HHE 2018 | Page 214

an important role in analgesia but evidence varies between preparations as to their safety profile with regard to bleeding , cardiovascular complications , renal failure , wound healing and anastomotic leakage after colonic surgery . Both selective ( for example , parecoxib , celecoxib ) and non-selective ( for example , diclofenac ) are thought to increase the risk of anastomotic leak but the non-selective drugs more so . 14

Lidocaine is effective when used as an intraperitoneal or intravenous infusion . Both techniques have recently begun to gain popularity in light of favourable study results when compared with epidural but remain controversial . Used as part of ERAS programmes , both techniques can improve analgesia with an opioid-sparing effect and faster GI recovery with a low side-effect profile . Lidocaine is also thought to have an intrinsic anti-bacterial and anti-inflammatory effect with evidence to suggest its use may contribute to

15 , 16 reduced cancer recurrence . Gabapentinoids reduce post-operative pain , opioid consumption and PONV , although they can cause sedation , visual disturbances and dizziness , and there is currently a lack of evidence to support their use for open abdominal surgery with pregabalin having a better pharmacological profile than gabapentin . The optimal dose of pregabalin remains unresolved with 150 – 300mg preoperatively being most commonly used although higher doses confer a higher rate of adverse effects . 17 These drugs may also help to prevent the onset of chronic post-surgical pain .

NMDA antagonists ( ketamine and magnesium ) are useful adjuncts in acute pain with effects on acute tolerance and hyperalgesia with central desensitisation . There is evidence to demonstrate the efficacy of morphine and ketamine mixtures in PCA but ketamine also has a role intraoperatively when used as a bolus or infusion . Optimal dose and duration of infusion remains unclear but even low doses reduce morphine consumption with a low adverse-effect profile and demonstrable anti-inflammatory response . Ketamine may be useful for patients who are opioid-tolerant and for reducing chronic pain , but there remains a lack of procedure-related evidence for its use at present . Magnesium has been shown to improve post-operative pain scores and reduce ileus but prolongs neuromuscular blockade .

Alpha-2-agonists ( clonidine and dexmedetomidine ) have an analgesic effect

As ERAS pathways evolve , together with the concept of anaesthetists practising as perioperative physicians , the involvement of patients at an earlier stage of their perioperative journey should be encouraged through reduction of sympathetic outflow and noradrenaline release within the central and peripheral nervous systems interrupting pain pathways , including the release of the substance P . Clonidine is often used as part of a nerve block or intrathecal preparation for its analgesic effect ; however , its adverse effect profile ( sedation , hypotension , bradycardias ) make it otherwise less popular .

Glucocorticoids can have an opioid-sparing effect alongside reducing PONV , length of stay and modifying the stress response to surgery . The use of glucocorticoids is currently controversial in surgery for malignant disease due to conflicting evidence regarding disease recurrence . There is insufficient evidence at present to suggest glucocorticoids should be omitted during cancer surgery . In orthopaedic surgery , there has been considerable success with the use of high-dose methylprednisolone , with concerns of hyperglycaemia and wound infections not being major issues .

Conclusions Optimal analgesia involves consideration of the most appropriate method for particular patients at an early stage of the perioperative process . A multi-modal approach reduces the need for systemic opioids and their adverse effects , with an epidural considered as the best option to offer suitable patients . There is an ever-growing arsenal of analgesic adjuncts with variable evidence to support or contest their use . The PROSPECT working group provides a fundamental way in which to view post-operative analgesic therapy , as it focuses on areas of procedure-specific analgesia ( www . postoppain . org ) including a very good resource for guiding anaesthetic practice based upon the latest evidence . As ERAS pathways evolve , together with the concept of anaesthetists practising as perioperative physicians , the involvement of patients at an earlier stage of their perioperative journey should be encouraged , in order that they can be fully informed of what to expect pre- and post-operatively in terms of pain management . As a result , patients feel more empowered to inform staff if they feel their pain is not under control . Finally , the ability to deep-breathe , cough effectively and mobilise early should be explained as vital targets for patients and if this is not possible , urgent intervention might be required .