Neuroprotective effect of low-dose lidocaine in a rat model of transient focal cerebral ischemia

The dose-response relationships of the direct scavenging activity of amide-based local anesthetics against multiple free radicals

This study aimed to illustrate the dose-response relationships of the direct scavenging activity of amide-based local anesthetics against multiple free radicals in vitro. We have demonstrated that amide-type local anesthetics selectively and directly scavenge some free radicals. Three kinds of free radicals were eliminated by all the four local anesthetics examined. Mepivacaine, lidocaine, bupivacaine, and dibucaine scavenged hydroxyl radicals in dose-dependent manners. Ascorbyl free radicals were also scavenged in dose-dependent manners, and lastly singlet oxygen was scavenged in dose-dependent manners. Three other free radicals were not scavenged by all of the four local anesthetics; tert-butoxyl radical was scavenged by all the anesthetics examined but dibucaine, nitric oxide by mepivacaine but not by the other three, and tyrosyl radical by mepivacaine and lidocaine but not by the other two. Some free radicals (superoxide anion, tert-butyl peroxyl radical, DPPH) were not scavenged by any of the four local anesthetics. The local anesthetics were also shown to inhibit lipid peroxidation by TBARS assay. These results suggest that local anesthetics have antioxidant properties through their free radical scavenging activities.

Lidocaine attenuates hypoxia/reoxygenation‑induced inflammation, apoptosis and ferroptosis in lung epithelial cells by regulating the p38 MAPK pathway

Lung ischemia-reperfusion (I/R) injury poses a serious threat to human health, worldwide. The current study aimed to determine the role of lidocaine in A549 cells, in addition to the involvement of the p38 MAPK pathway. Oxygen deprivation/reoxygenation-induced A549 cells were utilized to simulate I/R injury in vitro. Cell viability and apoptosis were detected using MTT and TUNEL assays, respectively. The levels of IL-6, IL-8, TNF-α, malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase, iron and reactive oxygen species (ROS) were measured using corresponding commercial kits. The corresponding protein expression levels were also measured using western blotting. Moreover, a monolayer cell paracellular permeability assay was performed to determine the permeability of A549 cells. The results demonstrated that, whilst lidocaine had no influence on untreated A549 cells, it significantly increased the viability of hypoxia/reoxygenation (H/R)-induced A549 cells. A549 cell apoptosis and the release of inflammatory cytokines in the H/R group were decreased after the addition of lidocaine. When compared with the H/R group, increased MDA level and decreased SOD level were observed in H/R-induced A549 cells following lidocaine treatment. In addition, the permeability of H/R-induced A549 cells was markedly decreased following lidocaine treatment. Compared with the H/R group, the expression levels of tight junction and ferroptosis-related proteins were significantly upregulated by lidocaine, whereas the expression of transferrin was downregulated. However, p79350, an agonist of p38, reversed the effects of lidocaine on H/R-induced A549 cells. In conclusion, lidocaine exerted a protective role in HR-induced lung epithelial cell injury, which may serve as a potential agent for the treatment of patients with lung I/R injury.

The effects of target-controlled infusion of lidocaine undergoing vocal cord polypectomy: A randomized controlled trial (CONSORT compliant)

BACKGROUND

The present study aimed to assess the efficacy and safety of general anesthesia-assisted target-controlled plasma infusion of lidocaine in patients with vocal cord polypectomy using a supporting laryngoscope.

METHODS

In total, 80 patients undergoing vocal cord polypectomy using a supporting laryngoscope were randomly divided into an intervention group and a control group; each group contained 40 subjects: both groups received general anesthesia; subjects in the intervention also received an additional 3 mg/L of lidocaine by target-controlled plasma infusion during induction and maintenance of anesthesia; heart rate (HR) mean arterial pressure (MAP), propofol and urapidil consumption (Uradil, which is a blood pressure drug that blocks alpha-1, is called Urapidi Hydrochloride Injection. It is produced by Germany, the enterprise name is Nycomed Deutschland GmbH, the import drug registration number is H20090715, and it is widely used in China), recovery time, and cough score (measured by Minogue et al's 5-grade scoring method) during extubation, and throat pain score (measured by visual analogue scale,[VAS]) after extubation and adverse events were recorded.

RESULTS

Significant differences were observed in HR (P < .05) and MAP (P < .05) immediately after intubation (T2), immediately after the operation starting to support laryngoscope exposure (T3), immediately after operation field adrenergic tampon hemostasis (T4), and 5 minutes after hemostasis (T5) between the 2 groups, and significant differences were also observed in HR (P < .05) before intubation (T1). Moreover, significant differences were observed in propofol consumption (P < .05), urapidil consumption (P < .05), cough score during extubation (P < .05), and throat pain score after extubation (P < .05). However, no significant difference was observed in the recovery time (P > .05). Furthermore, no adverse events were detected in either group.

CONCLUSION

The results of this study showed that target-controlled plasma infusion of lidocaine can reduce propofol consumption in patients undergoing vocal cord polypectomy by supporting laryngoscopy, and the hemodynamics are more stable and reduce the coughing reaction in the wake period and throat pain after extubation without adverse events.

Dexmedetomidine vs. lidocaine for postoperative analgesia in pediatric patients undergoing craniotomy: a protocol for a prospective, randomized, double-blinded, placebo-controlled trial

Background

Postoperative pain is a common problem that occurs in pediatric patients following neurosurgery which may lead to severe complications. Dexmedetomidine is a commonly used adjuvant medicine in craniotomy owing to its sedative, amnestic, analgesic, and neuroprotective properties. Besides, studies suggest that lidocaine has similar effects on sedation, analgesia, and neuroprotection. Both two adjuvants can reduce postoperative pain after neurosurgery in adults. However, it is still unknown whether dexmedetomidine or lidocaine can reduce postoperative pain in children undergoing craniotomy, and if yes, which is a better medicine choice. Therefore, we aimed to compare the effect of dexmedetomidine vs. lidocaine on postoperative pain in pediatric patients after craniotomy.

Methods/design

We will perform a randomized (1:1:1), double-blind, placebo-controlled, single-center trial. Children aged 1–12 years scheduled for craniotomy will be eligible for inclusion. The 255 recruited participants will be stratified by age in two strata (1–6 years and 7–12 years), and then each stratum will be equally randomized to three groups: group D (infusion of dexmedetomidine [intervention group]), group L (infusion of lidocaine [intervention group]), and group C (infusion of normal saline [control group]). Patients will be followed up at 1 h, 2 h, 4 h, 24 h, and 48 h after surgery. The primary outcome will be total sufentanil consumption within 24 h after surgery.

Discussion

In this clinical trial, we expect to clarify and compare the postoperative analgesic effect of dexmedetomidine vs. lidocaine infusion on pediatric patients undergoing craniotomy. We believe that the results of this trial will provide more choices for postoperative analgesia for the pediatric population.

Trial registration

Chinese ClinicalTrials.gov ChiCTR1800019411. Registered on 10 November 2018

Electrocorticographic description of the effects of anticonvulsant drugs used to treat lidocaine-induced seizures

INTRODUCTION

Local anesthetics are widely used in clinical practice. While toxicity is rare, these drugs can cause potentially lethal seizures.

OBJECTIVE

In the present study, we investigated the electrocorticographic (ECoG) and electromyographic patterns of seizures induced by acute lidocaine (LA) toxicity and treated with anticonvulsant drugs. The study used adult male Wistar rats to describe of the seizure-related behavior of LA and investigated the treatment with anticonvulsant drugs.

RESULTS

The use of LA resulted in clear changes in the ECoG pattern, which presented characteristics of Status epilepticus, with increased intensity in all brainwaves. The decomposition of the cerebral waves showed an increase in the beta and gamma waves that may be related to tonic-clonic seizure. Although the treatment with anticonvulsants drugs reduces the power of brainwaves at frequencies between 1 and 40 Hz compared to the LA group, but only diazepam (DZP) was able to decrease the intensity of oscillations. The muscle contraction power also indicated a difference in the effectiveness of the three treatments.

CONCLUSION

The sum of the evidence indicates that LA causes status epilepticus and that DZP is the most effective treatment for the control of these seizures, by restoring the systemic values to levels close to those recorded in the control group.

Regionally infused lidocaine can dose-dependently protect the ischemic spinal cord in rabbits and may be associated with the EAA changes

OBJECTIVE

In our previous study, we found that lidocaine, infused through the abdominal aorta, could protect the spinal cord against the ischemia-reperfusion (I/R) injury caused by aortic occlusion. However, whether lidocaine protective effects have dose-dependent properties and its underlying mechanisms still remain unclear. This study was designed to investigate whether regionally infused lidocaine could dose-dependently protect spinal cord against I/R injury in rabbits and its underlying mechanism.

METHODS

46 New Zealand white rabbits were randomized into six groups: Group NS (normal saline control); Group L10 (lidocaine 10 mg/kg); Group L20 (lidocaine 20 mg/kg); Group L40 (lidocaine 40 mg/kg); Group L80 (lidocaine 80 mg/kg) and Group Sham. In Group NS, Group L10, Group L20, Group L40 and Group L80, spinal cord ischemia was induced by infrarenal aortic occlusion for 30 min. The sham group did not receive spinal cord ischemia. During the occlusion, normal saline or lidocaine at different doses was infused continuously through a catheter into the clamped abdominal aorta respectively. Neurologic behavior functions were assessed according to the Tarlov scale system at the moments of 0, 6, 24 and 48 h after reperfusion. The neural injuries were evaluated by the histological examination and the count of normal α-motor neurons in the ventral horn. The levels of excitatory amino acids (EAAs) in the spinal cord, including glutamate (Glu) and aspartic acid (Asp), were analyzed by high performance liquid chromatography with fluorescence detection.

RESULTS

The Tarlov scales in the Group L20 and the Group L40 were significantly higher than those in the Group NS at 24 and 48 h after reperfusion (P < 0.05). 12.5 % animals in Group L40 and 25 % animals in Group L20 were paraplegic versus 75 % animals in Group NS at 48 h after reperfusion (P < 0.05). The median of normal α-motor neurons in the L20, L40 and L80 groups was 7.5, 9 and 5 respectively which was significantly higher than in the NS group (count 0, P < 0.05). The levels of L-ASP and L-Glu remarkably decreased in the Group L10 and the Group L40 compared to Group NS (P < 0.05).

CONCLUSIONS

These data revealed that regional administration of lidocaine through the abdominal aorta can provide dose-dependent protection on spinal cord I/R in rabbits. Inhibition of EAA release may be one of the underlying mechanisms.

Endotracheal administration for intraoperative acute massive pulmonary embolism during laparoscopic hepatectomy: A case report

INTRODUCTION

Acute pulmonary embolism (APE) during an operation is a very urgent occurrence, especially when the patient with hemodynamic instability. Generally, drugs are administered intravenously; however, these drugs have little effects under most circumstances. We present a case of successful resuscitation in a patient with endotracheal administration.

PATIENT CONCERNS

A 67-year-old female presented for laparoscopic hepatectomy. Acute pulmonary gas embolism occurred during the operation with hemodynamic instability. The total amount of carbon dioxide and argon reached 300 mL. We used a novel way of administering drugs instead of intravenous administration for rescuing and the patient condition had improved greatly and was discharged from the hospital without any neurological deficits.

DIAGNOSES

A diagnosis of APE was made because of a lot of gas was extracted out from central venous catheter and sudden observable decrease in end-tidal CO2.

INTERVENTIONS

These measures included endotracheal administration, position adjustment, manual ventilation, and gas extraction.

OUTCOMES

The patient was discharged from the hospital and had no signs of neurological deficits.

CONCLUSION

Intravenous administration may not the best appropriate way of administration when patients occurred APE. Endotracheal administration as a unique method may work wonders and has the value of research and application.

Amiodarone exacerbates brain injuries after hypoxic-ischemic insult in mice

Background

Sodium ion transportation plays a crucial role in the pathogenesis of hypoxic–ischemic brain injury. Amiodarone, a Vaughan-Williams class III antiarrhythmic drug, has been widely used to treat life-threatening arrhythmia and cardiac arrest worldwide. In addition to its inhibitory effects on the potassium channel, amiodarone also blocks various sodium ion transporters, including the voltage-gated sodium channel, sodium pump, and Na⁺/Ca⁺ exchanger. Considering these pharmacological profile, amiodarone may affect the influx–efflux balance of sodium ion in the hypoxic–ischemic brain. Previous studies suggest that the blockade of the voltage-gated sodium channel during hypoxic–ischemic brain injury exerts neuroprotection. On the contrary, the blockade of sodium pump or Na⁺/Ca⁺ exchanger during hypoxia–ischemia may cause further intracellular sodium accumulation and consequent osmotic cell death. From these perspectives, the effects of amiodarone on sodium ion balance on the hypoxic–ischemic brain can be both protective and detrimental depending on the clinical and pathophysiological conditions. In this study, we therefore investigated the effect of amiodarone on hypoxic–ischemic brain injury using a murine experimental model.

Results

Compared with the control group mice, mice that received amiodarone after induction of 40-min hypoxic–ischemic brain injury exhibited lower survival rates over 7 days and worse neurological function. After 25-min hypoxic–ischemic brain injury, amiodarone treated mice exhibited larger infarct volumes (16.0 ± 6.9 vs. 24.2 ± 6.8 mm³, P < 0.05) and worse neurological function. In addition, the brains harvested from the amiodarone-treated mice contained larger amounts of sodium (194.7 ± 45.1 vs. 253.5 ± 50.9 mEq/kg dry weight, P < 0.01) and water (259.3 ± 8.9 vs. 277.2 ± 12.5 mg, P < 0.01). There were no significant differences in hemodynamic parameters between groups.

Conclusions

Amiodarone exacerbated brain injuries and neurological outcomes after hypoxic–ischemic insults. Severe brain sodium accumulation and brain edema were associated with the detrimental effects of amiodarone. Amiodarone at the clinical dose can exacerbate brain injury after hypoxic–ischemic insult by affecting sodium ion transportation and facilitate intracellular sodium accumulation in the brain.

Using Single-Cell Amperometry and Intracellular Vesicle Impact Electrochemical Cytometry To Shed Light on the Biphasic Effects of Lidocaine on Exocytosis

Single cell amperometry and intracellular vesicle impact electrochemical cytometry were used to examine whether lidocaine can regulate neurotransmitter release or storage for PC12 cells to explain the biphasic effects whereby it can protect neurons and improve cognitive outcome at low concentration, but can cause neurotoxicity at high concentration. We show that lidocaine affects the behavior of PC12 cell exocytosis in a concentration dependent way, which exactly corresponds to its biphasic effects. At a relatively high concentration, it shows a much narrower pore size and a longer-duration fusion pore with less monoamine released than control cells. However, at a relatively low concentration, the fusion pore is open even longer than at high concentration, and with more monoamine released than control cells. Furthermore, intracellular vesicle impact electrochemical cytometry was used to confirm that lidocaine did not change the catecholamine content of the vesicles. These data provide a mechanism for the observed biphasic effects of the drug and suggest that lidocaine influences exocytosis through multiple mechanisms.

Neuroprotective effects of amiodarone in a mouse model of ischemic stroke

Background

Ion channels play a crucial role in the development of ischemic brain injury. Recent studies have reported that the blockade of various types of ion channels improves outcomes in experimental stroke models. Amiodarone, one of the most effective drugs for life-threatening arrhythmia, works as a multiple channel blocker and its characteristics cover all four Vaughan-Williams classes. Although it is known that amiodarone indirectly contributes to preventing ischemic stroke by maintaining sinus rhythm in patients with atrial fibrillation, the direct neuroprotective effect of amiodarone has not been clarified. The purpose of this study was to investigate the direct effect of amiodarone on ischemic stroke in mice.

Methods

Focal cerebral ischemia was induced via distal permanent middle cerebral artery occlusion (MCAO) in adult male mice. The amiodarone pre-treatment group received 50 mg/kg of amiodarone 1 h before MCAO; the amiodarone post-treatment groups received 50 mg/kg of amiodarone immediately after MCAO; the control group received vehicle only. In addition, the sodium channel opener veratrine and selective beta-adrenergic agonist isoprotelenol were used to elucidate the targeted pathway. Heart rate and blood pressure were monitored perioperatively. Infarct volume analysis was conducted 48 h after MCAO. The body asymmetry test and the corner test were used for neurological evaluation.

Results

Amiodarone pre-treatment and post-treatment reduced the heart rate but did not affect the blood pressure. No mice showed arrhythmia. Compared with the control group, the amiodarone pre-treatment group had smaller infarct volumes (8.9 ± 2.1% hemisphere [mean ± SD] vs. 11.2 ± 1.4%; P < 0.05) and improved functional outcomes: lower asymmetric body swing rates (52 ± 17% vs. 65 ± 18%; P < 0.05) and fewer left turns (7.1 ± 1.2 vs. 8.3 ± 1.2; P < 0.05). In contrast, amiodarone post-treatment did not improve the outcomes after MCAO. The neuroprotective effect of amiodarone pre-treatment was abolished by co-administration of veratrine but not by isoproterenol.

Conclusions

Amiodarone pre-treatment attenuated ischemic brain injury and improved functional outcomes without affecting heart rhythm and blood pressure. The present results showed that amiodarone pre-treatment has neuroprotective effects, at least in part, via blocking the sodium channels.

Administration of lidocaine to prevent cognitive deficit in patients undergoing coronary artery bypass grafting and valve plasty: a systematic review and meta-analysis

INTRODUCTION

The administration of lidocaine to maintain cognitive function following coronary artery bypass grafting (CABG) and valve plasty is a controversial concept in terms of its effectiveness. We performed a systematic review to determine the effectiveness of treatment with lidocaine in preventing the occurrence of cognitive deficit after cardiac surgery. Area covered: To review the current literature on the subject, we searched the PubMed database and the Cochrane Library database (up to May 2015) and compiled a list of retrieved articles. Our final review includes only randomized controlled trials (RCTs) that compared lidocaine to a control (placebo) following CABG and valve plasty. Statistical analysis of the odds ratio (OR) and corresponding 95% confidence interval (CI) were used to determine the overall effectiveness of lidocaine for the prevention of cognitive deficit with both procedures. The Mantel-Haenszel method was used to pool data of the outcomes of cognitive deficit occurrence into fixed-effect model meta-analyses. Five RCTs were included in this study, with a total of 688 patients. Perioperative administration of lidocaine in patients undergoing cardiac surgery reduced occurrence of cognitive deficit (OR 0.583 [95% CI 0.438-0.777]; Z = -3.680; P = 0.00; I² = 52%). No significant difference in the early occurrence of cognitive deficit was revealed in patients after cardiac surgery (OR 0.909 [95% CI 0.600-1.376]; Z = -0.451; P = 0.652; I² = 11%). Expert commentary: Cognitive deficit associated with cardiac surgery is a common postoperative event. Lidocaine is contributed to a significantly reduced occurrence of cognitive deficit. Cognitive deficit management is recommended.

Effects of Ranolazine on Astrocytes and Neurons in Primary Culture

Ranolazine (Rn) is an antianginal agent used for the treatment of chronic angina pectoris when angina is not adequately controlled by other drugs. Rn also acts in the central nervous system and it has been proposed for the treatment of pain and epileptic disorders. Under the hypothesis that ranolazine could act as a neuroprotective drug, we studied its effects on astrocytes and neurons in primary culture. We incubated rat astrocytes and neurons in primary cultures for 24 hours with Rn (10-7, 10-6 and 10-5 M). Cell viability and proliferation were measured using trypan blue exclusion assay, MTT conversion assay and LDH release assay. Apoptosis was determined by Caspase 3 activity assay. The effects of Rn on pro-inflammatory mediators IL-β and TNF-α was determined by ELISA technique, and protein expression levels of Smac/Diablo, PPAR-γ, Mn-SOD and Cu/Zn-SOD by western blot technique. In cultured astrocytes, Rn significantly increased cell viability and proliferation at any concentration tested, and decreased LDH leakage, Smac/Diablo expression and Caspase 3 activity indicating less cell death. Rn also increased anti-inflammatory PPAR-γ protein expression and reduced pro-inflammatory proteins IL-1 β and TNFα levels. Furthermore, antioxidant proteins Cu/Zn-SOD and Mn-SOD significantly increased after Rn addition in cultured astrocytes. Conversely, Rn did not exert any effect on cultured neurons. In conclusion, Rn could act as a neuroprotective drug in the central nervous system by promoting astrocyte viability, preventing necrosis and apoptosis, inhibiting inflammatory phenomena and inducing anti-inflammatory and antioxidant agents.

No Effect of Remote Ischemic Conditioning Strategies on Recovery from Renal Ischemia-Reperfusion Injury and Protective Molecular Mediators

Ischemia-reperfusion injury (IRI) is the major cause of acute kidney injury. Remote ischemic conditioning (rIC) performed as brief intermittent sub-lethal ischemia and reperfusion episodes in a distant organ may protect the kidney against IRI. Here we investigated the renal effects of rIC applied either prior to (remote ischemic preconditioning; rIPC) or during (remote ischemic perconditioning; rIPerC) sustained ischemic kidney injury in rats. The effects were evaluated as differences in creatinine clearance (CrCl) rate, tissue tubular damage marker expression, and potential kidney recovery mediators. One week after undergoing right-sided nephrectomy, rats were randomly divided into four groups: sham (n = 7), ischemia and reperfusion (IR; n = 10), IR+rIPC (n = 10), and IR+rIPerC (n = 10). The rIC was performed as four repeated episodes of 5-minute clamping of the infrarenal aorta followed by 5-minute release either before or during 37 minutes of left renal artery clamping representing the IRI. Urine and blood were sampled prior to ischemia as well as 3 and 7 days after reperfusion. The kidney was harvested for mRNA and protein isolation. Seven days after IRI, the CrCl change from baseline values was similar in the IR (δ: 0.74 mL/min/kg [-0.45 to 1.94]), IR+rIPC (δ: 0.21 mL/min/kg [-0.75 to 1.17], p > 0.9999), and IR+rIPerC (δ: 0.41 mL/min/kg [-0.43 to 1.25], p > 0.9999) groups. Kidney function recovery was associated with a significant up-regulation of phosphorylated protein kinase B (pAkt), extracellular regulated kinase 1/2 (pERK1/2), and heat shock proteins (HSPs) pHSP27, HSP32, and HSP70, but rIC was not associated with any significant differences in tubular damage, inflammatory, or fibrosis marker expression. In our study, rIC did not protect the kidney against IRI. However, on days 3-7 after IRI, all groups recovered renal function. This was associated with pAkt and pERK1/2 up-regulation and increased HSP expression at day 7.

Evaluation of potential topical and systemic neuroprotective agents for ocular hypertension-induced retinal ischemia-reperfusion injury

OBJECTIVE

To evaluate for drugs with superior neuroprotective efficacy and investigate their underlying mechanisms related to antioxidation.

PROCEDURES

Brinzolamide (1%), timolol (0.5%), minocycline (22 mg/kg), lidocaine (1.5 mg/kg), and methylprednisolone (30 mg/kg) were administered to Sprague-Dawley (SD) rats. The retina was evaluated by electroretinography and histological analysis. The antioxidative capacity of drugs was evaluated to clarify the underlying mechanism. The oxidant/antioxidant profiles of plasma, red blood cells, and retina were analyzed by lipid peroxidation (malondialdehyde) and by measuring the activities of antioxidants. Proteomic analysis was used to investigate the possible protective mechanisms of the drug against ischemia-reperfusion injury.

RESULTS

The results suggested that timolol, methylprednisolone, and minocycline protected retinal function. Methylprednisolone and minocycline possessed good antioxidative activity. Brinzolamide and lidocaine preserved the structural integrity of the retina, but not retinal function.

CONCLUSION

Methylprednisolone, minocycline, and timolol have potential acute or delayed benefit in retinal ischemia-reperfusion injury. Their neuroprotective actions depend at least partially on the ability to alleviate oxidative stress.

Effect of lidocaine on dynamic changes in cortical reduced nicotinamide adenine dinucleotide fluorescence during transient focal cerebral ischemia in rats

Rats were subjected to 90min of focal ischemia by occluding the left middle cerebral and both common carotid arteries. The dynamic changes in the formation of brain ischemic areas were analyzed by measuring the direct current (DC) potential and reduced nicotinamide adenine dinucleotide (NADH) fluorescence with ultraviolet irradiation. In the lidocaine group (n=10), 30min before ischemia, an intravenous bolus (1.5mg/kg) of lidocaine was administered, followed by a continuous infusion (2mg/kg/h) for 150min. In the control group (n=10), an equivalent amount of saline was administered. Following the initiation of ischemia, an area of high-intensity NADH fluorescence rapidly developed in the middle cerebral artery territory in both groups and the DC potential in this area showed ischemic depolarization. An increase in NADH fluorescence closely correlated with the DC depolarization. The blood flow in the marginal zone of both groups showed a similar decrease. Five minutes after the onset of ischemia, the area of high-intensity NADH fluorescence was significantly smaller in the lidocaine group (67% of the control; P=0.01). This was likely due to the suppression of ischemic depolarization by blockage of voltage-dependent sodium channels with lidocaine. Although lidocaine administration did not attenuate the number of peri-infarct depolarizations during ischemia, the high-intensity area and infarct volume were significantly smaller in the lidocaine group both at the end of ischemia (78% of the control; P=0.046) and 24h later (P=0.02). A logistic regression analysis demonstrated a relationship between the duration of ischemic depolarization and histologic damage and revealed that lidocaine administration did not attenuate neuronal damage when the duration of depolarization was identical. These findings indicate that the mechanism by which lidocaine decreases infarct volume is primarily through a reduction of the brain area undergoing NADH fluorescence increases which closely correlates with depolarization.

Delayed treatment with lidocaine reduces mouse microglial cell injury and cytokine production after stimulation with lipopolysaccharide and interferon γ

BACKGROUND

Neuroinflammation is an important pathological process for almost all acquired neurological diseases. Microglial cells play a critical role in neuroinflammation. We determined whether lidocaine, a local anesthetic with anti-inflammatory property, protected microglial cells and attenuated cytokine production from activated microglial cells.

METHODS

Mouse microglial cultures were incubated with or without 1 μg/mL lipopolysaccharide and 10 U/mL interferon γ (IFNγ) for 24 hours in the presence or absence of lidocaine for 1 hour started at 2, 3, or 4 hours after the onset of lipopolysaccharide and IFNγ stimulation. Lactate dehydrogenase release and cytokine production were determined after the cells were stimulated by lipopolysaccharide and IFNγ for 24 hours.

RESULTS

Lidocaine dose-dependently reduced lipopolysaccharide and IFNγ-induced microglial cell injury as measured by lactate dehydrogenase release. This effect was apparent with lidocaine at 2 μg/mL (30.3% ± 5.8% and 23.1% ± 9.7%, respectively, for stimulation alone and the stimulation in the presence of lidocaine, n = 18, P = 0.025). Lidocaine applied at 2, 3, or 4 hours after the onset of lipopolysaccharide and IFNγ stimulation reduced the cell injury. This lidocaine effect was not affected by the mitochondrial K(ATP) channel inhibitor 5-hydroxydecanoate. Similar to lidocaine, QX314, a permanently charged lidocaine analog that usually does not permeate through the plasma membrane, reduced lipopolysaccharide and IFNγ-induced microglial cell injury. QX314 also attenuated the stimulation-induced interleukin-1β production.

CONCLUSIONS

Delayed treatment with lidocaine protects microglial cells and reduces cytokine production from these cells. These effects may involve action site(s) on the cell surface.

Lidocaine attenuates cognitive impairment after isoflurane anesthesia in old rats

Post-operative cognitive dysfunction (POCD) is a clinical phenomenon that has drawn significant attention from the public and scientific community. Age is a risk factor for POCD. However, the contribution of general anesthesia/anesthetics to POCD and the underlying neuropathology are not clear. Here, we showed that 18-month-old male Fisher 344 rats exposed to 1.2% isoflurane, a general anesthetic, for 2h had significant learning and memory impairments assessed at 2-4 weeks after isoflurane exposure. These isoflurane effects were attenuated by intravenous lidocaine (1.5mg/kg as a bolus and then 2mg/kg/h during isoflurane exposure), a local anesthetic that has neuroprotective effect. Exposure to isoflurane or isoflurane plus lidocaine did not change the neuronal and synaptic density as well as the expression of NeuN (a neuronal protein), drebrin (a dendritic spine protein), synaptophysin (a synaptic protein), activated caspase 3 and caspase-activated DNase in the hippocampus at 29 days after isoflurane exposure when cognitive impairment was present. Isoflurane and lidocaine did not affect the amount of β-amyloid peptide, total tau and phospho-tau in the cerebral cortex as well as interleukin-1β and tumor necrosis factor-α in the hippocampus at 29 days after isoflurane exposure. Thus, isoflurane induces learning and memory impairment in old rats. Lidocaine attenuates these isoflurane effects. Isoflurane may not cause long-lasting neuropathological changes.

The neuroprotective effects of lidocaine and methylprednisolone in a rat model of retinal ischemia-reperfusion injury

Retinal ischemia is a common cause of visual impairment for humans and animals. The neuroprotective effects of lidocaine (LDC) and methylprednisolone (MP) upon retinal ischemic injury were investigated in a rat model. Sprague-Dawley rats were divided into 3 groups, the IR control, LDC and MP. A very high intraocular pressure (HIOP) and retinal ischemia were induced. In LDC group, LDC bolus (1.5 mg/kg) was i.v. injected 30 min before ischemia and then a constant rate infusion (CRI) with 2 mg/kg/hr was given until 60 min after reperfusion. In MP group, MP bolus (30 mg/kg) was i.v. administered twice at 2 min before and immediately after ischemia, respectively. The HIOP damage to retina was evaluated by electroretinogram (ERG) and morphometrical histology. The functional analysis of the retina by ERG revealed a 35.2% reduction of a-wave in the IR group, 49.7% reduction in the LDC group but no significant change in the MP group compared to normal controls. An 81.0% reduction of b-wave was observed in the IR group, 80.7% reduction in the LDC group and 17.6% reduction in the MP group. In the morphometrical histology, the retinal inner plexiform layer/outer nuclear layer (IPL/ONL) ratio was reduced to 48.8% in the IR group, 80.1% in the LDC group and 96.2% in MP group. In conclusion, the MP showed significantly good neuroprotective effects on retinal IR injury, and the LDC showed moderate neuroprotective effects demonstrated in retinal structure but not in retinal function.

Intravenous antiarrhythmic doses of lidocaine increase the survival rate of CA1 neurons and improve cognitive outcome after transient global cerebral ischemia in rats

Brain ischemia is often a consequence of cardiac or neurologic surgery. Prophylactic pharmacological neuroprotection would be beneficial for patients undergoing surgery to reduce brain damage due to ischemia. We examined the effects of two antiarrhythmic doses of lidocaine (2 or 4 mg/kg) on rats in a model of transient global cerebral ischemia. The occlusion of both common carotid arteries combined with hypotension for 10 min induced neuronal loss in the CA1 region of the hippocampus (18±12 vs. 31±4 neurons/200 μm linear distance of the cell body layer, X±SD; P<0.01). Lidocaine (4 mg/kg) 30 min before, during and 60 min after ischemia increased dorsal hippocampal CA1 neuronal survival 4 weeks after global cerebral ischemia (30±9 vs. 18±12 neurons/200 μm; P<0.01). There was no significant cell loss after 10 min of ischemia in the CA3 region, the dentate region or the amygdalae; these regions were less sensitive than the CA1 region to ischemic damage. Lidocaine not only increased hippocampal CA1 neuronal survival, but also preserved cognitive function associated with the CA1 region. Using an active place avoidance task, there were fewer entrances into an avoidance zone, defined by relevant distal room-bound cues, in the lidocaine groups. The untreated ischemic group had an average, over the nine sessions, of 21±12 (X±SD) entrances into the avoidance zone per session; the 4 mg/kg lidocaine group had 7±8 entrances (P<0.05 vs. untreated ischemic) and the non-ischemic control group 7±5 entrances (P<0.01 vs. untreated ischemic). Thus, a clinical antiarrhythmic dose of lidocaine increased the number of surviving CA1 pyramidal neurons and preserved cognitive function; this indicates that lidocaine is a good candidate for clinical brain protection.

Inhibition of acid sensing ion channel currents by lidocaine in cultured mouse cortical neurons

BACKGROUND

Lidocaine is a local anesthetic that has multiple pharmacological effects including antiarrhythmia, antinociception, and neuroprotection. Acid sensing ion channels (ASICs) are proton-gated cation channels that belong to the epithelial sodium channel/degenerin superfamily. Activation of ASICs by protons results in sodium and calcium influx. ASICs have been implicated in various physiological processes including learning/memory, nociception, and in acidosis-mediated neuron injury. In this study, we examined the effect of lidocaine on ASICs in cultured mouse cortical neurons.

METHODS

ASIC currents were activated and recorded using a whole-cell patch-clamp technique in cultured mouse cortical neurons. The effects of lidocaine at different concentrations were examined. To determine whether the inhibition of lidocaine on ASIC currents is subunit specific, we examined the effect of lidocaine on homomeric ASIC1a and ASIC2a currents expressed in Chinese hamster ovary cells.

RESULTS

Lidocaine significantly inhibits the ASIC currents in mouse cortical neurons. The inhibition was reversible and dose dependent. A detectable effect was noticed at a concentration of 0.3 mM lidocaine. At 30 mM, ASIC current was inhibited by approximately 90%. Analysis of the complete dose-response relationship yielded a half-maximal inhibitory concentration of 11.79 ± 1.74 mM and a Hill coefficient of 2.7 ± 0.5 (n = 10). The effect is rapid and does not depend on pH. In Chinese hamster ovary cells expressing different ASIC subunits, lidocaine inhibits the ASIC1a current without affecting the ASIC2a current.

CONCLUSION

ASIC currents are significantly inhibited by lidocaine. Our finding reveals a new pharmacological effect of lidocaine in neurons.

N-ethyl lidocaine (QX-314) protects striatal neurons against ischemia: an in vitro electrophysiological study

In this study, we have investigated the neuroprotective actions of the membrane impermeable, lidocaine analog, N-ethyl lidocaine (QX-314) in the striatum. The effects of this drug were compared with those caused by the strictly-related-compound and sodium channel blocker lidocaine. To address this issue, electrophysiological recordings were performed in striatal slices, in control condition (normoxia) and during combined oxygen and glucose deprivation (in vitro ischemia). Either QX-314 or lidocaine induced, to some extent, a protection of the permanent electrophysiological alteration (field potential loss) caused by a period (12 min) of ischemia. Thus, both compounds permitted a partial recovery of the ischemic depression of the corticostriatal transmission and reduced the amplitude of the ischemic depolarization in medium spiny neurons. However, while QX-314, at the effective concentration of 100 microM, slightly reduced the amplitude of the excitatory field potential and did not affect the current-evoked spikes discharge of medium spiny striatal neurons, equimolar lidocaine depressed the field potential and eliminated repetitive spikes on a depolarizing step. On the basis of these observations, our results suggest the use of QX-314 as a neuroprotective agent in ischemic brain disorders.

The combined neuroprotective effects of lidocaine and dexmedetomidine after transient forebrain ischemia in rats

BACKGROUND

We investigated whether coadministration of lidocaine and dexmedetomidine would reduce brain injury following transient forebrain ischemia in rats to a greater extent than either drug alone.

METHODS

Adult male Sprague-Dawley rats were anesthetized with halothane to maintain normocapnia and normoxia. Rats received subcutaneous injection of saline 1 ml/kg, lidocaine 10 mg/kg, dexmedetomidine 3 microg/kg, or lidocaine 10 mg/kg plus dexmedetomidine 3 microg/kg. Thirty minutes after the drug injection, forebrain ischemia was induced by hemorrhagic hypotension and occlusion of the bilateral carotid arteries, and was confirmed by isoelectric EEG. At the end of 10-min ischemia, rats were reperfused. The same dose of drugs was administered 3, 24, and 48 h after ischemia. Neurological examination was done at 1, 2, and 7 days after ischemia. Seven days after ischemia, the brain was stained with hematoxylin and eosin. We counted ischemic cells in the CA1 hippocampal region, striatum, and cerebral cortex. We also measured extracellular glutamate and norepinephrine concentration in hippocampal CA1 in the four groups.

RESULTS

As compared with saline-treated rats, rats receiving dexmedetomidine plus lidocaine showed less than neurological deficit scores at 2 and 7 days after ischemia, and had less ischemic cells in the CA1 region. However, administration of dexmedetomidine plus lidocaine did not alter the area under the glutamate concentration curve and norepinephrine concentration during ischemia in the CA1 region, compared with saline-treated rats.

CONCLUSIONS

Our results suggest coadministration of lidocaine and dexmedetomidine improves the neurological outcome without alteration of glutamate and norepinephrine concentrations during forebrain ischemia in rats.

Effects of desflurane and propofol on electrophysiological parameters during and recovery after hypoxia in rat hippocampal slice CA1 pyramidal cells

Cerebral ischemia is a major cause of death and disability and may be a complication of neurosurgery. Certain anesthetics may improve recovery after ischemia and hypoxia by altering electrophysiological changes during the insult. Intracellular recordings were made from CA1 pyramidal cells in hippocampal slices from adult rats. Desflurane or propofol was applied 10 min before and during 10 min of hypoxia (95% nitrogen, 5% carbon dioxide). None of the untreated CA1 pyramidal neurons, 46% of the 6% desflurane- and 38% of the 12% desflurane-treated neurons recovered their resting and action potentials 1 h after hypoxia (P<0.05). Desflurane (6% or 12%) enhanced the hypoxic hyperpolarization (4.9 or 4.7 vs. 2.6 mV), increased the time until the rapid depolarization (441 or 390 vs. 217 s) and reduced the level of depolarization at 10 min of hypoxia (-13.5 or -13.0 vs. -0.6 mV); these changes may be part of the mechanism of its protective effect. Either chelerythrine (5 microM), a protein kinase C inhibitor, or glybenclamide (5 microM), a K(ATP) channel blocker, prevented the protective effect and the electrophysiological changes with 6% desflurane. Propofol (33 or 120 microM) did not improve recovery (0 or 0% vs. 0%) 1 h after 10 min of hypoxia; it did not significantly enhance the hypoxic hyperpolarization (3.6 or 3.1 vs. 2.6 mV) or increase the latency of the rapid depolarization (282 or 257 vs. 217 s). The average depolarization at 10 m of hypoxia with 33 microM propofol (-4.1 mV) was slightly but significantly different from that in untreated hypoxic tissue (-0.6 mV). Desflurane but not propofol improved recovery of the resting and action potentials in hippocampal slices after hypoxia, this improvement correlated with enhanced hyperpolarization and attenuated depolarization of the membrane potential during hypoxia. Our results demonstrate differential effects of anesthetics on electrophysiological changes during hypoxia.

Evaluation of the neuroprotective effect of ketoprofen on rats submitted to permanent focal brain ischemia

OBJECTIVE: To study the neurobehavioral, biochemical and histopathological consequences of permanent focal brain ischemia, and the putative neuroprotective action of ketoprofen. METHOD: One-hundred-and-three Wistar rats divided into groups A and B were respectively submitted to 48 hours and 15 days of ischemia. Each group was divided into 4 subgroups: ischemic not treated, ischemic treated, sham not treated, and sham treated. Ischemic animals had the left middle cerebral artery coagulated. Ketoprofen was administered to treated subgroups 15 minutes before arterial coagulation (manipulation in the sham group). RESULTS: Exploratory activity and defecation were reduced in all ischemic animals in the first postoperative days and constant histopathological changes were observed in each group. The total brain glutamate levels were higher in treated animals 48 hours after surgery. CONCLUSION: No clear parallelism among behavioral, biochemical and histopathological findings was observed. Ketoprofen demonstrated no neuroprotective effect on the behavioral or histopathological aspects of focal permanent brain ischemia.

Hippocampus and amygdala neurotoxicity produced by systemic lidocaine in adult rats

There is evidence that using lidocaine-treated cellular culture produces cell damage. However, there are no studies in vivo demonstrating the potential injurious effect of lidocaine on the central nervous system. Therefore, the aim of our study was to investigate if lidocaine is involved in neuronal damage in the CA3 hippocampus and amygdala regions when using a single subconvulsive or a convulsive lidocaine dose. Two-month-old male Wistar rats (57) were used. The animals were randomly assigned to one of three groups. Group I received 0.9% saline ip (n=9), group II received a single lidocaine dose of 60 mg/kg (n=18), and group III received 90 mg/kg ip (n=12). At day 2, 7, and 10 after the dosing, three to six rats per group were sacrificed. The brains of the rats were removed and were embedded in paraffin. Coronal cuts of 7 microm were made. Each brain section was stained with cresyl-eosin. We evaluated the number of normal and abnormal neurons in the hippocampal CA3 (pyramidal) and basolateral amygdala (large and medium neurons) regions in a 10,000 microm2 section. To explore an association between lidocaine-induced seizure and neuronal damage, diazepam was used (10 mg/kg ig) as an anticonvulsant two hours before a 90 mg/kg dose of lidocaine. Lidocaine causes a morphological neuronal alteration in the CA3 hippocampal region and the basolateral amygdala and possibly an inhibition-excitation imbalance. Diazepam prevents lidocaine-induced seizures, but not neuronal damage in brain structures. Interaction of lidocaine with the membrane components produces disrupted Ca+2 homeostasis and causes neuronal damage. Moreover, it is possible that lidocaine or its metabolites could actively participate in the neuronal damage observed.

Novel local anaesthetics and novel indications for local anaesthetics

Research into local anaesthetic mechanisms over the past few years has focused on two main issues. First, attention has focused on development of compounds with fewer side effects, better sensory/motor separation and longer duration of action; this has resulted in the introduction of ropivacaine and levobupivacaine into clinical practice. These agents have a lesser cardiotoxic effect than older compounds, and ropivacaine may in addition offer better sensory/motor separation. Several other compounds, including tonicaine and sameridine, are under investigation. In addition, the local anaesthetic properties of amitryptiline are being studied, and liposome encapsulation of local anaesthetics appears able to confer new pharmacokinetic properties on common drugs. Second, the molecular basis for several local anaesthetic actions that are not mediated by sodium channels has become a topic of interest. The mechanisms that underlie anti-inflammatory and antithrombotic actions are at present being unravelled. How local anaesthetics potentiate antitumour agents, protect neuronal tissue and prevent bronchial reactivity is less clear, but the potential clinical benefits of these effects deserve further exploration.

Sevoflurane immediate preconditioning alters hypoxic membrane potential changes in rat hippocampal slices and improves recovery of CA1 pyramidal cells after hypoxia and global cerebral ischemia

Pretreatment with anesthetics before but not during hypoxia or ischemia can improve neuronal recovery after the insult. Sevoflurane, a volatile anesthetic agent, improved neuronal recovery subsequent to 10 min of global cerebral ischemia when it was present for 1 h before the ischemia. The mean number of intact hippocampal cornus ammonis 1 (CA1) pyramidal neurons in rats subjected to cerebral ischemia without any pretreatment was 17+/-5 (neurons/mm+/-S.D.) 6 weeks after the ischemia; naïve, non-ischemic rats had 177+/-5 neurons/mm. Rats pretreated with either 2% or 4% sevoflurane had 112+/-57 or 150+/-15 CA1 pyramidal neurons/mm respectively (P<0.01) 6 weeks after global cerebral ischemia. In order to examine the mechanisms of protection we used hypoxia to generate energy deprivation. Intracellular recordings were made from CA1 pyramidal neurons in rat hippocampal slices; the recovery of resting and action potentials after hypoxia was used as an indicator of neuronal survival. Pretreatment with 4% sevoflurane for 15 min improved neuronal recovery 1 h after the hypoxia; 90% of the sevoflurane-pretreated neurons recovered while none (0%) of the untreated neurons recovered. Pretreatment with sevoflurane enhanced the hypoxic hyperpolarization(-6.4+/-0.6 vs. -3.3+/-0.3 mV) and reduced the final level of the hypoxic depolarization (-39+/-6 vs. -0.3+/-2 mV) during hypoxia. Chelerythrine (5 muM), a protein kinase C/protein kinase M inhibitor, blocked both the improved recovery (10%) and the electrophysiological changes with 4% sevoflurane preconditioning. Two percent sevoflurane for 15 min before hypoxia did not improve recovery (0% recovery both groups) and did not enhance the hypoxic hyperpolarization or reduce the final depolarization during hypoxia. However if 2% sevoflurane was present for 1 h before the hypoxia then there was significantly improved recovery, enhanced hypoxic hyperpolarization, and reduced final depolarization. Thus we conclude that sevoflurane preconditioning improves recovery in both in vivo and in vitro models of energy deprivation and that preconditioning enhances the hypoxic hyperpolarization and reduces the hypoxic depolarization. Anesthetic preconditioning may protect neurons from ischemia by altering the electrophysiological changes a neuron undergoes during energy deprivation.

Anesthesia for Endovascular Neurosurgery

Endovascular neurosurgical procedures are complex, requiring significant planning, foresight, and coordination. The neuroanesthetist is an integral part of these procedures, organizing efforts of the technicians and nurses and responding to the needs of the neurointerventionalist. The purpose of this article is to review, in detail, the role of the neuroanesthetist in the endovascular operating room. An overview of all areas either partially or completely managed by the anesthetist is provided.

The differential effects of volatile anesthetics on electrophysiological and biochemical changes during and recovery after hypoxia in rat hippocampal slice CA1 pyramidal cells

Two volatile agents, isoflurane and sevoflurane have similar anesthetic properties but different potencies; this allows the discrimination between anesthetic potency and other properties on the protective mechanisms of volatile anesthesia. Two times the minimal alveolar concentration of an anesthetic is approximately the maximally used clinical concentration of that agent; this concentration is 2% for isoflurane and 4% for sevoflurane. We measured the effects of isoflurane and sevoflurane on cornus ammonis 1 (CA1) pyramidal cells in rat hippocampal slices subjected to 10 min of hypoxia (95% nitrogen 5% carbon dioxide) and 60 min of recovery. Anesthetic was delivered to the gas phase using a calibrated vaporizer for each agent. At equipotent anesthetic concentrations, sevoflurane (4%) but not isoflurane (2%), enhanced the initial hyperpolarization (6.7 vs. 3.4 mV), delayed the hypoxic rapid depolarization (521 vs. 294 s) and reduced peak hypoxic cytosolic calcium concentration (203 vs. 278 nM). While both agents reduced the final membrane potential at 10 min of hypoxia compared with controls, 4% sevoflurane had a significantly greater effect than 2% isoflurane (-24.4 vs. -3.5 mV). The effect of these concentrations of isoflurane and sevoflurane was not different for sodium, potassium or ATP concentrations at 10 min of hypoxia, the only difference at 5 min of hypoxia was that ATP was better maintained with 4% sevoflurane (2.2 vs. 1.3 nmol/mg). If the same absolute concentration (4%) of isoflurane and sevoflurane is compared then the cellular changes during hypoxia are similar for both agents and they both improve recovery. We conclude that an anesthetic's absolute concentration and not its anesthetic potency correlates with improved recovery of CA1 pyramidal neurons. The mechanisms of sevoflurane-induced protection include delaying and attenuating the depolarization and the increase of cytosolic calcium and delaying the fall in ATP during hypoxia.

Desflurane improves the recovery of the evoked postsynaptic population spike from CA1 pyramidal cells after hypoxia in rat hippocampal slices

Desflurane is a volatile anesthetic that allows rapid induction and emergence, reduces cerebral metabolism, and enhances tissue perfusion. We studied the effect of treatment with 4%, 6%, and 12% desflurane on hypoxic neuronal damage by comparing the size of the postsynaptic evoked population spike recorded from the cornu ammonis 1 (CA1) pyramidal cell layer of rat hippocampal slices before and 2 hours after a hypoxic insult. When the tissue was treated with 6% desflurane before, during, and after 3.5 minutes of hypoxia, recovery was significantly better in slices exposed to desflurane (37% +/- 9%) compared with untreated hypoxic slices (15% +/- 5%). A lower (4%) or higher (12%) concentration of desflurane did not significantly improve recovery after 3.5 minutes of hypoxia. In the period before hypoxia, 12% and 6% desflurane significantly increased the latency and decreased the amplitude of the postsynaptic population spike; 4% desflurane had a similar but nonsignificant effect on latency and amplitude. We conclude that 6% desflurane, a clinically useful concentration (1 minimal alveolar concentration), improved the recovery of postsynaptic evoked responses in rat hippocampal slices after 3.5 minutes of hypoxia. In vivo studies must be conducted to assess the potential clinical significance of 6% desflurane's neuroprotective activity.

The role of ECA transection in the development of masticatory lesions in the MCAO filament model

In the intraluminal suture model of middle cerebral artery occlusion (MCAO) in the rat, lesions of the masticator muscles associated with impaired functional outcome occur. We evaluated the role of external carotid artery (ECA) transection. We assessed whether isolated interruption of an arterial or a venous connection to the ECA territory was sufficient to induce masticatory hypoperfusion and lesions. We also evaluated a direct access to the common carotid artery (CCA) with subsequent vascular closure with regard to its feasibility, frequency of masticatory lesions, complications, and cerebral ischemia. Cerebral and masticatory lesions and perfusion deficits were assessed by in vivo magnetic resonance imaging (MRI). Vessel patency was evaluated using computerized tomography angiography and histology. An interruption of arterial blood flow led to masticatory hypoperfusion. Masticatory lesions occurred in 6% of the rats. Access to and closure of the CCA were feasible in all animals, leading to moderate or severe vessel stenosis in 20%, and intraarterial thrombosis in 25% of the rats. Reproducible cerebral infarctions were obtained in all animals. In 24% of the rats, hyperintense MRI signal changes were observed in the ipsilateral temporal muscle. Thus, the induction of masticatory hypoperfusion and lesions by arterial transection supports the role of the ECA in this context. Direct access to the CCA with subsequent vessel closure led to stenosis in most animals. Preservation of ECA continuity was not suitable to fully prevent masticatory lesions.

Pre- or Postinsult Administration of Lidocaine or Thiopental Attenuates Cell Death in Rat Hippocampal Slice Cultures Caused by Oxygen-Glucose Deprivation

Lidocaine and thiopental improve recovery when administrated during hypoxia and ischemia; however, the effect of pre- or postinsult treatment alone is unknown. We applied either lidocaine or thiopental to hippocampal slice cultures from 20-day-old rats either before or after 10 min of oxygen-glucose deprivation (OGD). Propidium iodide (PI) fluorescence was used as an indicator of neuronal death for 7 days after OGD. OGD-induced neuronal death, in both the Cornus Ammonis 1 (CA1) and the dentate gyrus regions, peaked the first day after ischemia. Preinsult administration of either lidocaine (10, 100 microM) or thiopental (250, 600 microM) significantly reduced the damage measured on the first and second days after OGD; these drugs also significantly decreased the summed daily post-OGD PI fluorescence in both regions. Postinsult administration of lidocaine (10, 100 microM) or thiopental (250, 600 microM) significantly decreased the PI fluorescence on the first day after OGD; postinsult administration of these drugs also attenuated the summed daily post-OGD PI. These data indicate that the administration of lidocaine or thiopental either before or directly after OGD reduced neuronal damage in this in vitro model of cerebral ischemia. Postischemic administration is frequently the first opportunity for treatment.

IMPLICATIONS

Lidocaine or thiopental applied either 10 min before or 10 min directly after oxygen-glucose deprivation reduced neuronal cell death in rat hippocampal slice cultures. Postinsult administration is often the first opportunity for treatment after stroke; lidocaine and thiopental reduced damage caused by oxygen-glucose deprivation, an in vitro model of stroke.

Clinical Pharmacology of Local Anesthetics

Whereas currently available local anesthetics may be suitable for intraoperative and in-hospital postoperative use, long-acting analgesia after outpatient procedures will require new techniques and drugs. Catheter delivery systems are rapidly gaining clinical acceptance and allow for great flexibility in dosing. Encapsulated local anesthetics can provide the slow release of drugs. Novel, long-acting local anesthetics are being investigated but are not yet ready for clinical use. In addition to the effects on the sodium channel, other actions of these novel compounds need to be explored, because both beneficial and detrimental effects may be induced with these compounds.

["Alternative" effects of local anesthetic agents]

The following article summarizes different aspects of local anesthetic effects that cannot be explained purely by a sodium channel blockade. Particularly remarkable is hereby their antiinflammatory activity, e.g. the inhibition of pathological changes such as excessive stimulation of the inflammatory system, without compromising the host defense system. In contrast to other immunosuppressive drugs commonly used for treating such conditions, local anesthetics look promising for the future as a new therapeutic option. Besides general anesthetic activity, local anesthetics exert cerebroprotective effects and are furthermore, in consideration of their cardiovascular stability, of interest during neuroanesthetic procedures. In addition, local anesthetics are known for their potency to minimize bronchial hyperreactivity, although details of the underlying mechanisms are not yet elucidated. These effects of local anesthetics may represent interesting prospects for which their relevance has to be determined.

Lidocaine attenuates apoptosis in the ischemic penumbra and reduces infarct size after transient focal cerebral ischemia in rats

Lidocaine is a local anesthetic and antiarrhythmic agent. Although clinical and experimental studies have shown that an antiarrhythmic dose of lidocaine can protect the brain from ischemic damage, the underlying mechanisms are unknown. In the present study, we examined whether lidocaine inhibits neuronal apoptosis in the penumbra in a rat model of transient focal cerebral ischemia. Male Wistar rats underwent a 90-min temporary occlusion of middle cerebral artery. Lidocaine was given as an i.v. bolus (1.5 mg/kg) followed by an i.v. infusion (2 mg/kg/h) for 180 min, starting 30 min before ischemia. Rats were killed and brain samples were collected at 4 and 24 h after ischemia. Apoptotic changes were evaluated by immunohistochemistry for cytochrome c release and caspase-3 activation and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) for DNA fragmentation. Cytochrome c release and caspase-3 activation were detected at 4 and 24 h after ischemia and DNA fragmentation was detected at 24 h. Double-labeling with NeuN, a neuronal marker, demonstrated that cytochrome c, caspase-3, and TUNEL were confined to neurons. Lidocaine reduced cytochrome c release and caspase-3 activation in the penumbra at 4 h and diminished DNA fragmentation in the penumbra at 24 h. Lidocaine treatment improved early electrophysiological recovery and reduced the size of the cortical infarct at 24 h, but had no significant effect on cerebral blood flow in either the penumbra or core during ischemia. These findings suggest that lidocaine attenuates apoptosis in the penumbra after transient focal cerebral ischemia. The infarct-reducing effects of lidocaine may be due, in part, to the inhibition of apoptotic cell death in the penumbra.

The poor man's epidural: systemic local anesthetics for improving postoperative outcomes

The inflammatory response is an important determinant of outcome after major surgery. Perioperative excessive stimulation of the inflammatory and hemostatic systems plays a role in the development of postoperative ileus, ischemia-reperfusion syndromes (e.g. myocardial infarction), hypercoagulation syndromes (e.g. deep venous thrombosis) and pain; together, these represent a significant fraction of major postoperative disorders. Epidurally administered local anesthetics prevent or modulate many of these processes. Since local anesthetics show inflammatory modulating properties in vitro and in vivo, they might also prevent these postoperative inflammatory processes when administered intravenously. Clinical studies have shown that perioperative local anesthetic administration significantly reduces the incidence of thrombosis and postoperative pain, shortens postoperative ileus and decreases hospital stay. On this basis we hypothesize that continuous intravenous administration of local anesthetic perioperatively might prevent or reduce several postoperative disorders resulting from excessive stimulation of inflammatory and hemostatic systems, and thereby improve surgical outcome.

Kappa-Opioid Receptor Selectivity for Ischemic Neuroprotection with BRL 52537 in Rats

Kappa-opioid receptors (KOR) have been implicated in neuroprotection from ischemic neuronal injury, but less work has been performed with transient focal cerebral ischemia to determine the role of KOR during reperfusion. We tested the effects of a selective and specific KOR agonist, BRL 52537 hydrochloride [(+/-)-1-(3,4-dichlorophenyl)acetyl-2-(1-pyrrolidinyl)methylpiperidine], and the standard KOR antagonist, nor-binaltorphimine dihydrochloride [nor-BNI; 17,17'-(dicyclopropylmethyl)-6,6',7,7'-6,6'-imino-7,7'-binorphinan-3,4',14,14'-tetrol], on functional and histological outcome after transient focal ischemia in the rat. By use of the intraluminal filament technique, halothane-anesthetized adult male Wistar rats were subjected to 2 h of middle cerebral artery occlusion confirmed by laser Doppler flowmetry. In a blinded, randomized fashion, rats were treated with 1). saline (vehicle) 15 min before reperfusion followed by saline at reperfusion for 22 h, 2). saline 15 min before reperfusion followed by BRL 52537 (1 mg x kg(-1) x h(-1)) at reperfusion for 22 h, 3). saline 15 min before reperfusion followed by nor-BNI (1 mg x kg(-1) x h(-1)) at reperfusion for 22 h, or 4) nor-BNI (1 mg/kg) 15 min before reperfusion followed by BRL 52537 (1 mgx kg(-1)x h(-1)) and nor-BNI (1 mg x kg(-1) x h(-1)) at reperfusion for 22 h. Infarct volume (percentage of ipsilateral structure) analyzed at 4 days of reperfusion was significantly attenuated in saline/BRL 52537 rats (n = 8; cortex, 10.2% +/- 4.3%; caudoputamen [CP], 23.8% +/- 6.7%) (mean +/- SEM) compared with saline/saline treatment (n = 8; cortex, 28.6% +/- 4.9%; CP, 53.3% +/- 5.8%). Addition of the specific KOR antagonist nor-BNI to BRL 52537 completely prevented the neuroprotection (n = 7; cortex, 28.6% +/- 5.3%; CP, 40.9% +/- 6.2%) conferred by BRL 52537. BRL 52537 did not produce postischemic hypothermia. These data demonstrate that KORs may provide a therapeutic target during early reperfusion after ischemic stroke.

IMPLICATIONS

The neuroprotective effect of selective kappa-opioid agonists in transient focal ischemia is via a selective action at the kappa-opioid receptors.

Safety of magnesium-lidocaine combination for severe head injury: the Turin lidomag pilot study

BACKGROUND

Neuroprotection in the setting of severe head injury (SHI) remains an unsettled problem. We tested a combination of high-dose magnesium and low-dose lidocaine, infused over 3 days, in a pilot study to assess safety. This combination appears indicated to protect both gray and white matter from secondary injury following SHI.

METHODS

We studied 32 consecutive patients admitted to the emergency department of our hospital, a large tertiary referral center.

RESULTS

No toxicity was observed. Mortality was lower than published statistics.

CONCLUSIONS

These results open the stage to a controlled randomized study.

The effect of lidocaine on early postoperative cognitive dysfunction after coronary artery bypass surgery

We investigated the effect of lidocaine on the incidence of cognitive dysfunction in the early postoperative period after cardiac surgery. One-hundred-eighteen patients undergoing elective coronary artery bypass surgery with cardiopulmonary bypass (CPB) were randomized to receive either lidocaine (1.5 mg/kg bolus followed by a 4 mg/min infusion during operation and 4 mg/kg in the priming solution of CPB) or placebo. A battery of nine neuropsychological tests was administered before and 9 days after surgery. A postoperative deficit in any test was defined as a decline by more than or equal to the preoperative SD of that test in all patients. Any patient showing a deficit in two or more tests was defined as having postoperative cognitive dysfunction. Eighty-eight patients completed pre- and postoperative neuropsychological tests. Plasma lidocaine concentrations (microg/mL) were 4.78 +/- 0.52 (mean +/- SD), 5.38 +/- 0.95, 4.52 +/- 0.39, 5.82 +/- 0.76, and 7.10 +/- 1.09 at 10 min before CPB; 10, 30, and 60 min of CPB; and at the end of operation, respectively. The proportion of patients showing postoperative cognitive dysfunction was significantly reduced in the lidocaine group compared with that in the placebo group (18.6% versus 40.0%; P = 0.028). We conclude that intraoperative administration of lidocaine decreased the occurrence of cognitive dysfunction in the early postoperative period.

IMPLICATIONS

Postoperative cognitive dysfunction is a commonly recognized complication after cardiac surgery. Intraoperative cerebral microembolism and hypoperfusion have been proposed to be the major mechanisms. The results of this study show that intraoperative administration of lidocaine decreased the occurrence of early postoperative cognitive dysfunction, perhaps because of its neuroprotective effects.