Regional Anesthesia in Patients With Preexisting Neuropathy

Foot Drop Following a Popliteal Sciatic Nerve Block with Ropivacaine, A Case Report and Literature Review

Although peripheral nerve blocks are deemed very safe, a significant number of patients for whom this anesthetic technique may be particularly appealing to apply may present with preexisting peripheral neuropathies, putting them at risk for further nerve damage. We present a case with a 74-year-old male with several risk factors for peripheral neuropathy who developed a foot drop following a popliteal sciatic nerve block with ropivacaine. We suggest that the vasoconstrictive properties of ropivacaine may have contributed to a preexisting neuronal ischemia, thus further damaging an already compromised nerve.

Nerve Injury Following Regional Nerve Block: A Literature Review of Its Etiologies, Risk Factors, and Prevention

PURPOSE OF REVIEW

Postoperative nerve injury after nerve block is complex and multifactorial. The mechanisms, etiologies, and risk factors are explored. This review article conducts a literature search and summarizes current evidence and best practices in prevention of nerve injury.

RECENT FINDINGS

Emerging technology such as ultrasound, injection pressure monitors, and nerve stimulators for peripheral nerve block have been incorporated into regular practice to reduce the rate of nerve injury. Studies show avoidance of intrafascicular injection, limiting concentrations/volumes of local anesthetic, and appropriate patient selection are the most significant controllable factors in limiting the negative consequences of nerve block. Peripheral nerve injury is an uncommon occurrence after nerve block and is obscured by surgical manipulation, positioning, and underlying neural integrity. Underlying neural integrity is not always evident despite an adequate history and physical exam. Surgical stress, independently of nerve block, may exacerbate these neurologic disease processes and make diagnosing a postoperative nerve injury more challenging. Prevention of nerve injury by surgical teams, care with positioning, and avoidance of intrafascicular injection with nerve block are the most evidence-based practices.

Anaesthetic management of people with multiple sclerosis

There is a lack of published guidelines on the management of patients with multiple sclerosis (MS) undergoing procedures that require anaesthesia and respective advice is largely based on retrospective studies or case reports. The aim of this paper is to provide recommendations for anaesthetists and neurologists for the management of patients with MS requiring anaesthesia. This review covers issues related to the anaesthetic management of patients with MS, with a focus on preoperative assessment, choice of anaesthetic techniques and agents, side-effects of drugs used during anaesthesia and their potential impact on the disease evolution, drug interactions that may occur, and the need to use monitoring devices. A systematic PubMed research was performed to retrieve relevant articles.

Outcomes Following Distal Nerve Blocks for Open Carpal Tunnel Release: A Single-Institution Retrospective Study

Background Severe cases of carpal tunnel syndrome (CTS) are treated with surgical decompression, for which regional nerve blocks are often administered. There is little data about complications associated with these regional techniques for this surgery. The primary objective was to assess the association of ultrasound-guided regional anesthesia nerve blocks in patients undergoing carpal tunnel release with symptom resolution. Methods This single-institution, retrospective study analyzed all patients undergoing open carpal tunnel release from March 2018 to November 2020. Primary exposure was either regional anesthesia (median and ulnar nerve blocks) or non-regional anesthesia (general anesthesia or local infiltration by surgeon). The primary outcome measurement was symptom resolution at postoperative follow-up at 30-60 days. Secondary outcomes were postoperative surgical site infection, time in operating room (minutes), and post-anesthesia care unit (PACU) length of stay (min). The primary outcome was analyzed using multivariable logistic regression. Results A total of 417 patients were included in this study. Of these, 269 (64.5%) subjects received regional anesthesia as their primary anesthetic. When adjusting for confounders, the use of regional anesthesia was not associated with symptoms not improving at postoperative visit (OR 0.52, 95% CI 0.22 - 1.26, P = 0.15), postoperative surgical site infection (OR 1.47, 95% CI 0.44 - 4.85, p = 0.53), or operating room time duration (p = 0.09). However, the use of regional anesthesia was associated with an approximately 15-minute decrease in PACU length of stay (p < 0.001). Conclusions Regional anesthesia is a safe, effective, and time-efficient method for anesthesia in patients undergoing open carpal tunnel release.

Bupivacaine Induces ROS-Dependent Autophagic Damage in DRG Neurons via TUG1/mTOR in a High-Glucose Environment

Bupivacaine (BP) is a commonly clinically used local anesthetic (LA). Current studies suggest that neurological complications are increased in diabetic patients after LA application, but the molecular mechanism is poorly understood. LA-induced autophagy and neuronal injury have been reported. We hypothesized that a high-glucose environment aggravates BP-induced autophagic damage. Mouse dorsal root ganglion (DRG) neurons were treated with BP in a high-glucose environment, and the results showed that reactive oxygen species (ROS) levels increased, autophagy was activated, autophagy flux was blocked, and cell viability decreased. Pretreatment with the ROS scavenger N-acetyl-cysteine (NAC) attenuated ROS-mediated autophagy regulation. Moreover, the expression of the long noncoding RNA (lncRNA) taurine upregulated gene 1 (TUG1) increased, and NAC and TUG1 siRNA inhibited the expression of TUG1/mammalian target of rapamycin (mTOR) in DRGs treated with BP in a high-glucose environment. Intriguingly, contrary to previous reports on a positive effect on neurons, we found that rapamycin, an autophagy activator, and chloroquine, an autophagy and lysosome inhibitor, both exacerbated autophagic damage. These data suggest that a high-glucose environment exacerbated BP induced ROS-dependent autophagic damage in DRG neurons through the TUG1/mTOR signaling pathway, which provides a theoretical basis and target for the clinical prevention and treatment of BP neurotoxicity in diabeties.

Regional anaesthesia in patients with diabetes

Diabetes is the most common metabolic condition worldwide and about 20% of surgical patients will have this condition. It is a major risk-factor for worse outcomes after surgery including mortality; infective and non-infective complications; and increased length of stay. However, diabetes is a modifiable risk-factor, and programs to improve medical management have the potential to reduce peri-operative complications and the risk of harm. Regional anaesthesia has well-documented benefits in promoting the restoration of function but there are legitimate concerns that the incidence of complications of regional anaesthesia in patients with diabetes is higher. The aim of this review is to explore in detail the various potential advantages and disadvantages of regional anaesthesia in patients with diabetes. This, in turn, will allow practitioners to undertake more informed shared decision-making and potentially modify their anaesthetic technique for patients with diabetes.

Effect of ropivacaine on peripheral neuropathy in streptozocin diabetes-induced rats through TRPV1-CGRP pathway

Objective To determine the effect of ropivacaine on peripheral neuropathy in diabetic rats and its possible mechanism.

Methods Forty-eight Sprague–Dawley rats were randomly divided into six groups: nondiabetic control group, nondiabetic group A (0.25% ropivacaine), nondiabetic group B (0.75% ropivacaine), diabetic control group (diabetic peripheral neuropathy (DPN) +artificial cerebrospinal fluid), diabetic group A (DPN+0.25% ropivacaine), and diabetic group B (DPN + 0.75% ropivacaine), with eight rats in each group. Within an hour of the last administration, the sciatic motor nerve conduction velocity (MNCV) of each group was measured, and the morphological changes of rat sciatic nerve were observed by HE, Weil’s staining and electron microscopy. The expression of transient receptor potential vanilloid (TRPV1) in the spinal cord dorsal horn of rats was analyzed by immunohistochemistry, and the expression of Calcitonin gene-related peptide (CGRP) protein in the spinal cord was analyzed by Western blot.

Results Compared with the nondiabetic control group, elevated blood glucose, decreased weight and reduced average mechanical withdrawal threshold (MWT), additionally, the sciatic nerves showed significantly slowed conduction velocity (both P<0.001) and damaged pathological structure, the expression of TRPV1 and CGRP were decreased (both P<0.001) in the diabetic groups. Compared with the diabetic control group, down-regulation of TRPV1 and CGRP in spinal cord was significant for the diabetic groups A and B treated with 0.25 and 0.75% ropivacaine, the higher concentration of ropivacaine correlated with a greater change.

Conclusion Ropivacaine can significantly block sciatic nerve conduction velocity in DPN rats in a concentration-dependent manner, which may be related to the expression of the TRPV1-CGRP pathway.

Neurotoxicity of local anesthetics in dentistry

During dental treatment, a dentist usually applies the local anesthesia. Therefore, all dentists should have expertise in local anesthesia and anesthetics. Local anesthetics have a neurotoxic effect at clinically relevant concentrations. Many studies have investigated the mechanism of neurotoxicity of local anesthetics but the precise mechanism of local anesthetic-induced neurotoxicity is still unclear. In addition, it is difficult to demonstrate the direct neurotoxic effect of local anesthetics because perioperative nerve damage is influenced by various factors, such as the anesthetic, the patient, and surgical risk factors. This review summarizes knowledge about the pharmacology of local anesthetics, nerve anatomy, and the incidence, risk factors, and possible cellular mechanisms of local anesthetic-induced neurotoxicity.

Inhibition of DNA Repair Protein Ku70 in High-Glucose Environment Aggravates the Neurotoxicity Induced by Bupivacaine in SH-SY5Y Cells

Bupivacaine, a common local anesthetic, causes serious nerve injury, especially in diabetic patients, as high glucose has been reported to enhance bupivacaine-induced neurotoxicity. However, the key regulator for synergism remains unknown. To our surprise, the expression of repair protein Ku70 is suppressed, while the high-glucose environment induces DNA oxidative damage in neurons. Here, we aim to investigate whether the inhibition of Ku70 by high-glucose conditions aggrandized bupivacaine-induced DNA damage. Consistent with previous results, bupivacaine induced reactive oxygen species production and upregulated Ku70 and cleaved caspase-3 expressions at both transcript and protein levels and ultimately caused nucleic acid damage and apoptosis in human neuroblastoma (SH-SY5Y) cells. High-glucose treatment inhibited the expression of Ku70 and enhanced bupivacaine-induced neurotoxicity. In contrast, the overexpression of Ku70 mitigated DNA damage and apoptosis triggered by bupivacaine and high glucose. In conclusion, our data indicated that local anesthetics may aggravate nerve toxicity in a high-glucose environment.

Neuraxial Anesthesia and Lower Extremity Peripheral Nerve Blocks for Ankle Surgery in a Patient With Chronic Inflammatory Demyelinating Polyneuropathy: A Case Report

Chronic inflammatory demyelinating polyneuropathy (CIDP) is a rare autoimmune disease that targets the peripheral nervous system. The literature on the use of regional anesthesia in CIDP is limited. We report a patient with CIDP who received a combined spinal-epidural (CSE) and saphenous and popliteal peripheral nerve blocks (PNBs) for ankle surgery. The CSE and PNBs resolved without incident. On approximately the fourth postoperative day, the patient reported a worsening of baseline CIDP symptoms in all extremities. Given the diffuse presentation, the CIDP exacerbation was attributed to the perioperative stress response. The exacerbation improved by 4 months postoperatively.

High glucose and bupivacaine‑induced cytotoxicity is mediated by enhanced apoptosis and impaired autophagy via the PERK‑ATF4‑CHOP and IRE1‑TRAF2 signaling pathways

Bupivacaine has previously been reported to induce neurotoxicity, which is further enhanced by high glucose levels. In the present study, the underlying molecular mechanisms via which bupivacaine induces cytotoxicity under high glucose conditions were investigated in cultured human SH-SY5Y cells. In order to identify the optimal concentrations of glucose and bupivacaine that induced cytotoxicity, SH-SY5Y cells were treated with 30–100 mM glucose and 0.5–1.0 mM bupivacaine. Based on the dose response experiments, 50 mM glucose and 0.5 mM bupivacaine was used in the present study. The effects that 3-MA (autophagy inhibitor) and rapamycin (RAPA; autophagy inducer) exerted on cell apoptosis, autophagy and the expression of protein kinase R-like endoplasmic reticulum kinase (PERK)-activating transcription factor 4 (ATF4)-C/EBP-homologous protein (CHOP) and inositol-requiring enzyme 1 (IRE1)-tumor necrosis factor receptor associated factor 2 (TRAF2) signaling proteins were measured in high glucose and bupivacaine-treated cells. Cell viability was measured using a Cell Counting Kit-8 assay, cell apoptosis was assessed using flow cytometry, and protein expression was determined using western blot analyses. Compared with the control group, high glucose and bupivacaine significantly increased ATF4, CHOP and caspase-12 expression, increased apoptosis, and decreased p-IRE1, TRAF2, LC3-II/LC3-I and Beclin1 expression. Promoting autophagy with RAPA partly reversed the high glucose and bupivacaine-induced changes in p-PERK, CHOP, TRAF2, Beclin1, caspase-12 and apoptosis, while inhibiting autophagy with 3-MA further enhanced the changes in ATF4, CHOP, p-IRE1, TRAF2 and apoptosis. High glucose and bupivacaine induced cytotoxicity in SH-SY5Y cells, at least in part, through enhancing cell apoptosis and inhibiting autophagy via the PERK-ATF4-CHOP and IRE1-TRAF2 signaling pathways.

Sex-dependent prolongation of sciatic nerve blockade in diabetes patients: a prospective cohort study

INTRODUCTION

Diabetes may affect the duration of nerve block after regional anesthesia. This study aimed to compare the durations of sensory and motor block in diabetes versus non-diabetes patients after lower limb nerve block and delineate any sex-based differences in the duration of sensory and motor blocks of both diabetes and non-diabetes patients.

METHODS

This prospective single-blinded cohort study recruited 86 patients who underwent unilateral lower extremity surgery; 52 patients were non-diabetic and 34 were diabetic. Each patient received an ultrasound-guided nerve stimulator-assisted subgluteal sciatic nerve block with 0.75% ropivacaine. Duration of sensory block was assessed with the Semmes-Weinstein monofilament test, and duration of motor block was assessed with dorsal and plantar flexion of the foot.

RESULTS

The sensory and motor block durations of diabetes patients were significantly prolonged versus non-diabetes patients (19.8±6.0 hours vs 15.6±5.1 hours; p<0.05) and (19.5±8.1 hours vs 14.8±5.7 hours, p=0.005), respectively. The durations of sensory and motor block were comparable between male diabetes and non-diabetes patients, but they were significantly longer in female diabetes patients. Multiple regression analysis further revealed that, after adjustment for age and preoperative sensory threshold, diabetes, fasting plasma glucose and HbA1c levels were significantly associated with sensory and motor blocks. Sex analysis showed the association was only present in female diabetes patients, not male diabetes patients.

CONCLUSION

The durations of sensory and motor block are significantly prolonged after subgluteal sciatic nerve block in diabetes patients. Furthermore, the prolonged nerve blockade is present only in diabetes women, not diabetes men.

TRIAL REGISTRATION NUMBER

NCT02482831.

Dexmedetomidine enhances ropivacaine-induced sciatic nerve injury in diabetic rats

BACKGROUND

Previous studies suggest that dexmedetomidine has a protective effect against local anaesthetic-induced nerve injury in regional nerve blocks. Whether this potentially protective effect exists in the context of diabetes mellitus is unknown.

METHODS

A diabetic state was established in adult male Sprague-Dawley rats with intraperitoneal injection of streptozotocin. Injections of ropivacaine 0.5%, dexmedetomidine 20 μg kg^-1 (alone and in combination), or normal saline (all in 0.2 ml) were made around the sciatic nerve in control and diabetic rats (n=8 per group). The duration of sensory and motor nerve block and the motor nerve conduction velocity (MNCV) were determined. Sciatic nerves were harvested at post-injection day 7 and assessed with light and electron microscopy or used for pro-inflammatory cytokine measurements.

RESULTS

Ropivacaine and dexmedetomidine alone or in combination did not produce nerve fibre damage in control non-diabetic rats. In diabetic rats, ropivacaine induced significant nerve fibre damage, which was enhanced by dexmedetomidine. This manifested with slowed MNCV, decreased axon density, and decreased ratio of inner to outer diameter of the myelin sheath (G ratio). Demyelination, axon disappearance, and empty vacuoles were also found using electron microscopy. An associated increase in nerve interleukin-1β and tumour necrosis factor-α was also seen.

CONCLUSIONS

Ropivacaine 0.5% causes significant sciatic nerve injury in diabetic rats that is greatly potentiated by high-dose dexmedetomidine. Although the dose of dexmedetomidine used in this study is considerably higher than that used in clinical practice, our data suggest that further studies to assess ropivacaine (alone and in combination with dexmedetomidine) use for peripheral nerve blockade in diabetic patients are warranted.

Strategies for Targeted Delivery to the Peripheral Nerve

Delivery of compounds to the peripheral nervous system has the potential to be used as a treatment for a broad range of conditions and applications, including neuropathic pain, regional anesthesia, traumatic nerve injury, and inherited and inflammatory neuropathies. However, efficient delivery of therapeutic doses can be difficult to achieve due to peripheral neuroanatomy and the restrictiveness of the blood-nerve barrier. Depending on the underlying integrity of the blood-nerve barrier in the application at hand, several strategies can be employed to navigate the peripheral nerve architecture and facilitate targeted delivery to the peripheral nerve. This review describes different applications where targeted delivery to the peripheral nervous system is desired, the challenges that the blood-nerve barrier poses in each application, and bioengineering strategies that can facilitate delivery in each application.

Obstetric anesthesia/analgesia does not affect disease course in multiple sclerosis: 10-year retrospective cohort study

OBJECTIVES

Multiple sclerosis (MS) often occurs in young women and the effect of obstetric anesthesia/analgesia on the disease is poorly understood. No previous study has investigated the course of the disease in women in labor in the Czech Republic. The aim of this study was to evaluate the occurrence or absence of relapses in the 6-month postpartum period in MS parturients with and without obstetric anesthesia/analgesia.

MATERIALS AND METHODS

We retrospectively studied all deliveries (n = 58,455) at the University Hospital Brno from 2004 to 2013 and identified those of the women with an ICD-10 code G35 (MS) recorded anytime in their medical history (n = 428). We included only deliveries of women with confirmed diagnosis at the time of labor (n = 70). Statistical analysis was performed using the Fischer Exact Test.

RESULTS

There were 70 deliveries of 65 women, including 45 vaginal deliveries and 25 Cesarean deliveries (16 under general anesthesia, 8 with epidural anesthesia and 1 with spinal anesthesia). Epidural obstetric analgesia was performed in 11 deliveries. There was no statistically significant difference in relapses between the vaginal delivery group (n = 15; 33%) and Cesarean section group (n = 10; 40%), p = 0.611.

CONCLUSION

Neither delivery mode (vaginal vs Caesarean) nor type of obstetric anesthesia/analgesia was found to have any impact on the course of MS at 6 months postpartum in women with this condition.

Comparison of peripheral nerve blockade characteristics between non-diabetic patients and patients suffering from diabetic neuropathy: a prospective cohort study

Animal data have demonstrated increased block duration after local anaesthetic injections in diabetic rat models. Whether the same is true in humans is currently undefined. We, therefore, undertook this prospective cohort study to test the hypothesis that type-2 diabetic patients suffering from diabetic peripheral neuropathy would have increased block duration after ultrasound-guided popliteal sciatic nerve block when compared with patients without neuropathy. Thirty-three type-2 diabetic patients with neuropathy and 23 non-diabetic control patients, scheduled for fore-foot surgery, were included prospectively. All patients received an ultrasound-guided popliteal sciatic nerve block with a 30 ml 1:1 mixture of lidocaine 1% and bupivacaine 0.5%. The primary outcome was time to first opioid request after block procedure. Secondary outcomes included the time to onset of sensory blockade, and pain score at rest on postoperative day 1 (numeric rating scale 0-10). These outcomes were analysed using an accelerated failure time regression model. Patients in the diabetic peripheral neuropathy group had significantly prolonged median (IQR [range]) time to first opioid request (diabetic peripheral neuropathy group 1440 (IQR 1140-1440 [180-1440]) min vs. control group 710 (IQR 420-1200 [150-1440] min, p = 0.0004). Diabetic peripheral neuropathy patients had a time ratio of 1.57 (95%CI 1.10-2.23, p < 0.01), experienced a 59% shorter time to onset of sensory blockade (median time ratio 0.41 (95%CI 0.28-0.59), p < 0.0001) and had lower median (IQR [range]) pain scores at rest on postoperative day 1 (diabetic peripheral neuropathy group 0 (IQR 0-1 [0-5]) vs. control group 3 (IQR 0-5 [0-9]), p = 0.001). In conclusion, after an ultrasound-guided popliteal sciatic nerve block, patients with diabetic peripheral neuropathy demonstrated reduced time to onset of sensory blockade, with increased time to first opioid request when compared with patients without neuropathy.

Pharmacodynamics and Pharmacokinetics of Lidocaine in a Rodent Model of Diabetic Neuropathy

Background

Clinical and experimental data show that peripheral nerve blocks last longer in the presence of diabetic neuropathy. This may occur because diabetic nerve fibers are more sensitive to local anesthetics or because the local anesthetic concentration decreases more slowly in the diabetic nerve. The aim of this study was to investigate both hypotheses in a rodent model of neuropathy secondary to type 2 diabetes.

Methods

We performed a series of sciatic nerve block experiments in 25 Zucker Diabetic Fatty rats aged 20 weeks with a neuropathy component confirmed by neurophysiology and control rats. We determined in vivo the minimum local anesthetic dose of lidocaine for sciatic nerve block. To investigate the pharmacokinetic hypothesis, we determined concentrations of radiolabeled (14C) lidocaine up to 90 min after administration. Last, dorsal root ganglia were excised for patch clamp measurements of sodium channel activity.

Results

First, in vivo minimum local anesthetic dose of lidocaine for sciatic nerve motor block was significantly lower in diabetic (0.9%) as compared to control rats (1.4%). Second, at 60 min after nerve block, intraneural lidocaine was higher in the diabetic animals. Third, single cell measurements showed a lower inhibitory concentration of lidocaine for blocking sodium currents in neuropathic as compared to control neurons.

Conclusions

We demonstrate increased sensitivity of the diabetic neuropathic nerve toward local anesthetics, and prolonged residence time of local anesthetics in the diabetic neuropathic nerve. In this rodent model of neuropathy, both pharmacodynamic and pharmacokinetic mechanisms contribute to prolonged nerve block duration.

A case of spinal anesthesia in a patient with progressive supranuclear palsy

Progressive supranuclear palsy (PSP) is one of the rare diseases. PSP is characterized by oculomotor dysfunction, postural instability, akinesia, dysarthria, and dysphagia. The major cause of death in patients with PSP is aspiration pneumonia. Considering these complications, spinal anesthesia is useful in patients with PSP. However, the potential harmful effects of spinal anesthesia including neurotoxicity of local anesthetics and neurologic complications for patients with PSP are unclear, because there has been no report. Here, we present spinal anesthesia for a patient with PSP. An 80-year-old man with progressive oculomotor dysfunction, dysphagia, and history of repeated aspiration pneumonia was scheduled for inguinal hernia surgery. Acutely concerning about perioperative pulmonary complications, we performed spinal anesthesia. Fortunately, there was no complication associated with respiration or neural system during perioperative period. We hope our experience and case report will be helpful in specific perioperative anesthetic care for patients with PSP.

Diphenyleneiodonium Mitigates Bupivacaine-Induced Sciatic Nerve Damage in a Diabetic Neuropathy Rat Model by Attenuating Oxidative Stress

BACKGROUND

Increased oxidative stress has been linked to local anesthetic-induced nerve injury in a diabetic neuropathy (DN) rat model. The current study explores the effects of diphenyleneiodonium (DPI) chloride, an NADPH oxidase (NOX) inhibitor, on bupivacaine-induced sciatic nerve injury in DN rats.

METHODS

A rat DN model was established through high-fat diet feeding and streptozotocin injection. The model was confirmed via testing (i) blood glucose, (ii) hindpaw allodynia responses to von Frey (VF) monofilaments, (iii) paw withdrawal thermal latency (PWTL), and (iv) nerve conduction velocity (NCV). Bupivacaine (Bup, 0.2 mL, 5 mg/mL) was used to block the right sciatic nerve. DPI (1 mg/kg) was injected subcutaneously 24 hours and 30 minutes before the sciatic block. At 24 hours after the block, NCV, various reactive oxygen species, and Caspase-3 were evaluated to determine the extent of sciatic nerve injury.

RESULTS

The DN rat model was successfully established. Compared with the DN control group, the postblock values of VF responses (DN-Con, 16.5 ± 1.3 g; DN + Bup, 19.1 ± 1.5 g, P < .001) and PWTL significantly increased (DN-Con, 13.3 ± 1.1 seconds; DN + Bup, 14.6 ± 1.1 seconds, P = .028); the NCV of sciatic nerve was significantly reduced (DN-Con, 38.8 ± 2.4 m/s, DN + Bup, 30.5 ± 2.0 m/s, P = .003), and sciatic nerve injury (as indicated by axonal area) was more severe in the bupivacaine-treated DN group (DN-Con, 11.6 ± 0.3 μm, DN + Bup, 7.5 ± 0.3 μm, P < .001). In addition, DPI treatment significantly improved nerve function (VF responses, 17.3 ± 1.3 g; PWTL, 13.4 ± 1.1 seconds; NCV, 35.6 ± 3.1 m/s) and mitigated loss of axonal area (9.6 ± 0.3 μm). Compared to the DN + Bup group (without DPI), the levels of lipid peroxides and hydroperoxides, as well as the protein expression of NOX2, NOX4, and Caspase-3, were significantly reduced in the DN + Bup + DPI group (P < .05).

CONCLUSIONS

Subcutaneous injection of DPI appears to protect against the functional and neurohistological damage of bupivacaine-blocked sciatic nerves in a high-fat diet/streptozotocin-induced DN model.

Effects of hyperbaric factors on lidocaine-induced apoptosis in spinal neurons and the role of p38 mitogen-activated protein kinase in rats with diabetic neuropathic pain

The application of lidocaine can lead to nerve damage. Evidence suggests that patients with diabetic neuropathy are at a higher risk for neurotoxicity. In the present study, the successful induction of diabetic neuropathic pain (DNP) in rats via a high-sugar, high-fat diet and intraperitoneal injection of 1% streptozotocin was verified and pronounced tactile allodynia was observed. It was found that intrathecal injections of hyperbaric lidocaine produced motor blocks of longer durations in the DNP model rats than in nondiabetic rats, or in DNP model rats injected with isobaric lidocaine. Histology of the lumbar 4-5 spinal cord revealed a significant difference in neuropathology between the DNP and nondiabetic rats. Moreover, edematous neurons and TUNEL-positive cells were observed in the hyperbaric lidocaine group. It was also found that the inhibition of p38 mitogen-activated protein kinase (p38MAPK) played a neuroprotective role in response to hyperbaric lidocaine-induced apoptosis in DNP rats, which indicates that p38MAPK plays a key role in the regulation of hyperbaric lidocaine-induced apoptosis in DNP rats. These findings suggest that hyperbaric lidocaine can promote spinal cord neuronal apoptosis in rats with DNP. Furthermore, p38MAPK might play a key role in the regulation of hyperbaric lidocaine-induced apoptosis in rats with DNP.

Brachial Plexus Blockade Causes Subclinical Neuropathy: A Prospective Observational Study

Background: The objective of this study is to determine subclinical changes in hand sensation after brachial plexus blocks used for hand surgery procedures. We used Semmes-Weinstein monofilament testing to detect these changes. We hypothesized that patients undergoing brachial plexus nerve blocks would have postoperative subclinical neuropathy detected by monofilament testing when compared with controls. Methods: In total, 115 hand surgery adult patients were prospectively enrolled in this study. All patients undergoing nerve-related procedures were excluded as well as any patients with preoperative clinically apparent nerve deficits. Eighty-four patients underwent brachial plexus blockade preoperatively, and 31 patients underwent general anesthesia (GA). Semmes-Weinstein monofilament testing of the hand was performed preoperatively on both the operative and nonoperative extremities and postoperatively at a mean of 11 days on both hands. Preoperative and postoperative monofilament testing scores were compared between the block hand and the nonoperated hand of the same patient, as well as between the block hands and the GA-operated hands. Results: There were no recorded clinically relevant neurologic complications in the block group or GA group. A statistically significant decrease in sensation in postoperative testing in the operated block hand compared with the nonoperated hand was noted. When comparing the operated block hand with the operated GA hand, there was a decrease in postoperative sensation in the operated block hand that did not reach statistical significance. Conclusions: Brachial plexus blockade causes subtle subclinical decreases in sensibility at short-term follow-up, without any clinically relevant manifestations.

Diabetic neuropathy increases stimulation threshold during popliteal sciatic nerve block

BACKGROUND

Peripheral nerve stimulation is commonly used for nerve localization in regional anaesthesia, but recommended stimulation currents of 0.3-0.5 mA do not reliably produce motor activity in the absence of intraneural needle placement. As this may be particularly true in patients with diabetic neuropathy, we examined the stimulation threshold in patients with and without diabetes.

METHODS

Preoperative evaluation included a neurological exam and electroneurography. During ultrasound-guided popliteal sciatic nerve block, we measured the current required to produce motor activity for the tibial and common peroneal nerve in diabetic and non-diabetic patients. Proximity to the nerve was evaluated post-hoc using ultrasound imaging.

RESULTS

Average stimulation currents did not differ between diabetic (n=55) and non-diabetic patients (n=52). Although the planned number of patients was not reached, the power goal for the mean stimulation current was met. Subjects with diminished pressure perception showed increased thresholds for the common peroneal nerve (median 1.30 vs. 0.57 mA in subjects with normal perception, P=0.042), as did subjects with decreased pain sensation (1.60 vs. 0.50 mA in subjects with normal sensation, P=0.038). Slowed ulnar nerve conduction velocity predicted elevated mean stimulation current (r=-0.35, P=0.002). Finally, 15 diabetic patients required more than 0.5 mA to evoke a motor response, despite intraneural needle placement (n=4), or required currents ≥2 mA despite needle-nerve contact, vs three such patients (1 intraneural, 2 with ≥2 mA) among non-diabetic patients (P=0.003).

CONCLUSIONS

These findings suggest that stimulation thresholds of 0.3-0.5 mA may not reliably determine close needle-nerve contact during popliteal sciatic nerve block, particularly in patients with diabetic neuropathy.

CLINICAL TRIAL REGISTRATION

NCT01488474.

Local Anesthetic-Induced Neurotoxicity

This review summarizes current knowledge concerning incidence, risk factors, and mechanisms of perioperative nerve injury, with focus on local anesthetic-induced neurotoxicity. Perioperative nerve injury is a complex phenomenon and can be caused by a number of clinical factors. Anesthetic risk factors for perioperative nerve injury include regional block technique, patient risk factors, and local anesthetic-induced neurotoxicity. Surgery can lead to nerve damage by use of tourniquets or by direct mechanical stress on nerves, such as traction, transection, compression, contusion, ischemia, and stretching. Current literature suggests that the majority of perioperative nerve injuries are unrelated to regional anesthesia. Besides the blockade of sodium channels which is responsible for the anesthetic effect, systemic local anesthetics can have a positive influence on the inflammatory response and the hemostatic system in the perioperative period. However, next to these beneficial effects, local anesthetics exhibit time and dose-dependent toxicity to a variety of tissues, including nerves. There is equivocal experimental evidence that the toxicity varies among local anesthetics. Even though the precise order of events during local anesthetic-induced neurotoxicity is not clear, possible cellular mechanisms have been identified. These include the intrinsic caspase-pathway, PI3K-pathway, and MAPK-pathways. Further research will need to determine whether these pathways are non-specifically activated by local anesthetics, or whether there is a single common precipitating factor.

Effects of early and late diabetic neuropathy on sciatic nerve block duration and neurotoxicity in Zucker diabetic fatty rats

BACKGROUND

The neuropathy of type II diabetes mellitus (DM) is increasing in prevalence worldwide. We aimed to test the hypothesis that in a rodent model of type II DM, neuropathy would lead to increased neurotoxicity and block duration after lidocaine-induced sciatic nerve block when compared with control animals.

METHODS

Experiments were carried out in Zucker diabetic fatty rats aged 10 weeks (early diabetic) or 18 weeks (late diabetic, with or without insulin 3 units per day), and age-matched healthy controls. Left sciatic nerve block was performed using 0.2 ml lidocaine 2%. Nerve conduction velocity (NCV) and F-wave latency were used to quantify nerve function before, and 1 week after nerve block, after which sciatic nerves were used for neurohistopathology.

RESULTS

Early diabetic animals did not show increased signs of nerve dysfunction after nerve block. In late diabetic animals without insulin vs control animals, NCV was 34.8 (5.0) vs 41.1 (4.1) ms s(-1) (P<0.01), and F-wave latency was 7.7 (0.5) vs 7.0 (0.2) ms (P<0.01), respectively. Motor nerve block duration was prolonged in late diabetic animals, but neurotoxicity was not. Late diabetic animals receiving insulin showed intermediate results.

CONCLUSIONS

In a rodent type II DM model, nerves have increased sensitivity for short-acting local anaesthetics without adjuvants in vivo, as evidenced by prolonged block duration. This sensitivity appears to increase with the progression of neuropathy. Our results do not support the hypothesis that neuropathy due to type II DM increases the risk of nerve injury after nerve block.

Multiple sclerosis in pregnancy

Multiple sclerosis is the most common chronic neurologic disability in young adults in their childbearing ages of 20 to 45. The disease affects more women than men, which prompts discussion of pregnancy-related issues in a woman with multiple sclerosis. Preconceptual counseling to discuss the safety of medications in pregnancy, the antepartum period along with what the patient can expect during birth, and the postpartum period will be discussed.

In Zucker diabetic fatty rats, subclinical diabetic neuropathy increases in vivo lidocaine block duration but not in vitro neurotoxicity

BACKGROUND AND OBJECTIVES

Application of local anesthetics may lead to nerve damage. Increasing evidence suggests that risk of neurotoxicity is higher in patients with diabetic peripheral neuropathy. In addition, block duration may be prolonged in neuropathy. We sought to investigate neurotoxicity in vitro and block duration in vivo in a genetic animal model of diabetes mellitus type 2.

METHODS

In the first experiments, neurons harvested from control Zucker diabetic fatty (ZDF) rats were exposed to acute (24 hours) or chronic (72 hours) hyperglycemia, followed by incubation with lidocaine 40 mM (approximately 1%). In a second experiment, neurons harvested from control ZDF rats, or diabetic ZDF rats, were incubated with lidocaine, with or without SB203580, an inhibitor of the p38 mitogen-activated protein kinase. Finally, we performed sciatic nerve block (lidocaine 2%, 0.2 mL) in control or diabetic ZDF rats and measured motor and nociceptive block duration.

RESULTS

In vitro, neither acute nor chronic hyperglycemia altered neurotoxic properties of lidocaine. In vitro, incubation of neurons with lidocaine resulted in a slightly decreased survival ratio when neurons were harvested from diabetic (57% ± 19%) as compared with control (64% ± 9%) rats. The addition of SB203580 partly reversed this enhanced neurotoxic effect and raised survival to 71% ± 12% in diabetic neurons and 66% ± 9% in control rats, respectively. In vivo, even though no difference was detected at baseline testing, motor block was significantly prolonged in diabetic as compared with control rats (137 ± 16 vs 86 ± 17 min).

CONCLUSIONS

In vitro, local anesthetic neurotoxicity was more pronounced on neurons from diabetic animals, but the survival difference was small. In vivo, subclinical neuropathy leads to substantial prolongation of block duration. We conclude that early diabetic neuropathy increases block duration, whereas the observed increase in toxicity was small.

A common anesthesiology procedure for a patient with an uncommon combination of diseases: a case report

Administering neuraxial anesthesia to a patient with an underlying neurological disease and a combination of four other pathological disorders can be challenging. We report in this paper the case of a 45-year-old woman with neurological deficit due to ischemic brain infarct, multiple sclerosis, antiphospholipid syndrome, and β-heterozygous thalassemia that was subjected to abdominal hysterectomy and bilateral salpingoophorectomy under epidural anesthesia for ovarian cancer.