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The use of supplemental analgesic consumption as an outcome measure has been questioned
in situations where pain scores are not similar (McQuay et al, 2008).
Physical functioning
Measures of physical functioning quantify many aspects of a patient’s life including their ability
to sleep, eat, think, deep breathe, cough, mobilise, perform activities of self‐care and daily
living, undertake their usual vocation, and to enjoy leisure activities and sport (Williams, 1999).
In acute pain this may be measured by pain intensity scores with movement or other
functional activity scores (see above).
Global or multidimensional measures of function attempt to combine various abilities or
disabilities to derive a summary measure. Scales that employ a large number of items might be
comprehensive but risk patient exhaustion or error, while scales with fewer items might be
patient‐friendly but risk becoming insensitive to state or change (Williams, 1999). These scales
have been used in some studies of acute spinal pain and cancer‐related pain:
• disability scales — generic scales include the Short Form 36 of Medical Outcomes Study
(SF‐36), the Sickness Impact Profile (SIP), and Roland & Morris Short SIP (Williams, 1999);
and CHAPTER 2
• Quality of life (QOL) measures — these measures are not widely used in pain studies other
than for cancer‐related pain (Higginson, 1997).
Disease‐specific measures quantify the impact of a specific pain problem on function and can
be used to track changes after an intervention (eg ability to cough after thoracotomy, ability to
lift a baby after Caesarean section) (Garratt et al, 2001). Generic measures facilitate
comparisons among the functional limitations of different conditions and treatments, and may
have advantages for audit of an acute pain service that includes patients with a range of
conditions (Patrick & Deyo, 1989).
Emotional functioning
Acute pain is an unpleasant sensory and emotional experience. The unpleasantness of the
experience and its meaning for the individual may have short‐term (anxiety, depression,
irritability) and long‐term consequences (lost confidence or self‐efficacy or post‐traumatic
stress disorder) for the individual’s emotional functioning.
Adverse symptoms and events
In trials of efficacy, adverse events are usually considered to be of secondary importance and
inadequate reporting has been found in as many as half of randomised trials reviewed
(Edwards et al, 1999; Ioannidis & Lau, 2001). If adverse events are sufficiently common (eg nausea
with opioids) they may be quantifiable in trials of efficacy and specifically measured using
dichotomous (present or absent), categorical (none, mild, moderate, severe) or interval
(analogue or Likert) scales. Analogous to NNTs, the number‐needed‐to‐harm (NNH) may be
used to describe the incidence of adverse effects.
Most efficacy trials will have inadequate power to detect rare adverse events and therefore
they are also absent from systematic reviews. Large clinical trials specifically designed to
detect adverse events are required (eg the VIGOR study investigated GI toxicity and NSAIDs)
(Bombardier et al, 2000). Case reports and postmarketing epidemiological research and
surveillance (eg the Australian Adverse Drug Reactions Advisory Committee) remain important
for detection of delayed events occurring after the initial trial period. More recently, results
from comprehensive large prospective audits and database reviews have provided a
sufficiently reliable denominator for incidence and risk factor evaluation in rare but serious
adverse outcomes in acute pain management (Cameron et al, 2007 Level IV; Wijeysundera et al,
2008 Level IV; Wijeysundera & Feldman, 2008).
Acute pain management: scientific evidence 41