OUCH! That Hurt! Pain Perception and Control

In this post we'll talk about what pain is and how it is perceived. Next post I'll talk about some specific pain medications and methods for dealing with pain.

We've all felt pain. Pain can be acute (cut finger, broken leg, twisted knee) or can be chronic (spinal pain, compressed disk, arthritis). Different types of pain require different approaches. I thought I'd do an overview of different types of pain management and talk a little bit about the way animals perceive pain.

First thing first. Let me say this loud and clear. ANIMALS FEEL PAIN.

All of us mammals are essentially wired the same way. The nerve endings, nerve fibers, and nerve junctions are all pretty darned similar. So a broken leg hurst no matter what species you are talking about. Where's the difference between people and animals?

Animals PERCEIVE pain differently than humans.

Even though we are wired the same, that signal has to be interpreted by the brain for you to have concious knowledge of that pain. This explains why I have seen many dogs walk into the emergency hospital DANGLING A LEG behind them. It is also why I've seen a cow get their horns sawed off and they walk right out into the field and start eating as if nothing ever happened.

There have been many excellent studies looking at pain perception in various animal species. Each have these have shown that animals definitely perceive pain. However, there is a difference in what kind of pain they perceive and what it does to their body.

Every individual is different.

Some people have a very high pain tolerance and don't seem to hurt too badly even though they have a broken arm. Others cry and are severely affected by a paper cut. This is also true in our pets. Some require more pain medication than others.

The Anatomy of Pain:

Pain perception starts at a nerve ending somewhere out in the body. Let's use the toe as an example. When the pain receptor is triggered (like the toe is squished or the skin is cut), those receptors fire off a signal to the spinal cord. The signal is linked in the cord to another nerve that sends the signal up to the brain. Once in the brain, the signal is perceived both consciously and sub-consciously. This is an over simplification, but the point here is that pain happens at multiple, yet different levels in the body. When considering the pain in the toe, there are at least three locations that I can treat to eliminate the pain being "felt" or "perceived" by the individual.

Ever had novacaine at the dentist? This is an anesthetic that numbs up the nerves at the sight that the medication is given. That way, the nerves never get a chance to fire.

Ever taken an ibuprofen? Drugs like this work by keeping the chemicals that stimulate the pain signal from being produced. The idea is that if you decrease the chemicals, you eliminate the pain signal all together. In other words, by cutting inflammation, it reduces the stimulation of the signal, and reduces pain. (NSAIDs, COXIIB)

Ever had morphine? Narcotics main action occurs in the spinal cord, although they do a fair amount in the brain as well. Narcotics keep that signal from jumping from the nerve that sent the signal to the nerve that carries the signal to the brain.

And then there are the drugs that affect the brain chemicals that make us either more sensitive to pain or take away that sensitivity. In other words, they help change whether or not we give a damn that we're painful.

So in people and in animals, there are many, many different places that pain can be modified. This helps explain why there are such different responses from different individuals. Depending on your body chemistry, your brain chemistry, your specific genetic make up, you may have more or less sensitivity to pain. Cows are NOT as sensitive to pain as poodles. It's a fact. They both FEEL pain, but they don't PERCEIVE it the same.

Acute pain is handled differently than chronic pain. Over time, these pathways I've described above can become hyper-active or can be blunted. So chronic pain may require different targets to get the pain response to either shut down or start up. Acute pain can be easier to manage for this reason. The pathways are more predictable and we can use drugs in the short term (narcotics that sedate) that wouldn't be smart to use long-term (narcotics and addiction).

I'll stop there for now. Next post we'll talk about specific pain medications and how they can help.

AMH