Assessment of sympathetic blocks

Photoplethysmographic signals to predict the success of lumbar sympathetic blockade for lower extremity pain

OBJECTIVE

A prospective, observational study to investigate how photoplethysmography (PPG) signals change during lumbar sympathetic blockade (LSB), and whether these changes can predict sympathetically mediated pain (SMP).

METHODS

Patients with unilateral lower extremity pain and self-reported cold hyperalgesia underwent LSB. Bilateral temperature and PPG signals (AC and DC) were recorded. Power spectrum analysis (PSA) was performed.

RESULTS

Of the total patient cohort (n = 38), eight patients (22.1%) had excellent pain-relief after LSB and were determined to have SMP. In all patients, the PPG AC signal changed immediately after drug administration, before any temperature change. DC signals decreased slowly in a linear fashion. PSA of DC signals showed significantly lower low-frequency/high-frequency (LF/HF) ratios in the SMP group than the sympathetically independent pain group, both before and after LSB. A cut-off value of 2.92 for LF/HF resulted in sensitivity, specificity and positive predictive values for SMP of 75.0%, 76.7% and 3.21 [1.5, 6.9], respectively.

CONCLUSIONS

PPG may be used as an early indicator of a successful LSB and could also be helpful in diagnosing SMP.

Translational advances in pain and anesthesia for cancer patients

Effective cancer pain management requires multidisciplinary approaches for multimodal analgesia. Although opioids have been the cornerstone, developments such as regional anesthesia and interventional pain techniques, complementary and alternative medicine, and new pharmaceuticals also have shown promise to relieve cancer pain. This overview of relevant clinical efforts and the modern day state of the science will afford a better understanding of pain mechanisms and multimodal approaches beneficial in optimizing analgesia for cancer patients.

The Cut-Off Rate of Skin Temperature Change to Confirm Successful Lumbar Sympathetic Block

The purpose of this study was to find the best cut-off value for the rate of change in temperature of the plantar surface of the foot for predicting the success of lumbar sympathetic block (LSB). A total of 185 LSBs were performed on 82 patients via a posterolateral approach under fluoroscopic guidance. Successful LSB was considered to have occurred when changes in the ipsilateral temperature between preblock and post-block were ≥ 2 °C. A receiver operating characteristic (ROC) curve for the minimum rate of temperature change was constructed as a predictor of the onset of a successful LSB. The area under the ROC curve was 0.971 at the rate of 0.4°C/min with a sensitivity of 89.5% and a specificity of 91.8%. Achieving a rate of temperature change of 0.4°C/min within approximately 5 min of the injection of local anaesthetic could be used as an indicator of the onset of successful LSB.

Management of lower limb complex regional pain syndrome type 1: an evaluation of percutaneous radiofrequency thermal lumbar sympathectomy versus phenol lumbar sympathetic neurolysis--a pilot study

BACKGROUND

Complex regional pain syndrome type 1 can be difficult to treat. The purpose of this study was to compare the safety and efficacy of two therapeutic options: percutaneous radiofrequency thermal lumbar sympathectomy and lumbar sympathetic neurolysis.

METHODS

We randomized 20 patients to receive percutaneous radiofrequency lumbar sympathectomy or lumbar sympathetic neurolysis with phenol 7% in lower limb complex regional pain syndrome type 1. The study end points were pain relief and side effects.

RESULTS

Within each group, there were statistically significant reductions from baseline in various pain scores after the procedure. However, there was no statistically significant difference in mean pain scores between the groups.

CONCLUSIONS

Based on this pilot study, radiofrequency lumbar sympathectomy may be comparable to phenol lumbar sympathectomy. A larger trial is required to confirm these findings.