Arteries go AWAY from the heart
How do we know the difference between an arterial bleed versus a venous bleed?
As a general rule, superficial veins sit closer to the surface of the skin than arteries. That being the case, they are often more likely to be nicked or cut accidentally. Our veins are responsible for carrying the blood back to the heart after a long trip around the body. Because of this, they are often less pressurised than arteries. Veins will ooze blood when cut and arteries will typically pulsate and spurt.
Since arteries are highly pressurised, they can be particularly difficult to stop blood flow. The patient is then at risk of exsanguination (a fancy term for bleeding out). We need to work quickly to close those vessels. To do that we need to physically force the blood vessel shut with sustained, direct pressure to the wound. If multiple dressings or manually applying pressure to the wound doesn’t work, we have one fail-safe up our sleeve – applying a tourniquet. By applying circumferential pressure to the limb with a tourniquet, we compress the soft tissue and any of those massive blood vessels that lie within. This effectively clamps off circulation in that area, affording the body’s natural clotting factors an opportunity to attempt to control the haemorrhage without being washed away and pushed through by the pressure. In the case of a serious haemorrhage, the body’s own clotting mechanisms are simply not effective enough and surgical intervention is required. A tourniquet simply buys us time to get to the hospital.
For years we have been told that we should only use a tourniquet as a last resort to stop an uncontrollable bleed. And while this is true, it doesn’t mean that you first have to apply several smaller dressings, when you know full well that they will bleed through immediately. Don’t waste your time.
Let’s consider a femoral artery bleed. One of the larger arteries in our body, measuring in at around 0.5cm – 1cm in diameter (or roughly as thick as the patient’s pinkie finger). If we wasted time without the application of a tourniquet here, death could occur within a matter of minutes. It’s better to use a tourniquet for a wound that didn’t absolutely need one, and revise that decision quickly, than to not use a tourniquet when it was absolutely necessary and have the patient bleed out.
If you read our last blog “Things they didn’t tell you about… Arterial Tourniquet’s” you’d know that by applying a tourniquet for extended periods of time, there is a real risk of causing additional tissue death by cutting off the blood supply. That being the case, why don’t we apply a tourniquet as close to the wound as possible?
Well, blood vessels are elastic so that they can swell and return to normal with any fluctuations in blood flow. Because of this, if an artery is severed it will spasm and retract slightly in an attempt to cut off blood supply to that area. One of the bodies self-preservation techniques. If we apply a tourniquet too low then we might miss this retracted artery and it can potentially continue to bleed higher up into the limb. For this reason, it is suggested that tourniquets should be applied 5-7cm above the wound or “high and tight”. If the wound is high up in the groin or armpit there is often no space to apply a tourniquet above the wound, so we might consider packing the wound instead.
If you take a look at the tourniquet pictured here, you will note there is a strap that loops around the injured limb. This strap feeds through a buckle or clip system (depending on the make and model). In the case of the CAT (Combat Application Tourniquet) seen here, the strap feeds through a buckle system and Velcro’s closed on itself. Since tourniquet’s are designed for use in the battle field, they can be applied single-handedly should the soldier be severely injured. A handy feature when you’ve only got one hand!
NOTE: Keep the tail of the tourniquet strap facing away from the casualty’s body so that it is easier to tighten the strap without getting caught up in the groin or armpit.
Whilst the application method is fairly straight forward, there is a notable lack of understanding about potential complications arising due to improper use. Without adequate education and training the misuse of this device can lead to serious and sometimes even fatal outcomes.
Disrupting the blood flow to a body part is the primary purpose of applying a tourniquet, but in doing so, we create a condition called ischaemia (lack of oxygen). Without oxygen, tissues will die. If we apply a tourniquet unnecessarily, we could kill off tissue and permanently debilitate a casualty.
Nerve damage can also be caused by the mechanical pressure of the tourniquet, leaving a patient unable to feel pressure, pain, heat or cold on the skin over those damaged nerves. If they have no feeling to a leg for example, they will be unable to walk. This could greatly impose on their livelihood.
Venous congestion occurs when the pressure applied by the tourniquet is enough to compress the low-pressure veins in the limb, but not quite high enough to stop the artery bleeding. Blood pools in the surrounding tissues, increasing tissue pressures, and the likelihood of complications. Completely avoidable if the tourniquet was applied correctly.
Reperfusion injuries can occur when the tourniquet is released. In an effort to remove waste products that built up while the tourniquet was on, the body sends extra blood to the affected area. Damaged arteries, veins and tissues cannot handle this excess fluid and may build up in the area causing swelling (oedema).
I would argue that if someone is suffering through the complications associated with tourniquet use… has it not done it’s job by keeping them alive in the first place??
The Australian Resuscitation Council continues to enforce the ruling that arterial tourniquets are to be used only as an intervention of last resort, when all other means of haemorrhage control have failed.
But if you read our last article called “Stop the Bleed” written by my fellow colleague, you know that often where major haemorrhage is concerned, other means of applying pressure may become null and void quite quickly.