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Progression of Acute to Chronic Pain - The Size of the Problem

David A Scott

 

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Abstract

As noted my Macrae, chronic pain is becoming increasingly accepted as an important outcome of surgery1. Evidence has been accumulating for over a decade that approximately 10% of surgical patients will develop subsequent chronic pain conditions related to their procedure2, 3, and this may rise to over 50% following procedures such as amputation or median sternotomy1, 4.  Many characteristics of chronic pain after surgery have neuropathic characteristics, and are related to tissue and wound trauma at the time of surgery5. By simply observing most surgical procedures, it is clear that damage to peripheral nerves is unavoidable although usually inadvertent. Central sensitization at the time of surgery may also contribute to both the degree of acute post-operative pain and also the likelihood of chronic neuropathic pain. Clinical studies have demonstrated that the development of chronic pain postoperatively is associated with the intensity of acute pain experienced6-8 and it is now known from laboratory research that evidence of neuropathic pain may appear within hours of nerve injury and persist for weeks to months thereafter. Other elements that may increase individual propensity to developing chronic post surgical pain include age, gender, psychosocial and genetic factors1.

The development of serious or intolerable chronic pain following surgery is less frequent but may be in the order of 1% of surgical procedures. The operations most likely to be associated with persistent pain are those in which injury to nerves or richly innervated structures is almost unavoidable. Thus chest wall operations (thoracotomy, cardiac surgery, mastectomy) carry from 20 to 50% incidence of chronic pain of which 5 to 10% is severe4. Nerve injury during limb amputation is unavoidable, and the results of such procedures include phantom sensations or pain as well as persistent wound pain. Often these symptoms subside over six to twelve months but they may persist for a lifetime.

The extent of disability from persistent post-surgical pain is hard to quantitate because it varies from individual to individual. In some it may impair sleep or the ability to wear certain clothes (because of tactile allodynia) but in others it may prevent ability to return to work or to function independently (e.g. inability to use a leg prosthesis). In addition to personal suffering, it also means these patients draw further on our limited health care and social support resources. Therefore any strategies that are likely to be of benefit in reducing the incidence of such chronic pain are likely to be worthwhile.

This has several implications for the anaesthetist. The first and most obvious is that the acute pain experienced by patients postoperatively may comprise elements of nociceptive (‘normal’ acute pain) and neuropathic pain, and that these pain types may respond to different treatment strategies. Thus there is a need for anaesthetists to become skilled at differentiating these types of pain. The second is that there may be different surgical techniques or analgesic approaches that can be implemented during surgery to minimise the occurrence of neuropathic or inflammatory pain postoperatively. Finally, the incidence of long-term chronic or persistent pain disorders following surgical procedures may be reduced by peri-operative interventions designed to minimise acute pain, avoid or treat acute neuropathic pain and facilitate mobilisation. Studies have shown that effective peri-operative analgesia using epidural analgesia reduces acute and chronic pain in thoracotomy9, 10 and major abdominal surgery11. The perioperative use of anti-neuropathic agents, such as gabapentin12 and venlafaxine13, has also been associated with improved long-term outcomes following mastectomy.

References

  1. Macrae, W.A., Chronic post-surgical pain: 10 years on. Br J Anaesth, 2008. 101(1): p. 77-86.

  2. Perkins, F.M. and H. Kehlet, Chronic pain as an outcome of surgery. A review of predictive factors. Anesthesiology, 2000. 93(4): p. 1123-33.

  3. Breivik, H. and A. Stubhaug, Management of acute postoperative pain: still a long way to go! Pain, 2008. 137(2): p. 233-4.

  4. Kehlet, H., T.S. Jensen, and C.J. Woolf, Persistent postsurgical pain: risk factors and prevention. Lancet, 2006. 367(9522): p. 1618-25.

  5. Jung, B.F., et al., Neuropathic pain following breast cancer surgery: proposed classification and research update. Pain, 2003. 104(1-2): p. 1-13.

  6. Kalso, E., K. Perttunen, and S. Kaasinen, Pain after thoracic surgery. Acta Anaesthesiol Scand, 1992. 36(1): p. 96-100.

  7. Katz, J., et al., Acute pain after thoracic surgery predicts long-term post-thoracotomy pain. Clin J Pain, 1996. 12(1): p. 50-5.

  8. Peters, M.L., M. Sommer, and J.M. de Rijke, Somatic and psychosocial predictors of long-term unfavourable outcome after surgical intervention. Ann Surg, 2007. 245: p. 487-94.

  9. Obata, H., et al., Epidural block with mepivacaine before surgery reduces long-term post-thoracotomy pain. Can J Anaesth, 1999. 46(12): p. 1127-32.

  10. Senturk, M., et al., The effects of three different analgesia techniques on long-term postthoracotomy pain. Anesth Analg, 2002. 94(1): p. 11-5, table of contents.

  11. Lavand'homme, P., M. De Kock, and H. Waterloos, Intraoperative Epidural Analgesia Combined with Ketamine Provides Effective Preventive Analgesia in Patients Undergoing Major Digestive Surgery. Anesthesiology, 2005. 103(4): p. 813-820.

  12. Fassoulaki, A., et al., The analgesic effect of gabapentin and mexiletine after breast surgery for cancer. Anesth Analg, 2002. 95(4): p. 985-91, table of contents.

  13. Reuben, S.S., G. Makari-Judson, and S.D. Lurie, Evaluation of efficacy of the perioperative administration of venlafaxine XR in the prevention of postmastectomy pain syndrome. J Pain Symptom Manage, 2004. 27(2): p. 133-9.

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