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September 2016
David Craig, PharmD | Editor

Summaries

The Journal of Pain

Highlights from The Journal of Pain (Volume 17, No. 9, September 2016 Issue)

Journal of Pain cover

Study Shows Tai Chi Can Help Relieve Chronic Neck Pain

Tai Chi, a low-impact mind-body exercise, can be as effective as neck exercises in relieving neck pain, according to the results of arandomized controlled trial published in The Journal of Pain.

An international team of researchers investigated the efficacy of group Tai Chi compared with group neck exercises and no treatment to improve neck pain, disability, and quality of life in groups of people with nonspecific chronic neck pain. They hypothesized that 12 weeks of Tai Chi would prove superior to no treatment for chronic neck pain. The study also explored whether Tai Chi was more or less effective than conventional neck exercises.

One hundred fourteen subjects were enrolled in the trial. Eligibility requirements were being age 18 years or older and having chronic neck pain for 3 consecutive months.

Tai Chi originated in China and involves integrated dynamic musculoskeletal breathing and meditation training. It often is used for healthcare purposes and evidence supports its potential to help people with back pain, rheumatologic disease, and psychological disorders. No studies had been performed to determine Tai Chi’s benefits in relieving chronic neck pain.

The results showed that 12 weeks of Tai Chi was more effective than no treatment to improve pain, disability, quality of life, and postural control in persons with chronic neck pain, and Tai Chi was neither superior nor inferior to 12 weeks of neck exercises.

Study Evaluates Cannabis for Treating Neuropathic Pain from Spinal Cord Injury or Disease

Experimental treatment with cannabis to relieve neuropathic pain caused by spinal cord injury or disease shows enough promise to warrant further and more extensive clinical trials, according to new research published in The Journal of Pain.

Researchers from the VA Northern California Health Care System compared the analgesic efficacy of different strengths of vaporized cannabis and hypothesized that pain relief could be achieved using whole-plant cannabis.

Forty-two subjects followed a standardized procedure for inhaling, on three separate occasions, four puffs of vaporized cannabis containing placebo or 2.9% or 6.7% THC.

Results showed the reductions in pain intensity were significant above and beyond subjective and psychoactive side effects. Because the two active doses did not differ in analgesic potency, the authors noted the lower dose offers the best risk-benefit ratio.

The study showed that vaporized cannabis can provide relief from neuropathic pain caused by spinal cord injury or disease. This is consistent with previous research indicating that cannabis is a promising treatment for selected pain syndromes caused by injury or diseases of the nervous system. The authors cautioned that the preliminary, phase 1 study does not justify routine use of cannabis. Further research is needed to measure pain management efficacy and adverse effects over time.


PAIN

Highlights from PAIN (Volume 157, No. 9, September 2016 Issue)

Pain Medicine Cover

The Reciprocal Associations Between Catastrophizing and Pain Outcomes in Patients Being Treated for Neuropathic Pain: A Cross-Lagged Panel Analysis Study

Mélanie Racine, Dwight E. Moulin, Warren R. Nielson, Patricia K. Morley-Forster, Mary Lynch, Alexander J. Clark, Larry Stitt, Allan Gordon, Howard Nathan, Catherine Smyth, Mark A. Ware, and Mark P. Jensen; Department of Clinical and Neurological Sciences, Schulich School of Medicine and Dentistry, University of Western Ontario, London, ON, Canada; Lawson Health Research Institute, London, ON, Canada; Department of Anesthesia and Perioperative Medicine, Western University, London, ON, Canada; Department of Anesthesia, Pain Management and Perioperative Medicine, Dalhousie University, Halifax, NS, Canada; LW Stitt Statistical Services, London, ON, Canada; Wasser Pain Management Centre, University of Toronto, Toronto, ON, Canada; Department of Anesthesiology, University of Ottawa, Ottawa, ON, Canada; Department of Family Medicine, McGill University, Montreal, QC, Canada; Department of Rehabilitation Medicine, University of Washington, Seattle, WA

Catastrophizing, defined as a tendency to focus on or exaggerate the negative aspects of pain, is consistently associated with heightened pain severity, physical disability, and pain-related interference. Neuropathic pain (NeP), which occurs as a result of a lesion or a disease affecting the somatosensory system, is one of the most refractory pain syndromes. There is growing interest in the influence of psychological factors, such as catastrophizing, on NeP outcomes. The aim of this study was to determine if changes in catastrophizing occurring early in NeP treatment predict subsequent changes in pain intensity and interference later in treatment, and vice versa. The investigators hypothesized that reciprocal temporal relationships( by which early changes in catastrophizing during treatment would predict later changes in pain intensity and interference) and early changes in pain outcomes would help clinicians predict subsequent changes in catastrophizing.

A total of 538 patients with neuropathic pain were recruited from six multidisciplinary pain clinics across Canada. Study participants were asked to complete measures of catastrophizing, pain intensity, and interference when first seen in the clinic and then again at 3- and 6-month follow-ups. Cross-lagged panel analyses were used to determine the temporal associations among the study variables. Consistent with the study hypotheses, investigators found that decreases in catastrophizing early in treatment predicted subsequent improvements in both pain intensity and interference, and a reduction of pain outcomes early in treatment predicted a decrease in catastrophizing later in treatment. Even after controlling for autocorrelation and synchronous correlation, the predictor variables accounted for an additional and statistically significant 4% to 7% of total variance, representing small-to-moderate effect sizes.

To the investigators’ knowledge, this is the first study to show a temporal association between catastrophizing and subsequent pain in patients with NeP. These findings suggest that catastrophizing may be a viable treatment target in this population, but more research is needed to evaluate the effects of changes in catastrophizing on subsequent changes in pain and other pain-related outcomes.

These results are consistent with theoretical models hypothesizing a causal influence of catastrophizing on pain and suggest the possibility of mutual causation among these factors. The findings also support catastrophizing as a primary treatment target that could influence other important outcomes and suggest that treatments that focus on and reduce pain also may decrease catastrophizing.

Pain Sensitivity Profiles in Patients with Advanced Knee Osteoarthritis

Laura A. Frey-Law, Nicole L. Bohr, Kathleen A. Sluka, Keela Herr, Charles R. Clark, Nicolas O. Noiseux, John J. Callaghan, M. Bridget Zimmerman, and Barbara A. Rakel; Department of Physical Therapy and Rehabilitation Science, College of Medicine, University of Iowa, Iowa City, IA; College of Nursing, University of Iowa, Iowa City, IA; Department of Orthopedics and Rehabilitation, College of Medicine, University of Iowa, Iowa City, IA; Department of Biostatistics, College of Public Health, University of Iowa, Iowa City, IA

The purpose of this cross-sectional study was to examine quantitative sensory testing (QST) pain sensitivity profiles in a population with advanced knee osteoarthritis (OA) using baseline visit data collected as part of a larger randomized control trial, the TENS after new knee (TANK) study. The TANK study evaluated the effects of transcutaneous electrical nerve stimulation on pain during rehabilitation exercises after total knee replacement. Investigators sought to determine the factor structure of baseline pain sensitivity measures in this population, identify clusters of individuals with similar pain sensitivity (QST) profiles, and compare clinical characteristics and quality of life across profiles. They hypothesized that patients with advanced knee OA would continue to differentiate into pain sensitivity clusters but with less heterogeneity than those observed in a healthy population.

Findings demonstrate that patients with advanced knee OA cluster into pain sensitivity profiles as hypothesized, with clusters being similar to those seen in healthy populations. Consequently, pain sensitivity heterogeneity is a robust finding even among a population with significant disease that exhibits both peripheral and central sensitivities. Furthermore, pain intensity and function differed between these profiles after adjusting for age and sex, which suggests that patients with advanced knee OA may benefit from individualized diagnosis and treatment.

Pain sensitivity components were differentiated by modality over location consistent with previous observations in healthy adults and clinical populations with knee OA, back pain, and neuropathic pain. Pressure and heat pain were the most strongly correlated components, which may be attributable to common activation of C-polymodal nociceptors that respond to both mechanical and heat stimuli. The independence of heat pain sensitivity from heat pain temporal summation (TS) and the enhanced pain response to repeated stimuli support the hypothesis that TS indicates centrally mediated sensitivity. Significant correlations between pain and catastrophizing, anxiety, and depression have been reported in patients with knee OA. However, these findings suggest that the pain sensitivity phenotypic differences in patients with advanced knee OA are not mediated by psychological traits.

This study extends pain sensitivity clusters first observed in healthy populations to an older, clinical population experiencing pain and dysfunction associated with advanced knee OA. This translation of pain sensitivity profiles suggests the unique individual differences described in healthy adults may be meaningful in a patient population. This study, coupled with previous findings, suggests that pain sensitivity profiles are robust and may prove clinically important. Future longitudinal studies are needed to determine the predictive value of pain sensitivity profiles, with the goal to optimize patient care through individualized pain management.


The Clinical Journal of Pain

Highlights from The Clinical Journal of Pain (Volume 32, No. 9, September 2016 Issue)

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Clinically Important Change in Insomnia Severity After Chronic Pain Rehabilitation

Keith G. Wilson, John Kowal, and Emma J. Ferguson; Department of Psychology, The Ottawa Hospital Rehabilitation Centre, Ottawa, ON, Canada; Clinical Epidemiology Program, The Ottawa Hospital Research Institute, Ottawa, ON, Canada; Departments of Medicine and Anaesthesiology and School of Psychology, University of Ottawa, Ottawa, ON, Canada

The prevalence of clinically significant insomnia among patients who receive treatment for chronic pain is estimated between 50% and 80%. In longitudinal research, patients often report that a night of poor sleep is followed by increased pain the next day. Several randomized controlled trials have demonstrated the beneficial effects of cognitive-behavior therapy for insomnia (CBT-I) among patients with comorbid chronic pain and insomnia. Although CBT-I is efficacious for people with chronic pain, it has yet to be implemented on a widespread basis within interdisciplinary rehabilitation programs, which generally maintain a focus on functional restoration rather than sleep.

This study had several goals. First, investigators verified whether an interdisciplinary rehabilitation program provides benefits for symptoms of insomnia even though specific interventions for sleep are not central to the treatment. Second, they examined whether patients with comorbid insomnia benefit from rehabilitation to the same extent as patients whose sleep is less disturbed. Third, they conducted a thorough investigation of the clinical relevance of changes in insomnia symptoms by comparing different approaches to the identification of clinically important change.

A total of 140 patients (43 men and 97 women) completed a 4-week outpatient day program for interdisciplinary rehabilitation that incorporated psychoeducation about pain, physical fitness, and group psychotherapy. The Insomnia Severity Index (ISI) was included as an outcome, along with measures of pain, mood, and function. The study’s finding of a 60% prevalence of moderate-severe insomnia is comparable to past research. Investigators found that ISI scores correlated with other measures of pain, mood, and function, which also is consistent with previous investigations. On most outcomes, patients with moderate-severe insomnia improved to the same extent as those with no or subthreshold sleep disturbance. On average, insomnia patients began and ended a chronic pain management program with higher levels of pain-related difficulties, but the amount of change was comparable. This is noteworthy because insomnia generally is associated with adverse daytime consequences of sleepiness and fatigue, which could impede patients’ capacity to engage in a daily rehabilitation program. The fact that the low and high insomnia groups registered similar amounts of change suggests that insomnia did not present a barrier to their achieving meaningful clinical gains. In fact, in the area of depressive symptoms, those with moderate-severe insomnia improved more than patients with fewer sleep issues.

Effective treatment of insomnia comorbid with chronic pain is likely to necessitate more intensive focus on sleep itself. An alternative is to offer CBT-I as a component of aftercare for patients who require further support.

Healthcare Costs and Utilization in Patients Receiving Prescriptions for Long-Acting Opioids for Acute Postsurgical Pain

Laura S. Gold, Scott A. Strassels, and Ryan N. Hansen; Departments of Radiology and Pharmacy and Pharmaceutical Outcomes Research and Policy Program, University of Washington, Seattle, WA; Health Economics and Outcomes Research, Mallinckrodt Pharmaceuticals, Hazelwood, MO

Acute pain after joint replacement surgery is common; about 58% of patients undergoing total knee replacement and 47% of patients who undergo total hip replacement report moderate to severe pain on their first postoperative day. Acute postsurgical pain also is associated with delayed ambulation, increased duration of hospital stay, and short-term mental decline. Acute pain is commonly managed with intravenous opioid analgesics and oral opioids. The purpose of this study was to describe patients who underwent hip, knee, and shoulder replacement surgery and received long-lasting opioid (LAO) prescriptions and compare healthcare utilization and costs with those of postsurgical patients who did not receive LAO prescriptions.

The investigators analyzed outcomes at 1 week and at 1, 3, 6, and 12 months after joint replacement surgery and found that patients who received LAO prescriptions within 30 days of surgery had higher healthcare costs and healthcare utilization than patients who did not receive these prescriptions. In particular, patients who received LAO prescriptions shortly after surgery were significantly more likely to have been hospitalized and have visited the emergency department at least once between 1 week and 12 months after their index surgeries. Patients who received LAO prescriptions had significantly longer lengths of stay for hospitalizations that began during the first week and continued during the subsequent 1, 3, 6, and 12 months following their joint replacement surgeries. These patients also tended to fill more prescriptions. Such significant associations suggest that these patients require more attention to reduce the variability in their postsurgical outcomes. However, investigators could not determine whether the increases in healthcare utilization among LAO prescription recipients directly resulted from actual use of LAOs or if the increased use could be attributed to other unmeasured factors that correlated with receipt of LAO prescriptions.

Future studies should attempt to elucidate a causal relationship between LAOs and increased resource use and determine the specific patient characteristics or behaviors that may be driving these associations. In particular, it would be useful to determine whether the increased healthcare utilization that was observed can be directly attributable to use of opioids.