March 2015
David Craig, PharmD | Editor


The Journal of Pain Highlights

The following highlights summarize selected articles from The Journal of Pain (Volume 16, Issue 3, March 2015).

Presurgical Psychosocial Predictors of Acute Postsurgical Pain and Quality of Life in Children Undergoing Major Surgery

Jennifer A. Rabbitts, Cornelius B. Groenewald, Gabrielle G. Tai, Tonya M. Palermo; University of Washington Seattle Department of Anesthesiology and Pain Medicine and Seattle Children’s Research Institute

Psychosocial risk factors such as sleep duration, anxiety, and parental fears can be important predictors for identifying children most likely to experience higher pain intensity, delayed recovery, and impaired quality of life following surgery. 

Some 5 million children undergo surgery every year in the United States, and it is estimated that up 60% have moderate to severe pain while in the hospital. Recent studies suggest that postsurgical pain may persist beyond the healing period for children, following general or orthopedic surgical procedures. Published research has established the importance of biopsychosocial factors in predicting pain after surgery in adults. 

Researchers with the University of Washington Seattle Department of Anesthesiology and Pain Medicine examined the impact of major surgery on pain and quality of life in children over time. They identified psychosocial and behavioral factors at baseline that predicted acute postsurgical pain intensity and impaired quality of life two weeks after surgery. They hypothesized that pre-surgical assessments of higher anxiety, pain catastrophizing, shorter sleep duration and higher parental catastrophizing about child pain would predict greater pain intensity and quality of life impairment.

Sixty families agreed to participate in the study. Children were assessed the week preceding surgery and follow-up occurred 2 weeks after the procedures. This is the first study to prospectively identify psychosocial risk factors for acute postsurgical pain in children after major surgery.

Results confirmed the hypothesis and showed that higher levels of parental catastrophizing and shorter child sleep duration significantly predicted higher levels of postsurgical pain. Also, higher child anxiety just before surgery predicted more quality of life impairments. 

The authors noted that inclusion of parent perceptions in the analysis yielded important information on the potential role of child and parent emotions prior to surgery. Further, child anxiety, parental catastrophizing, and sleep factors are modifiable factors that could be targets for preventative intervention strategies. 

Pregnancy Is Characterized by Widespread Deep Tissue Hypersensitivity Independent of Lumbopelvic Pain Intensity, a Facilitated Response to Manual Orthopedic Tests and Poorer Self-Reported Health 

Thorvaldur Skuli Palsson, Darren Beales, Helen Slater, Peter O'Sullivan, Thomas Graven-Nielsen ; Aalborg University, Denmark and Curtin University, Perth, Australia.

During pregnancy, eight in 10 women will develop pain to some extent in the lumbopelvic region, and for some it can be disabling. However, studies show most women perceive pain as a normal part of pregnancy and do not receive treatment for it.

Widespread deep tissue hypersensitivity is associated with lumbopelvic pain (LPP). The aim of the study, published in The Journal of Pain, was to evaluate a group of pregnant women suffering from different levels of LLP and compare their pain sensitivity and psychometric measures with a healthy nonpregnant control group. The authors assessed the relationship between disability, pain sensitivity, and psychometric variables. In addition to the clinical tests, subjects completed questionnaires to gauge emotional and physical well-being and to rate disability.

Results showed the pregnant group demonstrated significantly lower pressure pain thresholds at most assessment sites compared with the control group, but self-reported disability and pain did not correlate with pressure pain thresholds in the pregnant group. The high-pain group reported worse emotional health and poorer sleep quality than the control group. 

The authors concluded that pain sensitivity increases during pregnancy possibly due to physical changes in the body and emotional health. Clinical management of pregnant women with lumbopelvic pain, therefore, should address physical and emotional factors contributing to pain intensity.



PAIN Highlights

The following highlights summarize selected articles from PAIN (Volume 156, No. 3, March 2015 Issue).

Distinguishing Problematic from Nonproblematic Postsurgical Pain: A Pain Trajectory Analysis After Total Knee Arthroplasty

M. Gabrielle Page, Joel Katz, E. Manolo Romero Escobar, Noga Lutzky-Cohen, Kathryn Curtis, Samantha Fussa, and Hance A. Clarke; Department of Anesthesia, Faculty of Medicine, University of Toronto, Toronto, ON, Canada; Department of Psychology, Faculty of Health, York University, Toronto

The goal of this study was to follow a cohort of patients undergoing total knee arthroplasty over time to identify and describe their various pain trajectories before surgery and for up to 12 months after surgery, identify baseline predictors of trajectory group membership, and identify trajectory groups associated with poor psychosocial outcomes 12 months after surgery. Subjects completed pain and psychological questionnaires and functional performance tests preoperatively and 4 days, 6 weeks, 3 months, and 12 months after total knee arthroplasty.

Study results suggest that moderate preoperative pain, as opposed to low or high pain levels, is a risk factor for a poorer pain trajectory postoperatively and a poorer pain status outcome 12 months after surgery. Age and gender were not risk factors for persistent postsurgical pain, however. These results are in contrast to those of other studies, which found that younger age and female gender were risk factors for chronic postsurgical pain (CPSP) and opioid use for longer than 3 months after major surgery.

Results also suggest that a neutral or positive pain slope during the first several weeks after surgery leads to the continuation of pain and CPSP. In addition to levels of acute postoperative pain, levels of preoperative pain also influence patients’ pain trajectories.

Future research directions include replication of this pain trajectory model in other postoperative populations and examination of functional and psychological variables that can influence pain trajectories. Early identification of patients with a flat pain trajectory during the weeks after surgery can lead to the development of aggressive programs designed to decrease persistent postsurgical pain.


Variations in Potassium Channel Genes Are Associated with Distinct Trajectories of Persistent Breast Pain After Breast Cancer Surgery

Dale J. Langford, Steven M. Paul, Claudia M. West, Laura B. Dunn, Jon D. Levine, Kord M. Kober, Marylin J. Dodd, Christine Miaskowski, and Bradley E. Aouizerat; Schools of Nursing, University of California, San Francisco, CA; Schools of Medicine, University of California, San Francisco; Institute for Human Genetics, University of California, San Francisco

Most breast cancer survivors undergo a mastectomy or breast-conserving surgery that has potential to result in persistent breast pain. Prevalence estimates for this persistent pain condition vary between 25% and 60%. This wide variation may be attributable to differences in the definition of postmastectomy pain, multiple etiologies for persistent pain, and individual differences in phenotypic 3 and genotypic 29 characteristics. Persistent pain after breast cancer surgery also can occur as the result of intraoperative nerve injury that manifests as a neuropathic pain.

This study evaluated associations between variations in 10 potassium channel genes and persistent breast pain in the same sample of women. These candidate genes encode for 3 classes of potassium channels: voltage-gated potassium channels, inwardly rectifying potassium channels, and two-pore domain potassium channels. To determine genetic variations associated with low and high severity of persistent pain relative to no pain, the “no pain” class was used as the reference group, and differences in genotype frequencies between patients in the “no pain” vs. “mild pain” and “no pain” vs. “severe pain” classes were evaluated.

This study provides evidence that variations in potassium channel genes are associated with persistent breast pain after breast cancer surgery. Considerable overlap was found in genes that were associated with the “mild” and “severe pain” classes. Only 3.3% of patients who reported preoperative breast pain were classified in the “no pain” class. This finding suggests that preoperative breast pain is an important risk factor for persistent postsurgical breast pain. Both hardness in the breast before surgery and re-excision or mastectomy during the 6 months after surgery were significantly associated with membership in the “mild pain” class.

It is important to note that the majority of genes associated with the two persistent pain phenotypes were consistent. Only the voltage-gated potassium channel gene, KCNA1, differed between the two pain phenotypes. Moreover, KCNJ3, KCNJ6, and KCNK9 were associated with the occurrence of preoperative breast pain in this same sample. These findings suggest that potassium channel subtypes play a role in the development, maintenance, and severity of pain.





Clinical Journal of Pain Highlights

The following highlights summarize selected articles from Clinical Journal of Pain (Volume 31, No. 2, February 2015 Issue).

Barriers to Change in Depressive Symptoms After Multidisciplinary Rehabilitation for Whiplash: The Role of Perceived Injustice

Whitney Scott, Zina Trost, Maria Milioto, and Michael J. L. Sullivan; Department of Psychology, McGill University, Montreal, QC, Canada; Department of Psychology, University of North Texas, Denton, TX; Centre d’ Evaluation et de Réadaptation de l’Est, Montreal

Research suggests that approximately 40% to 60% of patients with persistent pain after musculoskeletal injury experience clinically meaningful symptoms of depression. Among patients with persistent pain, elevated levels of depressive symptoms have been associated with heightened pain intensity, more prolonged pain, reduced physical function, and more occupational disability. The purpose of this study was to identify barriers to change in depressive symptoms in patients undergoing multidisciplinary rehabilitation for persistent pain after whiplash injury.

Patients completed self-report measures of depressive symptoms, pain, disability, posttraumatic stress symptoms, pain catastrophizing, self-efficacy, and perceived injustice upon commencement and completion of a standardized multidisciplinary rehabilitation program. Analyses examined the pretreatment variables that were associated with change in depressive symptoms over the course of treatment and after treatment.

Results indicate that 58% of patients who began treatment with clinically significant levels of depressive symptoms continued to score above the clinical threshold for depressive symptoms after treatment. This study extended previous knowledge by demonstrating perceived injustice is a unique predictor of change in depressive symptoms and maintenance of clinically meaningful levels of depressive symptoms over the course of multidisciplinary rehabilitation for persistent pain after whiplash injury. Duration of work absence was a significant unique predictor of percentage of change in depressive symptoms in the linear regression analysis. These findings increase confidence in the role of perceived injustice in the persistence of depressive symptoms in patients receiving multidisciplinary rehabilitation for whiplash injury. These results suggest that screening for perceived injustice before multidisciplinary rehabilitation might help to identify patients who are least likely to benefit in terms of improvement in depressive symptoms. The use of intervention techniques targeting perceptions of injustice might enhance rehabilitation outcomes for those who sustain whiplash injury. Perceptions of injustice may stem in part from a sense of not being understood or believed, so validation of patients’ pain is likely a crucial first intervention step.

Future research examining the mechanisms underlying the impact of perceived injustice on recovery from depressive symptoms is necessary. Research examining targeted interventions to mitigate the impact of perceived injustice is also needed.


Pain Self-Efficacy Mediates the Relationship Between Depressive Symptoms and Pain Severity

Jay R. Skidmore, Alex L. Koenig, Sara J. Dyson, Amy E. Kupper, Melissa J. Garner, and Christopher J. Keller; Clinical Psychology Department, Seattle Pacific University, Seattle, WA

The importance of pain self-efficacy (PSE)—defined as a patient’s confidence in his or her ability to tolerate pain and perform daily activities despite their pain—has been well documented. Self-efficacy beliefs are often used to predict pain tolerance and aspects of pain experience and have been shown to be associated with pain-related variables in people with osteoarthritis, fibromyalgia, rheumatoid arthritis, and chronic low-back pain (CLBP). Higher levels of PSE are related to positive health outcomes such as lower pain ratings, fewer pain behaviors, and reduced levels of disability. Lower levels of PSE are associated with negative outcomes including higher levels of anxiety and depressive symptoms and lower levels of social support.

The aim of this study was to examine how change in depressive symptoms relates to change in PSE over the course of a multidisciplinary pain rehabilitation program, and whether or not PSE indirectly affects the relationship between change in depressive symptoms and change in pain severity. Investigators hypothesized that change in depressive symptoms over the course of treatment would be significantly related to changes in pain severity (i.e., affective, sensory, and evaluative pain) and PSE. They also predicted that there would be significant indirect effects of PSE on the relationship between depressive symptoms and pain severity.

Participants who had fewer depressive symptoms rated their pain as less severe over the course of treatment. The hypothesis stating that change in PSE would indirectly affect the relationship between change in depressive symptoms and change in pain severity was also supported. Change in depressive symptoms was related to change in sensory and evaluative pain partially because of the change that occurred in PSE beliefs. Participants who had fewer depressive symptoms over the course of treatment rated their sensory and evaluative pain as less severe, at least in part because of their increased confidence to tolerate pain and perform daily activities.

Increasing self-efficacy beliefs over the course of rehabilitation seems to be a central mechanism in the cognitive-behavioral treatment of chronic pain and in reducing pain-related depression. These findings highlight the importance of targeting self-efficacy beliefs as an intervention strategy to reduce depressive symptoms and pain severity in patients with CLBP.