Sympathetic Blocks for Sympathetic Pain

[Research Progress in Stellate Ganglion Block and Regulation of Autonomic Nervous Functions]

Stellate ganglion (SG), also known as the cervical thoracic sympathetic ganglion, is formed by the fusion of the inferior cervical ganglion and the first thoracic ganglia. It is responsible for transmitting sympathetic innervation to the upper extremities, head, neck, and heart. Stellate ganglion block (SGB) involves the injection of local anesthetics on or around the surface of SG, which induces a broad autonomic nerve blocking effect in the area controlled by SG. As a nerve block technique, ultrasound-guided SGB can be used to regulate autonomic nervous functions and achieve therapeutic effects of the relevant diseases by interfering sympathetic nerve activities of SG. In this article, we summarized and reviewed the research and clinical applications of ultrasound-guided SGB in regulating autonomic nervous functions, focusing on publications from the past five years. Furthermore, we discussed the prospective development in applying SGB in the treatment of diseases associated with high-altitude environment.

Use of a quadratus lumborum block in queens undergoing ovariectomy: a randomised controlled trial

OBJECTIVES

The aim of the study was to evaluate the perioperative analgesic effect of a quadratus lumborum (QL) block in queens undergoing ovariectomy.

METHODS

A total of 37 healthy queens admitted for elective ovariectomy were randomised into two groups: control (CTRL, n = 19) and QL block (QL, n = 18). All cats were premedicated with dexmedetomidine 0.005 mg/kg, alfaxalone 1 mg/kg and methadone 0.1 mg/kg IM. Under general anaesthesia, cats allocated to the QL group received a bilateral ultrasound-guided QL block with 0.4 ml/kg of ropivacaine 0.4% (3.2 mg/kg). No treatment was administered to cats in the CTRL group. Intraoperative rescue fentanyl boluses were administered if haemodynamic and/or respiratory parameters exceeded 30% of the pre-incisional values. Postoperative methadone boluses were administered based on Feline Grimace Scale scores. Demographics, baseline vital parameter values, requirement for rescue analgesia, incidence of hypotension, sialorrhoea, vomiting and dysphoria, and number of cats accepting food at 6 h after extubation were compared between groups.

RESULTS

A higher number of queens required intraoperative fentanyl in the CTRL group (14/18, 77.8%) compared with the QL group (1/19, 5.3%) (P <0.001). The median total fentanyl dose was 4 µg/kg (range 0-4) in the CTRL group and 0 µg/kg (range 0-4) in the QL group (P <0.001). No statistically significant difference was found between groups when comparing the number of animals requiring postoperative methadone, total methadone dose, episodes of hypotension, sialorrhoea, vomiting and dysphoria, and number of queens accepting food at 6 h postoperatively. No adverse effect or complication potentially related to the block was recorded.

CONCLUSIONS AND RELEVANCE

The QL block resulted in a lower intraoperative fentanyl requirement in queens undergoing ovariectomy. Further studies are needed to clarify the postoperative analgesic effect of this technique in cats.

Peripheral BDNF Regulates Somatosensory-Sympathetic Coupling in Brachial Plexus Avulsion-Induced Neuropathic Pain

Brachial plexus avulsion (BPA) is a combined injury involving the central and peripheral nervous systems. Patients with BPA often experience severe neuropathic pain (NP) in the affected limb. NP is insensitive to the existing treatments, which makes it a challenge to researchers and clinicians. Accumulated evidence shows that a BPA-induced pain state is often accompanied by sympathetic nervous dysfunction, which suggests that the excitation state of the sympathetic nervous system is correlated with the existence of NP. However, the mechanism of how somatosensory neural crosstalk with the sympathetic nerve at the peripheral level remains unclear. In this study, through using a novel BPA C7 root avulsion mouse model, we found that the expression of BDNF and its receptor TrκB in the DRGs of the BPA mice increased, and the markers of sympathetic nervous system activity including α1 and α2 adrenergic receptors (α1-AR and α2-AR) also increased after BPA. The phenomenon of superexcitation of the sympathetic nervous system, including hypothermia and edema of the affected extremity, was also observed in BPA mice by using CatWalk gait analysis, an infrared thermometer, and an edema evaluation. Genetic knockdown of BDNF in DRGs not only reversed the mechanical allodynia but also alleviated the hypothermia and edema of the affected extremity in BPA mice. Further, intraperitoneal injection of adrenergic receptor inhibitors decreased neuronal excitability in patch clamp recording and reversed the mechanical allodynia of BPA mice. In another branch experiment, we also found the elevated expression of BDNF, TrκB, TH, α1-AR, and α2-AR in DRG tissues from BPA patients compared with normal human DRGs through western blot and immunohistochemistry. Our results revealed that peripheral BDNF is a key molecule in the regulation of somatosensory-sympathetic coupling in BPA-induced NP. This study also opens a novel analgesic target (BDNF) in the treatment of this pain with fewer complications, which has great potential for clinical transformation.

Successful neurolytic thoracic sympathetic ganglion block using C-arm fluoroscopic cone-beam computed tomography in patients with postmastectomy pain syndrome: a report of 3 cases

BACKGROUND

Postmastectomy pain syndrome involves persistent neuropathic and sympathetically maintained neuropathic pain that can be improved using a thoracic sympathetic ganglion block. However, conventional fluoroscopic procedures pose technical difficulties and are associated with potential severe complications. We report the use of C-arm fluoroscopic cone-beam computed tomography to enhance procedural success and treatment safety.

CASE PRESENTATION

Three women diagnosed with postmastectomy pain syndrome and experiencing persistent pain underwent C-arm fluoroscopic cone-beam computed tomography-assisted ethanol neurolytic thoracic sympathetic ganglion block. Pain severity decreased substantially after the procedure. The therapeutic effects were sustained for 12 months in cases 1 and 2 and for 5 months in case 3. All patients experienced a remarkable decrease in allodynia and hyperalgesia intensities.

CONCLUSION

C-arm fluoroscopic cone-beam computed tomography-assisted neurolytic thoracic sympathetic ganglion block offers a valuable alternative for managing otherwise intractable postmastectomy pain syndrome before considering more invasive techniques.

Efficacy of the lumbar sympathetic ganglion block in lower limb pain and its application prospects during the perioperative period

The sympathetic nervous system is involved in the physiological pathogenesis of many different types of chronic pain. Sympathetic blocks can interrupt the reflex control system by intercepting the noxious afferent fibers accompanying autonomic nerves, resulting in changes in peripheral or central sensory processing. A lumbar sympathetic ganglion block (LSGB), as a treatment method, refers to the injection of nerve blockers into the corresponding lumbar sympathetic nerve segments, usually requiring imaging assistance (CT, X-ray, ultrasound) to guide. At present, LSGB has been widely used in the clinical treatment of lower limb pain, such as neuropathic pain, lower limb ischemic pain, and so on. Its mechanism of action may be through inhibiting sympathetic nerve activity and dilating blood vessels, thereby alleviating pain and inhibiting stress response. However, there are few reports of LSGB during the perioperative period, especially in postoperative pain and gastrointestinal function. Therefore, by studying the literature about LSGB-related studies, this article reviews the anatomy of the lumbar sympathetic nerve (LSN), with its clinical application and possible mechanism. We reviewed the analgesic effect of LSGB in patients with lower limb pain and postoperative pain and the potential application prospects in the recovery of gastrointestinal function, finally providing a reference for its clinical application.