The journal of pain : official journal of the American Pain Society
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Randomized Controlled Trial Multicenter Study
Predictors of long-term opioid use among patients with painful lumbar spine conditions.
Our objective was to assess predictors of self-reported opioid use among patients with back pain due to lumbar disc herniation or spinal stenosis. Data were from the Spine Patient Outcomes Research Trial (SPORT), a multi-site observational study and randomized trial. We examined characteristics shown or hypothesized to be associated with opioid use. Using generalized estimating equations, we modeled associations of each potential predictor with opioid use at 12 and 24 months. At baseline, 42% of participants reported opioid use. Of these participants, 25% reported continued use at 12 months and 21% reported use at 24 months. In adjusted models, smoking (RR = 1.9, P < .001 at 12 months; RR = 1.5, P = .043 at 24 months) and nonsurgical treatment (RR = 1.7, P < .001 at 12 months; RR = 1.8, P = .003 at 24 months) predicted long-term opioid continuation. Among participants not using opioids at baseline, incident use was reported by 8% at 12 months and 7% at 24 months. We found no significant predictors of incident use at 12 or 24 months in the main models. In conclusion, nonsurgical treatment and smoking independently predicted long-term continued opioid use. To our knowledge, this is the first longitudinal study to assess predictors of long-term and incident opioid use among patients with lumbar spine conditions. ⋯ This longitudinal study of patients with disc herniation or spinal stenosis found that nonsurgical treatment and smoking predicted long-term self-reported opioid use. The greater risk of opioid continuation with nonsurgical therapy may be helpful in decision-making about treatment. The relationship between opioid use, smoking, and other substance use deserves further study.
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Randomized Controlled Trial
An investigation into the hypoalgesic effects of high- and low-frequency transcutaneous electrical nerve stimulation (TENS) on experimentally-induced blunt pressure pain in healthy human participants.
Transcutaneous electrical nerve stimulation (TENS) is a noninvasive technique used to reduce pain. It is claimed that TENS frequency is a key determinant of outcome. This study compared TENS delivered at 3 pulses per second (pps) and 80 pps on blunt pressure pain in human participants when TENS intensity was standardized at a strong nonpainful level. Thirty-two pain-free participants completed an experiment in which they received TENS at 3 pps and 80 pps in a crossover fashion. An algometer was used to measure pain threshold for each frequency before and during 20 minutes of TENS. A statistically significant elevation in pain threshold relative to baseline was found for 80 pps when compared to 3 pps after 10 and 20 minutes of TENS (P = .001 and P < .001, respectively). After 20 minutes of TENS, 30 of 32 participants had exceeded a 10N elevation in threshold relative to baseline during 80 pps compared to 19 participants during 3 pps (odds ratio 10.3 (CI, 2.28, 44.78), P = .002). We suggest that the higher rates of impulse generation by TENS at 80 pps resulted in a stronger afferent input to the central nervous system, resulting in stronger segmental inhibition of nociceptive transmission of second-order neurones, in line with the gate control theory of pain. In conclusion, strong nonpainful TENS at 80 pps was superior to 3 pps at increasing pressure-pain threshold in healthy volunteers. We recommend a follow-up study using pain patients. ⋯ This study provides evidence that high frequency TENS at 80 pulses per second increases pain threshold to pressure algometry in healthy participants over and above that seen with low frequency TENS at 3 pulses per second when a strong nonpainful TENS sensation is experienced within the site of experimental pain.