many patients find intolerable, such as confusion
or agitation.
Opioid-induced hyperalgesia is currently topical
relating largely to perioperative remifentanil and
medium to long-term opioid use in chronic pain.
It remains unclear as to the clinical significance
of this effect; however, strategies such as the
concurrent use of N-methyl-D-aspartate (NMDA)
antagonists are thought to attenuate this effect.
this matter are widely available. 7 Patient refusal,
concurrent septicaemia (increasing the risk of
epidural abscess), and cardiac conditions in which
patients are dependent on a higher systemic
vascular resistance (for example, severe aortic
stenosis) are also contraindications.
A more common adverse occurrence is
accidental dural puncture, which can lead to severe
headache with the rare possibility of more serious
complications such as subdural haematoma. 8
Intrathecal (or spinal) analgesia, which is
a one-shot technique, although regarded as safer
than epidural, may be unsuitable for major open
surgery due to its limited duration of action
offering little in the way of ongoing post-operative
analgesia. For some small open incision surgical
techniques, it may be suitable providing excellent
short-term analgesia without the problems of
prolonged reduced mobility and hypotension.
Regional anaesthetic techniques
Central neuraxial blockade – epidural and spinal
Epidural analgesia is considered the gold standard
for open abdominal surgery due not only to its
excellent opioid-sparing effects but also other
described benefits. These include improved
post-operative pulmonary function (with
a reduced incidence of pulmonary complications)
and attenuation of aspects of the stress response
to surgery. The reduced sympathetic and pituitary
activation results in reduced adverse metabolic
effects (such as hyperglycaemia and protein
breakdown). However there is no effect on the
cytokine-mediated inflammatory response.
Epidural analgesia also reduces the incidence of
ileus and PONV, thromboembolic events and
blood loss, with an earlier return to diet and some
evidence to suggest a reduction in the rates of
myocardial infarction, renal failure and
mortality. 6
In order to be effective, several considerations
must be taken in account.
The level of insertion must be appropriate for
the surgery taking place including likely positions
of any surgical drains, with thoracic insertion
most likely to be effective for open surgery.
The choice of drugs administered into the
epidural space is crucial. It most often includes
a local anaesthetic combined with an opioid;
however, other adjuvants such as alpha-2-
adrenoreceptor agonists (for example, clonidine)
or adrenaline improve or hasten the analgesic
effect.
The post-operative environment must include
staff trained in the effective management of
epidurals to correctly titrate the rate of ongoing
epidural infusion and recognise, and effectively
treat, common side effects, particularly
hypotension or motor block.
Establishing the epidural is best undertaken
early to demonstrate that it is working effectively
before returning a patient to a ward.
Failed or inadequate blockade is commonplace
and its early recognition is vital so that topping
up with anaesthetic and/or opioid, re-siting or
switching to alternative analgesia can be instituted.
Excessive fluid administration in the event of
hypotension should be avoided, and the use of
vasoactive drugs in a critical care environment
is certainly more logical and may be preferable
to avoid potential for detrimental effects on the
cardiovascular and respiratory systems and any
surgical anastomoses from fluid overload.
Mobilisation can be impaired in the post-
operative period due to leg weakness, hypotension
and attachment to drips, etc.
There remain conditions in which an epidural
may not be suitable for patients. Those with
a known coagulopathy or concurrently receiving
coagulation-modifying drugs should be considered
on an individual basis and guidelines regarding
Peripheral local anaesthetic administration
In the context of major open abdominal surgery,
many methods of peripheral administration can
aid post-operative analgesia. Most are generally
regarded as safer than neuraxial blockade due to
the reduced risk of hypotension and motor block
alongside fewer more serious complications such
as neurological injury. The dose of local
anaesthetic required for effective analgesia can
be high, increasing the risk of local anaesthetic
toxicity.
Transversus abdominis plane (TAP) blocks can
block dermatomes T10 to L1 when using a large
volume of local anaesthetic and are more effective
when performed pre-operatively by the
anaesthetist. 9 This distribution of block is unlikely
to confer a benefit for open surgery requiring an
Epidural analgesia is considered
the gold standard for open
abdominal surgery because of its
excellent opioid-sparing effects
above-umbilical incision. When injected
surgically at the level of the subcostal margin,
analgesia can be improved for upper quadrant
abdominal surgery. 10 Multi-hole catheters can also
be considered to prolong the duration of block. 11
Rectus sheath blocks can offer a higher level of
analgesia than the TAP block and may also
include the use of infusion catheters.
Continuous wound infiltration catheters
themselves have shown to confer a number of
benefits for open surgery including comparable
analgesia to epidurals and accelerated recovery
post-operatively although study results vary in
this regard. 12,13
Systemic analgesia
Paracetamol (acetaminophen) remains popular,
offering effective, non-opioid analgesia with an
excellent safety record when used appropriately.
The intravenous preparation allows
administration in patients unable to take enteral
medication.
Non-steroidal anti-inflammatory drugs have
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