Because heating it makes it somewhat sterile (although it obviously won’t make it completely sterile!), it is far better than using a cold knife, which won’t do any good.
There’s a scene in the 1995 epic war movie Braveheart where the father of William Wallace’s best friend—a character played by the Scottish actor James Cosmo—is stabbed by an enemy trooper. After the quick skirmish concludes, the man’s well-wishers, including his son, gather around him to ‘treat’ his stab wound.
What they actually do is stick the red-hot tip of a spear against the wound on the man’s body. The man shrieks with pain, but then, a few seconds later, he seems alright, as if the wound no longer troubled him!
If you think about it, there are plenty of action movies where they show people sticking hot things, usually knives, blades, daggers, etc. into wounds as a form of first aid. In modern movies, you may have also seen people extracting a bullet lodged in their body by using something hot and metallic.
The question is, of course, why do people do that? Why do they stick red-hot metal in or around an already injured part of the body? Is there any scientific explanation behind this seemingly bizarre practice? Is it supposed to do any good, or help the person already in pain from the injury, or is it simply one of those things that movies get away with on the pretext of being a work of fiction?
Yes, there’s an explanation!
As it turns out, sticking a red-hot metallic object inside or near a wound on human flesh is not entirely devoid of logic or reason, as it may seem to be on the surface to the average, non-scientific moviegoer. There is indeed a reason (or two) why popular culture relies on this kind of crude first aid when a character (in a movie) doesn’t have instant access to appropriate medical care.
There are two probable reasons as to why movies show this kind of rudimentary first aid with wounds, so let’s take a look at them!
A sterile object or surface is completely devoid of living viruses and microorganisms. The process that makes an object sterile is called sterilization. In other words, you can say that sterilization refers to any process that deactivates, removes or kills all forms of life that are present in a given region/surface of an object.
One of the most common and crudest methods of sterilization involves heating the ‘target’ object. You see, thermal sterilization takes advantage of the thermal sensitivity of microorganisms to prevent their growth on a given surface.
Therefore, if one intends to stick a metallic object (such as a knife) in their body to temporarily fix or bind a wound, it’s always best to heat the object before bringing it in contact with bare skin. Because heating it makes it somewhat sterile (although it obviously won’t make it completely sterile!), it is far better than using a cold knife, which won’t do any good.
Cauterization is a very common medical practice wherein a small part of the body is burned to remove or close off a part of it. In the old days, cauterization was widely popular for the treatment of wounds. This technique is believed to be effective on multiple levels.
First, it helps prevent exsanguination, i.e., a condition where there is enough blood loss to cause death. Essentially, cauterizing a wound ensures that the patient won’t bleed to death. Furthermore, it also helps to close amputations.
The purposeful burning of a small part of the wound helps temporarily seal the wound, which is good news for the injured individual. In fact, surgeons still use electrical cauters to cauterize the cuts and incisions they make while performing surgical operations on their patients.
So, using a red-hot blade—as seen in movies—is obviously not the best way to deal with a wound sustained on the battlefield, but when medical aid and resources are scarce, it’s something that could keep an injured man alive until they receive dedicated and appropriate medical care.