Effect of Intraoperative Intravenous Lidocaine on Postoperative Delirium in Elderly Patients with Hip Fracture: A Prospective Randomized Controlled Trial.

Purpose: This study was performed to evaluate the effects of intraoperative intravenous lidocaine on postoperative delirium in elderly patients with hip fracture. Patients and methods: In total, 100 elderly patients undergoing hip fracture surgery were randomized to the lidocaine group (Group L) or saline (control) group (Group C). Before anesthetic induction, Group L received lidocaine at 1 mg/kg for more than 10 minutes followed by continuous infusion at 1.5 mg/kg/h until the end of surgery. Group C received normal saline, and the injection methods were consistent with those in Group L. General anesthesia was induced with propofol, sufentanil, and cis-atracurium. Anesthesia was maintained by propofol and remifentanil. The primary outcome was the incidence of postoperative delirium in the first 7 postoperative days. The secondary outcomes included the severity of delirium, onset and duration of delirium, emergence agitation, adverse events, total propofol dose, intraoperative opioid dosage, length of post-anesthesia care unit stay, extubation time, and patient satisfaction with postoperative pain management. Results: All 100 patients completed the study. The incidence of postoperative delirium was lower in Group L than in Group C (14% vs 36%, P = 0.011). The delirium severity scores were lower in Group L (3 [3-4]) than in Group C (4 [4-5]) (P = 0.017). In addition, the incidences of hypertension, tachycardia, and emergence agitation were significantly lower in Group L than in Group C. No cases of local anesthetic toxicity occurred in either group. Conclusion: Patients received lidocaine at 1 mg/kg for more than 10 minutes followed by continuous infusion at 1.5 mg/kg/h until the end of surgery, which can reduce the incidence of postoperative delirium in elderly patients undergoing hip fracture. In addition, the used regimen of lidocaine would not increase the risk of local anesthetic toxicity.

[Principles of the pharmacology of local anesthetics]. / Grundlagen der Pharmakologie von Lokalanästhetika.

The development of local anesthetics revolutionized the performance of painful interventions. Local anesthetics have an effect on voltage-gated sodium channels in nerve fibers and modulate the conduction of impulses. With respect to the chemical structure, local anesthetics can be divided into amide and ester types. The structural differences of local anesthetics have an influence on the duration of action, the degradation pathways and specific side effects. Severe adverse events include cardiotoxicity and neurotoxicity. In addition to basic measures, such as the monitoring and securing of vital parameters, lipid infusion represents a treatment option in cases of intoxication. The recent developments of local anesthetics are particularly concerned with the reduction of toxicity and prolonging the duration of action.

[Forensic medical assessment of lidocaine and bupivacaine systemic toxicity]. / Sudebno-meditsinskaya otsenka sistemnoi toksichnosti lidokaina i bupivakaina.

THE AIM OF THE STUDY: Was to assess the lidocaine and bupivacaine systemic toxicity in forensic medical practice. The number of patients' clinical observations equal three with local anesthetic systemic toxicity (LAST) from the practice of forensic medical experts were studied, and a search of scientific publications for the last 5 years in PubMed database was conducted. The amount of publications, describing cases with LAST, equal four were selected. Differential diagnostic features between LAST and anaphylaxis were considered. The literature data about relationship between lidocaine's concentration in the blood serum and clinical features are shown. The forensic medical assessment of LAST is proposed.

Activation of the Akt Attenuates Ropivacaine-Induced Myelination Impairment in Spinal Cord and Sensory Dysfunction in Neonatal Rats.

Prolonged exposure to local anesthetics (LAs) or intrathecal administration of high doses of LAs can cause spinal cord damage. Intraspinal administration of LAs is increasingly being used in children and neonates. Therefore, it is important to study LA-related spinal cord damage and the underlying mechanism in developmental models. First, neonatal Sprague-Dawley rats received three intrathecal injections of 0.5% ropivacaine, 1% ropivacaine, 2% ropivacaine or saline (90-min interval) on postnatal day 7. Electron microscopy, luxol fast blue staining and behavioral tests were performed to evaluate the spinal neurotoxicity caused by ropivacaine at different concentrations. Western blot analysis and immunostaining was performed to detect the expression changes of p-Akt, Akt, myelin gene regulatory factor (MYRF) and myelin basic protein (MBP) in the spinal cord treated with different concentrations of ropivacaine. Our results showed that 1% or 2% ropivacaine impaired myelination in the spinal cord and induced sensory dysfunction, but 0.5% ropivacaine did not. Moreover, 1% or 2% ropivacaine decreased the expression of p-Akt, MYRF and MBP in the spinal cord. Then, in order to further explore the role of these proteins in this model, the Akt-specific activator (SC79) was intraperitoneally injected 30 min before 2% ropivacaine treatment. Interestingly, SC79-mediated activation of Akt partly rescued ropivacaine-induced myelination impairments and sensory dysfunction. Overall, the results showed that ropivacaine caused spinal neurotoxicity in a dose-dependent manner in neonatal rats and that activation of the Akt partly rescued ropivacaine-induced these changes. These data provide insight into the neurotoxicity to the developing spinal cord caused by LAs.

The potencies and neurotoxicity of intrathecal levobupivacaine in a rat spinal model: Effects of concentration.

This study was aimed at examining the anesthetic effects and spinal cord injuries in the rats by intrathecal injection of levobupivacaine at different concentrations. Rats with successful intrathecal cannulation were selected and randomly divided into six groups (n = 72), and administered 0.1 mL of 0.125%, 0.25%, 0.5%, or 0.75% levobupivacaine, saline or 5% lidocaine via intrathecal catheters. The potency of levobupivacaine was evaluated by walking behavior. To identify the motor and sensory function, walking behavior and paw withdrawal thresholds (PWTs) were measured once a day. After 7 days, the L4-5 spinal cord segments were removed for histological examination. The onset time of 0.125% levobupivacaine intrathecal injection was 70.0 ± 8.9 s, and the maintenance time was 9.5 ± 1.8 min. The onset time of 0.75% levobupivacaine intrathecal injection was significantly shortened to 31.0 ± 5.5 s, and the maintenance time was significantly extended to 31.3 ± 5.4 min. The severe injury was observed in the 5% lidocaine group, while milder injury was observed in the 0.75% levobupivacaine group. The damage in the 0.5% levobupivacaine group was mild, and there were no histological abnormalities in the 0.125%, 0.25% levobupivacaine and saline groups. The neurotoxicity of intrathecally administered levobupivacaine was concentration dependent. In addition, higher concentrations of levobupivacaine were associated with shorter onset and longer maintenance times. The clinical concentration of levobupivacaine should not exceed 0.5% to avoid potential damage.

Establishment of an animal model of sciatic nerve injury induced by local anesthetics.

Peripheral neurotoxicity injury caused by local anesthetics is a common complication of clinical anesthesia. The study of its mechanism is helpful to prevent and treat the neurotoxic injury of local anesthetics. Previous studies on peripheral neurotoxicity injury caused by local anesthetics have mainly focused on in vitro cell experiments. Due to the lack of an animal model of peripheral neurotoxicity damage caused by local anesthetics, there are few in vivo experimental studies regarding this topic. Herein, 1% ropivacaine hydrochloride was injected into the sciatic nerve by direct incision and exposure of the sciatic nerve to create a local anesthetic neurotoxic injury model. The results showed that 1% ropivacaine hydrochloride could reduce the lower limb motor score and mechanical paw withdrawal threshold in mice 48 hours after injection. Pathological sections showed that 48 hours after treatment with 1% ropivacaine hydrochloride, the sciatic nerve showed increased axonal edema and degeneration, edema between nerve fiber bundles, increased degeneration of axon and myelin sheath vacuoles, edema of nerve bundle membrane and local degeneration and necrosis, and a large number of inflammatory cells around the nerve adventitia were soaked. The above results show that under open vision, 1% ropivacaine hydrochloride can cause injury to the sciatic nerve after 48 h of treatment, which can simulate the neurotoxic damage of local anesthetics. This animal model provides a research tool for studying the mechanism of neurotoxic injury caused by local anesthetics.

Oxidative DNA Damage-induced PARP-1-mediated Autophagic Flux Disruption Contributes to Bupivacaine-induced Neurotoxicity During Pregnancy.

OBJECTIVE: Severe neurologic complications after spinal anesthesia are rare but highly distressing, especially in pregnant women. Bupivacaine is widely used in spinal anesthesia, but its neurotoxic effects have gained attention. METHODS: Furthermore, the etiology of bupivacaine-mediated neurotoxicity in obstetric patients remains unclear. Female C57BL/6 mice were intrathecally injected with 0.75% bupivacaine on the 18th day of pregnancy. We used immunohistochemistry to examine DNA damage after bupivacaine treatment in pregnant mice and measured γ-H2AX (Ser139) and 8-OHdG in the spinal cord. A PARP-1 inhibitor (PJ34) and autophagy inhibitor (3-MA) were administered with bupivacaine in pregnant mice. Parp-1flox/flox mice were crossed with Nes-Cre transgenic mice to obtain neuronal conditional knockdown mice. Then, LC3B and P62 staining were performed to evaluate autophagic flux in the spinal cords of pregnant wild-type (WT) and Parp-1-/- mice. We performed transmission electron microscopy (TEM) to evaluate autophagosomes. RESULTS: The present study showed that oxidative stress-mediated DNA damage and neuronal injury were increased after bupivacaine treatment in the spinal cords of pregnant mice. Moreover, PARP-1 was significantly activated, and autophagic flux was disrupted. Further studies revealed that PARP-1 knockdown and autophagy inhibitors could alleviate bupivacaine-mediated neurotoxicity in pregnant mice. CONCLUSION: Bupivacaine may cause neuronal DNA damage and PARP-1 activation in pregnant mice. PARP-1 further obstructed autophagic flux and ultimately led to neurotoxicity.

Benzonatate as a local anesthetic.

INTRODUCTION: Benzonatate is an FDA-approved antitussive agent that resembles tetracaine, procaine, and cocaine in its chemical structure. Based on structural similarities to known local anesthetics and recent findings of benzonatate exerting local anesthetic-like effects on voltage-gated sodium channels in vitro, we hypothesized that benzonatate will act as a local anesthetic to yield peripheral nerve blockade. METHODS: Benzonatate was injected at the sciatic nerve of Sprague-Dawley rats. Sensory and motor blockade were assessed using a modified hot plate test and a weight-bearing test, respectively. Additionally, the effect of co-injection with tetrodotoxin and Tween 80 (a chemical permeation enhancer) was examined. Myotoxicity of benzonatate was assessed in vivo by histological analysis. RESULTS: Benzonatate produced a concentration-dependent sensory and motor nerve blockade with no appreciable systemic effects. Co-injection with tetrodotoxin or Tween 80 produced prolongation of sensory nerve blockade. Histologic assessment showed significant inflammation and myotoxicity from benzonatate injection, even at low concentrations. CONCLUSION: This study demonstrates that benzonatate does act as a local anesthetic at the peripheral nerve, with sensory and motor nerve blockade. Benzonatate interacts with tetrodotoxin and Tween 80 to prolong nerve blockade. However, benzonatate causes significant myotoxicity, even at subtherapeutic concentrations.

Mechanisms underlying lipid emulsion resuscitation for drug toxicity: a narrative review.

Currently, lipid emulsion (LE) is widely used to treat local anesthetic systemic toxicity (LAST). LE also ameliorates intractable cardiovascular collapse caused by lipid-soluble non-local anesthetic drug toxicity. This review aims to provide the underlying mechanism of LE resuscitation in drug toxicity (including LAST) and a detailed description of LE treatment and to discuss further research directions. We searched for relevant articles using the following keywords: "local anesthetic systemic toxicity or LAST or toxicity or intoxication or poisoning" and "Intralipid or lipid emulsion". The underlying mechanisms of LE treatment can be classified into indirect and direct effects. One indirect effect known as the lipid shuttle is a commonly accepted mechanism of LE treatment. The lipid shuttle involves the absorption of highly lipid-soluble drugs (e.g., bupivacaine) from the heart and brain through the lipid phase, which are then delivered to the muscle, adipose tissue, and liver for storage and detoxification. The direct effects include inotropic effects, fatty acid supply, attenuation of mitochondrial dysfunction, glycogen synthase kinase-3ß phosphorylation, and inhibition of nitric oxide. These mechanisms appear to act synergistically to treat drug toxicity. The recommended protocol for LE treatment of LAST is as follows: a bolus administration of 20% LE at 1.5 ml/kg over 2-3 min followed by 20% LE at 0.25 ml/kg/min. LAST most commonly occurs after intravenous administration of local anesthetics. However, non-local anesthetic drugs that cause drug toxicity are orally administered. Further studies are needed to determine the optimal dosing schedule of LE treatment for non-local anesthetic drug toxicity.

Sodium bicarbonate reverts electrophysiologic cardiotoxicity of ropivacaine faster than lipid emulsions in a porcine model.

Ropivacaine has been described as a safer local anaesthetic (LA); however, serious cardiotoxic accidents have been reported. Intravenous-lipid-emulsion (ILE) therapy during LA intoxication seems to act as an antidote. Sodium bicarbonate is the standard treatment for sodium channel blocker drug toxicity. We compared both antidotes on the reversion of electrophysiologic toxicity induced by ropivacaine. Ropivacaine 5 mg kg-1 was administered in 24 pigs, and 3 min later, the animals received ILE: 1.5 ml kg-1  + 0.25 ml kg-1  min-1 (ILE group); sodium bicarbonate: 2 mEq kg-1  + 1 mEq kg-1  h-1 (NaHCO3 group); saline solution (CTL group). Electrophysiological parameters were evaluated for 30 min. The area under the curve (AUC) for the first 5 or 30 min was compared between groups. Ropivacaine induced a lengthening of the PR interval by 17% (P = 0.0001), His-ventricle-interval by 58% (P = 0.001), sinus QRS complex by 56% (P = 0.0001), paced QRS at 150 bpm by 257% (P = 0.0001), and at 120 bpm by 143% (P = 0.0001) in all groups. At 5 min after treatment, sinus QRS in the NaHCO3 group was shorter than that in the CTL group (AUCQRS5 , P = 0.003) or ILE group (AUCQRS5 , P = 0.045). During the first minute, seven of the animals in the NaHCO3 group vs. two in the ILE or 0 in the CTL group recovered more than 30% of the sinus QRS previously lengthened by ropivacaine (P = 0.003). Sodium bicarbonate reversed the electrophysiological toxicity of ropivacaine faster than ILE and control groups.

Ropivacaine-induced seizures evoked pain sensitization in rats: Participation of 5-HT/5-HT3R.

Due to the increasing use of local anesthetic techniques in various healthcare settings, local anesthetic toxicity still occurs. Seizures are the most common symptom of local anesthetic toxicity. The relationship between local anesthetic-induced seizures and the sensation of pain has not been established till now. Here, we assessed the development of pain hypersensitivity after ropivacaine-induced seizures (RIS) and the influence of RIS on incision-induced postsurgical pain and formalin-induced acute inflammatory pain. In addition, the involvement of spinal 5-HT/5-HT3R in RIS-induced pain sensitization was investigated. According to a sequential exploratory experimental strategy, we first calculated the 50% seizure dosage of ropivacaine to be 42.66 mg/kg (95% confidence interval: 40.19-45.28 mg/kg). We showed that RIS induced significant bilateral mechanical pain hypersensitivity that lasted around 5 days, accompanied by an increase in spinal 5-HT. Moreover, RIS considerably protracted postsurgical pain and enhanced formalin-induced spontaneous flinching in the second phase. Depletion of spinal 5-HT with intrathecal injection of 5,7-dihydroxytryptamine (5,7-DHT) reduced RIS-induced pain hypersensitivity and prevented the prolonging of postsurgical pain following RIS. Likewise, blocking spinal 5-HT3R by intrathecal administration of ondansetron reversed RIS-induced pain hypersensitivity and attenuated the pronociception of RIS in the formalin test. Our findings revealed that acute RIS led to pain hypersensitivity and had pronociceptive effects on incision-induced postsurgical pain and formalin-induced acute inflammatory pain. Moreover, our data implied that RIS-induced pain sensitization depends on spinal 5-HT/5-HT3R signaling. Thus, targeting the descending serotonergic facilitation system should be an important element of the precise treatment for local anesthetic toxicity.

Local Anesthetic Cardiac Toxicity Is Mediated by Cardiomyocyte Calcium Dynamics.

BACKGROUND: Long-lasting local anesthetic use for perioperative pain control is limited by possible cardiotoxicity (e.g., arrhythmias and contractile depression), potentially leading to cardiac arrest. Off-target cardiac sodium channel blockade is considered the canonical mechanism behind cardiotoxicity; however, it does not fully explain the observed toxicity variability between anesthetics. The authors hypothesize that more cardiotoxic anesthetics (e.g., bupivacaine) differentially perturb other important cardiomyocyte functions (e.g., calcium dynamics), which may be exploited to mitigate drug toxicity. METHODS: The authors investigated the effects of clinically relevant concentrations of racemic bupivacaine, levobupivacaine, or ropivacaine on human stem cell-derived cardiomyocyte tissue function. Contractility, rhythm, electromechanical coupling, field potential profile, and intracellular calcium dynamics were quantified using multielectrode arrays and optical imaging. Calcium flux differences between bupivacaine and ropivacaine were probed with pharmacologic calcium supplementation or blockade. In vitro findings were correlated in vivo using an anesthetic cardiotoxicity rat model (females; n = 5 per group). RESULTS: Bupivacaine more severely dysregulated calcium dynamics than ropivacaine in vitro (e.g., contraction calcium amplitude to 52 ± 11% and calcium-mediated repolarization duration to 122 ± 7% of ropivacaine effects, model estimate ± standard error). Calcium supplementation improved tissue contractility and restored normal beating rhythm (to 101 ± 6%, and 101 ± 26% of control, respectively) for bupivacaine-treated tissues, but not ropivacaine (e.g., contractility at 80 ± 6% of control). Similarly, calcium pretreatment mitigated anesthetic-induced arrhythmias and cardiac depression in rats, improving animal survival for bupivacaine by 8.3 ± 2.4 min, but exacerbating ropivacaine adverse effects (reduced survival by 13.8 ± 3.4 min and time to first arrhythmia by 12.0 ± 2.9 min). Calcium channel blocker nifedipine coadministration with bupivacaine, but not ropivacaine, exacerbated cardiotoxicity, supporting the role of calcium flux in differentiating toxicity. CONCLUSIONS: Our data illustrate differences in calcium dynamics between anesthetics and how calcium may mitigate bupivacaine cardiotoxicity. Moreover, our findings suggest that bupivacaine cardiotoxicity risk may be higher than for ropivacaine in a calcium deficiency context.

Emulsiones lipídicas en la intoxicación por anestésicos locales y otros fármacos. Revisión sobre mecanismos de acción y recomendaciones de uso / Lipid emulsions in the treatment of intoxications by local anesthesics and other drugs. Review of mechanisms of action and recommendations for use

La emulsiones lipídicas intravenosas (ELI) se han utilizado ampliamente para el tratamiento de la intoxicación por anestésicos locales (AL) y se han propuesto como tratamiento de la intoxicación por otros fármacos. Sin embargo, el grado de evidencia de este tipo de terapias no es sólido, ya que proviene en su mayoría de casos clínicos. El objetivo de esta revisión narrativa es describir los mecanismos de acción propuestos para las ELI en la intoxicación por AL y otros fármacos, y evaluar los estudios recientes realizados en animales que sustentan las recomendaciones de su uso y la experiencia en humanos que apoyan el empleo de las ELI tanto en la intoxicación por AL como por otros fármacos. Para ello, se llevó a cabo una búsqueda en las bases de datos Embase, Medline, Cochrane y Google Scholar abarcando los artículos relevantes durante los últimos 10 años. En caso de intoxicación por AL, se recomienda aplicar los protocolos dictados por las guías internacionales, sabiendo que el grado de evidencia no es muy elevado. En la intoxicación por otros fármacos, las ELI están aconsejadas en situaciones graves inducidas por xenobióticos liposolubles que no responden al tratamiento estándar.(AU)

Intravenous lipid emulsions (ILEs) have been used widely for the treatment of local anesthetic (LA) poisoning and have been proposed as a treatment for intoxication by other drugs. However, the degree of evidence for this kind of therapy is not strong, as it comes mostly from clinical cases. The aim of this narrative review is to describe the proposed mechanisms of action for ILEs in poisoning by LA and other drugs and to evaluate recent studies in animals that support the recommendations for their use and the experience in humans that support the use of ILESs in both LA and other drug poisoning. For this purpose, a search was performed in the Embase, Medline and Google Scholar databases covering relevant articles over the last 10 years. In the case of AL poisoning, we recommend applying the protocols dictated by international guidelines, knowing that the degree of evidence is not very high. In poisoning by other drugs, ILEs are recommended in serious situations induced by liposoluble xenobiotics that do not respond to standard treatment.(AU)

Effects of intravenous lipid emulsions on the reversal of pacing-induced ventricular arrhythmias and electrophysiological alterations in an animal model of ropivacaine toxicity.

INTRODUCTION: Ropivacaine is considered to have a wider margin of cardiovascular safety. However, several reports of ventricular arrhythmias (VA) due to ropivacaine toxicity have been documented. Intravenous lipid emulsions (ILEs) have recently been used successfully in the treatment of local anesthetic intoxication. The main objective of the present study was to evaluate the efficacy of the ILEs in the prevention of pacing-induced-VA and electrophysiological alterations in an animal model of ropivacaine toxicity. METHODS: Nineteen pigs were anesthetized and instrumentalized. A baseline programmed electrical ventricular stimulation protocol (PEVSP) to induce VA was performed. Ropivacaine (5 mg·kg-1 + 100 µg·kg-1·min-1) followed by normal saline infusion (control group n = 8) or intralipid 20% (1.5 mL·kg-1 + 0.25 mL·kg-1·min-1) for the ILE group (n = 8), were administered three minutes after the ropivacaine bolus. PEVSP was repeated 25 min after the onset of ropivacaine infusion. Pacing-induced VA and electrophysiological abnormalities were assessed in both groups. A sham-control group (n = 3) without ropivacaine infusion was included. RESULTS: Most of the electrophysiological parameters evaluated were affected by ropivacaine: PR interval by 28% (p = 0.001), AV interval by 40% (p = 0.001), sinus QRS by 101% (p = 0.001), paced QRS at a rate of 150 bpm by 258% (p = 0.001), and at 120 bpm by 241% (p = 0.001). Seven animals (87.5%) in the control group and eight animals (100%) in the ILE group developed sustained-VA (p = 0.30). Successful resuscitation occurred in 100% of animals in the ILE group vs. 57% of animals in the control group, p = 0.038. Pacing-induced-VA terminated at the first defibrillation attempt in 75% of the animals in the ILE group vs. 0% in the control group, p = 0.01. CONCLUSION: Ropivacaine strongly altered the parameters of ventricular conduction, thus facilitating the induction of VA. ILEs did not prevent pacing-induced VA. However, facilitated resuscitation and termination of VA were delivered at the first defibrillation attempt compared to the control group.

Pharmacodynamics, toxicology and toxicokinetics of ropivacaine oil delivery depot.

BACKGROUND: Ropivacaine oil delivery depot (RODD) can be used to treat postoperative incision pain. The aim was to study pharmacodynamics, toxicity and toxicokinetics of RODD. METHODS: The base research of RODD were conducted. Thirty rabbits were randomly divided into saline, solvent, ropivacaine aqueous injection (RAI) 0.9 mg, RODD 0.9 mg and RODD 3 mg groups. The sciatic nerve of rabbits were isolated, dripped with RODD and the effect of nerve block were observed. In toxicity study, the rats were divided into saline, solvent and RODD 75, 150 and 300 mg/kg groups, 30 rats per group. In toxicokinetics, rats were divided into RODD 75, 150 and 300 mg/kg groups, 18 rats per group. The rats were subcutaneously injected drugs. RESULTS: The analgesic duration of RODD 3 mg and RAI 0.9 mg blocking ischiadic nerve lasted about 20 h and 2 h, respectively, and their blocking intensity was similar. The rats in RODD 75 mg/kg did not show any toxicity. Compared with saline group, in RODD 150 mg/kg group neutrophils and mononuclear cells increased, lymphocytes decreased and albumin decreased(P < 0.05), and pathological examination showed some abnormals. In RODD 300 mg/kg group, 10 rats died and showed some abnormalities in central nerve system, hematologic indexes, part of biochemical indexes, and the weights of spleen, liver, and thymus. However, these abnormal was largely recovered on 14 days after the dosing. The results of toxicokinetics of RODD 75 mg/kg group showed that the Cmax was 1.24 ± 0.59 µg/mL and the AUC(0-24 h) was 11.65 ± 1.58 h·µg/mL. CONCLUSIONS: Subcutaneous injection RODD releases ropivacaine slowly, and shows a stable and longer analgesic effect with a large safety range.

Effects of nalbuphine on the cardiotoxicity of ropivacaine in rats.

When combined with nalbuphine, local anesthetics show a longer duration of nerve block without increasing complications. However, no evidence is available concerning the effect of nalbuphine on the cardiotoxicity of local anesthetics. The objective of this work is to investigate whether nalbuphine pretreatment can increase the lethal dose threshold of ropivacaine in rats. Anesthetized Sprague Dawley rats were pretreated with different doses of nalbuphine (0.4, 0.8, 1.5, 3.0, 5.0 mg/kg) or NS (normal saline, negative control) or 30% LE (lipid emulsion, positive control) 2 ml/kg/min for 5 min (n = 6). Then 0.5% ropivacaine was infused at a rate of 2.5 mg/kg/min until asystole occurs. Time of arrhythmia, 50% mean arterial pressure- and 50% heart rate-reduction, and asystole were recorded, and ropivacaine doses were calculated. Nalbuphine (0.4-5.0 mg/kg) did not affect ropivacaine-induced arrhythmia, 50% mean arterial pressure-reduction and 50% heart rate-reduction, and asystole in rats compared with NS pre-treatment. The asystole dose threshold (in milligrams per kilogram) of group LE was higher than that of group NS (NS 28.25(6.32) vs. LE, 41.58(10.65); P = 0.04; 95% confidence interval 0.23 to 26.45), while thresholds of arrhythmia, 50% mean arterial pressure-reduction, and 50% heart rate-reduction were not affected by LE. Nalbuphine doses of 0.4-5.0 mg/kg pretreatment did not increase the threshold of ropivacaine cardiotoxicity compared with NS control; 30% LE increases the lethal dose threshold of ropivacaine in rats.

Chondrotoxic effects of intra-articular injection of local anaesthetics in the rabbit temporomandibular joint.

The aim of this study was to investigate the chondrotoxic effects of a single-dose intra-articular injection of articaine, lidocaine, and bupivacaine on the rabbit temporomandibular joint (TMJ). Twenty-four rabbits were divided into four groups: control (group 1), articaine (group 2), lidocaine (group 3), and bupivacaine (group 4). Synovial fluid samples and venous blood were taken to evaluate matrix metalloproteinase 3 (MMP-3) levels. One millilitre of local anaesthetic solution was injected in the study groups and saline solution in the control group. The rabbits were euthanized after 4 weeks and the mandibular condyles and articular discs were evaluated. On histological examination, the study group samples had irregular joint surfaces, decreased collagen, and a thinner cartilage layer. Apoptotic cells were evaluated with the TUNEL method. TUNEL-positive apoptotic cell counts were higher in all study groups compared to the control group, and the difference was significant (P < 0.001). The mean preoperative serum MMP-3 level for all groups was 5.71 ± 3.33 ng/mL, while the mean postoperative level was 22.61 ± 6.36 ng/mL; this difference was significant (P < 0.001). A single-dose intra-articular injection of local anaesthetic had apoptotic effects on chondrocytes, leading to degenerative changes in the TMJ articular structures. Articaine was found to have less harmful effects than lidocaine and bupivacaine. Intra-articular injection of local anaesthetics should be limited in the TMJ because of the potential toxic effects.

Lipid emulsions attenuate the inhibition of carnitine acylcarnitine translocase induced by toxic doses of local anesthetics in rat cardiomyoblasts.

The aim of this study was to examine the effects of lipid emulsions on carnitine palmitoyltransferase I (CPT-I), carnitine acylcarnitine translocase (CACT), carnitine palmitoyltransferase II (CPT-II), and the mitochondrial dysfunctions induced by toxic doses of local anesthetics in H9c2 rat cardiomyoblasts. The effects of local anesthetics and lipid emulsions on the activities of CPT-I, CACT, and CPT-II, and concentrations of local anesthetics were examined. The effects of lipid emulsions, N-acetyl-L-cysteine (NAC), and mitotempo on the bupivacaine-induced changes in cell viability, reactive oxygen species (ROS) levels, mitochondrial membrane potential (MMP), and intracellular calcium levels were examined. CACT, without significantly altering CPT-I and CPT-II, was inhibited by toxic concentration of local anesthetics. The levobupivacaine- and bupivacaine-induced inhibition of CACT was attenuated by all concentrations of lipid emulsion, whereas the ropivacaine-induced inhibition of CACT was attenuated by medium and high concentrations of lipid emulsion. The concentration of levobupivacaine was slightly attenuated by lipid emulsion. The bupivacaine-induced increase of ROS and calcium and the bupivacaine-induced decrease of MMP were attenuated by ROS scavengers NAC and mitotempo, and the lipid emulsion. Collectively, these results suggested that the lipid emulsion attenuated the levobupivacaine-induced inhibition of CACT, probably through the lipid emulsion-mediated sequestration of levobupivacaine.

A Systematic Review on Nerve-Related Adverse Effects following Mandibular Nerve Block Anesthesia.

Inferior alveolar nerve (IAN) block injections are commonly used in clinical practice, but they are not free from complications. The aim of the present systematic review is to assess the nerve-related adverse effects of IAN block anesthesia. A structured and systematic search was performed on the major electronic databases (PubMed, Cochrane Library, Web of Science, Scopus and CINAHL) for studies published in English until 30 September 2021. A total of 131 articles were identified through database searching using combinations of keywords. Fifteen papers were included and assessed for eligibility. Overall, nerve damage following an IAN block anesthesia injection is a rare occurrence, probably due to the direct nerve trauma of the needle, a neurotoxic effect of the used anesthetic solution and/or a combination of them. From a medico-legal point of view, a balanced discussion prior to nerve block anesthesia should be pursued in order to avoid patients' reluctance to undergo necessary dental treatment due to the remote eventuality of nerve injury.