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Reflections on ED analgesia 79
interpreting) pain research. One of the most important confounders deals
with the population – patients with extremity fractures – making up many
pain studies. While the common practice of focusing analgesia studies on
these patients is sensible, clinical experience teaches us that a significant
proportion of such patients achieve pain relief if the extremity is simply left at
rest (even without splinting). The smaller the study number, the more likely
the presence of residual confounding that may be missed by even prospective
methodology.
Therefore, in studying pain, we must allow for the fact that no two patients
perceive pain in the same way; that certain kinds of injury that produce
maximum pain as perceived by some patients produce none in others. We
must also understand that we have no objective method of measuring pain,
or its relief. We are forced to rely on what the patient tells us about the
individual perception of pain.
As well, there are the methodologic difficulties in our science of pain relief.
Because of issues of the type just described, it is hard to constitute a uniform
control group. Nevertheless, even assuming that we have a large enough
patient population to allow for these vagaries of perception in the control
group, we often make errors in the study group. While we are the first to
applaud planning and execution of RCTs in acute care analgesia, such trials
are not infallible, and emergency physicians should be wary of common
shortcomings. When an ED clinician encounters RCT results that contradict
years of experience, a vigilant search for oft-encountered study flaws can be
enlightening.
For example, if one attempts to compare the efficacy of morphine with that
of meperidine (pethidine), what do you think would be the outcome if the
morphine were administered IV in a dose of 10 mg, and the meperidine IM in
a dose of 50 mg? Even if the 50 mg meperidine dose were to be given IV, the
outcome of such a study is predictable. Yet there are many studies that
commit precisely that kind of relative dosing error. The effective dose of
meperidine is 1–1.5 mg/kg; how many patients will achieve relief from a dose
of 50 mg?
Non-analgesic adjunctive care also makes a difference to a pain management
study. We cannot take a population of humans and alter only one