Cardiac Arrest and Seizures Caused by Local Anesthetic Systemic Toxicity After Peripheral Nerve Blocks: Should We Still Fear the Reaper?

Cardiac Arrest From Local Anesthetic Systemic Toxicity (LAST): A Rare Complication of Ultrasound-Guided Sternal Hematoma Block

Local anesthetic systemic toxicity (LAST) is a rare but serious complication of ultrasound-guided nerve and hematoma blocks, affecting the cardiovascular and central nervous systems. Clinicians performing these procedures should be aware of the possibility of LAST, recognize the early signs and symptoms, and understand the current accepted treatment. We present a case of cardiovascular collapse caused by LAST following an ultrasound-guided sternal hematoma block and discuss potential systems-based improvements to enhance the management and prevention of this life-threatening emergency. Thoracic blocks may pose a higher risk of LAST because of the close proximity to the heart, and we recommend using lower doses of local anesthetic when performing these blocks.

Intravenous Lidocaine for Gut Function Recovery in Colonic Surgery: A Randomized Clinical Trial

Importance

Despite the recovery advantages of minimally invasive surgical techniques, delayed return of gut function after colectomy is a common barrier to timely discharge from hospital.

Objective

To evaluate the effect of 2% perioperative intravenous lidocaine infusion on return of gut function after elective minimally invasive colon resection.

Design, Setting, and Participants

The ALLEGRO trial was a randomized, placebo-controlled, double-blind trial conducted in 27 UK hospitals. A total of 590 adults scheduled for elective minimally invasive colon resection for benign or malignant disease were randomized 1:1 to 2% intravenous lidocaine or saline placebo. Enrollment occurred from August 13, 2018, to April 11, 2023, with a pause in recruitment from March 20, 2020, through July 6, 2020; final follow-up was on August 10, 2023.

Interventions

The intervention patients received 2% intravenous lidocaine administered as 1.5-mg/kg bolus at induction of anesthesia followed by 1.5 mg/kg/h for 6 or 12 hours. Control patients received 0.9% saline placebo for 6 or 12 hours.

Main Outcomes and Measures

The primary outcome was the proportion of patients with return of gut function at 72 hours after surgery, defined by the GI-3 composite end point of tolerating diet (ingestion of food and drink without significant nausea or vomiting for 3 consecutive meals) and passage of flatus or stool. There were 11 secondary outcomes, including time to GI-3 recovery, time to GI-2 recovery (tolerance of oral diet and passage of stool), prolonged postoperative ileus, postoperative nausea and vomiting score, Overall Benefit of Analgesia Score, postoperative opioid consumption, Quality of Recovery-15, quality of life (EuroQol 5-Dimension 5-Level), enhanced recovery protocol adherence, time to meeting medically defined criteria for discharge, and time to patient self-assessed readiness for discharge.

Results

The trial enrolled 590 patients (295 intervention, 295 control); after 33 postrandomization exclusions, 557 patients were included (279 intervention, 278 control; 249 female patients [44.7%]; mean [SD] age, 66 [10.9] years); 532 (96%) received the randomized treatment. Return of gut function as defined by the GI-3 composite outcome was achieved at 72 hours by 160 patients (57.3%) in the intravenous lidocaine group vs 164 patients (59.0%) in the placebo group (adjusted absolute difference, -1.9% [95% CI, -8.0% to 4.2%]; relative risk, 0.97 [95% CI, 0.88 to 1.07]). There was no significant difference between the intervention and control groups in any of the 11 secondary end points.

Conclusions and Relevance

Among patients undergoing elective minimally invasive colon resection, perioperative administration of 2% intravenous lidocaine did not improve return of gut function at 72 hours.

Trial Registration

isrctn.org Identifier: ISRCTN52352431.

Impact of a Mobile App (LoAD Calc) on the Calculation of Maximum Safe Doses of Local Anesthetics: Protocol for a Randomized Controlled Trial

BACKGROUND

Local anesthetics (LAs) are regularly used to alleviate pain during medical or surgical procedures. Their use is generally considered safe, but exceeding the maximum recommended doses can lead to LA systemic toxicity, a rare but potentially lethal complication. Determining maximum safe doses is therefore mandatory before performing local anesthesia, but rules are often unclear and the factors affecting dose calculation are numerous. Mobile health apps have been shown to help clinical decision-making, but most currently available apps present significant limitations. The Local Anesthetics Dose Calculator (LoAD Calc) app was designed to overcome these limitations by taking all relevant parameters into account. Before deploying this app in a clinical setting, it should be tested to determine its effectiveness and whether clinicians would be willing to use it.

OBJECTIVE

The primary objective will be to evaluate the effectiveness of the LoAD Calc app through written simulated cases. The secondary objective will be to determine whether physicians find this app easier, faster, and safer than the methods they generally use.

METHODS

We describe a parallel-group randomized controlled trial protocol. Anesthesiologists working at the Geneva University Hospitals will be invited to participate. Participants will be asked to compute the maximum dose of LA in 10 simulated clinical cases using 3 different LAs. The maximum safe dose will be determined manually using the same calculation rules that were used to develop LoAD Calc, without using the app itself. An overdose will be considered any dose higher than the correct dose, rounded to the superior integer, while an underdose will be defined as the optimal calculated dose minus 20%, rounded to the inferior integer. Randomization will be stratified according to current position (resident vs registrar). The participants allocated to the LoAD Calc (experimental) group will use the LoAD Calc app to compute the maximum safe LA doses. Those allocated to the control group will be asked to use the method they generally use. The primary outcome will be the overall overdose rate. Secondary outcomes will include the overdose rate according to ideal and actual body weight and to each specific LA, the overall underdose rate, and the time taken to complete these calculations. The app's usability will also be assessed.

RESULTS

A sample size of 46 participants will be needed to detect a difference of 10% with a power of 90%. Thus, a target of 50 participants was set to allow for attrition and exclusion criteria. We expect recruitment to begin during the winter of 2023, data analysis in the spring of 2024, and results by the end of 2024.

CONCLUSIONS

This study should determine whether LoAD Calc, a mobile health app designed to compute maximum safe LA doses, is safer and more efficient than traditional LA calculation methods.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

PRR1-10.2196/53679.

Local Anesthetic Systemic Toxicity During Transversus Abdominis Plane Block With Liposomal Bupivacaine

Local anesthetic systemic toxicity (LAST) is a rare but potentially fatal outcome associated with local anesthetic administration. Liposomal bupivacaine (LB; EXPAREL®) is a widely used local anesthetic with extended-release and liposomal formulation that carries an improved cardiac and central nervous system safety profile. However, there is limited data regarding LAST associated with liposomal bupivacaine. Here is described a case of local anesthetic systemic toxicity in a 68-year-old male who presented with obstructing sigmoid adenocarcinoma and underwent open sigmoidectomy with end descending colostomy. The operation was complicated by LAST following transversus abdominis plane block injection with liposomal bupivacaine resulting in cardiac arrest. Return of spontaneous circulation was achieved following advanced cardiac life support and infusion of 20% I.V. fat emulsion. Given the widespread use of local anesthetics, providers must be aware of the pathophysiology, diagnosis, and immediate treatment of LAST.

Local anesthetic systemic toxicity: A narrative review for emergency clinicians

INTRODUCTION

Emergency clinicians utilize local anesthetics for a variety of procedures in the emergency department (ED) setting. Local anesthetic systemic toxicity (LAST) is a potentially deadly complication.

OBJECTIVE

This narrative review provides emergency clinicians with the most current evidence regarding the pathophysiology, evaluation, and management of patients with LAST.

DISCUSSION

LAST is an uncommon but potentially life-threatening complication of local anesthetic use that may be encountered in the ED. Patients at extremes of age or with organ dysfunction are at higher risk. Inadvertent intra-arterial or intravenous injection, as well as repeated doses and higher doses of local anesthetics are associated with greater risk of developing LAST. Neurologic and cardiovascular manifestations can occur. Early recognition and intervention, including supportive care and intravenous lipid emulsion 20%, are the mainstays of treatment. Using ultrasound guidance, aspirating prior to injection, and utilizing the minimal local anesthetic dose needed are techniques that can reduce the risk of LAST.

CONCLUSIONS

This focused review provides an update for the emergency clinician to manage patients with LAST.

Ultrasound-guided peripheral trunk block technique: A new approach gradually stepping onto the stage of clinical anesthesia

In recent years, with the continuous development and validation of new visualization, the ultrasound-guided peripheral trunk block becomes more mature and has a more extensive and broader implementation scope in clinical anesthesia. Based on this, we reviewed and summarized the literature on peripheral trunk nerve block include: paraspinal block, retrolaminar block, plane block of erect spinal muscle, transverse convex to pleural midpoint block, block of the trapezius muscle and anterior serratus muscle, anterior serratus muscle block, thoracic nerve block, abdominal transverse fascia block, type-I block of quadratus lumborum, type-II block of quadratus lumborum, type-III block of quadratus lumborum, block of the sheath of rectus abdominis. This paper reviews the ultrasound-guided peripheral trunk block technique, including development history, anatomic basis, implementation methods, advantages and disadvantages of nerve block technique, and describes the bottleneck and difficulties of nerve block technique at present.

Local anesthetic systemic toxicity: What nurses should know

ABSTRACT

Local or regional anesthetics are becoming more common pain management options for patients, especially considering concerns regarding opioid use disorders. Though mostly safe, these interventions may carry serious risks such as local anesthetic systemic toxicity (LAST). This article discusses LAST and the importance of recognizing its signs and symptoms.

Bupivacaine inhibits a small conductance calcium-activated potassium type 2 channel in human embryonic kidney 293 cells

Background

Bupivacaine blocks many ion channels in the heart muscle, causing severe cardiotoxicity. Small-conductance calcium-activated potassium type 2 channels (SK2 channels) are widely distributed in the heart cells and are involved in relevant physiological functions. However, whether bupivacaine can inhibit SK2 channels is still unclear. This study investigated the effect of bupivacaine on SK2 channels.

Methods

The SK2 channel gene was transfected into human embryonic kidney 293 cells (HEK-293 cells) with Lipofectamine 2000. The whole-cell patch-clamp technique was used to examine the effect of bupivacaine on SK2 channels. The concentration–response relationship of bupivacaine for inhibiting SK2 currents (0 mV) was fitted to a Hill equation, and the half-maximal inhibitory concentration (IC50) value was determined.

Results

Bupivacaine inhibited the SK2 channels reversibly in a dose-dependent manner. The IC50 value of bupivacaine, ropivacaine, and lidocaine on SK2 currents was 16.5, 46.5, and 77.8µM, respectively. The degree of SK2 current inhibition by bupivacaine depended on the intracellular concentration of free calcium.

Conclusions

The results of this study suggested the inhibitory effect of bupivacaine on SK2 channels. Future studies should explore the effects of SK2 on bupivacaine cardiotoxicity.

New composite scale for evaluating peripheral nerve block quality in upper limb orthopaedics surgery

INTRODUCTION

Developments in ultrasound guided (UG) peripheral nerve block (PNB) techniques have significant advantages for patients undergoing trauma surgery. Brachial plexus blockade (BPB) for upper extremity surgery provide superior analgesia, improve recovery and patient satisfaction. To the best of our knowledge there is no tool for evaluation of the quality of UG PNB which concerns the quality of PNB, the tolerance of the patient towards the anaesthetic approach, and postoperative analgesia as well.

PATIENTS AND METHODS

Standardized UG BPB anaesthesia - was performed; interscalene-supraclavicular (ISC-SC) and axillary-supraclavicular (AX-SC) approach for upper limb surgery. A GCS like tool was developed with which the Sensory, Motor, Coping of patient and Postoperative (SMCP) pain qualities were measured. The quality of PNBs were evaluated by a quality of anaesthesia graded by anaesthesiologist (QAGA) and the SMCP scale as well, the means of midazolam and opioid consumption during surgery, vital parameters, postoperative pain intensity (VNRS) were compared between the two groups.

RESULTS

Ninety three unpremedicated adult patients with ASA I-III were scheduled for unilateral upper limb surgery. Nearly the same mean volumes of local anaesthetic solution were used in the AX-SC and ISC-SC groups (28.3-31.0 ml). There were no significant difference in the quality of PNB measured by QAGA or SMCP scale between the AX-SC and the ISC-SC groups, however 75 patients were assessed as Excellent with the SMCP scale vs. 39 with the QAGA. 97.8% of the patients were in the Excellent and Good category evaluated with SMPC vs. 86% with QAGA (p < 0.001). There was no surgery abandoned due to failed PNB and no tourniquet pain was detected. There was no evidence of side effects or complications of PNB during the follow-up period.

DISCUSSION

This composite tool is designed for evaluating the loss of sensory and motor function; the coping of the patient and the postoperative pain as well. Our novel SMCP evaluation tool focuses on the overall condition of the patient during surgery and in the postoperative period. This more precise outcome evaluating scale is significantly superior to the formerly used QAGA in representing the high success rate of UG PNB.

Intrathecal chloroprocaine or hyperbaric prilocaine for ambulatory knee surgery? A prospective randomized study

Purpose

The aim of this study was to compare intrathecal 1% chloroprocaine with 2% hyperbaric prilocaine in the setting of ambulatory knee arthroscopy. We hypothesized that complete resolution of the sensory block was faster with chloroprocaine.

Methods

Eighty patients scheduled for knee arthroscopy were included in this prospective randomized double-blind study. Spinal anesthesia was performed with either chloroprocaine (50 mg) or hyperbaric prilocaine (50 mg). Characteristics of sensory and motor blocks and side effects were recorded.

Results

Mean time to full sensory block recovery was shorter with chloroprocaine (169 (56.1) min vs 248 (59.4)). The characteristics of the sensory blocks were similar at the T12 dermatome level between the two groups. Differences appeared at T10: the percentage of patients with a sensory block was higher, onset quicker and duration longer with hyperbaric prilocaine. The number of patients with a sensory block at T4 dermatome level in both groups was minimal. Times to full motor recovery were identical in both groups (85 (70–99) vs 86 (76–111) min). Time to spontaneous voiding was shorter with chloroprocaine (203 (57.6) min vs 287.3 (47.2) min). Incidence of side effects was low in both groups.

Conclusions

When considering the characteristics of the sensory block, the use of chloroprocaine may allow an earlier discharge of patients. Cephalic extension was to a higher dermatomal level and the sensory block at T10 level was of prolonged duration with hyperbaric prilocaine, suggesting that the choice between the two drugs should also be performed based on the level of the sensory block requested by the surgery.

This study is registered in the US National Clinical Trials Registry, registration number: NCT030389, the first of February 2017, Retrospectively registered.

Local Anesthetic Toxicity in the Geriatric Population

This article provides a concise overview of local anesthetic systemic toxicity, its history, mechanisms, risk factors, prevention, clinical presentation, and treatment, with a special emphasis on issues specific to the geriatric population. The authors used MEDLINE, Scopus, and Google Scholar to search for original research articles (human and animal studies), registries data, case reports, review articles, and pertinent online publications using the combinations of the following search terms: local anesthetics, local anesthetic systemic toxicity, intralipid, lipid emulsion, Exparel, ultrasound-guidance, regional anesthesia, lidocaine, bupivacaine, ropivacaine, cocaine, procaine, tetracaine, levobupivacaine, liposomal bupivacaine, lignocaine. Local anesthetic systemic toxicity continues to occur despite the use of putatively less cardiotoxic formulations of local anesthetics and more common use of ultrasound guidance. The elderly appear to be at a disproportionately increased risk for toxicity owing to the presence of relevant comorbidities and decreased muscle mass. Examination of recent case reports involving patients over the age of 65 years demonstrates that inadvertent overdosing is responsible for some cases of local anesthetic systemic toxicity. Elderly patients are at increased risk of local anesthetic systemic toxicity. When considering use of local anesthetics in older patients, special attention should be paid to the presence of systemic disease and muscle wasting. The safety of regional anesthesia and multi-modal analgesia among these at-risk patients will be improved by educating physicians and staff to recognize and manage local anesthetic systemic toxicity.

In Vitro Negative Inotropic Effect of Low Concentrations of Bupivacaine Relates to Diminished Ca2+ Sensitivity but Not to Ca2+ Handling or β-Adrenoceptor Signaling

BACKGROUND

Systemic toxicity of local anesthetics is predominantly complicated by their myocardial toxicity. Especially long-acting local anesthetics exert a negative inotropic effect that has been described at lower concentrations than defined for blockade of myocardial ion channels. We evaluated the negative inotropic effect of bupivacaine at a concentration described for clinical toxicity testing the hypothesis that negative inotropy is a result of reduced Ca sensitivity rather than blockade of ion channels.

METHODS

We simultaneously measured force development and action potentials in guinea pig right papillary muscles (n = 5 to 7). L-type Ca currents (n = 8 to 16) and Ca transients (n = 10 to 11) were measured in isolated cardiomyocytes. Sensitivity of myofilaments to Ca was assessed in skinned fibers (n = 10). Potential effects of bupivacaine on 3',5'-cyclic adenosine monophosphate concentrations were measured using Förster Resonance Energy Transfer (n = 12 to 14) microscopy.

RESULTS

Bupivacaine reduced force in a concentration-dependent manner from 173 ± 119 µN at baseline to 28 ± 13 µN at 300 µM (mean ± SD). At concentrations giving half-maximum negative inotropic effects (5 µM), the maximum upstroke velocity of action potentials, as a surrogate of sodium channel activity, was unaffected. Maximum positive inotropic effects of isoprenaline were also reduced to 50%. Neither basal nor isoprenaline-induced 3',5'-cyclic adenosine monophosphate accumulation, L-type Ca currents, or Ca transients were affected by 5 µM bupivacaine, but this concentration significantly decreased Ca sensitivity of myofilaments, changing the negative logarithm of the half-maximum effective Ca concentrations from 5.66 to 5.56 -log[M].

CONCLUSIONS

We provide evidence that the negative inotropic effect of bupivacaine may be caused mainly by a reduction in myofilament sensitivity to Ca.

LOCAL ANESTHETICS AND STEROIDS: CONTRAINDICATIONS AND COMPLICATIONS - CLINICAL UPDATE

The objective of this clinical update, based on recently published literature, was to discuss incidence and characteristics of the most relevant clinical adverse effects associated with local anesthetic and steroid use in regional anesthesia and treatment of acute or chronic pain. A comprehensive review of the English-language medical literature search utilizing PubMed, Ovid Medline® and Google Scholar from 2015 to 2018 was performed. This narrative review provides anesthesia practitioners with updated evidences on complications and contraindications of local anesthetic and steroid use with emphasis on current points of view regarding prevention, early diagnosis and treatment of adverse events.

Lower extremity regional anesthesia: essentials of our current understanding

The advent of ultrasound guidance has led to a renewed interest in regional anesthesia of the lower limb. In keeping with the American Society of Regional Anesthesia and Pain Medicine's ongoing commitment to provide intensive evidence-based education, this article presents a complete update of the 2005 comprehensive review on lower extremity peripheral nerve blocks. The current review article strives to (1) summarize the pertinent anatomy of the lumbar and sacral plexuses, (2) discuss the optimal approaches and techniques for lower limb regional anesthesia, (3) present evidence to guide the selection of pharmacological agents and adjuvants, (4) describe potential complications associated with lower extremity nerve blocks, and (5) identify informational gaps pertaining to outcomes, which warrant further investigation.

Updated Retrospective Single-Center Comparative Analysis of Peripheral Nerve Block Complications Using Landmark Peripheral Nerve Stimulation Versus Ultrasound Guidance as a Primary Means of Nerve Localization

OBJECTIVES

The purpose of this study was to perform an updated analysis of complications associated with upper and lower extremity peripheral nerve blocks (PNBs) performed with ultrasound (US) guidance versus the landmark approach.

METHODS

We conducted a single-center retrospective cohort analysis to compare the incidence of PNB complications between the techniques. The primary outcome was local anesthetic systemic toxicity (LAST), whereas the secondary outcomes included short- and long-term nerve injuries. The current query included cases performed between 2012 and 2015. A combined analysis included data extending to 2006. The Statistical examination relied on the χ² test.

RESULTS

During this 4-year period, we performed 7789 US-guided and 498 landmark-guided blocks with no statistically significant difference in the incidence of nerve injury or LAST between the groups. Our 10-year analysis, however, revealed a significant increase (P < .01) in the rate of LAST with the landmark technique: 7 of 5932 versus 0 of 16,858 cases. The combined data also revealed a significant increase (P < .01) in short-term injuries associated with the landmark approach (30 of 5932 versus 33 of 16,858) but no significant difference in the incidence of long-term injuries.

CONCLUSIONS

Our analysis supports a conclusion that the use of US guidance during PNBs leads to a significant reduction in the incidence of LAST, adding to growing evidence from similar investigations. The impact of US on the incidence of nerve injuries remains unclear, considering that the nature of transient deficits is thought to be multifactorial, and the frequency of lasting injuries did not differ significantly in this study.

Local Anesthetic Systemic Toxicity in Total Joint Arthroplasty: Incidence and Risk Factors in the United States From the National Inpatient Sample 1998-2013

BACKGROUND

Local anesthetic systemic toxicity (LAST) is a rare and potentially devastating complication of regional anesthesia. Single-institution registries have reported a decreasing incidence, but these results have limited broad applicability. A recent study using a US database found a relatively high incidence of LAST. We used the National Inpatient Sample, a US database of inpatient admissions, to identify the national incidence and associated risk factors for LAST in total joint arthroplasties.

METHODS

In this retrospective study, we studied patients undergoing hip, knee, or shoulder arthroplasty, from 1998 to 2013, with an adjunct peripheral nerve blockade. We used a multivariable logistic regression to identify patient conditions, hospital level variables, and procedure sites associated with LAST.

RESULTS

A total of 710,327 discharges met inclusion criteria. The average adjusted incidence was 1.04 per 1000 peripheral nerve blocks, with decreasing trend over the 15-year study period (odds ratio [OR], 0.90; P = 0.002). Shoulder arthroplasty (OR, 4.35; P = 0.0001) compared with knee or hip arthroplasty and medium-size (OR, 3.34; P = 0.003) and large-size (OR, 2.40; P = 0.025) hospitals as compared with small hospitals were associated with increased odds of LAST.

CONCLUSIONS

The incidence of LAST nationally in total joint arthroplasty with adjunct nerve blocks is similar to recent estimates from academic centers, with a small decreasing trend through the study period. Despite an overall low incidence rate, practitioners should continue to maintain vigilance for manifestations of LAST, especially as the use of regional anesthesia continues to increase.

Factors associated with intravenous lidocaine in pediatric patients undergoing laparoscopic appendectomy - a retrospective, single-centre experience

BACKGROUND

Due to its potential beneficial effects, intra- and postoperative application of intravenous lidocaine has become increasingly accepted over the last couple of years, e.g. in patients undergoing laparoscopic surgical procedures. Based on its beneficial properties, lidocaine was introduced to the standard of care for all pediatric laparoscopic procedures in our institution in mid-2016. In contrast to adult care, scarce data is available regarding the use of perioperative intravenous lidocaine administration in children undergoing laparoscopic procedures, such as an appendectomy.

METHODS

Retrospective analysis of all pediatric patients undergoing laparoscopic appendectomy at the University Children's Hospital Zurich in 2016. Perioperative data, as recorded in the electronic patient data management system, were evaluated for any signs of systemic lidocaine toxicity (neurological and cardiovascular), behavioral deterioration, as well as for hemodynamic instability. Additionally, the incidence of postoperative nausea and vomiting, administration of pain rescue medication, time to hospital discharge and to first bowel movement, as well as any postoperative complications were recorded. Starting on 01/07/2016, all patients undergoing laparoscopic surgery received intravenous lidocaine (1.5 mg/kg body weight (BW) bolus after induction of anesthesia followed by continuous infusion of 1.5 mg/kgBW/h). These patients were then compared to children without lidocaine administration who had undergone laparoscopic appendectomy between 01/01/2016 and 30/06/2016.

RESULTS

Data of 116 patients was analyzed. Of these, 60 patients received lidocaine. No signs of systemic toxicity, neurologic impairment or circulatory disturbances were noted in any of these patients. A (non-significant) difference in the incidence of emergence delirium was observed (0 cases in the lidocaine group vs. 4 cases in the control group, p = 0.05).

CONCLUSION

This retrospective analysis did not reveal any adverse effects in pediatric patients receiving intravenous lidocaine for laparoscopic appendectomy under general anesthesia. However, further trials investigating beneficial effects as well as pharmacokinetic properties of intravenous lidocaine in children are required.

Pharmacokinetic and clinical effects of two bupivacaine concentrations on axillary brachial plexus block

Introduction

The risk of systemic bupivacaine toxicity is a persistent problem, which makes its pharmacokinetic study fundamental for regional anesthesia safety. There is little evidence of its influence on plasma peak at different concentrations. The present study compares two bupivacaine concentrations to establish how the concentration affects this drug plasma peak in axillary brachial plexus block. Postoperative latency and analgesia were also compared.

Methods

30 patients were randomized. In the 0.25% Group, 0.25% bupivacaine (10 mL) was injected per nerve. In the 0.5% Group, 0.5% bupivacaine (5 mL) was injected per nerve. Peripheral blood samples were collected during the first 2 h after the blockade. For sample analyses, high performance liquid chromatography mass spectrometry was used.

Results

Plasma peak occurred 45 min after the blockade, with no difference between groups at the assessed time-points. Plasma peak was 933.97 ± 328.03 ng.mL⁻¹ (mean ± SD) in 0.25% Group and 1022.79 ± 253.81 ng.mL⁻¹ in 0.5% Group (p = 0.414). Latency was lower in 0.5% Group than in 0.25% Group (10.67 ± 3.71 × 17.33 min ± 5.30, respectively, p = 0.004). No patient had pain within the first 4 h after the blockade.

Conclusion

For axillary brachial plexus block, there was no difference in bupivacaine plasma peak despite the use of different concentrations with the same local anesthetic mass. The concentration inversely influenced latency.

Incidence of Local Anesthetic Systemic Toxicity in Orthopedic Patients Receiving Peripheral Nerve Blocks

BACKGROUND AND OBJECTIVES

Peripheral nerve blocks are increasingly used. However, despite low complication rates, concerns regarding local anesthetic systemic toxicity remain. Although recent studies suggest that this severe complication has decreased considerably, there is a paucity of data about it on a national level. We sought to elucidate the incidence of local anesthetic systemic toxicity on a national level and therefore provide guidance toward the need for preparedness in daily anesthetic practice.

METHODS

We searched a large administrative database for patients who received peripheral nerve blocks for total joint arthroplasties from 2006 to 2014. Their discharge and billing data were analyzed for International Classification of Diseases, Ninth Revision, Clinical Modification codes coding for local anesthetic systemic toxicity or surrogate outcomes including cardiac arrest, seizures, and use of lipid emulsion on the day of surgery. Rates for these outcomes were determined cumulatively and over time.

RESULTS

We identified 238,473 patients who received a peripheral nerve block within the study period. The cumulative rate of outcomes among these patients in the study period was 0.18%. There was a significant decrease of overall outcome rates between 2006 and 2014. Use of lipid emulsion on the day of surgery increased significantly in total knee replacement from 0.02% 2006 to 0.26% in 2014.

CONCLUSIONS

The incidence of local anesthetic systemic toxicity is low but should be considered clinically significant. Since it may cause substantial harm to the patient, appropriate resources and awareness to identify and treat local anesthetic systemic toxicity should be available wherever regional anesthesia is performed.

The effects of intravenous lipid emulsion on hemodynamic recovery and myocardial cell mitochondrial function after bupivacaine toxicity in anesthetized pigs

Local anesthetic toxicity is thought to be mediated partly by inhibition of cardiac mitochondrial function. Intravenous (i.v.) lipid emulsion may overcome this energy depletion, but doses larger than currently recommended may be needed for rescue effect. In this randomized study with anesthetized pigs, we compared the effect of a large dose, 4 mL/kg, of i.v. 20% Intralipid® ( n = 7) with Ringer’s acetate ( n = 6) on cardiovascular recovery after a cardiotoxic dose of bupivacaine. We also examined mitochondrial respiratory function in myocardial cell homogenates analyzed promptly after needle biopsies from the animals. Bupivacaine plasma concentrations were quantified from plasma samples. Arterial blood pressure recovered faster and systemic vascular resistance rose more rapidly after Intralipid than Ringer’s acetate administration ( p < 0.0001), but Intralipid did not increase cardiac index or left ventricular ejection fraction. The lipid-based mitochondrial respiration was stimulated by approximately 30% after Intralipid ( p < 0.05) but unaffected by Ringer’s acetate. The mean (standard deviation) area under the concentration–time curve (AUC) of total bupivacaine was greater after Intralipid (105.2 (13.6) mg·min/L) than after Ringer’s acetate (88.1 (7.1) mg·min/L) ( p = 0.019). After Intralipid, the AUC of the lipid-un-entrapped bupivacaine portion (97.0 (14.5) mg·min/L) was 8% lower than that of total bupivacaine ( p < 0.0001). To conclude, 4 mL/kg of Intralipid expedited cardiovascular recovery from bupivacaine cardiotoxicity mainly by increasing systemic vascular resistance. The increased myocardial mitochondrial respiration and bupivacaine entrapment after Intralipid did not improve cardiac function.