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7.2 EPIDURAL ANALGESIA
Epidural analgesia (ie the provision of pain relief by continuous administration of
pharmacological agents into the epidural space via an indwelling catheter) has become a
widely used technique for the management of acute pain in adults and children, particularly
after surgery and sometimes trauma, and in parturients.
7.2.1 Efficacy
The difficulty with interpretation of available data is that epidural analgesia is not a single
entity but can be provided by a number of pharmacological agents administered into different
levels of the epidural space for a wide variety of operations.
However, the consistent efficacy of epidural analgesia has been well demonstrated. Regardless
of analgesic agent used, location of catheter, type of surgery and type or time of pain
assessment, it provided better pain relief than parenteral opioid administration (Werawatganon
& Charuluxanun, 2005 Level I; Wu et al, 2005 Level I; Guay, 2006 Level I; Nishimori et al, 2006 Level I;
Marret et al, 2007 Level I).
One meta‐analysis of systemic opioids via PCA versus epidural analgesia concluded that
epidural analgesia provides better pain relief at rest and with movement after all types of
surgery — with the exception of epidural analgesia using hydrophilic opioids only. The epidural
group had a lower incidence of nausea/vomiting and sedation, but a higher incidence of
pruritus, urinary retention and motor block (Wu et al, 2005 Level I). Another meta‐analysis
reviewed studies looking at the benefits of epidural analgesia in addition to general
anaesthesia (Guay, 2006 Level I). It included a wide variety of surgical procedures and epidural
regimens and reported a reduction in a range of adverse outcomes with epidural analgesia
including reduced rate of arrhythmias, earlier extubation, reduced intensive care unit (ICU)
CHAPTER 7 stay, reduced stress hormone, cortisol and glucose concentrations as well as reduced
incidence of renal failure, when local anaesthetics were used.
Improved pain relief with epidural local anaesthetic drugs led to increased PaO 2 levels and a
decreased incidence of pulmonary infections and pulmonary complications overall when
compared with systemic opioids (Ballantyne et al, 1998 Level I). Similar results were confirmed in
a subsequent meta‐analysis; however, it is of note that from 1971 to 2006 the baseline risk of
pneumonia decreased from 34% to 12% in the opioid group, but remained at 8% in the
epidural group, suggesting a decrease in relative benefit of epidural analgesia over time
(Popping et al, 2008 Level I).
The benefits of epidural analgesia were confirmed when used in patients undergoing
abdominal surgery. After a variety of different types of intra‐abdominal surgery, pain relief
was better but pruritus was also noted to be more likely with epidural analgesia than with PCA
opioids (Werawatganon & Charuluxanun, 2005 Level I). The majority of trials included in the latter
two reviews used thoracic epidural analgesia (TEA) with a local anaesthetic/opioid infusion.
After abdominal aortic surgery and in comparison with systemic opioid administration,
epidural analgesia resulted in significantly lower pain scores in the first 3 postoperative days,
and reduced duration of intubation and ventilation, rates of cardiovascular (CV) complications,
myocardial infarction, acute respiratory failure, gastrointestinal (GI) complications and renal
insufficiency (Nishimori et al, 2006 Level I). Benefits were found in particular when thoracic
epidural catheters were used, but these did not translate into reduced mortality.
After colorectal surgery, epidural analgesia in comparison to systemic opioid analgesia
reduced pain scores and duration of ileus, but had no effect on hospital stay; rates of pruritus,
182 Acute Pain Management: Scientific Evidence
