Unveil the pain of endometriosis: from the perspective of the nervous system

Endometriosis is a chronic inflammatory disease with pelvic pain and uncharacteristic accompanying symptoms. Endometriosis-associated pain often persists despite treatment of the disease, thus it brings a deleterious impact on their personal lives as well as imposing a substantial economic burden on them. At present, mechanisms underlie endometriosis-associated pain including inflammatory reaction, injury, aberrant blood vessels and the morphological and functional anomaly of the peripheral and central nervous systems. The nerve endings are influenced by the physical and chemical factors surrounding the lesion, via afferent nerve to the posterior root of the spinal nerve, then to the specific cerebral cortex involved in nociception. However, our understanding of the aetiology and mechanism of this complex pain process caused by endometriosis remains incomplete. Identifying the pathogenesis of endometriosis is crucial to disease management, offering proper treatment, and helping patients to seek novel targets for the maintenance and contributors of chronic pain. The main aim of this review is to focus on every possible mechanism of pain related to endometriosis in both peripheral and central nervous systems, and to present related mechanisms of action from the interaction between peripheral lesions and nerves to the changes in transmission of pain, resulting in hyperalgesia and the corresponding alterations in cerebral cortex and brain metabolism.

Comparison of liposomal and 2-hydroxypropyl-β-cyclodextrin–lidocaine on cell viability and inflammatory response in human keratinocytes and gingival fibroblasts

Objectives

The aim of this study was to observe the effect multilamellar liposomes (MLV) and 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) in the in-vitro effects of lidocaine in cell viability, pro-inflammatory cytokines and prostaglandin E2 release of both human keratinocytes (HaCaT) and gingival fibroblasts (HGF) cells.

Methods

HaCaT and HGF cells were exposed to lidocaine 100–1 μm in plain, MLV and HP-β-CD formulations for 6 h or 24 h. The formulation effects in cell viability were measured by XTT assay and by fluorescent labelling. Cytokines (IL-8, IL-6 and TNF-α) and PGE2 release were quantified by ELISA.

Key findings

MLV and HP-β-CD formulations did not affect the HaCaT viability, which was significantly decreased by plain lidocaine after 24 h of exposure. Both drug carriers increased all cytokines released by HGF after 24-h exposure, and none of the carriers was able to reduce the PGE2 release induced by lidocaine.

Conclusion

The effect of drug carrier in the lidocaine effects was dependent on the cell type, concentration and time of exposure. MLV and HP-β-CD showed benefits in improving cell viability; however, both of them showed a tendency to increase cytokine release when compared to the plain solution.

Simultaneous percutaneous implantation of a microdialysis probe for monitoring perineural concentrations of local anaesthetics during peripheral nerve block in rabbits

OBJECTIVE

To develop a technique that allows simultaneous percutaneous implantation of both a microdialysis probe and injection catheter in order to monitor the perineural pharmacokinetics of local anaesthetics (LA) after a femoral block.

STUDY DESIGN

Prospective experimental study.

ANIMALS

Five anaesthetized male New Zealand rabbits with a mean ± SD weight of 3.2 ± 0.2 kg.

METHODS

After femoral nerve localization by electrostimulation, an injection catheter and a microdialysis probe were slowly and simultaneously inserted into a cannula left into place in the perineural region. Both were then secured into place, after removal of the cannula. At the end of the experiment, methylene blue was injected to confirm the distance from the femoral nerve during subsequent postmortem anatomical dissection of the injection site.

RESULTS

Staining was adequate and the catheter found to be located within 4 mm of the femoral nerve in three out of five rabbits.

CONCLUSIONS AND CLINICAL RELEVANCE

This procedure allows direct implantation of a microdialysis probe near the injection site of LA during a femoral nerve block without loosing nerve localization accuracy. This procedure has been used successfully to monitor the regional pharmacokinetics of LA after a peripheral nerve block.

Update on local anesthetics

PURPOSE OF REVIEW

Local anesthetics are not only used as drugs to block the sodium channel to provide analgesia and antiarrhythmic action. The purpose of this review is to highlight the new indications and limitations of this class of drugs.

RECENT FINDINGS

Recent research has focused on the use of intravenous local anesthetics to improve bowel function after surgery or trauma, to protect the central nervous system, to find new clues about local anesthetic effects in chronic neuropathic pain, and to investigate the long-term effect of anesthesia/analgesia provided by local anesthetics on cancer recurrence. Recent facts dealing with myotoxicity and chondrotoxicity are presented.

SUMMARY

There is growing evidence that local anesthetics have a broad spectrum of indications in addition to analgesia and antiarrhythmic effect. Most of them are still insufficiently known and investigated. These new indications will no doubt be intensively studied in the coming years.