WHAT IS IT?
Definitions of pain vary widely, and post-surgical pain is no different. 2017 was the Global Year Against Pain After Surgery as declared by the IASP (International Association for the Study of Pain).
A working definition of chronic post-surgical pain (CPSP) is pain that:
persists for at least 3 months after surgery,
was not present before surgery and/or different characteristics or increased intensity from pre-operative pain,
occurs in surgical site and/or referred area, and
is not due to other causes, e.g. infection, disease recurrence, or surgical complication .
The term CPSP is used interchangeably with persistent post-surgical pain (PPSP).
HOW COMMON IS IT?
Various epidemiological studies have been done with differing rates, but broadly:
1-2/10 surgical patients,
Intolerable pain after 1/100 operations,
2.2% report severe CPSP 12 months after surgery .
CPSP often has a neuropathic component . Neural injury can occur directly through the surgical process itself, or via associated treatment such as radiotherapy or chemotherapy. Neural injury through surgery is common and doesn’t inevitably lead to pain, thus other factors come into play .
WHO GETS IT?
CPSP is more common in those who have:
Certain types of surgery which has coined certain terms such post-thorocotomy pain, post-mastectomy pain,
Difficult-to-control severe post-operative pain,
Severe preoperative pain,
Chronic pain elsewhere,
Pre-operative opioid use,
Anxiety and other psychological vulnerability such as catastrophising beliefs [1,2].
WHY DOES IT OCCUR?
Risk factors themselves are not causal. The proposed mechanism for the development of CPSP describes peripheral and central sensitisation of the nociceptive and pain systems, but it remains only a poorly understood and inferred mechanism. All chronic pain states are best viewed through a biopsychosocial paradigm, as pain is a complex experience.
CAN IT BE PREVENTED?
Given the identified risk factors, attention to those that are modifiable could reduce the severity and even occurrence of CPSP.
It has remained difficult to prove the effectiveness of psychological interventions to reduce the development of CPSP, but there is some evidence that specific patient education can improve the post-operative experience .Discussion with the patient around their expectations can be useful. It can be helpful for the patient to understand that the aim is not so much complete pain elimination as good pain control to facilitate recovery and prevention of complications - such as ability to mobilise, cough and regain optimal gastro-intestinal function.
Good post-operative pain management is crucial, and a wealth of information exists in support, such as Acute Pain Management: Scientific Evidence  and PROSPECT guidelines . The cornerstone of acute post-operative pain management is multi-modal therapy, whereby procedure-specific management of multiple analgesics with different sites and/or modes of action improves pain control with reduction of adverse effects . The ability of multi-modal therapy to reduce opioid consumption is an important part of this outcome. In the opioid-tolerant patient this is especially relevant.
A typical multi-modal regime for would consist of:
Regular paracetamol 1g QID,
A non-steroidal anti-inflammatory, if there are no contra-indications. (A cox-2 inhibitor is preferred as they confer no increased bleeding risk, e.g. celecoxib 200mg bd for 5-7 days)
A regular opioid – the choice of which depends on extent of surgery, comorbidities, other medications. For example tramadol is a partial weak opioid, but often not sufficient in more extensive procedures, and because of its serotonin re-uptake inhibition limits use in those on SSRI’s or with epilepsy. Tapentadol is a relatively new partial opiate, that has no activity against serotonin and experience in the post-operative setting is accumulating, benefits include less risk of respiratory depression and less gastrointestinal side effects.
An alpha-2-delta ligand such as pregabalin (75-150mg bd, dose reduced for the elderly to 25-50mg) or gabapentin (100-300mg tds) is also often included used, especially if acute neuropathic pain is suspected. Neuropathic pain is more common in certain procedures, but can occur in any surgical procedure. It is often less responsive to opiate analgesia, thus a clue can be unmanaged pain on appropriate opiate therapy. Neuropathic pain is also identified by typical neuropathic pain descriptors – sharp, burning, pins/needles, numbness. Questionnaires are available to help identify neuropathic pain such as DN4. Pain occurring in hypoaesthetic areas in the surgical field, or areas of allodynia or hyperalgesia are other clues. There is conflicting evidence on whether the inclusion of alpha-2-delta ligands can prevent CPSP.
Other analgesic adjuvants and techniques may utilised depending on the clinical situation. For example, ketamine infusion is beneficial for (1) severe post-operative pain that has not responded to opiate therapy, (2) the highly opioid-tolerant patient, or (3) severe neuropathic pain. Low-dose amitriptyline 10mg is another useful adjunct. Regional anaesthetic interventions are also incorporated in the multi-modal approach.
There is evidence that specific medications and/or techniques peri-operatively can reduce the risk of CPSP. Examples include perioperative ketamine, proposed to reduce up-regulation of nociceptive system via NMDA receptor), which has level-1 evidence . Regional anaesthesia techniques like perioperative epidural analgesia are also supported, reducing the incidence of severe phantom limb pain (Level III-2) and CPSP post thoracotomy.
Acute Pain Services (APS) available in some institutions are an invaluable tool; identification of patients whose postoperative pain may be difficult to control (see who gets it) and early review by APS can prevent severe post-operative pain. If pain is proving difficult to manage, involvement of an APS or pain specialist can help.
Management of pain post-discharge also requires consideration. The patient needs guidance about appropriate weaning off medications. With multimodal therapy opiates are rarely required at discharge, though the length of stay in hospital and type of surgery should be considered. If opiates are still required at discharge, education about the risk of harm with these medications is crucial. As a rough rule of thumb, opiates (or increased dosages) are not often needed for longer than 7-10 days post discharge , and the minimum amount of opiate required should be dispensed. Patients should be encouraged to have a review with their general practitioner within two weeks of discharge and encouraged to seek help should pain control prove difficult. The current public-health crisis of chronic opioid medication dependence, misuse, and its subsequent harms is well known; the extent to which opiates provided on discharge from hospital contribute to the situation is unknown.
HOW IS CHRONIC (PERSISTENT) POST-SURGICAL PAIN TREATED?
In general, early recognition of CPSP enables appropriate treatment to be instigated and a greater chance of improved management of pain. This is the case with most varieties of pain.
Thorough assessment to identify all the contributors to CPSP enables targeted treatment.
When the pain is neuropathic, which is often the case, a practitioner may employ such treatments as lignocaine patches, topical neuropathic creams, neuropathic medications, direct neuromodulation from blocks and injections, and sometimes radiofrequency and stimulators.
Other contributors to the pain state are addressed through education, medication optimisation, and targeted interventions, all of which support return to function. The multidisciplinary team can be invaluable in facilitating improved function.
· Act early if a patient has more pain than is typical, especially when complications have been excluded. Early referral to a pain specialist may be of benefit.
· Ask whether a pre-operative surgical consult would be helpful in those you have identified as at greater risk.
· Talk to your anaesthetist or acute pain services team for options for those with hard-to-control pain.
1. Schug SA, Palmer GM, Scott DA, Halliwell R, Trinca J; APM:SE Working Group of the Australian and New Zealand College of Anaesthetists and Faculty of Pain Medicine (2015), Acute Pain Management: Scientific Evidence (4th edition), ANZCA & FPM, Melbourne.
2. IASP Fact sheet No 4 CPSP Definition, Impact and Prevention Patricia Lavand’homme, MD, PhD and Esther Pogatzki-Zahn, Prof. Dr.med. 2017
3. PROSPECT – procedure specific post-operative pain management, www.postoppain.org