Chronic post-surgical pain: prevention and management

With Dr Deepak Ravindran  |  23 Feb 2015  |  Print

Chronic post-surgical pain: prevention and management

Dr Deepak Ravindran is consultant in anesthesia and pain medicine, Royal Berkshire Hospital, Reading, UK.

In the last 10 years, there has been increasing recognition of the fact that a significant percentage of patients report chronic pain after a wide variety of surgeries. Chronic postsurgical pain (CPSP) is a major problem with societal consequences and effect on quality of life. Up to about a third of patients report persistent or intermittent pain one year after common surgical procedures.[1] It is therefore important to identify possible risk factors, understand pathological mechanisms and establish preventive strategies.

Definition

The following criteria[2] have been suggested to define CPSP:

  • Pain that develops after a surgical procedure
  • Pain lasting at least two months
  • Other causes such as chronic infection have been excluded
  • The possibility that the pain is continuing from a pre-existing problem has been excluded.

Prevalence

A survey of 5,130 patients attending outpatient pain clinics revealed that 22.5% of patients cited surgery as their main cause of chronic pain.[3] The figure for the general population is likely to be significantly higher since not all patients come into secondary care. A more recent cross-sectional survey of 12,982 participants showed that, among respondents who had undergone surgery more than three months prior to being surveyed (n=2,043), 40.4% reported chronic pain, 18.3% reported moderate to severe pain and sensory abnormalities were reported by 24.5%.[4]

The common surgical procedures include inguinal hernia repair and breast, orthopedic and cardiothoracic surgery.[1] The incidence of chronic pain is 12% for patients undergoing hernia repair[5] and is now the most common long-term problem after such surgery.[6] Rates of CPSP are much higher after mastectomy with reconstruction (49%) compared with mastectomy alone (31%).[7]

Risk factors

A number of putative risk factors have been identified that may contribute to development of CPSP (Table 1).[8]

Genetic susceptibility is likely to play a role in the development of CPSP. For example, single nucleotide polymorphisms coding for the catechol-O-methyltransferase enzyme are associated with the development of chronic pain conditions such as temporomandibular joint disorder.[9] Genetic variability in the expression of enzymes responsible for neurotransmitter synthesis in the dorsal root ganglion is associated with persistent pain after lumbar discectomy.[10]

There are no studies as yet that have included all the above factors and therefore there is no clear consensus on the mechanisms involved and hence prevention and management of the problem.

Table 1. Putative risk factors for chronic postsurgical pain

Pre-operative factors
  • Psychological factors such as lack of resilience and catastrophizing leading to vulnerability
  • Pre-existing pain syndromes such as fibromyalgia, headache, low back pain, irritable bowel syndrome
  • Pre-operative pain in surgical site
  • Younger age group
  • Genetic and environmental components
Intra-operative factors
  • Nerve handling and injury
  • Type of incision
  • Not utilizing nerve-sparing techniques
  • Type of surgery (location, use of mesh, stapling, sternal wire)
Post-operative factors
  • Presence of acute post-operative pain
  • Disease recurrence at surgical site
  • Use of chemotherapy or radiotherapy

Preventive strategies and treatment

A positive correlation between sensory abnormalities and pain as reported[7]suggests that neuropathic mechanisms are responsible in a majority of pain cases.[1] Once nerve injury has occurred, a wide variety of inflammatory mechanisms are activated leading to peripheral and central sensitization by release of various neuro-transmitters. Our knowledge of acute pain physiology and its transition to chronic pain would suggest that one therapeutic strategy or single modality treatment is unlikely to work once this diffuse and complex neural pathway activation occurs.
This increase in awareness of CPSP has led to a huge body of research looking into pre-emptive and preventive strategies. The challenge is to accurately identify at-risk patients and target suitable interventions.

Pre-emptive epidural analgesia (regional analgesia commenced before surgery) has not shown much benefit for preventing CPSP. A meta-analysis of pre-emptive epidural compared with epidural commenced after completion of thoracic surgery did not affect development of CPSP.[11]

Many of the risk factors are difficult to influence or alter but there is no doubt that severity of acute postoperative pain influences CPSP.[1] Effective treatment of acute pain after surgery can reduce the incidence of CPSP by preventing sensitization of the CNS.[1] A combined systematic review and meta-analysis looked at the utility of using gabapentin and pregabalin in preventing CPSP.[12]Eight trials were included in the meta-analysis and they showed that six of the gabapentin trials demonstrated moderate-to-large reduction in the development of CPSP, while two of the pregabalin trials showed a very large reduction in development of CPSP.[12] Pre-emptive analgesia using drugs such as gabapentin or pregabalin (off-license) administered pre-operatively and continued postoperatively are now part of most procedure-specific pain management protocols in the UK, and are included in enhanced recovery pathways.

Regional blockade by itself is often insufficient and therefore a multimodal approach utilizing regional blockade (central/peripheral), NSAIDs, drugs for neuropathic pain and other analgesics including opioids is the best way forward.

A major preventive factor often less discussed is not having the surgical procedure itself. Inappropriate or unnecessary surgery needs to be prevented. Alternatives to surgery should be explored and patients must be made aware of risks so that a truly informed choice is made. Public education should be improved to both patients and their carers in order to help remove the belief that something must have gone wrong at the time of surgery.

Once CPSP has occurred it is difficult to cure, but there are a number of interventions that can be helpful in reducing pain. Initial management in primary care would include patient education, counselling and self-management followed by the use of anti-neuropathic medication such as amitriptyline, gabapentin and pregabalin. Depending on the extent and severity of the pain and its effect on quality of life, pain specialists can employ a variety of interventions such as local infiltrations of steroids[13,14] and diagnostic nerve blocks followed by neuromodulation techniques within a multidisciplinary model. Although the evidence base for these techniques is limited, when chosen appropriately, they can provide hope.

Conclusion

CPSP is a significant public health issue. As its development is likely to be multifactorial, large scale, multicenter randomized studies are urgently needed to aid better understanding of CPSP. Meanwhile, our aim should be to minimize unnecessary and inappropriate surgery, provide sustained and effective perioperative pain relief and detect and treat postoperative neuropathic pain in an early and aggressive manner using a multimodal strategy.

References:

1. Kehlet H, Jensen TS, et al. Persistent postsurgical pain: risk factors and prevention. Lancet 2006;367:1618-1625.
2. Macrae WA, Davies HT. Chronic postsurgical pain. In Crombie IK, Croft PR, et al (editors). Epidemiology of Pain. Seattle, IASP Press, 1999.
3. Crombie IK, Davies HT, et al. Cut and thrust: antecedent surgery and trauma among patients attending a chronic pain clinic. Pain 1998;76:167-171.
4. Johansen A, Romundstad L, et al. Persistent postsurgical pain in a general population: prevalence and predictors in the Tromsø study. Pain 2012;153:1390-1396.
5. Aasvang E, Kehlet H. Chronic postoperative pain: the case of inguinal herniorrhaphy. Br J Anaesth 2005;95:69-76.
6. Jenkins JT, O’Dwyer PJ. Inguinal hernias. Br Med J 2008;336:269-272.
7. Wallace MS, Wallace AM, et al. Pain after breast surgery: a survey of 282 women. Pain 1996;66:195-205.
8. Kehlet H. Persistent postsurgical pain: surgical risk factors and strategies for prevention. In Castro-Lopes J, Raja S, et al (editors). Pain 2008: An Updated Review. Seattle, IASP Press, 2008.
9. Diatchenko L, Slade GD, et al. Genetic basis for individual variations in pain perception and the development of a chronic pain condition. Hum Mol Genet 2005;14:135-143.
10. Searle RD, Simpson KH. Chronic post surgical pain. CEACCP 2010;10:12-14.
11. Bong CL, Samuel M, et al. Effects of preemptive epidural analgesia on post-thoracotomy pain. J Cardiothor Vasc Anesth 2005;19:786-793.
12. Clarke H, Bonin RP, et al. The prevention of chronic postsurgical pain using gabapentin and pregabalin: a combined systematic review and meta-analysis. Anesth Analg 2012;115:428-442.
13. Aroori S, Spence RA. Chronic pain after hernia surgery–an informed consent issue. Ulster Med J 2007;76:136-140.
14. Macrae WA. Chronic pain after surgery. Br J Anaesth 2001;87:88-98.

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