Law of Hemoglobin Capacity

Blood Loss in Anime

Law of Hemoglobin Capacity– The human body contains over 12 gallons of blood, sometimes more, under high pressure. (Darrin Bright and Ryan Shellito)

Ah yes the classic anime trope of giant rivers of blood gushing out of the body to signify a grievous injury that doesn’t actually manage to slow anyone down, unless it’s needed for dramatic effect. Also, this particular trope is not in any way limited to anime, as Hollywood and other media outlets love to use it as well. This classic bit of British comedy exemplifies the blood loss trope.

If British comedy didn’t work for you, then this should suffice.

Anime blood loss
Anime blood loss

The law of hemoglobin capacity can be broken down into two parts.
1- The human body contains over 12 gallons of blood
2- The blood is kept at high pressure and has a tendency to explode from the body at high speed when the body is cut.

Blood Loss- Real World Biology

The human body actually contains around 5 liters of blood, depending on the size of the person in question. This accounts for about 8% of the individual’s body weight. To give you an idea, the total amount of blood in the body is equal to this:

5 liters of Mongolian Milk
5 liters of Mongolian Milk

The next item to consider about blood loss is the ability of a character to lose nearly all of it and still manage to continue doing whatever it was they were doing, as seen here.

bloody nose
bloody nose

In this case our poor heroine was rather excited and had a considerable amount of blood loss through a nosebleed (something I will address at a later date). So much blood loss that it is doing a rather good job of painting the walls red. Sadly, this would be a rather bad thing if it were to occur in the real world.

Blood Loss- Shock

Shock is a condition where the body is shutting down due to the immense amount of stress being put on it, and there are a variety of types depending on the cause of the shock. Today we will be talking about circulatory shock. This occurs when an individual is losing a lot of due to an injury or illness, although injury is far more common, specifically called hypovolemic shock. Hypovolemic shock can be broken down into several categories based on the amount of blood that is lost.

Class Amount of blood lost Bodies response Outcome
1 <15% (0.75L) Increased HR Fine
2 15-30% (0.75-1.5L) Increased HR+ decreased BP Probably fine with treatment
3 30-40% (1.5-2L) All of the above+ Confusion+ clammy skin+ shallow breathing+ weakness+ pallor Survivable with immediate treatment
4 >40% (2L+) All of the above plus loss of consciousness Potential of death even with aggressive treatment

As for our previous example, given the amount of blood that is staining the walls, she should be in class 3 shock. Thus, there is no way she is standing there red-faced, rather she should be lying on the ground pale-faced, and confused. As such we can call the first part of the law of hemoglobin capacity busted.


Blood Loss- Blood pressure

As one of my students might say, “but Mr. Meharg, in anime, TV, and movies, blood always spurts out at high pressure.”
high pressure blood
high pressure blood

Now let me tell you just how wrong you are.

Blood pressure is a measure of how much force the blood has as it moves through your blood vessels and is measure of how hard the heart is working. The higher the blood pressure the more force the blood has and the harder a person’s heart is actually working. Also for a frame of reference the average water pressure in a house is between 40PSI (2068mm Hg) to 60 PSI (3103m Hg) and atmospheric pressure is 760mm Hg.

In humans the normal resting blood pressure should be between 120mm Hg, and 80mm Hg (systolic). However, atmospheric pressure is higher at 760mm Hg- so how is it that blood leaves the body at all if the atmosphere is pressing down on the body with more than 9 times the force of the blood flow? This is because the actual blood pressure is between 840 and 880mm Hg. The atmospheric pressure is subtracted from the numbers you would normally hear in the doctor’s office. So in normal circumstances blood will leave the body at 42% of the force of a standard house faucet.

Now I know what you are thinking, that means blood has some force when it leaves the body and you would be correct to a point. There is such a thing in the medical profession called a pumper. A pumper occurs when you cut an artery, specifically a major artery, as the blood flow in a major artery (80-120mm Hg) is much stronger than a vein (5-10mm Hg). Some of these arteries include, the carotid artery in the neck, and the radial in the arm, and the femoral in the leg. You will see a stronger flow of blood out of these arteries when cut and the blood flow will pulse with the heartbeat. So yes you can have blood spurt a small amount, but nowhere near the degree that the injured person begins to imitate a fire hose. In closing, we can call high pressure blood busted.


Blood Loss- Conclusion

Sadly, while it might add to the drama and or humor of your favorite anime, the law of hemoglobin capacity is busted on both counts. The human body can’t hold 12 gallons of blood, nor is it contained at high pressure. If you have any comments or questions please leave them below.


Thanks for reading and please leave any comments or questions below.

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