I just received a rather hefty cut to my arm, but thought it was nothing because there was not blood at first, just pain. Then about a minute later some blood started to come out of the wound and eventually I examined it and found it to be rather deep!
This got me to thinking about how quickly blood is normally expelled out of the body when one is cut skindeep. Was my reaction normal? Do I have too little blood (Hypohemia)?
My only frame of reference is movies and chaotic street-violence, so I am interested in any sort of data on how much blood is normal (and how soon).
How much and how copiously a cut bleeds depends on a number of things:
Cleanness of the cut: Cuts by razor sharp edges often produce very little trauma to the surrounding tissues (compared to rips and shreds made by jagged edges, claws, teeth, and the like), and thus will take longer to stimulate the histamine response that promotes capillary bleeding.
Vascularization of the area: How many blood vessels were severed? Are there any larger vessels, or just capillarys? I once closed a very sharp pocketknife on my finger and it cut deeply – right into my writing callus. It never bled - just oozed a bit over the next hour.
Local blood pressure: Blood pressure isn’t the same in all parts of your body. An elevated arm has a lower pressure, and the veins in your legs and ankles generally have higher pressure. Areas with a poor blood supply also have lower pressure.
Blood properties. You already guessed blood volume. There’s also blood “thickness,” or the amount of water it contains, plus the number of platelets and other congealing agents.
Where exactly is your cut? “Rather deep” is how deep, exactly? What caused the cut?
I’m sure I don’t have to advise you to seek medical attention, appropriate to the severity of your wound… right?
[nitpick]I think the term you are looking for is hypovolemic (low volume of fluid inside your blood vessels and tissues)[/nitpick]
How much you bleed depends on what area of your body is cut (the face and scalp are highly vascular and bleed like crazy, whereas, elbows and knees bleed much less), whether you sever any major vessels (please don’t try this at home), and the body’s fluid status.
If you were hypovolemic, your body responds by clamping down on non-critical blood vessels (for instance those to the skin). This is what happens when folks lose large amounts of blood and go into shock. If you’ve ever seen someone in shock, you’d note that they have cold, pale skin; this is because the vascular beds in the skin have clamped down, allowing blood to be diverted to the brain and kidneys. If you came across such an individual and gave them a paper cut, not only would you be guilty of being a poor samaritan, you’d note little blood loss.
That’s not to say I think hypovolemia is your problem. It’s much more likely that you cut a poorly vascularized area and missed any significant vessels.
Yeah, Mats; I picked my nephew up off the ground after he slipped and gashed his knee on a sharp rock. The entire dermis was split through, and you could see the yellowish fatty tissue underneath, but no blood at all.
I suppose the human knee area, being prone to a lot of bashing, is not likely to be highly vascularized.