Why do we treat pain the way we do?

Here recently, I found myself reviewing the pain management protocol for one of the services I work for.  I was reviewing it because I had received a QA flag for one of my runs; it seems I gave morphine (4mg, to be precise) to a patient with abdominal pain.  Now, I was clearly in violation of the service's protocols.  In my defense, I instinctively followed a protocol for another service I had worked for, which specifically indicated analgesia for abdominal pain on standing orders.  But in any case, as I reviewed the protocol like I promised to, I found statements that got my brain in motion:

"Abdominal pain is a contraindication for pain management under this protocol."

"Traumatic chest injury or multisystem trauma is a contraindication for pain management under this protocol."

"Administer morphine 2mg IV/IM, to a maximum of 10mg total."

(For the record, I am paraphrasing because I don't have the actual protocol book in front of me.  But hopefully you get the idea.)

Image:  http://www.sindh.gov.pk/dpt/Transport/rule.html

Why do we have so many rules for administering pain medications?  Why do we have such tight restrictions on how much to give?

Now, I'm sure that there's a wide range of pain management protocols, some less restrictive than others.  However, many medics that I interact with seem to have similar restrictions, so the answer is not just "Because your service sucks!".

EMSWorld recently published a nice column that looks at the origins of WHEN this idea of withholding analgesia in abdominal pain came about :  http://www.emsworld.com/article/10862823/its-ok-to-relieve-abdominal-pain

What I get out of this article are two things:

1)  This idea of letting people with certain types of pain suffer came along shortly after trepanning went out of style.

2)  If the ED doc can reverse the medication I gave with naloxone should they so desire, AND if they're not going to make a diagnosis without a CT scan to back up the physical exam, what the hell are we arguing about?

Now as far as withholding for traumatic chest pain goes, it strikes me as odd that prehospital treatment does a 180 from ED management of cracked or broken ribs (as any of you who have suffered such an injury can attest):

"Yep, the X-ray shows that you broke/cracked some ribs.  Here's some pain medicine.  Good luck sleeping."

(my good friend, co-instructor, and former climbing partner Dave Ramsey gets all the credit for that one.)

But for me, my biggest question is why we treat a subjective symptom with objective doses.

Pain is a subjective thing; no one except the patient can experience it (although we may feel sympathy pains from time to time!).  We rely TOTALLY on the patient to relay their level of pain to us, either verbally with a 0-10 scale, or non-verbally with something like the VAS or Wong-Baker.  Then, we dictate a one-size-fits-all solution to the pain.

That doesn't make sense to me!  We recognize that many medications aren't that way; hence all the weight-based calculations we have to do (I'm especially sensitive to this fact because it's PALS month at the medic program.  Good grief, I hate PALS.).  Why are pain medications, which treat a condition that everyone feels just a little bit uniquely, so static in their doses and max doses?  You can't tell me that 2mg of morphine or 50mcg of fentanyl will affect a ballerina and a sumo wrestler the same way.

Hospitals seem to recognize this fact; they may specify a max dose that you can give at a time, but they base their endpoints off the patient.  If your pain level is still above a 3 out of 10, you get more meds.

What if we just changed our protocols to read "Administer morphine in 2mg doses every 5-10 minutes until the patient's pain level is 50% less than their initial pain score"?  What harm would that do?  Would it be more effective?

What do you all think?