Arterial tourniquets HURT!
If it’s been applied tight enough to effectively stem the blood flow, expect your conscious casualty to be in severe pain from the device. Whatever you do, make sure you DO NOT release the tourniquet to ease the pain. Doing so could result in catastrophic/ uncontrollable bleeding that could lead to hypovolaemic shock (HYPO – low, VOL – volume, AEMIA – blood = Low blood volume).
If there’s not enough blood circulating around the body, then there’s little to no oxygen getting to the vital organs and ultimately this can be fatal. So, leave your tourniquet in place, checking it regularly after application to ensure it hasn’t loosened (particularly if you’ve moved the patient) and use pain relief where appropriate. Other than that, there’s not a lot you can do. This patient needs surgical intervention. Quickly.
The bone marrow may continue to bleed.
Bones are very vascular; that is, they have lots of blood vessels running through them. This is because bone marrow is where most of our blood cells are produced. In the case of an amputation, not only are blood vessels severed and actively bleeding, but the bone marrow itself may bleed.
To put it into perspective, a long bone such as the femur (thigh) can hold up to 2 litres of blood. The average human body only has about 6 Litres of blood (depending on the size of the person). So, an amputation of the leg could potentially mean 1/3 of our total circulating blood volume is lost! Consequently, blood pressure will drop and the heart will struggle to compensate for this. Initially it may beat harder and faster until it eventually fatigues and simply gives up. Because let’s not forget that our heart is a muscle, and it too requires a good oxygen supply to work effectively.
Back to the tourniquet…
While a tourniquet will close off veins and arteries when effectively applied to the leg, it cannot put pressure onto the rigid structure of the bone itself. It is important to understand that this bone marrow may still be a source of blood loss despite tourniquet application. So, what should you do?
- Stop the arterial bleed first with your tourniquet
- Then use a pressure dressing and elevate the limb to control the additional bleeding from the bone itself.
Tourniquets can cause irreversible damage to a limb after roughly 3-4 hours of being applied.
How many times has your first aid trainer told you to write the time of application on the tourniquet, without telling you why it is clinically significant?!
The long and short of it is; tissues need blood flow to provide oxygen and remove waste products.
As soon as we put a tourniquet on, we interrupt this process. Time is tissue. Therefore, any tissue below the tourniquet will no-longer receive blood flow and will eventually begin to die off.
There is no absolute safe time-frame for a tourniquet to remain in place without long-term complications. Evidence would suggest that after 3-4 hours the risk of limb loss significantly increases, and after 6 hours it is almost inevitable. That being said, a tourniquet that has been left in place for 6 or more hours should NOT be removed unless the casualty is in a medical facility where they can be closely monitored.
What actually happens after that 6 hours?
Well, the lack of circulation can result in toxic metabolites building up in the tissue beneath the tourniquet (similar to that of a crush injury). If we released the tourniquet after this time-frame, that stagnant blood will start pumping around the system again.
Those toxic metabolites would travel back to the heart, putting the patient at risk of toxic shock and cardiac arrest. To be on the safe side current practices work towards a 2-hour time-frame. After this period, hospitals may remove the tourniquet and swap it out for a haemostatic or pressure dressing where appropriate.
We DO NOT recommend doing this in a first aid setting because you simply don’t have adequate resources or training to manage the bleed there-after.
Whilst these side effects can be dangerous, we should bare-in-mind that arterial tourniquets are typically only used as a last resort, for life-saving management of serious/ uncontrollable bleeds.
If the patient survives long enough to suffer from long-term complications of tourniquet placement, then it is likely that the device has done its job! Don’t be put off by the potential risks involved with using arterial tourniquets, but certainly make sure you brush up on your advanced first aid training.
Know when they are required and be confident in your decision and application process.