It’s possible that the first stab or slash will not kill you. Keep fighting and get control of the weapon to prevent further injuries that will! (source)
Getting the Point Knife Wounds & You – Pt 1 Freelance Phlebotomy Written by Corey O. Audio by Jonathan Fader

Freelance Phlebotomy

You’ve experienced the business end of a blade. In the case of self-defence we are talking about an armed assailant, but the vast majority of the following also applies to kitchen mishaps or accidents with power tools (not all sharp force injuries are crime-related). So, for our purposes here, imagine that an unqualified person has invited your blood on an excursion outside of your body, where it generally has no right to be. This is a problem.

But, why?

You probably know, by education or experience, that our cells and muscle tissue require oxygen to function. This oxygen is extracted from the air we draw into our lungs, it is then distributed throughout the body via our circulatory system, blood being the medium within which that oxygen is transported. Obviously this only works so long as our blood stays where it is supposed to be; inside us!

Humans benefit from what is known as a “closed” circulatory system, meaning our blood is contained in an expansive network of tubing (as opposed to those freaky invertebrates with an “open” system, in which a single bodily liquid acts as blood, lymph, and other internal fluids, and kinda squishes around the organs wherever it is needed). Our fancy network of tubes, aka the vascular system, is comprised of three varieties of blood vessels: veins, arteries, and capillaries. The difference is important when blades are involved!

  • Artery – Transports blood away from the heart to the rest of the body under high pressure. (higher if you are stressed)
  • Capillary – Thin walled vessels that permeate tissue and allow substances (oxygen, carbon dioxide, etc.) to pass to or from the blood in order to distribute them to, or collect them from, the cells.
  • Vein – Transports blood back to the heart under negative pressure (pulled back into the heart).

On average, death by way of blood loss can occur in the surprisingly (and frighteningly) wide range of 5sec to 6min. Fortunately or unfortunately, how long it takes for you, personally, to “bleed out” (die from blood loss) will be influenced by several factors. You gain or lose time based on the location of your injury, whether it is a laceration or puncture, the depth of the wound, your overall fitness, your emotional/mental state, and, as a bonus, what action is taken to stop the bleeding.

Speed Kills

Damage to your capillaries is the least life-threatening and easiest to deal with, they occur whenever the skin is broken (if the injury doesn’t break the skin you bleed internally and end up with a contusion, a.k.a. a bruise). Since the blood is gently permeating our tissues at this point, it makes its way out quite slowly; think back to the droplets of blood emerging from a bad scrape on your knee or elbow. The pressure is insufficient to cause death in most cases, just a mess; it oozes out of you.

If you experience a vein cut (venous bleeding) you will bleed out in about 4-6 minutes. You have the luxury of a few minutes on account of these vessels being the leisurely path by which your essential liquid is pulled back to the heart, so the pressure under which it leaves any unexpected opening is relatively low; it leaks out of you.

However, if a sharp object opens one of your arteries (arterial bleeding), the increased pressure of the heart pushing the blood outward to your extremities will put your life expectancy in the 5-15sec range; it spurts out of you.

Who Needs All That Blood?

The big issue here is how much life juice you can share with the outside world prior to death, which, as always, depends on a few factors: age, sex (men have more blood on average), overall body size, and overall fitness (funny how that relates to everything). If you had an infinite amount, you could freely use your arteries to paint the walls or engage in fun family “blood fights.” But, tragically, we only contain about 4.3-5.7L (7.5-10 imperial pints), accounting for around 7-8% of our body weight (70 ml/kg), and we need almost all of it to function properly.

Hemorraghic Shock Class 1

An adult could lose up to 14% of their total blood volume before experiencing major negative effects. Of course, if you lose that 14% in a short period of time it will cause a drop in blood pressure. A sudden drop in blood pressure means less of your oxygen-filled-human-claret is making it up to your brain, thus resulting in dizziness. Your heartrate will increase, as your body tries to circulate the remaining blood with greater urgency (technical term: tachycardia). You are now feeling the onset of shock, specifically Hemorrhagic shock (or hypovolemic shock). This is only Class 1, so you are still something of a “hemorrhagic shock tourist.”

Hemorraghic Shock Class 2

When you arrive in the neighbourhood of 15-30% loss, your body has to make some tough decisions about where to spend its, now limited, oxygen supply; welcome to Hemorrhagic shock Class 2! You will likely start breathing more quickly in order to draw in more oxygen (technical term: tachypnea), and your slightly enjoyable dizziness may be upgraded to the much-less-desirable state of anxiety. Immediately, the arteries in your muscles will constrict in order to pull less blood from the area of your heart, meaning your muscle-fuel is limited and you will begin to feel weak.

With much of the blood being drawn out of your exterior tissues in favour of supporting your internals, you are going to start looking pale and feeling cold, possibly resulting in numbness of the extremities as well. In other words, you get to experience that rapid onset anemia you were always curious about (the lack of red blood cells to transport oxygen effectively).

Hemorraghic Shock Class 3

As the available oxygen, and your ability to distribute it, is reduced so too is the efficiency of your organs. When you round the corner into Class 3 Hemorrhagic shock (or perhaps on the way to it), your body has decided that, with 30-40% of your blood being AWOL, it’s time to start prioritizing which functions will be maintained and which can be put on (hopefully temporary) hold. Your kidneys may be shutting down, your intestinal tract will likely grind to a halt, and several other organs will already be on strike. If this is not rectified soon, permanent organ damage may result. This isn’t helped by the fact that hypothermia is likely creeping in on account of your blood being drawn inward this entire time (simply being pale and cold in Class 2 seems alright by comparison.)

The brain is still prioritized as the heart doles out oxygen rations, but the buddy system is essential at this stage of blood loss, as you aren’t going to be much use to yourself since this is typically when your anxiety (which you may have been no stranger to anyway) gives way to confusion.

Your body will also employ some clever tricks to increase blood volume, such as increasing thirst to encourage more liquids coming in, and even reducing urine flow to keep them there.

Hemorraghic Shock Class 4

When you arrive at your final destination, Class 4 Hemorrhagic shock, you or someone else has managed to release more than 40% of your total blood volume into the wild. (Congratulations?) Your heart is racing, trying to force oxygenated blood to where it is needed most, yet your blood pressure is bottoming out and you are sucking wind just to keep enough fresh air cycling in.

At this point, you definitely aren’t making it home without a stop at a hospital (unless you know a friend with blood transfusion gear on hand and a decent grasp of surgical procedures.) Plus, you won’t likely be getting there by yourself, as the lack of oxygen to your muscles, brain, lungs, etc. means your confusion is going to become lifelong friends with lethargy.

Summary of changes in bodily function as hemorrhagic shock due to blood loss progresses. (modified from source)

Stoppage Time

Assuming the source of the sharp force trauma has been dealt with, via control or escape, it is time to call emergency services, put them on speaker if you can so that both hands are free, and perform a self-check in order for you to apply targeted First Aid. (In my opinion everyone should seek training in proper first aid).

If you have been stabbed or slashed you must get to a hospital! Depending on the 911/999 dispatch routing in your area they may ask if you need police or ambulance, or they may send both; but if I have to choose I’m prioritizing whichever increases my chance of survival based on the situation. (You may also want to consider hitching a ride, as early research indicates a decrease in mortality related to the “Scoop & Run” option, ie. transport in a private vehicle.)

Ideally, you are requesting aid from a friend or passerby to assist you with self-checking, first aid, and calling for emergency services on your behalf, as, depending on state of your Estimated Blood Volume (EBV), you may already be experiencing confusion and lethargy.

What are you checking for?

Well, your sympathetic nervous system did you a favour a few minutes back, it kicked in when you were initially attacked, flooding your body with a heady brew of hormones to make you faster, stronger, more focused, and generally more capable of responding to the threat. Of these epinephrine (aka Adrenaline) has helped out by blocking the pain of the stab or slash wounds you tried to politely refuse, but were treated to anyway. So you are taking a moment to quickly and efficiently inspect yourself, looking and feeling for obvious or unseen wounds.

  • Breathe and try to stay calm (increased panic = increased blood flow and poor decisions)
  • Visually assess what you can (has your favourite shirt been ruined by a slash or a rapidly expanding blood strain?)
  • At the same time do a “wet check”
    • Feel around with your hands; are there wet spots? (blood may blend into your black pants)
    • Frequently check your hands to assess the colour of any discovered wetness
      • Clear (rain/Sprite/sweat) = okay
      • Red (blood) = bad
  • Have you discovered any new holes or gashes on you?
Keep Blood on the Inside

If you identify a bleeding injury you must address it posthaste, as your 5sec-6min clock is ticking (and may have been since the initial attack). We are ignoring capillary oozing, it’s cute, but we are focused on venous leakage and arterial spurting; the latter being the most life threatening. Apply pressure directly over the crimson wellspring to limit/slow the blood escaping your body, ideally with a clean-ish compress of some sort (eg. a shirt, toque, etc.) in order to spread the pressure evenly and form a seal. In both cases, elevate the area of the wound, if possible, as gravity will hinder your blood’s access to the exit.

If there are multiple stabs and slashes, triage as best you can: Which one is bleeding most profusely? Deal with it first!

There is some debate surrounding the efficacy of civilian tourniquet use, but this is largely rooted in fears related to improper application of this life-saving tool. Get trained in First Aid, so that you know how and when to make and use a tourniquet. If you have three slashes and an arterial puncture on your right arm, even the best of us ain’t applying even pressure to all of that, so it is time to consider occluding the distal arterial flow.

What if, over the course of your self-check, you discover that the offending sharp object is still stuck in you?


The object damaged you on the way in and could inflict further damage on the way out! Plus, it may actually be buying you time by applying pressure to a severed artery, or acting as a plug for your new, unwanted, blood-escape-hatch. Rather than applying pressure directly over the wound, apply it to the sides of the wound around the impaled object while trying to keep it from moving and causing further internal damage.

(modified from source)

(Dr. Martin Luther King Jr. famously refused to let bystanders pull an 18cm letter opener out of his chest after an assassination attempt in 1958. During his subsequent 4hr surgery it was discovered that the blade had come to rest against his aorta, the largest artery in the body; removing it could have nicked that artery, causing him to bleed out. One of his physicians later noted that Dr. King was “just a sneeze away from death.”)

But Wait, There’s More!

With consideration of the above, how quickly things can go South once a blade opens you up followed by your fast eroding ability to do anything about it, spending time training in self-defence suddenly doesn’t seem like such a frivolous use of one’s time.

Rather than memorizing all of the above you could opt out of this voyage of the damned by not getting stabbed. If you see a knife being wielded in a context in which it’s dangerous or out of place (anywhere other than a kitchen, workshop, knife appreciation society meeting, etc.), go the other way (Avoid!) If you can’t avoid, talk your way out of conflict with the wielder (De-escalate!). Otherwise you better be willing to strike first, or know how to respond to a common knife attack patterns.

Now that you know everything about bleeding out, I have some bad news for you… if you do find you’ve been wounded in bladed-based conflict (sorry, but statistically, you will be), you also have to be concerned about where the sharp object meets your heretofore unblemished form.

Since depth, type, and placement of a sharp force injury is so important, we will take the time to look at the location aspect of how knives kill you, in the (aptly named) follow up post “Getting the Point: Knife Wounds & You – Pt 2: Location, Location, Location!

Written by: Corey O. – UTKM Yellow Belt

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