This very topic was the topic of a previous research paper that I wrote and consequently turned into a presentation. I would be happy to email it to you if you provide your email address in a PM.
As far as your question, here are my thoughts:
Patient assessment is actually much easier following appropriate analgesia (this is supported by mounds of research as well as anecdotally). What was previously diffuse abdominal pain with a patient writhing is not tenderness concentrated to a very defined area.
Effective analgesia is one of the few times we can make an actual difference in someone's life. Pain is not just a nuisance, it is a significant problem which must be treated.
Eric
P.S. Short of posting the entire paper in this forum, here are my references:
[1] Position Paper: Prehospital Pain Management. National Association of EMS Physicians. Prehospital Emergency Care. October-December 2003. 482-488.
[2] Why Don’t We Do a Better Job of Treating Pain?. Bryan Bledsoe, DO.
http://www.bryanbledsoe.com/pdf/handouts/PowerPoint/Pain Management.ppt#256,1,Why Don’t We Do a Better Job of Treating Pain?
[3] Pain Management in the Prehospital Environment. McManus MD, Sallee MD. Emergency Medical Clinics of North America. 2005. 415-431.
[4] Prehospital Pain Management: Current Status and Future Direction. Hennes MD, Kim MD. Clinical Pediatric Emergency Medicine. 2006. 7:25-30.
[5] Pain Medication Administration in Pediatric Trauma Patients with Long Bone Fractures Before Emergency Department Arrival. Mader MD, Letourneau MD. Annals of Emergency Medicine. October 2004. 44.
[6] Inadequate Analgesia in Emergency Medicine. Rupp MD, Delaney MD. Annals of Emergency Medicine. April 2004. 494-503.
[7] Refusal of Base Station Physicians to Authorize Narcotic Analgesia. Gabbay MD, ****inson MD. Prehospital Emergency Care. July-September 2001. 293-295.
[8] Simplyifying Prehospital Analgesia. Bledsoe DO, Braude MD, Dailey MD, Myers DO, Richards MD, Wesley MD. Journal of Emergency Medical Services. July 2005. 57-59.
[9] Changing Attitudes About Pain and Pain Control in Emergency Medicine. Fosnocht MD, Swanson MD, Barton MD. Emergency Medicine Clinics of North America. 2005. 297-306.
[10] The Epidemiology of Pain in the Prehospital Setting. McLean MD, Maio MD, Domeier MD. Prehospital Emergency Care. October-December 2002. 401-405.
[11] Few Emergency Medical Services Patients with Lower-extremity Fractures Receive Prehospital Analgesia. McEachin BSN, McDermott EMT-P, Swor DO. Prehospital Emergency Care. October-December 2002. 406-410.