Prevention of Local Anesthetic Systemic Toxicity:

Evaluation of the Pediatric Regional Anesthesia Time-Out Checklist: A Simulation Study

INTRODUCTION

The Society for Pediatric Anesthesia Quality and Safety Committee developed the Pediatric Regional Anesthesia Time-Out Checklist, consisting of 14 safety items intended to be reviewed by an anesthesia team prior to a regional anesthetic. Primarily, we hypothesized that use of this Checklist would increase the number of safety items performed compared with no checklist, evaluating the usefulness of this tool. Secondarily, we hypothesized that, after checklist training, subjects would show better clinical judgment by electing to perform a regional anesthetic in scenarios in which no programmed error existed and electing to not perform a regional anesthetic in scenarios in which a programmed error did exist.

METHODS

Each anesthesia attending/trainee pair participated in 12 different randomized video-recorded medium-fidelity regional anesthesia simulation scenarios, receiving checklist training after half of the scenarios had been completed by each pair. In four of the scenarios, subjects were expected to decline to perform the regional anesthetic because of an error programmed into the scenario. Two errors consisted of a maximum dose of local anesthetic given by the surgeon immediately prior to the planned regional anesthetic and two errors consisted of coagulation issues prior to neuraxial block (1 with a low platelet count and 1 receiving low molecular weight heparin). Scenarios were scored for the number of safety items identified and performed by the subjects. Additionally, the team's choice to perform the regional anesthetic or abort was recorded.

RESULTS

One-hundred and thirty-two scenarios were performed by 22 physicians. A greater number of safety items were completed after training on the Pediatric Regional Anesthesia Time-Out Checklist, for each of 11 individual groups and when data from all groups was pooled, p < 0.001, 95% CI (0.33, 0.41). Overall, 78% of safety items studied were performed after checklist training compared to 41% of safety items performed prior to training. The team's choice to perform or abort the regional anesthetic occurred as expected more often (92% of scenarios) after Checklist training, compared to before checklist training (77% of scenarios), t = 3.41; p = 0.001, 95% CI (0.03, 0.27). Teams chose to perform the regional anesthetic despite a programmed error in three scenarios (0.05%) prior to Checklist training and no scenarios (0%) after Checklist training.

CONCLUSION

Pediatric Regional Anesthesia Time-Out Checklist training led to an increased number of safety items performed prior to a simulated anesthetic.

Intravenous lipid emulsion for local anaesthetic systemic toxicity in pregnant women: a scoping review

BACKGROUND

Local anaesthetic systemic toxicity (LAST) is a rare but life-threatening complication that can occur after local anaesthetic administration. Various clinical guidelines recommend an intravenous lipid emulsion as a treatment for local anaesthetic-induced cardiac arrest. However, its therapeutic application in pregnant patients has not yet been established. This scoping review aims to systematically identify and map the evidence on the efficacy and safety of intravenous lipid emulsion for treating LAST during pregnancy.

METHOD

We searched electronic databases (Medline, Embase and Cochrane Central Register Controlled Trials) and a clinical registry (lipidrescue.org) from inception to Sep 30, 2022. No restriction was placed on the year of publication or the language. We included any study design containing primary data on obstetric patients with signs and symptoms of LAST.

RESULTS

After eliminating duplicates, we screened 8,370 titles and abstracts, retrieving 41 full-text articles. We identified 22 women who developed LAST during pregnancy and childbirth, all presented as case reports or series. The most frequent causes of LAST were drug overdose and intravascular migration of the epidural catheter followed by wrong-route drug errors (i.e. intravenous anaesthetic administration). Of the 15 women who received lipid emulsions, all survived and none sustained lasting neurological or cardiovascular damage related to LAST. No adverse events or side effects following intravenous lipid emulsion administration were reported in mothers or neonates. Five of the seven women who did not receive lipid emulsions survived; however, the other two died.

CONCLUSION

Studies on the efficacy and safety of lipids in pregnancy are scarce. Further studies with appropriate comparison groups are needed to provide more robust evidence. It will also be necessary to accumulate data-including adverse events-to enable clinicians to conduct risk-benefit analyses of lipids and to facilitate evidence-based decision-making for clinical practice.

A Comprehensive Review on the Efficacy of Nerve Blocks in Reducing Postoperative Anesthetic and Analgesic Requirements

The purpose of this article review is to investigate whether or not nerve blocks are beneficial in minimizing the amount of postoperative anesthetic and analgesic medication required, hence improving patient outcomes and reducing healthcare costs. This review investigates several different kinds of nerve blocks, their administration techniques, and the anatomical and physiological aspects that influence nerve block effectiveness. It analyzes the impact of nerve blocks on opioid use, postoperative pain scores, and the incidence of opioid-related adverse effects by compiling the findings of numerous large-scale, randomized, controlled trials. Infection, hematoma, nerve injury, and systemic toxicity are some potential complications of nerve blocks discussed in the article. It concludes with recommendations for optimizing nerve block techniques in clinical practice and identifies areas that require further research, such as the development of new anesthetics and the identification of patient subgroups that would benefit the most from nerve blocks. In addition, it provides recommendations for optimizing nerve block techniques in clinical practice.

Optimization of Carpal Tunnel Syndrome Using WALANT Method

As surgical management of carpal tunnel release (CTR) becomes ever more common, extensive research has emerged to optimize the contextualization of this procedure. In particular, CTR under the wide-awake, local-anesthesia, no-tourniquet (WALANT) technique has emerged as a cost-effective, safe, and straightforward option for the millions who undergo this procedure worldwide. CTR under WALANT is associated with considerable cost savings and workflow efficiencies; it can be safely and effectively executed in an outpatient clinic under field sterility with less use of resources and production of waste, and it has consistently demonstrated standard or better post-operative pain control and satisfaction among patients. In this review of the literature, we describe the current findings on CTR using the WALANT technique.

A Case of Late-Onset Local Anesthetic Toxicity Observed as Seizure Activity

Most of the local anesthetic toxicity cases develop within the first five minutes of peripheral block administration. Late local anesthetic toxicity has been rarely reported in the literature. However, it is an important life-threatening problem that can lead to seizures, hemodynamic collapse, and cardiac arrest if it is ignored and not considered. Here we present the case of an 18-year-old male patient who had ultrasonography-guided infraclavicular brachial plexus block administration with a 30 mL local anesthetic. The patient had convulsions 210 minutes after the block administration and was treated with intravenous diazepam. Intraoperative and postoperative courses were uneventful. He had no neurologic signs or symptoms afterward. All laboratory tests and radiologic investigation tests were normal. This report demonstrates that late local anesthetic toxicity is still possible after several hours of the uneventful peripheral neural blockade, although it is rarely reported.

A meta-analysis on the efficacy of the ropivacaine infiltration in comparison with other dental anesthetics

OBJECTIVES

The aim of this meta-analysis was to assess the clinical efficacy and safety profile of ropivacaine in comparison with other dental anesthetics in different clinical conditions. MATERIALS AND METHODS: This meta-analysis was registered in the National Institute for Health Research PROSPERO (ID: CRD42020205580). PubMed and Scholar Google were consulted to identify clinical trials using ropivacaine in comparison with other local anesthetic drugs for any dental procedure. Articles comparing ropivacaine and other dental anesthetics were assessed with the Cochrane Collaboration's risk of bias tool. Data from reports without a high risk of bias were extracted (anesthetic and adverse effects) and analyzed using the Review Manager Software 5.3. for Windows and the Risk Reduction Calculator.

RESULTS

Ropivacaine produces a longer anesthetic time when compared with lidocaine/adrenaline (n = 260; p = 0.00001) and similar anesthesia than bupivacaine (n = 190).

CONCLUSIONS

Data of this study indicate that ropivacaine infiltration produces a longer anesthetic time when compared with lidocaine and articaine but not when compared to bupivacaine in dental procedures.

CLINICAL RELEVANCE

Ropivacaine was more effective than lidocaine for dental anesthesia. For this reason, the manufacture of a ropivacaine dental cartridge with a suitable concentration could be an important advancement for clinical practice.

Knowledge, attitude and practice on usage and toxicity of local anaesthetic agents (LA) amongst health care professionals in obstetrics and gynaecology

A sound knowledge of LA and their dosage is essential for effective anaesthesia and patient safety as LA toxicity could be potentially life-threatening and clinicians undertaking LA procedures must be competent in early recognition of toxicity and instigating remedial measures timely. This is a prospective national-level survey using self-administered questionnaires among health care professionals in Obstetrics and Gynaecology primarily based in Worcestershire Acute Hospital NHS Trust and further extended to other regions of the United Kingdom. The survey was focussed on evaluating the knowledge, attitude and practice (KAP) of the common local anaesthetic agents, their dosage, early recognition and management of LA systemic toxicity(LAST). We understood that all groups of health care professionals did not demonstrate adequate knowledge of safe and effective use of LA agents. We thereby propose an accredited knowledge-based learning module, laminated safety information cards for LA use and ensuring availability of Lipid-emulsion therapy in clinical areas.IMPACT STATEMENTWhat is already known on this subject? Health care professionals using LA should have sufficient knowledge of LA including the required and maximum dose allowance, pharmacokinetic properties, possible complications and management of systemic toxicity. The lack this can trigger potentially fatal and life-threatening complications if misused. Therefore, the key objectives of the use of LA in clinical settings are to optimise pain management while ensuring safe practice.What do the results of this study add? We understood that all groups of health care professionals did not demonstrate adequate knowledge of the safe and effective use of LA agents and appropriate management of its toxicity. This highlights the urgent need for extending awareness among the professionals on the safe administration of LA, early identification and prompt management of LAST. This will improve not only the safety but also the overall patient experience and quality of care.What are the implications of these findings for clinical practice and/or further research? We thereby propose that an accredited knowledge-based module on safe administration and safety concerns of LA must be made compulsory for all those administering LA. Laminated safety information cards on LA with explicit algorithms/guidelines should be made available in all clinical areas to avoid any delays in the management of toxicity. Moreover, all health-care institutions must ensure the availability of Lipid Emulsion Therapy.

Perineural Epinephrine for Brachial Plexus Block Increases the Incidence of Hypotension during Dexmedetomidine Infusion: A Single-Center, Randomized, Controlled Trial

Background: Sedation using dexmedetomidine is frequently associated with hypotension. In contrast, epinephrine, a commonly used adjunctive agent in regional anesthesia, is a potent vasopressor. We hypothesized that perineural epinephrine used in brachial plexus blockade may reduce hypotension during dexmedetomidine infusion. Methods: Patients scheduled for upper extremity surgery were randomly allocated into a control and an epinephrine group. All patients received brachial plexus blockade, consisting of 25 mL of a 1:1 mixture of 1% lidocaine and 0.75% ropivacaine, with patients in the epinephrine group also receiving 125 μg epinephrine. Intraoperative sedation was induced using dexmedetomidine at a loading dose of 1 µg/kg and maintenance dose of 0.4 µg/kg/hr. The primary outcome was the incidence of intraoperative hypotension or hypotension in the post-anesthesia care unit (PACU). Results: One hundred and thirty patients were included (65 per group). The incidence of hypotension was significantly higher in the epinephrine than in the control group (80.6% vs. 56.9%, p = 0.009). The duration of hypotension and the maximal change in blood pressure were also greater in the epinephrine group. Conclusions: Perineural epinephrine for brachial plexus blockade does not reduce hypotension due to dexmedetomidine infusion and may actually augment the occurrence of hypotensive events.

Chloroquine for prolonged skin analgesia in rats

The purpose of this study was to investigate the ability of chloroquine and chloroquine in combination with vasoconstrictor epinephrine to act as a local anesthetic in skin analgesia. After subcutaneous injection of drugs in rats, the inhibition of the cutaneous trunci muscle reflex (CTMR) is designed for evaluation of the cutaneous analgesic effect. The analgesic effect of chloroquine was compared with that of bupivacaine or coadministration of chloroquine and epinephrine. Chloroquine produced exactly the same local anesthesia as bupivacaine did in a dose-dependent manner. On the ED₅₀ (50 % effective dose) basis, the analgesic potency was chloroquine (4.81 [4.45-5.20] μmol) < bupivacaine (0.46 [0.40‒0.52] μmol) (p <  0.01). At every equipotent dose tested (ED₂₅, ED₅₀ and ED₇₅), chloroquine had a longer duration of cutaneous analgesia than bupivacaine (p <  0.01). Epinephrine enhanced the potency and duration of chloroquine-induced cutaneous analgesia. We found that chloroquine and bupivacaine elicit dose-dependent cutaneous analgesia. Chloroquine is not as potent as bupivacaine, but acts as an infiltrative anesthetic for a longer duration of time and is more potent and effective when used in combination with epinephrine.

Practical guide for the management of systemic toxicity caused by local anesthetics

Systemic toxicity from local anesthetics can occur in any of the wide range of situations in which these agents are used. This practical guide is created to generate a shared awareness of the prevention, diagnosis, and treatment of local anesthetic systemic toxicity among all medical professionals who perform nerve blocks. Systemic toxicity of local anesthetic is induced by an increase of its protein-unbound plasma concentration. Initial symptoms are characterized by central nervous system signs such as excitation, convulsions, followed by loss of consciousness and respiratory arrest. These symptoms are often accompanied with cardiovascular signs such as hypertension, tachycardia and premature ventricular contractions. Further increase of plasma concentration of local anesthetic induces bradycardia, conduction disturbances, circulatory collapse and asystole. The incidence of local anesthetic systemic toxicity is 1-11 cases per 10,000. Infants, patients with decreased liver function and low cardiac output are vulnerable to systemic toxicity. When performing regional anesthesia, the guideline-directed monitoring, securing a venous line, preparation of medication to treat convulsions and lipid emulsions are required. For prevention of local anesthetic systemic toxicity, small-dose, divided administration, using agents with low toxicity such as ropivacaine and levobupivacaine, performing an aspiration test are recommended. If systemic toxicity is suspected, halt administration of local anesthetic, request assistance, secure venous line, airway, administration of 100% oxygen and if necessary tracheal intubation and artificial respiration should be immediately performed. Benzodiazepines are recommended to treat convulsions. Administration of 20% lipid emulsion according to the protocol is recommended to treat severe hypotension and arrhythmia.

Epidural Local Anesthetics Versus Opioid-Based Analgesic Regimens for Postoperative Gastrointestinal Paralysis, Vomiting, and Pain After Abdominal Surgery: A Cochrane Review

BACKGROUND

The aim of this review was to compare the effects of postoperative epidural analgesia with local anesthetics to postoperative systemic or epidural opioids in terms of return of gastrointestinal transit, postoperative pain control, postoperative vomiting, incidence of gastrointestinal anastomotic leak, hospital length of stay, and cost after abdominal surgery.

METHODS

Trials were identified by computerized searches of the Cochrane Central Register of Controlled Trials (CENTRAL) (2014, Issue 12), Medical Literature Analysis and Retrieval System Online (MEDLINE) (from 1950 to December, 2014) and Excerpta Medica dataBASE (EMBASE) (from 1974 to December 2014) and by checking the reference lists of trials retained. We included parallel randomized controlled trials comparing the effects of postoperative epidural local anesthetic with regimens based on systemic or epidural opioids. The quality of the studies was rated according to the Cochrane tool. Two authors independently extracted data. We judged the quality of evidence according to the Grading of Recommendations, Assessment, Development and Evaluations (GRADE) working group scale.

RESULTS

Based on 22 trials including 1138 participants, an epidural containing a local anesthetic will decrease the time required for return of gastrointestinal transit as measured by time required to observe the first flatus after an abdominal surgery standardized mean difference (SMD) -1.28 (95% confidence interval [CI], -1.71 to -0.86; high quality of evidence; equivalent to 17.5 hours). The effect is proportional to the concentration of local anesthetic used. Based on 28 trials including 1559 participants, we also found a decrease in time to first feces (stool): SMD -0.67 (95% CI, -0.86 to -0.47; low quality of evidence; equivalent to 22 hours). Based on 35 trials including 2731 participants, pain on movement at 24 hours after surgery is also reduced: SMD -0.89 (95% CI, -1.08 to -0.70; moderate quality of evidence; equivalent to 2.5 on a scale from 0 to 10). Based on 22 trials including 1154 participants, we did not find a difference in the incidence of vomiting within 24 hours: risk ratio 0.84 (95% CI, 0.57-1.23); low quality of evidence. Based on 17 trials including 848 participants we did not find a difference in the incidence of gastrointestinal anastomotic leak: risk ratio 0.74 (95% CI, 0.41-1.32; low quality of evidence). Based on 30 trials including 2598 participants, epidural analgesia reduces length of hospital stay for an open surgery: SMD -0.20 (95% CI, -0.35 to -0.04; very low quality of evidence; equivalent to 1 day). Data on cost were very limited.

CONCLUSIONS

An epidural containing a local anesthetic, with or without the addition of an opioid, accelerates the return of the gastrointestinal transit (high quality of evidence). An epidural containing a local anesthetic with an opioid decreases pain after an abdominal surgery (moderate quality of evidence). An epidural containing a local anesthetic does not affect the incidence of vomiting or anastomotic leak (low quality of evidence). For an open surgery, an epidural containing a local anesthetic would reduce the length of hospital stay (very low quality of evidence).

Identifying and Managing Local Anesthetic Allergy in Dermatologic Surgery

BACKGROUND

Local anesthetic (LA) allergy is a concern for dermatologic surgeons given the large number of procedures performed yearly with LAs. Many patients also have anxiety about past or potential anesthesia allergy.

OBJECTIVE

This article will review the symptoms of IgE-mediated allergic reactions, the prevalence of IgE-mediated LA allergy, discuss common mimics of LA, and propose a practical approach for diagnostic and therapeutic options for LA allergy for the dermatologic surgeon in practice.

MATERIALS AND METHODS

A literature search of Pubmed using keywords "lidocaine," "local anesthetic," "hypersensitivity," and "allergy" was performed.

RESULTS

Amide anesthetics result in the most reports of true local anesthetic immediate hypersensitivity.

CONCLUSION

True IgE-mediated anaphylaxis to local anesthesia is very rare. Dermatologic surgeons should be aware of the symptoms of anesthetic allergy and its mimickers, as well as how to manage allergic reactions in their clinical practice.

The effects of adding epinephrine to ropivacaine for popliteal nerve block on the duration of postoperative analgesia: a randomized controlled trial

BACKGROUND

Duration of peripheral nerve blocks depends on multiple factors. Both technique and type of local anesthetic used, either with or without adjuncts, may result in different duration times of the block. The purpose of the present study was to compare the duration of postoperative analgesia of 30 mL ropivacaine 0.75 % with or without epinephrine for popliteal sciatic nerve block.

METHODS

Thirty-eight patients were included to receive ultrasound guided continuous popliteal nerve block with ropivacaine 0.75 % either without (ROPI) or with epinephrine 5 μg/mL (ROPI-EPI) for ankle fusion, subtalar fusion, or a combination of both. The primary outcome parameter was the duration of postoperative analgesia as reflected by the time to first request for postoperative analgesia (TTFR) through the popliteal nerve catheter. Secondary outcome measures included the onset of sensory and motor block and NRS score for pain at rest and during movement.

RESULTS

Thirty patients, 15 in each group, were studied. Eight patients were withdrawn because of specific withdrawal criteria described in the protocol and replaced according to their group allocation. Median [interquartile range] TTFR was 463 [300-1197] min and 830 [397-1128] min for the ROPI vs ROPI-EPI group respectively. Hodges Lehman median difference between groups was 71 min (95 % CI -415 - 473 min). There was no difference in any clinical outcome measure between the groups.

CONCLUSION

The results of this study did not show any significant increase in the duration of postoperative analgesia by adding epinephrine to ropivacaine for popliteal nerve block. This may be due to the intrinsic vasoconstrictive properties of ropivacaine. The absence of a significant difference can also be the result of a type II error caused by a large variation in the individual TTFR.

TRIAL REGISTRATION

Trial register.nl identifier: NTR3330 , keyword TTFR.

The toxic impact of local anaesthetics in menopausal women: causes, prevention and treatment after local anaesthetic overdose. Local anaesthetic systemic toxicity syndrome

Gynaecologists often use local anaesthetics in their medical practice. Some concomitant diseases during the menopausal period may cause problems during the qualification of postmenopausal women for general anaesthesia in gynaecological surgery. Many authors suggest the application of local analgesia for particular kinds of gynaecological surgery procedures performed on postmenopausal women, taking into consideration health determinants. While applying local anaesthetics, the possibility of their overdose has to be taken into account. Generalised toxic symptoms which appeared after the local anaesthesia are rare, but potentially are lethal complications. Toxic symptoms after local anaesthetic administration are manifested after accidental administration of a medicine into a blood vessel, when extravascular administration of a large volume of a local anaesthetic is absorbed into a bloodstream or with the reproducible doses of local anaesthetics which are administered when metabolism does not work sufficiently and cannot eliminate these substances. Clinical overdose of local anaesthetics is manifested by disorders in two systems. Firstly, the pathological symptoms come from the central nervous system (CNS). In the second phase, the pathological symptoms will additionally appear in the cardiovascular system. The aim of the present thesis is to remind clinical manifestations of the local anaesthetic overdose and suggest the management of patients with the aforementioned symptoms, especially in the case of intravenous lipid emulsions which have the status of an antidote in life-threatening conditions caused by cardiotoxic effects of local anaesthetics.

Evidence-based medicine for ultrasound-guided regional anesthesia

Available evidence favoring the use of ultrasound for regional anesthesia is reviewed, updated, and critically assessed. Important outcome advantages include decreased time to block onset; decreased risk of local anesthetic systemic toxicity; and, depending on the outcome definition, increased block success rates. Ultrasound guidance, peripheral nerve blocks, and central neuraxial blocks are discussed.

Ultrasound guidance reduces the risk of local anesthetic systemic toxicity following peripheral nerve blockade

BACKGROUND AND OBJECTIVES

Local anesthetic systemic toxicity (LAST) is a potentially life-threatening complication of local anesthetic administration. In this article, the results of the Australian and New Zealand Registry of Regional Anaesthesia were analyzed to determine if ultrasound-guided peripheral nerve blockade (PNB) was associated with a reduced risk of LAST compared with techniques not utilizing ultrasound technology.

METHODS

The period of study for this multicenter study involving 20 hospitals was from January 2007 through May 2012. The primary outcome was LAST comprising minor, major, and cardiac arrest (due to toxicity) events determined using standardized definitions. Multivariable logistic regression models and propensity score analyses were used to determine significant event predictors.

RESULTS

The study population comprised 20,021 patients who received 25,336 PNBs. There were 22 episodes of LAST, resulting in an incidence of LAST of 0.87 per 1000 PNBs (95% confidence interval, 0.54-1.3 per 1000). Ultrasound guidance was associated with a reduced incidence of local anesthetic toxicity. Site of injection, local anesthetic type, dose per weight, dose, and patient weight were all predictors of LAST.

CONCLUSIONS

This study provides the strongest evidence, to date, that ultrasound guidance may improve safety because it is associated with a reduced risk of LAST following PNB.

Pharmacokinetics of 450 mg ropivacaine with and without epinephrine for combined femoral and sciatic nerve block in lower extremity surgery. A pilot study

AIMS

No pharmacokinetic data exist on doses of ropivacaine larger than 300 mg for peripheral nerve block in man, although in clinical practice higher doses are frequently used. The purpose of the present study was to describe the pharmacokinetic profile in serum of 450 mg ropivacaine with and without epinephrine in patients undergoing anterior cruciate ligament reconstruction.

METHODS

Twelve patients were randomly allocated to receive a single shot combined sciatic/femoral nerve block with 60 ml of either ropivacaine 0.75% alone (group R, n = 6) or ropivacaine 0.75% plus epinephrine 5 μg ml(-1) (group RE, n = 6). Venous blood samples for total and free ropivacaine serum concentrations were obtained during 48 h following block placement. Pharmacokinetic parameters were calculated using a non-compartmental approach.

RESULTS

Results are given as mean (SD) for group R vs. group RE (95% CI of the difference). Total Cmax was 2.81 (0.94) μg ml(-1) vs. 2.16 (0.21) μg ml(-1) (95% CI -0.23, 1.53). tmax was 1.17 (0.30) h vs. 1.67 (0.94) h (95% CI -1.40, 0.40). The highest free ropivacaine concentration per patient was 0.16 (0.08) μg ml(-1) vs. 0.12 (0.04) μg ml(-1) (95% CI -0.04, 0.12). t(1/2) was 6.82 (2.26) h vs. 5.48 (1.69) h (95% CI -1.23, 3.91). AUC was 28.35 (5.92) μg ml(-1)  h vs. 29.12 (7.34) μg ml(-1)  h (95% CI -9.35, 7.81).

CONCLUSIONS

Free serum concentrations of ropivacaine with and without epinephrine remained well below the assumed threshold of 0.56 μg ml(-1) for systemic toxicity. Changes in pharmacokinetics with epinephrine co-administration did not reach statistical significance.

Phenylephrine as a simulated intravascular epidural test dose in pediatrics: a pilot study

BACKGROUND

A test dose is used to detect intravascular injection during neuraxial block in pediatrics. Accidental intravascular epidural local anesthetic injection might be unrecognized in anesthetized children leading to potential life-threatening complications. In children, sevoflurane anesthesia blunts the hemodynamic response when intravascular cathecolamines are administered. No studies have explored the hemodynamics and the criteria for a positive test dose result following phenylephrine in sevoflurane anesthetized children.

METHODS

Healthy children undergoing minor procedures were randomly assigned to receive intravenous placebo, or 5 μg∙kg(-1) phenylephrine (n = 11/group) during sevoflurane anesthesia. Hemodynamic response was assessed using electrocardiography, pulse oxymetry and non-invasive blood pressure monitoring for 5 min following drug administration in anesthetized patients.

RESULTS

All patients receiving phenylephrine showed a decreased heart rate (HR) but not all of them met the positive criterion for test dose response. Overall, at 1 min, patients receiving phenylephrine showed a 25% decrease in HR from the baseline while an increase in blood pressure was noticed in 54% of patients receiving phenylephrine.

DISCUSSION

Phenylephrine might be a future indicator of positive intravascular test dose. Further investigation is needed to find out the phenylephrine dose that elicits a reliable hemodynamic response and whether phenylephrine needs to be dose age-adjusted in order to appreciate relevant hemodynamic changes in children receiving neuraxial blocks undergoing general anesthesia.

Adverse outcomes associated with nerve stimulator-guided and ultrasound-guided peripheral nerve blocks by supervised trainees: update of a single-site database

BACKGROUND

We previously published a retrospective review of complications related to peripheral nerve blocks performed by supervised trainees, from our quality assurance and billing data, guided by either ultrasound, with nerve stimulator confirmation, or landmark-based nerve stimulator techniques. This report updates our results, for the period from May 2008 through December 2011, representing ongoing transition to near-complete combined ultrasound/nerve stimulator guidance in a block-oriented, outpatient orthopedic anesthesia practice.

METHODS

We queried our deidentified departmental quality improvement electronic database for adverse outcomes associated with peripheral nerve blocks. Billing records were also deidentified and used to provide the denominator of total number of blocks using each technique of neurolocation. The types of blocks considered in this analysis were interscalene, axillary, femoral, sciatic, and popliteal-sciatic blocks. Nerve block complications based on each type of guidance were then compared for the entire recent 30-month time period, as well as for the 6-year period of this report.

RESULTS

There were 9062 blocks performed by ultrasound/nerve stimulator, and 5436 by nerve stimulator alone over the entire 72-month period. Nerve injuries lasting longer than 1 year were rare, but similar in frequency with both nerve guidance techniques. The incidence of local anesthetic systemic toxicity was found to be higher with landmark-nerve stimulator technique than with use of ultrasound-guided nerve blocks (6/5436 vs 0/9069, P = 0.0061).

CONCLUSIONS

We report a large series of combined ultrasound/nerve stimulator nerve blocks by supervised trainees without major local anesthetic systemic toxicity. While lacking the compelling evidence of randomized controlled trials, this observational database nonetheless allows increased confidence in the safety of using combined ultrasound/nerve stimulator in the setting of anesthesiologists-in-training.

Lipid emulsion for local anesthetic systemic toxicity

The accidental overdose of local anesthetics may prove fatal. The commonly used amide local anesthetics have varying adverse effects on the myocardium, and beyond a certain dose all are capable of causing death. Local anesthetics are the most frequently used drugs amongst anesthetists and although uncommon, local anaesthetic systemic toxicity accounts for a high proportion of mortality, with local anaesthetic-induced cardiac arrest particularly resistant to standard resuscitation methods. Over the last decade, there has been convincing evidence of intravenous lipid emulsions as a rescue in local anesthetic-cardiotoxicity, and anesthetic organisations, over the globe have developed guidelines on the use of this drug. Despite this, awareness amongst practitioners appears to be lacking. All who use local anesthetics in their practice should have an appreciation of patients at high risk of toxicity, early symptoms and signs of toxicity, preventative measures when using local anesthetics, and the initial management of systemic toxicity with intravenous lipid emulsion. In this paper we intend to discuss the pharmacology and pathophysiology of local anesthetics and toxicity, and the rationale for lipid emulsion therapy.

The acute toxicity of local anesthetics

IMPORTANCE OF THE FIELD

Systemic toxicity, usually from overdose or intravascular dose, is feared because it mainly affects the heart and brain, and may be acutely life-threatening.

AREAS COVERED IN THIS REVIEW

Pharmacological studies of local anesthetic toxicity have largely been reviewed primarily relating to the evaluation of ropivacaine and levobupivacaine during the past decade. This review/opinion focuses more on the principles and concepts underlying the main models used, from chemical pharmacological and pharmacokinetic perspectives.

WHAT THE READER WILL GAIN

Research models required to produce pivotal toxicity data are discussed. The potencies for neural blockade and systemic toxicity are associated across virtually all models, with some deviations through molecular stereochemistry. These models show that all local anesthetics can produce direct cardiovascular system toxicity and CNS excitotoxicity that may further affect the cardiovascular system response. Whereas the longer-acting local anesthetics are more likely to cause cardiac death by malignant arrhythmias, the shorter-acting agents are more likely to cause cardiac contraction failure. In most models, equi-anesthetic doses of ropivacaine and levobupivacaine are less likely to produce serious toxicity than bupivacaine.

TAKE HOME MESSAGE

Of the various models, this reviewer favors a whole-body large animal preparation because of the comprehensive data collection possible. The conscious sheep preparation has contributed more than any other, and may be regarded as the de facto 'standard' experimental model for concurrent study of local anesthetic toxicity ± pharmacokinetics, using experimental designs that can reproduce the toxicity seen in clinical accidents.