Page 84 Acute Pain Management

consistent results if done properly (Moore et al, 2003). Self‐report measures may be influenced
by mood, sleep disturbance and medications (Scott & McDonald, 2008).
In some instances it may not be possible to obtain reliable self‐reports of pain (eg patients
with impaired consciousness or cognitive impairment, young children (see Section 10.3),
elderly patients (see Section 11.2.3), or where there are failures of communication due to
language difficulties, inability to understand the measures, unwillingness to cooperate or
severe anxiety). In these circumstances other methods of pain assessment will be needed.
There are no objective measures of ‘pain’ but associated factors such as hyperalgesia
(eg mechanical withdrawal threshold), the stress response (eg plasma cortisol concentrations),
behavioural responses (eg facial expression), functional impairment (eg coughing, ambulation)
or physiological responses (eg changes in heart rate) may provide additional information.
Analgesic requirements (eg patient‐controlled opioid doses delivered) are commonly used as
post hoc measures of pain experienced (Moore et al, 2003).
Recording pain intensity as ‘the fifth vital sign’ aims to increase awareness and utilisation of
CHAPTER 2 pain assessment (JCAHO & NPC, 2001) and may lead to improved acute pain management (Gould
et al, 1992 Level III‐3). Regular and repeated measurements of pain should be made to assess
ongoing adequacy of analgesic therapy. An appropriate frequency of reassessment will be
determined by the duration and severity of the pain, patient needs and response, and the type
of drug or intervention (Gordon et al, 2005). Such measurements should incorporate different
components of pain. For example, in the postoperative patient this should include
assessments of static (rest) and dynamic (on sitting, coughing or moving the affected part)
pain. Whereas static measures may relate to the patient’s ability to sleep, dynamic measures
can provide a simple test for mechanical hyperalgesia and determine whether analgesia is
adequate for recovery of function (Breivik et al, 2008).
Uncontrolled pain should always trigger a reassessment of the diagnosis and consideration of
alternatives such as developing surgical or other complications, or the presence of neuropathic
pain. Review by an acute pain service or other specialist group should be considered.

2.2.1 Unidimensional measures of pain
A number of scales are available that measure either pain intensity, or the degree of pain relief
following an intervention. Pain relief scales, although less commonly used, have some
advantage when comparing the response to different treatments, as all patients start with the
same baseline relief score (zero), whereas they may have differing levels of baseline pain
intensity (Moore et al, 2003; Breivik et al, 2008).
Categorical scales
Categorical scales use words to describe the magnitude of pain or the degree of pain relief
(Moore et al, 2003). The verbal descriptor scale (VDS) is the most common example (eg using
terms such as none, mild, moderate, severe and excruciating or agonising) typically using four
or five graded descriptors.
These terms can then be converted to numeric scores (eg 0, 2, 5, 8, 10) for charting and easy
comparison over time. There is a good correlation between descriptive verbal categories and
visual analogue scales (Banos et al, 1989 Level III‐2), but the VDS is a less sensitive measure of
pain treatment outcome than the VAS (Jensen et al, 2002 Level IV). Pain relief may also be
graded as none, mild, moderate or complete using a VDS.
Categorical scales have the advantage of being quick and simple and may be useful in the
elderly or visually impaired patient and in some children. However, the limited number of
choices in categorical compared with numerical scales may make it more difficult to detect

36 Acute Pain Management: Scientific Evidence