Forty Years of Sodium Channels: Structure, Function, Pharmacology, and Epilepsy

Voltage-gated sodium channels initiate action potentials in brain neurons. In the 1970s, much was known about the function of sodium channels from measurements of ionic currents using the voltage clamp method, but there was no information about the sodium channel molecules themselves. As a postdoctoral fellow and staff scientist at the National Institutes of Health, I developed neurotoxins as molecular probes of sodium channels in cultured neuroblastoma cells. During those years, Bruce Ransom and I crossed paths as members of the laboratories of Marshall Nirenberg and Philip Nelson and shared insights about sodium channels in neuroblastoma cells from my work and electrical excitability and synaptic transmission in cultured spinal cord neurons from Bruce's pioneering electrophysiological studies. When I established my laboratory at the University of Washington in 1977, my colleagues and I used those neurotoxins to identify the protein subunits of sodium channels, purify them, and reconstitute their ion conductance activity in pure form. Subsequent studies identified the molecular basis for the main functions of sodium channels-voltage-dependent activation, rapid and selective ion conductance, and fast inactivation. Bruce Ransom and I re-connected in the 1990s, as ski buddies at the Winter Conference on Brain Research and as faculty colleagues at the University of Washington when Bruce became our founding Chair of Neurology and provided visionary leadership of that department. In the past decade my work on sodium channels has evolved into structural biology. Molecular modeling and X-ray crystallographic studies have given new views of sodium channel function at atomic resolution. Sodium channels are also the molecular targets for genetic diseases, including Dravet Syndrome, an intractable pediatric epilepsy disorder with major co-morbidities of cognitive deficit, autistic-like behaviors, and premature death that is caused by loss-of-function mutations in the brain sodium channel NaV1.1. Our work on a mouse genetic model of this disease has shown that its multi-faceted pathophysiology and co-morbidities derive from selective loss of electrical excitability and action potential firing in GABAergic inhibitory neurons, which disinhibits neural circuits throughout the brain and leads directly to the epilepsy, premature death and complex co-morbidities of this disease. It has been rewarding for me to use our developing knowledge of sodium channels to help understand the pathophysiology and to suggest potential therapeutic approaches for this devastating childhood disease.

Local infiltration analgesia: a 2-year follow-up of patients undergoing total hip arthroplasty

Purpose

Local infiltration analgesia (LIA) is commonly used for postoperative pain management following total hip arthroplasty (THA). However, the long-term effects of the component drugs are unclear. The aim of our study was to investigate functional outcome, quality of life, chronic post-surgical pain, and adverse events in patients within 2 years of undergoing THA.

Methods

The study was a secondary analysis of data from a previous larger study. Eighty patients were randomized to receive either intrathecal morphine (Group ITM) or local infiltration analgesia (Group LIA) for pain management in a double-blind study. The parameters measured were patient-assessed functional outcome [using the Hip dysfunction and Osteo-arthritis Outcome Score (HOOS) questionnaire], health-related quality of life [using the European Quality of Life–5 dimensions (EQ-5D) questionnaire and the 36-Item Short Form Health Survey (SF-36) score], and pain using the numeric rating score (NRS), with persistent post-surgical pain having a NRS of > 3 or a HOOS pain sub-score of > 30. All complications and adverse events were investigated during the first 2 years after primary surgery.

Results

Pain intensity and rescue analgesic consumption were similar between the groups after hospital discharge. No differences were found in HOOS or SF-36 score between the groups up to 6 months after surgery. A significant group × time interaction was seen in the EQ 5D form in favor of the LIA group. No between-group difference in persistent post-surgical pain was found at 3 or 6 months, or in adverse events up to 2 years after surgery.

Conclusion

Analysis of functional outcome, quality of life, and post-discharge surgical pain did not reveal significant differences between patients receiving LIA and those receiving ITM. LIA was found to be a safe technique for THA during the long-term follow-up. However, it should be noted that these conclusions are based on a limited number of patients.

Adjuvants to local anesthetics: Current understanding and future trends

Although beneficial in acute and chronic pain management, the use of local anaesthetics is limited by its duration of action and the dose dependent adverse effects on the cardiac and central nervous system. Adjuvants or additives are often used with local anaesthetics for its synergistic effect by prolonging the duration of sensory-motor block and limiting the cumulative dose requirement of local anaesthetics. The armamentarium of local anesthetic adjuvants have evolved over time from classical opioids to a wide array of drugs spanning several groups and varying mechanisms of action. A large array of opioids ranging from morphine, fentanyl and sufentanyl to hydromorphone, buprenorphine and tramadol has been used with varying success. However, their use has been limited by their adverse effect like respiratory depression, nausea, vomiting and pruritus, especially with its neuraxial use. Epinephrine potentiates the local anesthetics by its antinociceptive properties mediated by alpha-2 adrenoreceptor activation along with its vasoconstrictive properties limiting the systemic absorption of local anesthetics. Alpha 2 adrenoreceptor antagonists like clonidine and dexmedetomidine are one of the most widely used class of local anesthetic adjuvants. Other drugs like steroids (dexamethasone), anti-inflammatory agents (parecoxib and lornoxicam), midazolam, ketamine, magnesium sulfate and neostigmine have also been used with mixed success. The concern regarding the safety profile of these adjuvants is due to its potential neurotoxicity and neurological complications which necessitate further research in this direction. Current research is directed towards a search for agents and techniques which would prolong local anaesthetic action without its deleterious effects. This includes novel approaches like use of charged molecules to produce local anaesthetic action (tonicaine and n butyl tetracaine), new age delivery mechanisms for prolonged bioavailability (liposomal, microspheres and cyclodextrin systems) and further studies with other drugs (adenosine, neuromuscular blockers, dextrans).

Probing the dynamics of complexed local anesthetics via neutron scattering spectroscopy and DFT calculations

Since potential changes in the dynamics and mobility of drugs upon complexation for delivery may affect their ultimate efficacy, we have investigated the dynamics of two local anesthetic molecules, bupivacaine (BVC, C₁₈H₂₈N₂O) and ropivacaine (RVC, C₁₇H₂₆N₂O), in both their crystalline forms and complexed with water-soluble oligosaccharide 2-hydroxypropyl-β-cyclodextrin (HP-β-CD). The study was carried out by neutron scattering spectroscopy, along with thermal analysis, and density functional theory computation. Mean square displacements suggest that RVC may be less flexible in crystalline form than BVC, but both molecules exhibit very similar dynamics when confined in HP-β-CD. The use of vibrational analysis by density functional theory (DFT) made possible the identification of molecular modes that are most affected in both molecules by insertion into HP-β-CD, namely those of the piperidine rings and methyl groups. Nonetheless, the somewhat greater structure in the vibrational spectrum at room temperature of complexed RVC than that of BVC, suggests that the effects of complexation are more severe for the latter. This unique approach to the molecular level study of encapsulated drugs should lead to deeper understanding of their mobility and the respective release dynamics.

Pharmacologic Properties of Novel Local Anesthetic Agents in Anesthesia Practice

Therapeutic duration of traditional local anesthetics when used in peripheral nerve blocks is normally limited. This article describes novel approaches to extend the duration of peripheral nerve blocks currently available or in development. Three newer approaches on extending the duration of peripheral nerve blocks include site-1 sodium channel blockers, novel local anesthetics delivery systems, and novel adjuvants of local anesthetics. Compared with plain amide-based and ester-based local anesthetics, alternative approaches show significant promise in decreasing postoperative pain, rescue opioid requirement, hospital length-of-stay, and overall health care cost, without compromising the established safety profile of traditional local anesthetics.

Ipsilateral and contralateral sensory changes in healthy subjects after experimentally induced concomitant sensitization and hypoesthesia

BACKGROUND

In unilateral neuropathic pain. e.g. after peripheral nerve injury, both positive and negative sensory signs occur often, accompanied by minor but equally directed contralateral sensory changes. To mimic this feature, we experimentally aimed to induce concomitant c-fibre sensitization and block in healthy subjects and analyzed the bilateral sensory changes by quantitative sensory testing (QST) using the protocol of the German Research Network on Neuropathic Pain.

METHODS

Twenty eight healthy subjects were firstly randomized in 2 groups to receive either topical capsaicin (0.6%, 12 cm², application duration: 15 min.) or a lidocaine/prilocaine patch (25/25 mg, 10 cm², application duration: 60 min.) on the right volar forearm. Secondly, 7-14 days later in the same area either at first capsaicin (for 15 min.) and immediately afterwards local anesthetics (for 60 min.) was applied (Cap/LA), or in inversed order with the same application duration (LA/Cap). Before, after each application and 7-14 days later a QST was performed bilaterally.

STATISTICS

Wilcoxon-test, ANOVA, p < 0.05.

RESULTS

Single application of 0,6% capsaicin induced thermal hypoesthesia, cold hypoalgesia, heat hyperalgesia and tactile allodynia. Lidocaine/prilocaine alone induced thermal and tactile hypoesthesia as well as mechanical and cold hypoalgesia, and a heat hyperalgesia (to a smaller extent). Ipsilaterally both co-applications induced a combination of the above mentioned changes. Significant contralateral sensory changes occurred only after the co-application with concomitant sensitization and hypoesthesia and comprised increased cold (Cap/LA, LA/Cap) and mechanical detection as well as cold pain threshold (LA/Cap).

CONCLUSION

The present experimental model using combined application of capsaicin and LA imitates partly the complex sensory changes observed in patients with unilateral neuropathic pain and might be used as an additional surrogate model. Only the concomitant use both agents in the same area induces both positive and negative sensory signs ipsilaterally as well as parallel contralateral sensory changes (to a lesser extent).

TRIAL REGISTRATION

ClinicalTrials.gov Identifier NCT01540877 , registered on 23 February 2012.

Exparel/Peripheral Catheter Use in the Ambulatory Setting and Use of Peripheral Catheters Postoperatively in the Home Setting

PURPOSE OF REVIEW

With the increasing number of ambulatory surgeries being performed, regional anesthesia has become an increasingly popular anesthetic modality, and many choices exist to provide efficient, effective quality perioperative analgesia. In this paper, we will review the various regional anesthesia options in addition to the advantages and disadvantages of each. Lastly, we will discuss liposomal bupivicaine, a long acting local anesthetic, and its future role in the anesthesiologist's armamentarium. The aim of the publication is to provide a general overview of regional anesthesia as well as to discuss the advantages and disadvantages of this modality. Additionally, we sought to review the basics of liposomal bupivicaine as well as the relevant literature.

RECENT FINDINGS

The results regarding liposomal bupivicaine are mixed and mainly focuses on local infiltration and intra-articular injections. There are no known studies specifically comparing liposomal bupivicaine to bupivicaine hydrochloride in ultrasound-guided nerve blocks. There is some encouraging data regarding liposomal bupivicaine, but further studies are needed before it is adopted as a mainstay of treatment. In addition to efficacy, additional investigations are needed to evaluate cost as this could be a major impediment to its implementation.

3D ultrasound estimation of the effective volume for popliteal block at the level of division

Local anaesthetic injection between the tibial and commmon peroneal nerves within connective tissue sheath results in a predictable diffusion and allows for a reduction in the volume needed to achieve a consistent sciatic popliteal block. Using 3D ultrasound volumetric acquisition, we quantified the visible volume in contact with the nerve along a 5cm segment.

METHODS

We included 20 consecutive patients scheduled for bunion surgery. Ultrasound guided popliteal block was performed using a posterior, out of plane approach at the level of división of the sciatic nerve. Thirty ml of mepivacaine 1.5% and levobupivacaine 0.5% were slowly injected while assessing the injection pressure and the diffusion of the local anaesthetic. Volumetric acquisition was performed before and after the block to quantify the the volume of the sciatic nerve and the volume of the surrounding hypoechoic halo contained inside the connective tissue in a 5cm segment.

RESULTS

All blocks were successful within 20min after the injection. The total estimated volume contained inside the common connective tissue sheath was 6.8±2.6cm³. Of this, the volume of the halo sorrounding the nerve was 4.4±1.7cm³ and the volume inside the sciatic nerve was 2.4±1.7cm³.

CONCLUSIONS

The volume of local anaesthetic in close contact with the sciatic nerve can be estimated by volumetric acquisition. Our results suggest that the effective volume of local anaesthetic needed for a successful sciatic popliteal block could be reduced to less than 7ml.

Intravenous lidocaine for effective pain relief after bimaxillary surgery

OBJECTIVES

The aim of this prospective, randomized, double-blind, placebo-controlled study was to evaluate the analgesic effect of intravenous lidocaine on postoperative pain in bimaxillary surgery.

MATERIALS AND METHODS

Between July 2015 and November 2015, 52 consecutive patients that underwent bimaxillary surgery were recruited to the present study. The patients were randomly divided into two groups: group L (1.5 mg/kg bolus and 2 mg/kg/h continuous infusion during the operation) and group C (normal saline). To measure pain intensity, a visual analog scale (VAS) was used at 2, 4, 8, 12, 24, and 48 h after surgery. Rescue ketorolac use was measured in the first 4, 4-8, 8-24, and 24-48 h after surgery. Total ketorolac consumption (the sum of rescue and eight-hourly fixed schedule ketorolac injection), WBC count, neutrophil count, and postoperative swelling were recorded.

RESULTS

There were no significant differences between the two groups with respect to demographics. VAS pain scores were significantly lower in group L compared with group C up to 8 h after surgery. Rescue ketorolac use up to 8 h after surgery and total ketorolac consumption were significantly lower in group L than in group C. Postoperative WBC and neutrophil counts were significantly decreased in group L. Compared with group C, the amount of calibrated postoperative swelling was lower in group L.

CONCLUSIONS

Systemic lidocaine infusion during bimaxillary surgery reduces postoperative pain, analgesic consumption, and facial swelling.

CLINICAL RELEVANCE

Systemic lidocaine is simple, economic, and a safe procedure reducing pain and soft tissue swelling after bimaxillary surgery.

Distribution of local anesthetics between aqueous and liposome phases

Liposomes were used as biomimetic models in capillary electrokinetic chromatography (EKC) for the determination of distribution constants (K_D) of certain local anesthetics and a commonly used preservative. Synthetic liposomes comprised phosphatidylcholine and phosphatidylglycerol phospholipids with and without cholesterol. In addition, ghost liposomes made from red blood cell (RBC) lipid extracts were used as pseudostationary phase to acquire information on how the liposome composition affects the interactions between anesthetics and liposomes. These results were compared with theoretical distribution coefficients at pH 7.4. In addition to 25°C, the distribution constants were determined at 37 and 42°C to simulate physiological conditions. Moreover, the usability of five electroosmotic flow markers in liposome (LEKC) and micellar EKC (MEKC) was studied. LEKC was proven to be a convenient and fast technique for obtaining data about the distribution constants of local anesthetics between liposome and aqueous phase. RBC liposomes can be utilized for more representative model of cellular membranes, and the results indicate that the distribution constants of the anesthetics are greatly dependent on the used liposome composition and the amount of cholesterol, while the effect of temperature on the distribution constants is less significant.

New Updates Pertaining to Drug Delivery of Local Anesthetics in Particular Bupivacaine Using Lipid Nanoparticles

Lipid nanoparticles (liposomes) were first described in 1965, and several work have led to development of important technical advances like triggered release liposomes and drug-loaded liposomes. These advances have led to numerous clinical trials in such diverse areas such as the delivery of anti-cancer, antifungal, and antibiotic drugs; the delivery of gene medicines; and most importantly the delivery of anesthesia drugs. Quite a number of liposomes are on the market, and many more are still in developmental stage. Lipid nanoparticles are the first nano-medicine delivery system to be advanced from laboratory concept to clinical application with high considerable clinical acceptance. Drug delivery systems for local anesthetics (LAs) have caught the interest of many researchers because there are many biomedical advantages connected to their application. There have been several formulation techniques to systemically deliver LA that include encapsulation in liposomes and complexation in cyclodextrins, nanoparticles, and to a little extent gold nanoparticles. The proposed formulations help to decrease the LA concentration utilized, increase its permeability, and most importantly increase the localization of the LA for a long period of time thereby leading to increase in the duration of the LA effect and finally to reduce any local and systemic toxicity. In this review, we will highlight on new updates pertaining to drug delivery of local anesthetics in particular bupivacaine using lipid nanoparticles.

The effects of ropivacaine hydrochloride on the expression of CaMK II mRNA in the dorsal root ganglion neurons

In this study, we identified the subtype of Calcium/calmodulin-dependent protein kinase II (CaMK II) mRNA in dorsal root ganglion neurons and observed the effects of ropivacaine hydrochloride in different concentration and different exposure time on the mRNA expression. Dorsal root ganglion neurons were isolated from the SD rats and cultured in vitro. The mRNA of the CaMK II subtype in dorsal root ganglion neurons were detected by real-time PCR. As well as, the dorsal root ganglion neurons were treated with ropivacaine hydrochloride in different concentration (1mM,2mM, 3mM and 4mM) for the same exposure time of 4h, or different exposure time (0h,2h,3h,4h and 6h) at the same concentration(3mM). The changes of the mRNA expression of the CaMK II subtype were observed with real-time PCR. All subtype mRNA of the CaMK II, CaMK II_α, CaMK II_β, CaMK II _δ, CaMK II_γ, can be detected in dorsal root ganglion neurons. With the increased of the concentration and exposure time of the ropivacaine hydrochloride, all the subtype mRNA expression increased. Ropivacaine hydrochloride up-regulate the CaMK II_β, CaMK II_δ, CaMK II_g mRNA expression with the concentration and exposure time increasing. The nerve blocking or the neurotoxicity of the ropivacaine hydrochloride maybe involved with CaMK II.

Effect of lidocaine with and without epinephrine on lymphatic contractile activity in mice in vivo

A local anesthetic, lidocaine, is known to affect cutaneous blood flow when injected into the skin. However, it is unknown if dermal lymphatic function can also be affected. Therefore, we characterized lymphatic function in response to administration of lidocaine with and without epinephrine. Non-invasive near-infrared fluorescence imaging (NIRFI) with intradermal injection of indocyanine green (ICG) was used to characterize the lymphatic "pumping" function in mice after subcutaneous injection of 2 % lidocaine with and without 1:100,000 epinephrine or saline. NIRFI was performed for 10-20 min immediately after and 1, 3, and 5 h after these interventions. Lymphatic contraction frequencies significantly decreased 10 min after subcutaneous injection of lidocaine and remained plateaued for another 5 min, before returning to baseline. However, addition of 1:100,000 epinephrine to 2 % lidocaine rapidly increased lymphatic contraction frequencies at 5 min post-injection, which returned to baseline levels 15 min later. Injection of saline also increased lymphatic contraction frequency 5 min after injection, which returned to baseline 10 min post-injection. Although lidocaine administration showed a decrease in lymphatic function, the combination of epinephrine with lidocaine resulted in a predominant net effect of increased contractile activity.

Amide-linked local anesthetics induce apoptosis in human non-small cell lung cancer

BACKGROUND

A retrospective analysis of patients undergoing cancer surgery suggested that using local anesthetics could reduce cancer recurrence and improve survival rate. Previous studies have indicated that local anesthetics may induce apoptosis in several kinds of cells in vitro, but the mechanism is unclear.

METHODS

Cell viability was analyzed by MTS; reactive oxygen species (ROS), mitochondrial membrane potential (MMP, ∆Ψm), cell cycle distribution, and cell apoptosis assay were detected by flow cytometry; DNA damage was measured by comet assay; cell invasion and migration were observed by microscopy; The expression level of related proteins was detected by western blot assay.

RESULTS

The results indicated that lidocaine and ropivacaine could decrease viability, induce G0/G1 phase arrest and apoptosis in human non-small cell lung cancer (NSCLC) cells A549 and H520. Invasion and migration were suppressed. Western blot indicated the related apoptotic pathways proteins changed accordingly. Additionally, lidocaine and ropivacaine downregulated ∆Ψm, provoked DNA damage, upregulated ROS production and activated mitogen-activated protein kinase (MAPK) pathways in A549 and H520 cells.

CONCLUSIONS

The cytotoxic effect of amide-linked local anesthetics on NSCLC cells were mainly due to apoptosis. The antitumor mechanism of lidocaine and ropivacaine may involve apoptotic pathways and MAPK pathways.

Analgesic efficacy of ropivacaine wound infusion after laparoscopic colorectal surgery

Purpose

Local anesthetic wound infusion has been previously investigated in postoperative pain management. However, a limited number of studies have evaluated its use in laparoscopic colorectal surgery. This study aims to evaluate whether ropivacaine wound infusion is effective for postoperative pain management after laparoscopic surgery in patients with colorectal cancer.

Methods

This prospective study included 184 patients who underwent laparoscopic surgery for colorectal cancer between July 2012 and June 2013. The patients were grouped as the combined group (intravenous patient-controlled analgesia [IV-PCA] plus continuous wound infusion with ropivacaine, n = 92) and the PCA group (IV-PCA only, n = 92). Efficacy and safety were assessed in terms of numeric rating scale (NRS) pain score, opioid consumption, postoperative recovery, and complications.

Results

The total quantity of PCA fentanyl was significantly less in the combined group than in the PCA group (P < 0.001). The NRS score of the combined group was not higher than in the PCA group, despite less opioid consumption. There were no differences between groups for postoperative recovery and most complications, including wound complications. However, the rate of nausea and vomiting was significantly lower in the combined group (P = 0.022).

Conclusion

Ropivacaine wound infusion significantly reduced postoperative opioid requirements and the rate of nausea/vomiting. This study showed clinical efficacy of ropivacaine wound infusion for postoperative pain control in colorectal cancer patients undergoing laparoscopic surgery.

Randomized trial of subfascial infusion of ropivacaine for early recovery in laparoscopic colorectal cancer surgery

Background

There is a need for investigating the analgesic method as part of early recovery after surgery tailored for laparoscopic colorectal cancer (LCRC) surgery. In this randomized trial, we aimed to investigate the analgesic efficacy of an inverse ‘v’ shaped bilateral, subfascial ropivacaine continuous infusion in LCRC surgery.

Methods

Forty two patients undergoing elective LCRC surgery were randomly allocated to one of two groups to receive either 0.5% ropivacaine continuous infusion at the subfascial plane (n = 20, R group) or fentanyl intravenous patient controlled analgesia (IV PCA) (n = 22, F group) for postoperative 72 hours. The primary endpoint was the visual analogue scores (VAS) when coughing at postoperative 24 hours. Secondary end points were the VAS at 1, 6, 48, and 72 hours, time to first flatus, time to first rescue meperidine requirement, rescue meperidine consumption, length of hospital stay, postoperative nausea and vomiting, sedation, hypotension, dizziness, headache, and wound complications.

Results

The VAS at rest and when coughing were similar between the groups throughout the study. The time to first gas passage and time to first rescue meperidine at ward were significantly shorter in the R group compared to the F group (P = 0.010). Rescue meperidine was administered less in the R group; however, without statistical significance. Other study parameters were not different between the groups.

Conclusions

Ropivacaine continuous infusion with an inverse ‘v ’ shaped bilateral, subfascial catheter placement showed significantly enhanced bowel recovery and analgesic efficacy was not different from IV PCA in LCRC surgery.

Infrared image monitoring of local anesthetic poisoning in rats

BACKGROUND AND OBJECTIVES

To evaluate the thermographic predictive value of local anesthetic poisoning in rats that indicates the early recognition of thermal signs of intoxication and enable the immediate start of advanced life support.

METHODS

Wistar rats underwent intraperitoneal injection of saline and ropivacaine; they were allocated into pairs, and experiments performed at baseline and experimental times. For thermography, central and peripheral compartment were analyzed, checking the maximum and average differences of temperatures between groups. Thermographic and clinical observations were performed for each experiment, and the times in which the signs of intoxication occurred were recorded. In the thermal analysis, the thermograms corresponding to the times of interest were sought and relevant data sheets extracted for statistical analysis.

RESULTS

Basal and experimental: the display of the thermal images at times was possible. It was possible to calculate the heat transfer rate in all cases. At baseline it was possible to see the physiology of microcirculation, characterized by thermal distribution in the craniocaudal direction. It was possible to visualize the pathophysiological changes or thermal dysautonomias caused by intoxication before clinical signs occur, characterized by areas of hyper-radiation, translating autonomic nervous system pathophysiological disorders. In animals poisoned by ropivacaine, there was no statistically significant difference in heat transfer rate at the experimental time.

CONCLUSIONS

The maximum temperature, medium temperature, and heat transfer rate were different from the statistical point of view between groups at the experimental time, thus confirming the systemic thermographic predictive value.

Study of procaine and tetracaine in the lipid bilayer using molecular dynamics simulation

Despite available experimental results, the molecular mechanism of action of local anesthetics upon the nervous system and contribution of the cell membrane to the process are still controversial. In this work, molecular dynamics simulations were performed to investigate the effect of two clinically used local anesthetics, procaine and tetracaine, on the structure and dynamics of a fully hydrated dimyristoylphosphatidylcholine lipid bilayer. We focused on comparing the main effects of uncharged and charged drugs on various properties of the lipid membrane: mass density distribution, diffusion coefficient, order parameter, radial distribution function, hydrogen bonding, electrostatic potential, headgroup angle, and water dipole orientation. To compare the diffusive nature of anesthetic through the lipid membrane quantitatively, we investigated the hexadecane/water partition coefficient using expanded ensemble simulation. We predicted the permeability coefficient of anesthetics in the following order: uncharged tetracaine > uncharged procaine > charged tetracaine > charged procaine. We also shown that the charged forms of drugs are more potent in hydrogen bonding, disturbing the lipid headgroups, changing the orientation of water dipoles, and increasing the headgroup electrostatic potential more than uncharged drugs, while the uncharged drugs make the lipid diffusion faster and increase the tail order parameter. The results of these simulation studies suggest that the different forms of anesthetics induce different structural modifications in the lipid bilayer, which provides new insights into their molecular mechanism.

Control Release Anesthetics to Enable an Integrated Anesthetic-mesenchymal Stromal Cell Therapeutic

While general anesthetics control pain via consciousness regulation, local anesthetics (LAs) act by decreasing sensation in the localized area of administration by blocking nerve transmission to pain centers. Perioperative intra-articular administration of LAs is a commonly employed practice in orthopedic procedures to minimize patient surgical and post-surgical pain and discomfort. LAs are also co-administered with cellular mesenchymal stromal cell (MSC) therapies for a variety of tissue regenerative and inflammatory applications including osteoarthritis (OA) treatment; however, LAs can affect MSC viability and function. Therefore, finding an improved method to co-administer LAs with cells has become critically important. We have developed a sustained release LA delivery model that could enable the co-administration of LAs and MSCs. Encapsulation of liposomes within an alginate matrix leads to sustained release of bupivacaine as compared to bupivacaine-containing liposomes alone. Furthermore, drug release is maintained for a minimum of 4 days and the alginate-liposome capsules mitigated the adverse effects of bupivacaine on MSC viability.

Interventional pain therapy in cervical post-surgery syndrome

Fifteen percent to forty percent of patients present with persistent disabling neck pain or radicular pain after cervical spine surgery. Persistent pain after cervical surgery is called cervical post-surgery syndrome (CPSS). This review investigates the literature about interventional pain therapy for these patients. Because different interventions with different anatomical targets exist, it is important to find the possible pain source. There has to be a distinction between radicular symptoms (radicular pain or radiculopathy) or axial pain (neck pain) and between persistent pain and a new onset of pain after surgery. In the case of radicular symptoms, inadequate decompression or nerve root adherence because of perineural scarring are possible pain causes. Multiple structures in the cervical spine are able to cause neck pain. Hereby, the type of surgery and also the number of segments treated is relevant. After fusion surgery, the so-called adjacent level syndrome is a possible pain source. After arthroplasty, the load of the facet joints in the index segment increases and can cause pain. Further, degenerative alterations progress. In general, two fundamentally different therapeutic approaches for interventional pain therapy for the cervical spine exist: Treatment of facet joint pain with radiofrequency denervation or facet nerve blocks, and epidural injections either via a transforaminal or via an interlaminar approach. The literature about interventions in CPSS is limited to single studies with a small number of patients. However, some evidence exists for these procedures. Interventional pain therapies are eligible as a target-specific therapy option. However, the risk of theses procedures (especially transforaminal epidural injections) must be weighed against the benefit.

Oral surgery under local anesthesia with dexmedetomidine sedation in a morbidly obese patient with aortic dissection

We report a case of a morbidly obese man with an aortic aneurysm, in whom dental surgery was performed before elective cardiac surgery. His aortic aneurysm required emergency surgery. However, because of his morbid obesity, elective cardiac surgery was planned. Considering the high risk of infective endocarditis, dental surgery was required. Our patient was at a high risk of aortic rupture caused by hypertension and breathing difficulty in the supine position. Dexmedetomidine (DEX) is an anti-anxiety, sedative, and analgesic medicine that can stabilize circulatory dynamics and minimize blood pressure fluctuations. We administered intravenous DEX for sedation of the patient in Fowler's position. In conclusion, our understanding of the risk factors of DEX enabled us to perform safe invasive oral treatment.

Curcumin Attenuated Bupivacaine-Induced Neurotoxicity in SH-SY5Y Cells Via Activation of the Akt Signaling Pathway

Bupivacaine is widely used for regional anesthesia, spinal anesthesia, and pain management. However, bupivacaine could cause neuronal injury. Curcumin, a low molecular weight polyphenol, has a variety of bioactivities and may exert neuroprotective effects against damage induced by some stimuli. In the present study, we tested whether curcumin could attenuate bupivacaine-induced neurotoxicity in SH-SY5Y cells. Cell injury was evaluated by examining cell viability, mitochondrial damage and apoptosis. We also investigated the levels of activation of the Akt signaling pathway and the effect of Akt inhibition by triciribine on cell injury following bupivacaine and curcumin treatment. Our findings showed that the bupivacaine treatment could induce neurotoxicity. Pretreatment of the SH-SY5Y cells with curcumin significantly attenuated bupivacaine-induced neurotoxicity. Interestingly, the curcumin treatment increased the levels of Akt phosphorylation. More significantly, the pharmacological inhibition of Akt abolished the cytoprotective effect of curcumin against bupivacaine-induced cell injury. Our data suggest that pretreating SH-SY5Y cells with curcumin provides a protective effect on bupivacaine-induced neuronal injury via activation of the Akt signaling pathway.

Comparison of spinal anesthesia dosage based on height and weight versus height alone in patients undergoing elective cesarean section

Background

Spinal anesthesia with bupivacaine, typically used for elective and emergency cesarean section, is associated with a significant incidence of hypotension resulting from sympathetic blockade. A variety of dosing regimens have been used to administer spinal anesthesia for cesarean section. The objective of this study was to compare the incidence of hypotension following two different fixed dosing regimens.

Methods

This was a randomized double-blind clinical trial with a two-sided design, 5% significance level and 80% power. After approval of the hospital ethics review committee, 60 patients were divided randomly into two groups. In one group, the local anesthetic dose was adjusted according to height and weight, and in the other, the dose was adjusted according to height only.

Results

Sixty women with a singleton pregnancy were included. Of the factors that could affect dose and blood pressure, including age, weight, height, and dose, only height differed between the groups. Mean heart rate was similar between the groups. Hypotension was significantly more frequent with dosage based on height alone than with two-factor dose calculation (56.7% vs. 26.7%; P = 0.018).

Conclusions

Adjusting the dose of isobaric bupivacaine to a patient's height and weight provides adequate anesthesia for elective cesarean section and is associated with a decreased incidence and severity of maternal hypotension and less use of ephedrine.

Modeling interactions between blocking and permeant cations in the NavMs channel

Mechanisms of sodium channel block by local anesthetics (LAs) are still a matter of intensive studies. In the absence of high-resolution structures of eukaryotic channels, atomic details of LA-channel interactions are analyzed using homology modeling. LAs are predicted to access the closed channel through a sidewalk (fenestration) between the channel repeats, bind in a horizontal orientation, and leave its aromatic moiety in the interface. Recent X-ray structure of a bacterial sodium channel NavMs with a cationic molecule Pl1, which is structurally similar to LAs, has confirmed this theoretical prediction and demonstrated a reduced selectivity filter occupancy by the permeant ions in the Pl1-bound channel. However, the nature of the antagonism between LAs and permeant ions is still unclear. Here we used the NavMs structure and Monte Carlo energy minimizations to model Pl1 binding. Our computations predict that Pl1 can displace permeant ion(s) from the selectivity filter by both steric and electrostatic mechanisms. We hypothesize that the electrostatic mechanism is more general, because it is applicable to many LAs and related drugs, which lack a moiety capable to enter the selectivity filter and sterically displace the permeant ion. The electrostatic mechanism is also consistent with the data that various cationic blockers of potassium channels bind in the inner pore without entering the selectivity filter.