There is a relative paucity of research involving prehospital analgesia for traumatic injuries. It is recognized, however, that standard practices are likely inadequate. A retrospective record review by White et al found that, among 1073 patients with suspected extremity fractures, only 1.8% received prehospital analgesia.13 McEachin et al, in a smaller cohort of 124 patients, found an 18.3% rate of prehospital analgesia administration.14 Vassiliadis et al found that, of 176 patients admitted with a diagnosis of hip fracture, 49% did not receive prehospital analgesia.15 Swor et al showed a similar trend of hypoanalgesia, with only 21% of pediatric patients and 26% of adult patients receiving analgesia during transport for their traumatic injuries.16
The most-studied agents in prehospital analgesia are fentanyl, morphine, and nitrous oxide. Fentanyl has a favorable pharmacokinetic and side-effect profile, and it has demonstrated efficacy and safety in the prehospital setting in several trials with both adults and children.17-21 Its use, however, is limited by availability in many systems, and morphine is a more popular alternative that has shown equally efficacious analgesic effects in a randomized controlled double-blind trial of 54 patients by Galinski et al.22 Nitrous oxide was first described in the prehospital setting in 1970.23,24 Its efficacy is around 85% in the prehospital setting,25 although it is associated with vomiting in up to 15% of patients, and its use is limited by unfamiliarity, risk to providers (inadequate ventilation), lack of portability, and availability of alternative agents (ie, intravenous [IV] opioids).
Partial opioid agonists (particularly butorphanol and nalbuphine) have been studied in the prehospital environment. Both provide the theoretical benefit for a lower incidence of side effects but are also associated with increased dosing of opioids inhospital, likely due to the competitive partial agonist effects.26,27 Ketamine has been described for use in prehospital settings,28,29 and its increasing application in the ED may pave the way for more widespread use.
Regional anesthesia has shown promise in the prehospital setting. Barker et al demonstrated improved pain and anxiety with a femoral nerve block compared to metamizole in a prospective randomized trial of 52 patients with knee trauma.30 This was studied in a prehospital system that uses on-site emergency physicians and may not be applicable to all situations.
A small, but growing, body of literature suggests a possible role for acupuncture and acupressure techniques in the prehospital setting, though experience and training for these techniques in the United States are limited.31,32
Protocolized treatment is an essential part of effective prehospital care. In a before-and-after study including 13,492 patients transported with traumatic injuries, Pointer et al showed that, with protocol modification, prehospital morphine administration for traumatic injuries increased from 6.2% to 7.8%.33 Fullerton-Gleason et al significantly decreased time to analgesia administration in a prospective review of 963 patients before and after a protocol modification that allowed paramedics to administer morphine without a physician order.34 In addition, providers should continue to provide nonpharmacologic means of analgesia in the prehospital setting, particularly for fracture immobilization and reassurance.