An Open-Label Pilot Study Investigating Noninvasive High-Frequency Peripheral Nerve Fiber Stimulation in Chronic Pain

OBJECTIVE

Providing sustained and effective treatment via the peripheral nervous system for the management of chronic pain is challenging. Application of noninvasive high-frequency stimulation at or near the painful area may benefit those with chronic pain. This open-label pilot survey examined the impact of this stimulation on pain intensity, activities of daily living, functional capacity, and medication consumption after 2 weeks of treatment.

METHODS

Stimulation was administered at home using the summation of two high-frequency sinusoidal alternating signals at 3858 and 3980 Hz delivered between two electrodes placed directly over one or two locations of pain. Individuals completed a survey after 2 weeks to assess pain, activities of daily living (ADL), pain medication consumption, quality of life (QoL), mood, sleep, functional outcomes, and satisfaction.

RESULTS

463 individuals (372 males; 91 females) retuned the completed survey after 2 weeks of treatment. Pain and ADL scores significantly improved at follow-up compared with baseline (pain mean difference: 3.05; 95% confidence interval [CI]: 2.86, 3.24; ADL mean difference: 1.82; 95% CI: 1.60, 2.04). Corresponding improvements in QoL, sleep, mood, functional outcomes, and satisfaction were noted. On average, 8.00 ± 11.11 hours of pain relief were reported with 54% experiencing reductions in pain medication consumption. 98% would use the stimulation in the future.

CONCLUSION

Two weeks of noninvasive high-frequency peripheral nerve fiber stimulation appeared to confer positive effects in individuals with chronic pain. Future research employing a control group/arm is needed to establish the long-term impact of this bioelectric technique in specific pain cohorts.

Multivariate Prognostic Modeling of Persistent Pain Following Lumbar Discectomy

Background: Persistent postsurgical pain (PPSP) affects between 10% and 50% of surgical patients, the development of which is a complex and poorly understood process. To date, most studies on PPSP have focused on specific surgical procedures where individuals do not suffer from chronic pain before the surgical intervention. Individuals who have a chronic nerve injury are likely to have established peripheral and central sensitization which may increase the risk of developing PPSP. Concurrent analyses of the possible factors contributing to the development of PPSP following lumbar discectomy have not been examined. Objective: The aim of this study is to identify risk and protective factors that predict the course of recovery following lumbar discectomy and to develop an easily applicable preoperative multivariate prognostic model for the occurrence of PPSP in this patient cohort. Study Design: A prospective study of elective lumbar discectomy with a 3 month follow-up. Setting: University setting in Ireland Methods: All ASA I-II patients, (n = 53, 18-65 years old), undergoing elective lumbar discectomy at a single institute were included and followed for a 3 month period postsurgery. Preoperative potential predictors were collected: age, gender, pain intensity (McGill score, visual analog scale [VAS], Present Pain Intensity), degree of dysfunction (Roland-Morris Function score), psychological status (pain catastrophizing, anxiety, and depression scores), health-related quality of life (SF36), quantitative sensory testing (QST), inflammatory biomarkers, and a genetic pain profile. The proposed primary outcome was significant pain reduction (VAS > 70%) 3 months following surgery compared to the preoperative pain intensity. Results: A final prediction model was obtained using a multivariate logistic regression in combination with bootstrapping techniques for internal validation. Twenty (37.7%) patients developed PPSP. Independent predictor factors included age (odds ratio [OR] = 1.0 per year), present pain intensity (OR = 0.6), and degree of dysfunction (OR = 1.2). The concordance index C (.658) supports a good monotonic association (where perfect prediction is 1) and the Akaike’s information criteria indicated a good fit of the model. Inclusion of additional measured parameters (QST, biomarker, or genotyping) did not improve the model. Limitations: Before this internally validated model can be integrated into clinical practice, and used for patient counselling and quality assurance purposes, external validation studies are necessary. Conclusions: We demonstrated that the occurrence of PPSP can be predicted using a small set of variables easily obtained at the preoperative visit. This a prediction rule that could further optimize perioperative pain treatment and reduce attendant complications by allowing the preoperative classification of surgical patients according to their risk of developing PPSP. Key words: Persistent post surgical pain, predictive modeling, prognostic, lumbar discectomy

A Randomised, Placebo-controlled Trial of the Effects of Preoperative Pregabalin on Pain Intensity and Opioid Consumption following Lumbar Discectomy

BACKGROUND

Pregabalin has been shown to have analgesic effect in acute pain models. The primary objective was to examine the efficacy a single dose of pregabalin, would have on morphine consumption following lumbar discectomy.

METHODS

With ethical approval a randomized, placebo-controlled prospective trial was undertaken in 32 patients (ASA I-II, 18-65 years) with radicular low back pain for > 3 months undergoing elective lumbar discectomy. Patients received either oral pregabalin 300 mg (PG Group) or placebo (C Group) one hour before surgery. Pain intensity, the accumulative morphine consumption and adverse effects were recorded for 24 hours following surgery. Functional, psychological and quantitative sensory testing were also assessed.

RESULTS

Fourteen patients out of the 32 recruited were randomized to receive pregabalin. Morphine consumption was reduced (absolute difference of 42.3%) between groups with medium effect size. (Mann-Whitney; U = 52.5, z-score= 2.84, P = 0.004, r = 0.14). This was not associated with a significant difference in the incidence of adverse effects between the two groups. The median pain intensity (VAS) on movement was not significantly different between groups.

CONCLUSIONS

A single pre-operative dose of pregabalin (300 mg) did not result in a reduction in pain intensity compared to placebo in this patient cohort but the significant reduction in morphine consumption suggests that a fixed peri-operative dosing regime warrants investigation.