The journal of pain : official journal of the American Pain Society
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Randomized Controlled Trial
Adjusting pulse amplitude during transcutaneous electrical nerve stimulation (TENS) application produces greater hypoalgesia.
Transcutaneous electrical nerve stimulation (TENS) is a noninvasive technique used for pain modulation. During application of TENS there is a fading of current sensation. Textbooks of electrophysical agents recommend that pulse amplitude should be constantly adjusted. This seems to be accepted clinically despite the fact that there is no direct experimental evidence. The aim of the current study was to investigate the hypoalgesic effect of adjusting TENS pulse amplitude on pressure pain thresholds (PPTs) in healthy humans. Fifty-six healthy TENS naïve participants were recruited and randomly assigned to 1 of 4 groups (n = 14 per group): control, placebo TENS, fixed pulse amplitude TENS, and adjusted pulse amplitude TENS. Both active and placebo TENS were applied to the dominant forearm. PPTs were recorded from 2 points on the dominant forearm and hand before, during, and after 40 minutes of TENS. TENS increased the PPTs on the forearm (P = .003) and hand (P = .003) in the group that received the adjusted pulse amplitude when compared to all other groups. The mean final pulse amplitude for the adjusted pulse amplitude TENS group was 35.51 mA when compared to the fixed pulse amplitude TENS group, which averaged 31.37 mA (P = .0318). ⋯ These results suggest that it is important to adjust the pulse amplitude during TENS application to get the maximal analgesic effect. We propose that the fading of current sensation allows the use of higher pulse amplitudes, which would activate a greater number of and deeper tissue afferents to produce greater analgesia.
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Randomized Controlled Trial Multicenter Study
Subcutaneous methylnaltrexone for treatment of opioid-induced constipation in patients with chronic, nonmalignant pain: a randomized controlled study.
Methylnaltrexone is effective for opioid-induced constipation (OIC) in advanced illness patients. This 4-week, double-blind, randomized, placebo-controlled study investigated the effect of subcutaneous methylnaltrexone on OIC in patients receiving opioids for chronic, nonmalignant pain. Patients (N = 460) received subcutaneous methylnaltrexone 12 mg once daily (QD) or every other day (alternating with placebo) compared with placebo. Assessments included bowel movement count, time of bowel movement, straining, sense of complete evacuation, Bristol Stool Form Scales, and quality of life. Within 4 hours of first dose, 34.2% of patients in both methylnaltrexone groups had rescue-free bowel movements (RFBMs) versus 9.9% on placebo (P < .001). The estimated number needed to treat was about 4. On average, 28.9% of methylnaltrexone QD and 30.2% of methylnaltrexone alternate-day dosing resulted in RFBMs within 4 hours versus 9.4% QD and 9.3% alternate-day placebo injections (both P < .001). Both methylnaltrexone groups had significantly shorter time to first RFBM (P < .001) and greater increase in number of weekly RFBMs (P < .05) versus placebo. Adverse events included abdominal pain, diarrhea, nausea, and hyperhidrosis. Bristol Stool Form Scale scores (P = .002) and sensation of complete evacuation (P < .04) were significantly superior with methylnaltrexone QD; both methylnaltrexone groups reported no or mild straining during RFBMs in the first 2 weeks (P < .02). At 4 weeks, a significantly greater improvement in patient-reported, constipation-specific quality of life was seen in the alternate-day dosing (P < .05) and QD (P < .001) groups. ⋯ We present data demonstrating that subcutaneous methylnaltrexone 12 mg given once daily (QD) or every other day provides significant relief of OIC and was generally well tolerated in patients with chronic, nonmalignant pain. These results expand on prior effectiveness observed for the treatment of OIC in advanced illness patients to a broader population.
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The purpose of this study was to evaluate the prevalence and characteristics of pain in patients with chronic obstructive pulmonary disease (COPD) compared to a sample from the Norwegian general population. This cross-sectional study evaluated 100 COPD patients with and without pain and 333 individuals from the Norwegian population with pain. After controlling for age and sex, a significantly higher percentage of patients with COPD (45%) reported pain than the general population (34%; P = .02). No differences were found in pain intensity scores, pain interference score, or number of pain locations between COPD patients and the general population. COPD patients reported moderate-to-severe pain located primarily in the chest, shoulders, neck, and thorax. For both groups, the most common pain treatment was analgesic use. Acupuncture/transcutaneous electrical nerve stimulation was used more frequently by COPD patients (P < .001) while physiotherapy was used more frequently by the general population (P = .007) to treat their pain. Pain is a significant problem for COPD patients. Additional research is warranted to replicate these findings and to provide a more detailed characterization of how pain changes over time and influences COPD patients' ability to function and their quality of life. ⋯ Compared to the general population, pain is more common in patients with COPD and ranges from moderate to severe in its intensity.
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Irritable bowel syndrome (IBS), characterized mainly by abdominal pain, is a functional bowel disorder. The present study aimed to examine changes in the excitability and the activity of the voltage-gated K(+) channel in dorsal root ganglia (DRG) neurons innervating the colon of rats subjected to neonatal maternal separation (NMS). Colonic DRG neurons from NMS rats as identified by FAST DiI™ labeling showed an increased cell size compared with those from nonhandled (NH) rats. Whole cell current-clamp recordings showed that colonic DRG neurons from NMS rats displayed: 1) depolarized resting membrane potential; 2) increased input resistance; 3) a dramatic reduction in rheobase; and 4) a significant increase in the number of action potentials evoked at twice rheobase. Whole cell voltage-clamp recordings revealed that neurons from both groups exhibited transient A-type (I(A)) and delayed rectifier (I(K)) K(+) currents. Compared with NH rat neurons, the averaged density of I(K) was significantly reduced in NMS rat neurons. Furthermore, the Kv1.2 expression was significantly decreased in NMS rat colonic DRG neurons. These results suggest that NMS increases the excitability of colonic DRG neurons mainly by suppressing the I(K) current, which is likely accounted for by the downregulation of the Kv1.2 expression and somal hypertrophy. ⋯ This study demonstrates the alteration of delayed rectifier K current and Kv1.2 expression in DRG neurons from IBS model rats, representing a molecular mechanism underlying visceral pain and sensitization in IBS, suggesting the potential of Kv1.2 as a therapeutic target for the treatment of IBS.
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Substantial literature suggests that diverse biological, psychological, and sociocultural mechanisms account for differences by race and ethnicity in the experience, epidemiology, and management of pain. Many studies have examined differences between Whites and minority populations, but American Indians (AIs), Alaska Natives (ANs), and Aboriginal peoples of Canada have been neglected both in studies of pain and in efforts to understand its biopsychosocial and cultural determinants. This article reviews the epidemiology of pain and identifies factors that may affect clinical assessment and treatment in these populations. We searched for peer-reviewed articles focused on pain in these populations, using PubMed, CINAHL, Cochrane, and the University of New Mexico Native Health Database. We identified 28 articles published 1990 to 2009 in 3 topic areas: epidemiology of pain, pain assessment and treatment, and healthcare utilization. A key finding is that AI/ANs have a higher prevalence of pain symptoms and painful conditions than the U.S. general population. We also found evidence for problems in provider-patient interactions that affect clinical assessment of pain, as well as indications that AI/AN patients frequently use alternative modalities to manage pain. Future research should focus on pain and comorbid conditions and develop conceptual frameworks for understanding and treating pain in these populations. ⋯ We reviewed the literature on pain in AI/ANs and found a high prevalence of pain and painful conditions, along with evidence of poor patient-provider communication. We recommend further investigation of pain and comorbid conditions and development of conceptual frameworks for understanding and treating pain in this population.