Editorial: Advances in pain

Abstract

Developments in our understanding of the aetiology and management of acute and chronic pain are progressing at a pace and the time is right for a Postgraduate Educational Issue of the British Journal of Anaesthesia to consider this important area. The British Journal of Anaesthesia is very grateful to the many expert contributors to this issue which represents a comprehensive and authoritative review of several important areas of scientific and clinical interest. The emphasis of this edition is clinical. However, the first two articles give an excellent overview of advances in our understanding of the basic sciences with respect to pain. Kidd and Urban1Kidd BL Urban LA Mechanisms of inflammatory pain.Br J Anaesth. 2001; 87: 3-11Abstract Full Text Full Text PDF PubMed Scopus (400) Google Scholar describe mechanisms of inflammatory pain and summarize the role of receptors, ion channels and neurotransmitters in the modulation of chemical, thermal and mechanical transduction. They describe how research in this field is driving the development of analgesics and anti-inflammatory drugs with novel modes of action. Neuropathic pain originates in a damaged or abnormal nervous system and differs in many respects to nociceptive pain and Bridges, Thompson and Rice review its aetiology.2Bridges D Thompson SWN Rice ASC Mechanisms of neuropathic pain.Br J Anaesth. 2001; 87: 12-26Abstract Full Text Full Text PDF PubMed Scopus (353) Google Scholar They emphasize that a single mechanism is not likely to explain all syndromes of neuropathic pain and that improved understanding of this complex topic may allow mechanism- rather than disease-based approaches to therapy as suggested recently by Woolf and Mannion.3Woolf CJ Mannion RJ Pain: Neuropathic pain: aetiology, symptoms, mechanisms and management.Lancet. 1999; 353: 1959-1964Abstract Full Text Full Text PDF PubMed Scopus (1769) Google Scholar However, without the availability of new drugs acting at a variety of sites this is not, as yet, a practical proposition and Bridges and colleagues point towards future developments in this area. For many years, bupivacaine has been the standard local anaesthetic for perioperative neural blockade. Concerns with respect to its safety, and our appreciation of the relative toxicities of stereoisomers, has led to the introduction of ropivacaine and levobupivacaine. Whiteside and Wildsmith4Whiteside JB Wildsmith JAW Developments in local anaesthetic drugs.Br J Anaesth. 2001; 87: 27-35Abstract Full Text Full Text PDF PubMed Scopus (98) Google Scholar review the clinical efficacy of these new local anaesthetic agents in various clinical settings and compare their properties with bupivacaine. There is a world-wide drive to increase the number of surgical procedures performed on a day-case basis and adequate post-operative pain relief is essential if this is to succeed. Rawal reviews the techniques available for analgesia after day-case surgery and emphasizes the need for rapid return to ‘street fitness’ in these patients, the efficay of balanced analgesia utilizing local anaesthetic techniques and oral non-opioid analgesia and the role of post-discharge patient follow up.5Rawal N Analgesia for day case surgery.Br J Anaesth. 2001; 87: 73-87Abstract Full Text Full Text PDF PubMed Scopus (125) Google Scholar He also considers more ambitious approaches, such as the use of spinal anaesthesia and patient-controlled regional analgesia systems. Patient-controlled analgesia (PCA) and epidural analgesia have become the mainstay of post-operative pain relief in most countries and the literature with respect to their efficacy and safety is extensive. The nature of the data (e.g. poor study design) make interpretation difficult and time-consuming but our contributors have produced excellent reviews. Macintyre demonstrates that PCA can be very safe and effective but she emphasizes that prescriptions need to be adjusted to fit individual patients if maximum efficacy is to be achieved.6Macintyre PE Safety and efficacy of patient-controlled analgesia.Br J Anaesth. 2001; 87: 36-46Abstract Full Text Full Text PDF PubMed Scopus (245) Google Scholar For many years, Wheatley has been a major advocate for the use of epidural analgesia after surgery and, with his colleagues Schug and Watson, considers the evidence for its efficacy and safety.7Wheatley RG Schug SA Watson D Safety and efficacy of postoperative epidural analgesia.Br J Anaesth. 2001; 87: 47-61Abstract Full Text Full Text PDF PubMed Scopus (226) Google Scholar The scope of the review is extensive and includes consideration of factors such as choice of drug (e.g. opioid, local anaesthetic or mixture), site of epidural insertion, bolus vs infusion vs patient-controlled administration and the use of adjuvants. Safety is of major concern and the authors are able to give likely incidences of rare but serious side-effects, such as major neurological complications. The Holy Grail of many workers investigating methods of optimal post-operative analgesia has been to demonstrate improved surgical outcome e.g. morbidity, mortality, hospital stay. Most have been disappointed. Kehlet has led the way in this field for several years and, with his colleague Holte, he reviews the relevant literature.8Kehlet H Holte K Effect of postoperative analgesia on surgical outcome.Br J Anaesth. 2001; 87: 62-72Abstract Full Text Full Text PDF PubMed Scopus (562) Google Scholar They conclude that better pain relief in itself is not likely to improve outcome, especially with respect to mobilization and hospital stay, unless it is part of a muti-disciplinary rehabilitation programme which maximizes the benefits of improved pain relief. Unfortunately, evidence from pain clinics suggests that chronic pain may be an outcome of surgery for many patients. Macrae describes the common syndromes and gives some indication of their incidence.9Macrae WA Chronic pain after surgery.Br J Anaesth. 2001; 87: 88-98Abstract Full Text Full Text PDF PubMed Scopus (530) Google Scholar He argues that this is a major problem and, until recently, a neglected topic. Pain may be relatively common after a number of procedures (e.g. breast surgery, thoracotomy, cholecystectomy, hernia repair) and he emphasizes the need for further research of good quality in order to elucidate the true incidence, risk factors and causes of this phenomenon. Phantom limb pain is a common example of chronic pain after surgery and, although this is described briefly by Macrae, the syndrome is comprehensively reviewed by Nikolajsen and Jensen;11Nikolajsen L Jensen TS Phantom limb pain.Br J Anaesth. 2001; 87: 107-116Abstract Full Text Full Text PDF PubMed Scopus (307) Google Scholar workers who have made an enormous contribution to our understanding of this problem. They stress the importance of the differentiation between stump pain, phantom sensation and phantom pain and that a number of mechanisms are involved in the aetiology of this syndrome, including factors in the peripheral nervous system, spinal cord and brain. Evidence with respect to treatment and prevention is reviewed and they conclude that it may not be possible to prevent phantom pain with pre-emptive approaches. There have been recent advances in our understanding of several chronic pain conditions and, in this issue, both complex regional pain syndrome (CRPS) and trigeminal neuralgia are reviewed. In a masterful review of the extensive and confusing literature on CRPS (formerly reflex sympathetic dystrophy), Harden considers important controversial factors such as epidemiology, diagnostic criteria and treatment.10Harden RN Complex regional pain syndrome.Br J Anaesth. 2001; 87: 99-106Abstract Full Text Full Text PDF PubMed Scopus (52) Google Scholar He emphasizes that a multidisciplinary approach (i.e. doctors, physiotherapists, occupational therapists, psychologists) in the management of this devastating condition is essential and, although data from good quality clinical trials are lacking, patients often require the expert use of pharmacotherapy and blocks to support the multidisciplinary approach. One of the most unpleasant conditions that can befall a patient is trigeminal neuralgia and this is reviewed by Nurmikko and Eldridge.12Nurmikko TJ Eldridge PR Trigeminal neuralgia.Br J Anaesth. 2001; 87: 117-132Abstract Full Text Full Text PDF PubMed Scopus (278) Google Scholar Again, diagnostic criteria can be confusing and several causes are likely to be responsible for the syndrome. The authors give expert guidance on diagnosis and show that the trigeminal nerve, rather than the central nervous system, is the likely site of pain generation. They also present clearly the published evidence for the short- and long-term efficacy of the numerous treatments for trigeminal neuralgia. The controlled use of opioids for non-cancer chronic pain has been advocated by many and Collett reviews this controversial area.13Collett B-J Chronic opioid therapy for non-cancer pain.Br J Anaesth. 2001; 87: 133-143Abstract Full Text Full Text PDF PubMed Scopus (79) Google Scholar She evaluates current practice and examines the evidence for and against this therapy. There are many published guidelines but most conform to a consensus view which is described in the article. Finally, pain is a subjective, emotional complaint and, to manage it successfully, the practitioner must have an understanding of the psychological aspects. Eccleston reviews pain-related fear and depression and the phenomenon of coping and explains why extent of injury and disability are often poorly related to pain.14Eccleston C Role of psychology in pain management.Br J Anaesth. 2001; 87: 144-152Abstract Full Text Full Text PDF PubMed Scopus (154) Google Scholar These factors play a central role in pain management programmes for patients with chronic pain and the efficacy of this approach is reviewed. The article is essential reading for all those involved in the management of acute and chronic pain. We believe that this Postgraduate Educational Issue of the British Journal of Anaesthesia is an important addition to the literature on pain and pain management. We hope that it will be of use to specialists in this area but also inspire others to develop an interest in pain and even consider a career in this complex, challenging but rewarding area of clinical practice. David J. Rowbotham Department of Anaesthesia, Intensive Care and Pain Management, University of Leicester Infirmary Road Leicester LE1 5WW