity of consequence. I'll definitely want some to be effectively unharmed. I'll probably want some to be injured moderately seriously, perhaps to the degree of suffering permanent damage (such as kidney failure to the point where they now need regular dialysis). I may want some to die of either immediate blood loss, or from complications that develop later. It would also be advantageous if I can come up with one victim suffering prolonged unconsciousness (coma?) but eventually having a full recovery with no long term medical consequences.