Originally posted by Fisherman
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While we wait for your pathologist to ponder the question, I found another pathologist on the net, who answered a question about whether people would bleed out quicker from a severed femoral artery than from a severed carotid artery. Here is what was said:
As a forensic pathologist, I get asked these kinds of questions fairly often. As for this one, just off the top of my head (so to speak) the way that I would approach it is: About 20-25% of cardiac output (CO, or blood leaving the heart for any given time period) goes to the brain. Most of that goes through the carotids, with smaller amounts going through other vessels. Since there are 2 carotids, lets say about 10% of CO goes through one carotid. By contrast, the skeletal muscles at rest get about 15% of CO at most, and that's all of the muscles. (That % will go up a lot with activity, whereas the % to the brain stays pretty much constant) The legs, fed by the femoral arteries, have a lot of muscle, so to estimate let's say about 3/4 of the blood to muscle goes to the legs, and since there are two of them let's say in total 1/2 of 3/4 of 15% of CO goes to each leg (while at relative rest). So that comes out to......5-6%.
So, roughly, a femoral artery passes about half as much blood per unit time as a carotid artery.
As for how long it would take to "bleed to death"? The comparative short answer of course is it would take about half as long with the severed carotid than a severed femoral, and about the same amount of time with one severed carotid or two severed femorals.
But as for an estimated time: CO at rest is about 5 liters/min. That goes up substantially with activity and stress, and I think it's probably underestimating to double it, but that would give us a conservative estimate as well as the number 10 to work with, which is always easier. So a person would lose about 10 % of 10 liters (= 1 liter) of blood per minute through a severed carotid, and about half that much through a severed femoral. A person has about 70mL of blood per kg body weight, and so for a 100 kg person ( about 220 pounds), that comes out to 7 liters of blood. Well before 50% blood loss, it's lights out, but using 50% of 7, that's 3.5, and at 1 liter per min with the severed carotid, that's 3.5 mins. About 7 mins for the femoral.
I repeat these are rough estimates and they don't take into accounts things like efforts to stop the bleeding.
There are a number of things that should be added here:
- this estimation speaks of a person where the heart is pumping when he or she dies. That means that we should expect a slower rate for Nichols.
- this estimation has only ONE carotid severed. Nichols had BOTH carotids severed - plus all the other vessels in the neck.
-this estimation works from an assumption of a 100 kg person, with 7 liters of blood. Nichols would have been more like half that weight, and therefore around 3.5 liters of blood only.
In the example above, all the blood left the body in 3,5 minutes, with just the one artery cut. Is it really feasible that Nichols could have bled for, say, twenty minutes?
I will be interested to hear from your expert, Trevor.
The best,
Fisherman
As a forensic pathologist, I get asked these kinds of questions fairly often. As for this one, just off the top of my head (so to speak) the way that I would approach it is: About 20-25% of cardiac output (CO, or blood leaving the heart for any given time period) goes to the brain. Most of that goes through the carotids, with smaller amounts going through other vessels. Since there are 2 carotids, lets say about 10% of CO goes through one carotid. By contrast, the skeletal muscles at rest get about 15% of CO at most, and that's all of the muscles. (That % will go up a lot with activity, whereas the % to the brain stays pretty much constant) The legs, fed by the femoral arteries, have a lot of muscle, so to estimate let's say about 3/4 of the blood to muscle goes to the legs, and since there are two of them let's say in total 1/2 of 3/4 of 15% of CO goes to each leg (while at relative rest). So that comes out to......5-6%.
So, roughly, a femoral artery passes about half as much blood per unit time as a carotid artery.
As for how long it would take to "bleed to death"? The comparative short answer of course is it would take about half as long with the severed carotid than a severed femoral, and about the same amount of time with one severed carotid or two severed femorals.
But as for an estimated time: CO at rest is about 5 liters/min. That goes up substantially with activity and stress, and I think it's probably underestimating to double it, but that would give us a conservative estimate as well as the number 10 to work with, which is always easier. So a person would lose about 10 % of 10 liters (= 1 liter) of blood per minute through a severed carotid, and about half that much through a severed femoral. A person has about 70mL of blood per kg body weight, and so for a 100 kg person ( about 220 pounds), that comes out to 7 liters of blood. Well before 50% blood loss, it's lights out, but using 50% of 7, that's 3.5, and at 1 liter per min with the severed carotid, that's 3.5 mins. About 7 mins for the femoral.
I repeat these are rough estimates and they don't take into accounts things like efforts to stop the bleeding.
There are a number of things that should be added here:
- this estimation speaks of a person where the heart is pumping when he or she dies. That means that we should expect a slower rate for Nichols.
- this estimation has only ONE carotid severed. Nichols had BOTH carotids severed - plus all the other vessels in the neck.
-this estimation works from an assumption of a 100 kg person, with 7 liters of blood. Nichols would have been more like half that weight, and therefore around 3.5 liters of blood only.
In the example above, all the blood left the body in 3,5 minutes, with just the one artery cut. Is it really feasible that Nichols could have bled for, say, twenty minutes?
I will be interested to hear from your expert, Trevor.
The best,
Fisherman
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