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monitoring and early diagnosis using MRI. In five of their six patients diagnosed with an
epidural abscess, both fever and epidural insertion site infection were present. They
therefore suggested that MRI investigation may be warranted if this combination is present
and that urgent investigation is especially indicated if there is a third sign that could indicate
an abscess, such as back pain or neurological change. If the diagnosis of epidural abscess
can be made before the onset of any neurological deficit, conservative treatment (antibiotics
only) may be effective (Cameron et al, 2007). The presence of severe or increasing back pain,
even in the absence of a fever, may indicate epidural space infection and should be
investigated promptly.
A review of data from publications reporting adverse events after obstetric epidural analgesia
reported a risk estimate of 1: 145 000 for epidural space infection (Ruppen et al, 2006a Level IV).
Bacterial colonisation of epidural catheter tips is reported to occur in 0% to 28% of patients.
(Simpson et al, 2000 Level IV; Steffen et al, 2004 Level IV; Mishra et al, 2006 Level IV; Yuan et al, 2008
Level IV). The most common organism cultured from the catheter tips was coagulase‐negative
staphylococcus.
Chlorhexidine‐impregnated dressings of epidural catheters in comparison to placebo or
povidone‐iodine‐impregnated dressings reduced the incidence of catheter colonisation
(Ho & Litton, 2006 Level I).
An in vitro comparison of the antibacterial activity of drugs used in epidural solutions
showed that the minimal inhibitory concentration of bupivacaine for Staphylococcus aureus,
Enterococcus faecalis and Escherichia coli (growth of Pseudomonas aeruginosa was not
affected at any of the concentrations investigated) was at concentrations between 0.125%
and 0.25%; levobupivacaine and ropivacaine showed no activity against Staphylococcus
aureus, Enterococcus faecalis and Pseudomonas aeruginosa, even at the highest
concentrations tested, and minimal activity against Escherichia coli (minimum inhibitory
CHAPTER 7 adrenaline did not improve antibacterial activity (Coghlan et al, 2009 Level III‐2).
concentrations 0.5% and 1% respectively); and the addition of fentanyl, clonidine and

A comprehensive review of infectious complications associated with central neuraxial and
peripheral nerve blockade, including epidemiology, factors affecting bacterial colonisation of
the epidural catheter as well as use in febrile, infected and immunocompromised patients was
published by Horlocker and Wedel (Horlocker & Wedel, 2008).
Respiratory depression
The incidence of respiratory depression with epidural analgesia depends on the criteria used
to define respiratory depression. In a review of published case series and audit data, the
reported incidence of respiratory depression ranged from 1.1 (0.6% to 1.9%) to 15.1
(5.6% to 34.8%) using respiratory rate and oxygen saturation, respectively, as indicators
(see Section 4.1.3 for comments on respiratory rate as an unreliable indicator of respiratory
depression); this was very similar to the incidence reported for PCA (Cashman & Dolin, 2004
Level IV).
Hypotension
The incidence of hypotension depends on the dose of local anaesthetic and criteria used to
define hypotension. In the same review as above, the reported incidence of hypotension was
5.6 (3.0% to 10.2%) (Cashman & Dolin, 2004 Level IV). It is often the result of hypovolaemia
(Wheatley et al, 2001).
Postdural puncture headache
Headache following dural puncture may occur with an incidence of 0.4% to 24%. Postdural
puncture headache (PDPH) is classically postural in nature and is more common in patients
188 Acute Pain Management: Scientific Evidence