MR guidance of sympathetic nerve blockade: measurement of vasomotor response initial experience in seven patients

Quantitative Analysis of Real-Time Infrared Thermography for the Assessment of Lumbar Sympathetic Blocks: A Preliminary Study

Lumbar sympathetic blocks (LSBs) are commonly performed to treat pain ailments in the lower limbs. LSBs involve injecting local anesthetic around the nerves. The injection is guided by fluoroscopy which is sometimes considered to be insufficiently accurate. The main aim was to analyze the plantar foot skin temperature data acquired while performing LSBs in patients with complex regional pain syndrome (CRPS) affecting the lower limbs. Forty-four LSBs for treating lower limb CRPS in 13 patients were assessed. Pain medicine physicians visualized the infrared thermography (IRT) video in real time and classified the performance depending on the observed thermal changes within the first 4 min. Thirty-two percent of the cases did not register temperature variations after lidocaine was injected, requiring the needle to be relocated. Differences between moments are indicated using the 95% confidence intervals of the differences (CI 95%), the Cohen effect size (ES) and the significance (p value). In successful cases, after injecting lidocaine, increases at minute 7 for the mean (CI 95% (1.4, 2.1 °C), p < 0.001 and ES = 0.5), at minute 5 for maximum temperature (CI 95% (2.3, 3.3 °C), p < 0.001 and ES = 0.6) and at minute 6 for SD (CI 95% (0.2, 0.3 °C), p < 0.001 and ES = 0.5) were observed. The results of our preliminary study showed that the measurement of skin temperature in real time by infrared thermography is valuable for assessing the success of lumbar sympathetic blocks.

An overview of interventional strategies for the management of oncologic pain

Pain is a ubiquitous part of the cancer experience. Often the presenting symptom of malignancy, pain becomes more prevalent in advanced or metastatic disease and often persists despite curative treatment. Although management of cancer pain improved following publication of the WHO's analgesic ladder, when used in isolation, conservative approaches often fail to control pain and are limited by intolerable side effects. Interventional strategies provide an option for managing cancer pain that remains refractory to pharmacologic therapy. The purpose of this review is to investigate these strategies and discuss the risks and benefits which must be weighed when considering their use. Therapies anticipated to have an increasingly important role in the future of cancer pain management are also discussed.

1.5 T augmented reality navigated interventional MRI: paravertebral sympathetic plexus injections

PURPOSE

The high contrast resolution and absent ionizing radiation of interventional magnetic resonance imaging (MRI) can be advantageous for paravertebral sympathetic nerve plexus injections. We assessed the feasibility and technical performance of MRI-guided paravertebral sympathetic injections utilizing augmented reality navigation and 1.5 T MRI scanner.

METHODS

A total of 23 bilateral injections of the thoracic (8/23, 35%), lumbar (8/23, 35%), and hypogastric (7/23, 30%) paravertebral sympathetic plexus were prospectively planned in twelve human cadavers using a 1.5 Tesla (T) MRI scanner and augmented reality navigation system. MRI-conditional needles were used. Gadolinium-DTPA-enhanced saline was injected. Outcome variables included the number of control magnetic resonance images, target error of the needle tip, punctures of critical nontarget structures, distribution of the injected fluid, and procedure length.

RESULTS

Augmented-reality navigated MRI guidance at 1.5 T provided detailed anatomical visualization for successful targeting of the paravertebral space, needle placement, and perineural paravertebral injections in 46 of 46 targets (100%). A mean of 2 images (range, 1-5 images) were required to control needle placement. Changes of the needle trajectory occurred in 9 of 46 targets (20%) and changes of needle advancement occurred in 6 of 46 targets (13%), which were statistically not related to spinal regions (P = 0.728 and P = 0.86, respectively) and cadaver sizes (P = 0.893 and P = 0.859, respectively). The mean error of the needle tip was 3.9±1.7 mm. There were no punctures of critical nontarget structures. The mean procedure length was 33±12 min.

CONCLUSION

1.5 T augmented reality-navigated interventional MRI can provide accurate imaging guidance for perineural injections of the thoracic, lumbar, and hypogastric sympathetic plexus.

Magnetic resonance imaging-guided spine injections

Magnetic resonance (MR)-guided spine injections describe techniques for selective spine injection procedures, in which MR imaging is used to visualize spinal targets and needle placement, monitor the injected drugs, and detect spread to potentially confounding nearby structures. The introduction of clinical high-field wide-bore MR imaging systems has increased the practicability and availability of MR-guided spine injections. The use of 1.5-T field strength, modern coils, and parallel imaging technology increases the MR signal, which can be utilized for faster temporal image acquisition, higher image resolution, better image contrast, or combinations thereof. Magnetic resonance imaging guidance provides excellent osseous and soft-tissue detail of spinal structures and is well suited to avoid radiation exposure. In this article, we discuss the technical background of interventional MR imaging, review the literature, and illustrate interventional MR imaging techniques of commonly performed spinal injection procedures, including sacroiliac joint injections, lumbar facet joint injections, selective spinal nerve root infiltration, and percutaneous drug delivery to the lumbar sympathetic nerves.

Sympathetic skin response: monitoring of CT-guided lumbar sympathetic blocks

PURPOSE

To prospectively evaluate accuracy of sympathetic skin response (SSR) for monitoring computed tomography (CT)-guided lumbar sympathetic blocks, with palpable temperature increase in the foot 30 minutes after injection serving as the reference standard.

MATERIALS AND METHODS

Institutional review board approval and written informed consent were obtained. Seventy individual lumbar sympathetic blocks were performed in 13 patients (six female, seven male; mean age, 45 years) with reflex sympathetic dystrophy of the foot. A 22-gauge needle was advanced to the sympathetic trunk at midlumbar level with CT fluoroscopic guidance, and 1 mL of iopamidol (200 mg of iodine per milliliter) and 5 mL of 0.5% bupivacaine were injected. SSR was monitored in both feet before and after bupivacaine injection. SSRs were activated with painless low-strength (5-20-mA) electrical stimuli. SSR ratio (SSR in the injected foot versus SSR in the contralateral foot) was calculated before injection and repeatedly at 1-minute intervals thereafter. Needle tip position and distribution of bupivacaine were measured on CT images. Receiver operating characteristic curves for SSR ratio were calculated until 7 minutes after injection. Logistic regression analyses adjusted for clustering were calculated for SSR ratio, injection parameters, needle tip position, and bupivacaine distribution.

RESULTS

Thirty minutes after injection, 83% of procedures were considered clinically successful. An SSR cutoff ratio of 1:10 was used, and sensitivity, specificity, and accuracy of SSR for prediction of clinical success were 84%, 92%, and 86%, respectively, 4 minutes after injection and 95%, 92%, and 94%, respectively, 7 minutes after injection. Needle tip position (P = .19), medial and lateral borders of bupivacaine distribution (P = .11 and .056), and distance between bupivacaine distribution and the vertebral body (P = .41) were not significantly different between successful and unsuccessful injections.

CONCLUSION

SSR can be used to correctly identify needle tip position in lumbar sympathetic blocks 6 and 7 minutes after injection.