Reports

This report is based on medical evidence presented at sanctioned medical congress, from peer reviewed literature or opinion provided by a qualified healthcare practitioner. The consumption of the information contained within this report is intended for qualified Canadian healthcare practitioners only.

2007 Annual Conference of the Canadian Pain Society

Ottawa, Ontario / May 23-26, 2007

Severe pain, especially that associated with neuropathy, substantially heightens health resource and medication utilization and associated costs. According to a recent study of data from the Régie de l’assurance maladie du Québec, patients with neuropathic pain had at least twice as many physician visits, procedures and days of hospitalization as those with non-neuropathic pain (Lachaine et al. Pain Res Manage 2007;12:31-7). According to Dr. John Clark, Clinical Professor of Anesthesiology and Medical Director, Chronic Pain Centre, University of Calgary, Alberta, the average annual cost of neuropathic pain is more than $10,000 per patient, most of which is accounted for by lost work and inability to perform daily activities.

Psychological Impact

Patients with chronic pain consistently have a higher incidence of psychological distress than those with other severe illnesses, including stroke or cancer. Pain, sleep disturbance and psychological symptoms may be described as a comorbid triad, observed Dr. Clark. Sleep deprivation and its sequelae (e.g. drowsiness, lack of energy and inability to concentrate) and psychological symptoms (e.g. anxiety and depression) are common in patients with pain and can worsen pain symptoms. Singly and collectively, the elements of the “pain triad” can substantially impair daily functioning and quality of life.

“There does seem to be something unique that significantly increases the incidence of anxiety disorders and mood disorders in the pain population,” remarked Dr. Robert Hewko, Clinical Manager, Complex Pain Service, Vancouver General Hospital and Clinical Professor of Psychiatry, University of British Columbia. The relationship is strongest for neuropathic pain. In a study of patients with postherpetic neuralgia, for example, anxiety or depression were reported by 41%, 55% and 68% of those with mild, moderate and severe pain, respectively (Oster et al. J Pain 2005;6:356-63). Animal studies suggest the pathogenesis of these psychological symptoms relates to alterations in the hypothalamic-pituitary axis and/or the limbic system. “Given the neurochemistry involved in neuropathic pain, there may in fact be good reasons why there’s a higher incidence of anxiety and depression in this population,” Dr. Hewko added.

The association of pain and psychological distress runs deeper still, because once psychological symptoms have taken hold, they adversely affect the patient’s pain threshold and/or his ability to tolerate pain, Dr. Hewko stated. “The process starts to reciprocate on itself.” For this reason, he stressed, treating the pain and the psychological symptoms as separate entities generally leads to poor outcomes. “It is very clear if you are going to treat these people effectively, you have got to treat both processes simultaneously [...] The linear treatment approach is just fraught with disaster.” Medications with activity against both neuropathic pain and psychiatric disorders are ideal in this setting, Dr. Hewko indicated, as their use can reduce the total number of medications required.

Consequences of Sleep Deprivation

A similar relationship exists between pain and sleep or sleep quality. Sleep disruption may be a direct result of the pain or attributable to medications used for its treatment. According to Dr. Brian Murray, Director, Sleep Program, Sunnybrook Health Sciences Centre and Assistant Professor of Medicine, University of Toronto, Ontario, a particularly relevant research finding is that benzodiazepines may suppress slow-wave or delta sleep, which is the most restful of the sleep stages. Tricyclic antidepressants and SSRIs tend to suppress rapid-eye-movement (REM) sleep. Benzodiazepines and opiates can aggravate obstructive and central sleep apnea, respectively.

In turn, sleep deprivation can be an important factor in pain, noted Dr. Murray. Sleep loss has been shown to aggravate pain by as much as 25% to 30%. A recent study determined that sleep loss (especially that of REM sleep) can induce hyperalgesia. Animal data suggest sleep deprivation may hinder the analgesic effects of opioids. “This is worth paying attention to because if you can address sleep deprivation in your complex pain patients, you may be able to offer them another modality, another way of taking the edge off their problem.... Good control of the pain/sleep problem really does mean that you have to take care of both components—improving pain to allow sleep to occur and making sure sleep disorders are treated in order to improve pain symptoms,” Dr. Murray explained. Newly published guidelines on the management of neuropathic pain (Moulin et al. Pain Res Manage 2007;12(1):13-21) note that anticonvulsants such as pregabalin are recommended as first-line treatment, and have a demonstrated ability to improve sleep quality as well as manage pain.

Dr. Clark stressed that patients with neuropathic pain may exhibit all three elements of the triad. However, “optimal management means you’ve got to deal with everything. You’ve got to deal with the comorbid psychiatric issues as well as the sleep issues.”

Dr. Hewko concurred and remarked that even medical specialists might be inadequately equipped to deal with complicated pain in a solo practice setting. In many cases, the patient’s best bet is a pain clinic with integrated multidisciplinary care, he commented.

Wait Times and Health-related Quality of Life

Unfortunately, access to multidisciplinary treatment facilities is frequently difficult for Canadian patients with pain. The STOP-PAIN research project determined that there are more than 100 public and non-public multidisciplinary pain treatment facilities in Canada, 80% of which are in major urban centres. None exist in Prince Edward Island or the northern territories. Although the median wait for an appointment is eight weeks, the range of wait times is an astounding 0 to 260 weeks. The key factor in wait times is funding, noted Dr. Philip Peng, Department of Anesthesia, Toronto Western Hospital, and Assistant Professor, University of Toronto. At publicly funded centres, the average wait is six months but one-third of facilities report a wait time of more than one year. The wait at non-publicly funded treatment centres is about two weeks on average, and 90% report wait times of less than two months. “A lot of patients with pain don’t have enough resources for their pain management,” he concluded. “[Many public pain clinics] are not able to meet the demand in terms of reasonable accessibility and reasonable wait times for a first appointment.”

The Canadian Pain Society’s Wait Times Task Force arose from the society’s concern that chronic pain, despite affecting up to a million Canadians, was not one of the priority areas cited by the federal government in its 10-year plan for reducing health care wait times. Its aim was to determine the impact of waiting for appropriate pain treatment, explained Dr. Mary Lynch, Director of Research, Pain Management Unit, Queen Elizabeth II Health Sciences Centre, Halifax, Nova Scotia. The task force confirmed that a patient who waits for six months or longer experiences a significant drop in health-related quality of life and psychological well-being. Some studies reported deterioration with as few as five weeks of waiting. In fact, Dr. Lynch added, the patients’ suffering may be underestimated, given that the six-month waiting period tended to start at the point the patient sought treatment or was referred, not the onset of pain. “The estimates we are giving are very conservative,” she indicated. The society plans to ask the federal government to consider wait times for chronic pain a national health care priority. It is also seeking the co-operation of the International Association for the Study of Pain in developing further evidence on the clinical impact of waiting for appropriate pain management.

Summary

Chronic pain, especially that caused by neuropathic processes, presents a clinical challenge. Comorbidities are common and their concurrent treatment is a crucial element of management. While referral to a multidisciplinary pain clinic is often ideal for a patient with complicated pain, timely access to such facilities is frequently difficult. New guidelines on neuropathic pain can assist the clinician in initiating timely and appropriate steps and agents to address the patient’s symptoms, ideally as close as possible to their onset.