The journal of pain : official journal of the American Pain Society
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Chronic pain after breast cancer treatment is a major clinical problem, affecting 25 to 60% of patients. Development of chronic pain after breast cancer treatment, as well as other surgical procedures, involves a complex pathophysiology that involves pre-, intra- and post-operative factors. This review is a systematic analysis on methodology and evidence in research into persistent pain after breast cancer treatment during the period 1995 to 2010, in order to clarify the significance and relative role of potential risk factors. Literature was identified by a search in PubMed and OVID, as well as by obtaining relevant studies from a systematic review of reference lists. Sixty papers were identified, most of these being retrospective or questionnaires. Only 2 studies included quantitative sensory testing and only 26 studies were prospective. Furthermore, about a third of the studies did not apply modern principles of surgical and adjuvant therapy. In summary, the data show inconsistencies in definition of chronic pain and treatment groups, as well as in the collection of pre- intra- and post-operative data, precluding conclusions with regard to pathophysiologic mechanisms as well as rational strategies for prevention and treatment. However, nerve damage and radiotherapy appear to be significant risk factors for chronic pain. A proposal for the design of future prospective studies is presented. ⋯ A comprehensive and systematic approach to research in chronic pain after breast cancer treatment is necessary in order to understand the pathophysiology and thus develop strategies for prevention and treatment.
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Randomized Controlled Trial
Efficacy of low-dose celecoxib in patients with acute pain.
The sore throat pain model was used to evaluate single-dose effects of celecoxib 50 and 100 mg over 6 hours in the treatment of acute pharyngeal pain. Multiple-dose effects of 50-mg bid and 100 mg followed by 50 mg over 6 to 24 hours were also evaluated. Under double-blind, randomized, placebo-controlled conditions, 269 adults with confirmed acute pharyngitis rated throat pain intensity, throat soreness, difficulty swallowing, and sore throat pain relief over 24 hours. For the primary efficacy analysis (SPID2), patients receiving celecoxib 100 mg during the first 2 hours after the first dose had significantly higher mean scores than patients in the placebo group (P < .0003). Efficacy was also demonstrated for celecoxib 50 and 100 mg compared with placebo for all end points (including total pain relief, summed pain intensity differences, total reduction of throat soreness, and difficulty swallowing) at all time points after the first dose and after the second 50-mg dose (P < .01). There were no differences between the dosage regimens, although a supplementary 50-mg dose of celecoxib 6 to 12 hours after the first dose appeared to provide additional efficacy over 24 hours. No serious adverse events (AEs) or discontinuations due to an AE were reported. The results of this study demonstrate that in this pain model, celecoxib is a well tolerated and efficacious analgesic in 50- and 100-mg doses. ⋯ In a double-blind, randomized, placebo-controlled trial utilizing the sore throat pain model, low-dose celecoxib (50- and 100-mg doses) was well tolerated and provided effective analgesia in patients with acute pain.
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Postoperative pain remains a significant problem despite optimal treatment with current pharmaceutical agents. In an effort to provide better postoperative pain control, there is a need to understand the factors that contribute to the development of pain after surgery. Leukemia inhibitory factor (LIF) is a pleiotropic cytokine released from tissues after injury. We hypothesized that LIF expression in skin, muscle, and dorsal root ganglion (DRG) would increase after plantar incision. The mRNA and protein expression of LIF and LIF receptor (LIF-R) were measured after plantar incision in the rat. Pain behaviors, immunohistochemistry, and C-fiber heat responses to LIF were also studied. LIF expression increased after incision in skin and muscle, and LIF-R was present in large and small DRG neurons. LIF administration to the hindpaw increased pain behaviors, a process that was reversed by anti-LIF. However, LIF and anti-LIF treatment at the time of incision did not augment or ameliorate pain behaviors. LIF treatment activated the second messenger system, JAK-STAT3, in cultured DRG neurons, but failed to alter spontaneous activity or heat responses in C-fiber nociceptors. In conclusion, LIF is not a target for postoperative analgesia; LIF may be important for skin and muscle repair and regeneration after incision. ⋯ This article highlights an incision pain model for the study of factors involved in nociception. The study demonstrates that LIF in is an unlikely target for novel early postoperative analgesics.
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Comparative Study
Patterns and predictors of health service utilization in adolescents with pain: comparison between a community and a clinical pain sample.
There is limited research describing the patterns of healthcare utilization in adolescents with chronic pain. This study describes healthcare utilization in a clinical chronic pain sample, and compares the patterns of service use of this group to a community sample with intermittent pain complaints. We also investigated demographic and clinical factors that predicted healthcare visits and medication use in the clinical sample. Data on 117 adolescents (aged 12-18; n = 59 clinical pain sample, n = 58 community) were collected. Caregivers and adolescents reported on sociodemographics, medical visits, current medications, pain, activity limitations, and depression. As hypothesized, the clinical pain sample had higher rates of healthcare consultation on all types of medical visits (general, specialty care, complementary medicine, mental health, OT/PT), and higher medication use compared to the community sample. Regression analyses revealed that higher annual income, greater pain frequency, and higher levels of caregiver-reported activity limitations were associated with a greater number of healthcare visits for the total sample. Within the clinical pain sample, higher pain frequency and greater activity limitations (caregiver report) predicted more specialty care visits. Additionally, higher income and greater levels of depressive symptoms predicted a higher number of prescribed medications. ⋯ This study contributes to the limited available data on health service and medication use in a clinical chronic pain sample versus a community sample of adolescents. We also identify clinical factors (pain frequency, parent-reported activity limitations, depressive symptoms) and demographic factors (gender, income) associated with healthcare utilization.
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Randomized Controlled Trial
Reliability and validity of a brief method to assess nociceptive flexion reflex (NFR) threshold.
The nociceptive flexion reflex (NFR) is a physiological tool to study spinal nociception. However, NFR assessment can take several minutes and expose participants to repeated suprathreshold stimulations. The 4 studies reported here assessed the reliability and validity of a brief method to assess NFR threshold that uses a single ascending series of stimulations (Peak 1 NFR), by comparing it to a well-validated method that uses 3 ascending/descending staircases of stimulations (Staircase NFR). Correlations between the NFR definitions were high, were on par with test-retest correlations of Staircase NFR, and were not affected by participant sex or chronic pain status. Results also indicated the test-retest reliabilities for the 2 definitions were similar. Using larger stimulus increments (4 mAs) to assess Peak 1 NFR tended to result in higher NFR threshold estimates than using the Staircase NFR definition, whereas smaller stimulus increments (2 mAs) tended to result in lower NFR threshold estimates than the Staircase NFR definition. Neither NFR definition was correlated with anxiety, pain catastrophizing, or anxiety sensitivity. In sum, a single ascending series of electrical stimulations results in a reliable and valid estimate of NFR threshold. However, caution may be warranted when comparing NFR thresholds across studies that differ in the ascending stimulus increments. ⋯ This brief method to assess NFR threshold is reliable and valid; therefore, it should be useful to clinical pain researchers interested in quickly assessing inter- and intra-individual differences in spinal nociceptive processes.