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 .
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 postoperative 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 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 .
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
12 , 13 this regard .
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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