The average adult's body contains between 4.5 liters (roughly 9 pints) and 5.5 liters (roughly 11 pints) of blood.
Blood doesn't have to leave the body to become unavailable. Your circulatory system can leak into your abdominal cavity and thoracic cavity in large enough quantities to be a problem. Dehydration can also impact blood volume.
Loss of 15% is likely to lead to dizziness.
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| Ötzi, the Tyrolian Ice-man, had many injuries at the time of his death, including a severed left subclavian artery. The dude went down fighting! |
Loss between 20% and 30% is enough to generate a traumatic response sometimes called Hypovolemic Shock. Symptoms of Hypovolemic Shock include:
- rapid breathing
- weakness or fatigue
- confusion
- cool, pale skin (caused by the body shutting down blood-flow to non-critical organs)
- sweaty, moist skin
- anxiety or unease
- low urine output
- drowsiness
- unconsciousness
Key Point: It doesn't matter how strong of a will you have, once you start experiencing Hypovolemic Shock you stop being able to take care of yourself. You need outside help.
At 40% blood-loss the body runs out of "tricks" to maintain function of critical organs. Those organs start dying and the patient is in dire danger.
At about 50% blood-loss, damage is irreversible and even if you are given massive transfusions of whole blood, there is no guarantee that you will live. (SOURCE)
That may be counter-intuitive to athletes. "I can exercise for hours at 15 Metabolic Equivalents and you are saying that my body only has 100% redundancy?"
The issue isn't the number of red blood cells or the efficiency of your lungs exchanging oxygen and carbon dioxide. The problem is INADEQUATE VOLUME. It is like a bicycle chain that is too short. It doesn't matter how strong the chain is if it isn't long enough.
Protocols for first responders when the patient has lost a lot of blood is to push volume extenders like Ringer's or plasma. They will even put a blood-pressure cuff around the bag to generate positive-pressure to push it into the patient's vein.
The Golden Hour
In Emergency Medicine there was a (now partially discredited) concept called The Golden Hour that was suggested by R. Adam Cowley at University of Maryland's Shock Trauma Center.
The concept was that if you can get the patient to the Emergency Room with a pulse within the first hour of when the trauma was experienced, there is a darned good chance that he can be saved.
Consider the body-parts that can be damaged by trauma. Some of them are so critical that even if the patient was already coming through the doors of the Emergency room, doctors would not be able to save the patient...massive damage to the Central Nervous system or a severed aorta, carotid or femoral arteries for instance. Carotid and femoral get mentioned because they are not only large, but they run close to the skin.
(The Golden Hour might be a good example of the Survivor Bias. Your chances of surviving are much higher if you don't die before you get to the Emergency Room. Not controlling for those "suspended data points" can bias perceptions)
Due to the rapidly branching nature of arteries, most of the high-pressure side of your circulatory system are smaller and often run close to a bone. They are still too big for your body's clotting system to seal but you have a more time before you exsanguinate. Since these smaller arteries are dispersed, it takes a lot of cutting or punctures to sever enough of these to come anywhere close to the volume potential of a femoral artery, for instance.
I am pretty sure that I have at least three readers who work in Emergency Medicine. Please feel free to pick this post to pieces.
Having lost well over 2 pints once, I can tell you that the trauma makes you pretty much incapable of coherent thinking at that point,
ReplyDeleteYou go kinda shocky and dizzy and weak...then leading to near unconsciousness shortly after. You can function if you have to but it is pretty hard to stay focused.
Do Not Recommend.
YMMV and all the other disclaimers.
Hmpfffff.
ReplyDeleteDidn't the Golden Hour hypothesis arise during the the Korean War when they started airlifting casualties to mobile hospitals - the so-called M*A*S*H field hospitals?
Not disagreeing - but the narrative I have is that they revolutionized warfare and succeeded spectacularly in saving patients and even getting a stunning majority of them back on the line...?
I'd be most interested on the response from any ERT and first responders too...
If you follow the second link, it references French WWI data.
DeleteThe University of Maryland data is from Baltimore which is gang-shootem-up-central. Lots of FMJ .380 ACP and 9mm wounds.
Draw your own conclusions.
The Golden Hour protocols were formalized by Maryland Shock Trauma but the concept was around long before that. And bleeding is a big deal...thus the A B C s of resuscitation. Airway, Breathing, Circulation. The circulation part includes stopping visible bleeding. External bleeding is relatively easy to stop, even larger arterial bleeding can be stopped or slowed with a tourniquet. It's internal bleeding that is difficult to diagnose , especially quickly enough to intervene. The advent of high speed spiral CT scanners a quarter century ago made it feasible to screen almost any trauma patient for internal bleeding. Knowing that few will actually be bleeding but that those who are will be diagnosed early enough to save before they suffer circulatory collapse. Even today with "modern" medicine many people die from exsanguination, usually due to delays in getting to definitive care.
ReplyDeleteOne of the other (newish) diagnostic tools is a specific rapid look-see with ultrasound in the ED, done by the ED or Trauma physician. It saves minutes (as well as does not require relocation, can be done while other interventions take place, etc.) and is effective in revealing large bleeding into the thoracic or abdominal spaces (ie, not external as ERJ was discussing)
DeleteI don't work in the ER but I do maintenance and repair of the equipment they use. They have a machine called a rapid infusor that both pressurizes and heats the fluids they are infusing into the patient. Used for hypothermia and such. I also once drank half a glass of wine after giving blood.......Bad ideer..........
ReplyDeleteRed liquid out replaced with red liquid.
DeleteWhat could go wrong?
From the other side of the clipboard....if I am asked to terminate a subject I can do it with a pencil, in the middle of the ER with a vascular surgeon and all his trimmings on tap. It is worse outside without the specialists. Brachial arteries are Aorta's brothers, and if I make an effort the clavicles are what I use instead of pencils. They snap like carrots. ER teams don't see those guys. Selah...
ReplyDelete