Lipid emulsion combined with epinephrine and vasopressin does not improve survival in a swine model of bupivacaine-induced cardiac arrest

Predicting the efficacy of opioid sequestration by intravenous lipid emulsion using biologically relevant in vitro models of drug distribution

Intravenous lipid emulsions (ILE), among other uses, are utilized in the treatment of poisonings caused by lipophilic substances. The body of evidence regarding the benefits of this treatment is growing but information about opioids-ILE interaction is still very scarce. In this work, the impact of ILE on the distribution of buprenorphine, fentanyl and butorphanol used in various concentrations (100-500 ng/ml) was investigated. Two different in vitro models were used: disposition of the drugs in plasma after ultracentrifugation and distribution into the simulated biophase (cell monolayer of 3T3 fibroblasts or J774.E macrophages). We confirmed the ability of ILE to sequester the three drugs of interest which results in their decrease in the aqueous part of the plasma by 34.2-38.2%, 11.7-28.5% and 6.0-15.5% for buprenorphine, fentanyl and butorphanol, respectively. Moreover, ILE affected the drug distribution to the biophase in vitro, however, in this case the drug concentration in cells decreased by 97.3 ± 3.1%, 28.6 ± 5.4% and 13.0 ± 7.5% for buprenorphine, fentanyl and butorphanol, respectively. The two models revealed notable differences in ILE's potential for drug sequestration, especially for buprenorphine. Similar, but not as pronounced tendencies were observed for the two other drugs. These discrepancies may result from the difference in protein abundance and resulting drug-protein binding in both systems. Nevertheless, the results obtained with both in vitro models correlated well with the partition coefficient (logP) values for these drugs.

[Cardiac arrest under special circumstances]

These guidelines of the European Resuscitation Council (ERC) Cardiac Arrest under Special Circumstances are based on the 2020 International Consensus on Cardiopulmonary Resuscitation Science with Treatment Recommendations. This section provides guidelines on the modifications required for basic and advanced life support for the prevention and treatment of cardiac arrest under special circumstances; in particular, specific causes (hypoxia, trauma, anaphylaxis, sepsis, hypo-/hyperkalaemia and other electrolyte disorders, hypothermia, avalanche, hyperthermia and malignant hyperthermia, pulmonary embolism, coronary thrombosis, cardiac tamponade, tension pneumothorax, toxic agents), specific settings (operating room, cardiac surgery, cardiac catheterization laboratory, dialysis unit, dental clinics, transportation [in-flight, cruise ships], sport, drowning, mass casualty incidents), and specific patient groups (asthma and chronic obstructive pulmonary disease, neurological disease, morbid obesity, pregnancy).

European Resuscitation Council Guidelines 2021: Cardiac arrest in special circumstances

These European Resuscitation Council (ERC) Cardiac Arrest in Special Circumstances guidelines are based on the 2020 International Consensus on Cardiopulmonary Resuscitation Science with Treatment Recommendations. This section provides guidelines on the modifications required to basic and advanced life support for the prevention and treatment of cardiac arrest in special circumstances; specifically special causes (hypoxia, trauma, anaphylaxis, sepsis, hypo/hyperkalaemia and other electrolyte disorders, hypothermia, avalanche, hyperthermia and malignant hyperthermia, pulmonary embolism, coronary thrombosis, cardiac tamponade, tension pneumothorax, toxic agents), special settings (operating room, cardiac surgery, catheter laboratory, dialysis unit, dental clinics, transportation (in-flight, cruise ships), sport, drowning, mass casualty incidents), and special patient groups (asthma and COPD, neurological disease, obesity, pregnancy).

Heterogeneity and bias in animal models of lipid emulsion therapy: a systematic review and meta-analysis

INTRODUCTION

Clinicians utilize lipid emulsion to treat local anesthetic toxicity and non-local anesthetic toxicities, a practice supported by animal experimentation and clinical experience. Prior meta-analysis confirmed a mortality benefit of lipid emulsion in animal models of local anesthetic toxicity but the benefit of lipid emulsion in models of non-local anesthetic toxicity remains unanswered. Further, swine suffer an anaphylactoid reaction from lipid emulsions calling into question their role as a model system to study lipid, so we examined swine and non-swine dependent outcomes in models of intravenous lipid emulsion.

METHODS

We conducted a systematic review and meta-analysis examining the use of lipid emulsion therapy in animal models of cardiac toxicity. We quantified mortality using a random-effects odds-ratio method. Secondary outcomes included survival in the following subgroups: local-anesthetic systemic toxicity, non-local anesthetic toxicity, swine-based models, and non-swine models (e.g., rat, rabbit and dog). We assessed for heterogeneity with Cochran's Q and I². We examined bias with Egger's test & funnel plot analysis.

RESULTS

Of 2784 references screened, 58 met criteria for inclusion. Treatment with lipid emulsion reduced chance of death in all models of toxicity with an odds ratio of death of 0.26 (95% CI 0.16-0.44, Z-5.21, p < 0.00001, Cohen's-d = 0.72, n = 60). Secondary outcomes confirmed a reduced chance of death in models of local anesthetic toxicity (OR 0.16 {95% CI 0.1-0.33}) and non-local anesthetic toxicity (OR 0.43 {95% CI 0.22-0.83}). Heterogeneity (Cochran's Q 132 {df = 59, p < 0.01}, I ² = 0.55) arose primarily from animal-model and disappeared (I ² < = 0.12) when we analyzed swine and non-swine subgroups independently. Swine only benefited in models of local anesthetic toxicity (OR 0.28 {95% CI 0.11-0.7}, p = 0.0033) whereas non-swine models experienced a homogeneous benefit across all toxins (OR 0.1 {95% CI 0.06-0.16}, p < 0.00001). Egger's test identified risk of bias with outliers on funnel plot analysis.

DISCUSSION

Lipid emulsion therapy reduces mortality in animal models of toxicity. Heterogeneity arises from the animal-model used. Swine only benefit in models of local anesthetic toxicity, potentially due to lipid dose, experimental design or swine's anaphylactoid reaction to lipid. Outlier analysis reinforced the need for appropriate dosing of lipid emulsion along with airway management and chest compressions in the setting of cardiac arrest.

Superior Efficacy of Lipid Emulsion Infusion Over Serum Alkalinization in Reversing Amitriptyline-Induced Cardiotoxicity in Guinea Pig

BACKGROUND

Tricyclic antidepressants (TCAs) are a major cause of fatal drug poisoning due to their cardiotoxicity. Alkalinization by sodium bicarbonate (NaHCO3) administration, the first-line therapy for TCA-induced cardiotoxicity, can occasionally yield insufficient efficacy in severe cases. Because most TCAs are highly lipophilic, lipid emulsion may be more effective than alkalinization. However, it remains to be determined whether lipid emulsion is more beneficial than alkalinization in reversing amitriptyline-induced cardiotoxicity.

METHODS

Hemodynamic variables were recorded from in vivo guinea pig models and Langendorff-perfused hearts. Whole-cell patch-clamp experiments were conducted on enzymatically isolated ventricular cardiomyocytes to record fast sodium currents (INa). Lipid solutions were prepared using 20% Intralipid. The pH of the alkaline solution was set at 7.55. We assessed the effect of lipid emulsion on reversing amitriptyline-induced cardiotoxicity, in vivo and in vitro, compared to alkalinization. The data were evaluated by Student t test, 1-way repeated-measures analysis of variance, or analysis of covariance (covariate = amitriptyline concentration); we considered data statistically significant when P < .05.

RESULTS

In the in vivo model, intervention with lipids significantly reversed the amitriptyline-induced depression of mean arterial pressure and prolongation of QRS duration on electrocardiogram more than alkalinization (mean arterial pressure, mean difference [95% confidence interval]: 19.0 mm Hg [8.5-29.4]; QRS duration, mean difference [95% confidence interval] -12.0 milliseconds [-16.1 to -7.8]). In the Langendorff experiments, perfusion with 1% and 2% lipid solutions demonstrated significant recovery in left ventricular developed pressure (LVdevP), maximum change rate of increase of LVdevP (dP/dtmax) and rate-pressure product compared with alkaline solution (LVdevP [mm Hg], alkaline 57 ± 35, 1% lipid 94 ± 12, 2% lipid 110 ± 14; dP/dtmax [mm Hg/s], alkaline 748 ± 441, 1% lipid 1502 ± 334, 2% lipid 1753 ± 389; rate-pressure product [mm Hg·beats·minute], alkaline 11,214 ± 8272, 1% lipid 19,025 ± 8427, 2% lipid 25,261 ± 4803 with analysis of covariance). Furthermore, lipid solutions (0.5%-4%) resulted in greater recovery of hemodynamic parameters at 3 μM amitriptyline. Amitriptyline inhibited INa in a dose-dependent manner: the half-maximal inhibitory concentration (IC50) was 0.39 μM. The IC50 increased to 0.75 μM in the alkaline solution, 3.2 μM in 1% lipid solution, and 6.1 μM in 2% lipid solution. Furthermore, the lipid solution attenuated the use-dependent block of sodium channels by amitriptyline more than alkaline solution. On 30 consecutive pulses at 1 Hz, the current decreased to 50.1 ± 2.1, 60.3 ± 1.9, and 90.4% ± 1.8% in standard, alkaline, and 1% lipid solution, respectively. Even 0.5% lipid solution showed greater effects than the alkaline solution in all experiments.

CONCLUSIONS

Lipid emulsion significantly suppressed amitriptyline-induced INa, inhibition, which was likely related to the marked improvement in hemodynamic status observed in vivo and in isolated perfused hearts. These results suggest the superiority of lipid emulsion as the first-line therapy for TCA-induced cardiotoxicity compared to alkalinization therapy.

Free Fatty Acid Receptor G-protein-coupled Receptor 40 Mediates Lipid Emulsion-induced Cardioprotection

BACKGROUND

We have previously shown that intralipid (lipid emulsion) protects the heart against ischemia/reperfusion injury and bupivacaine-induced cardiotoxicity. However, the precise underlying mechanisms are not fully understood. Here we explored the hypothesis that free fatty acid receptor-1 or G-protein-coupled receptor 40 is expressed in the heart and that cardioprotective effects of lipid emulsion are mediated through G-protein-coupled receptor 40 in two animal models of ischemia/reperfusion injury and bupivacaine-induced cardiotoxicity.

METHODS

Langendorff-perfused male mouse hearts were subjected to ischemia/reperfusion with lipid emulsion alone (1%) or with G-protein-coupled receptor 40 antagonist (GW1100, 10 µM). Additionally, cardiotoxicity was achieved in male rats with bupivacaine bolus (10 mg/kg, IV) followed by lipid emulsion alone (20%, 5 ml/kg bolus, and 0.5 ml · kg · min maintenance, IV) or with GW1100 pretreatment (2.5 mg/kg, IV).

RESULTS

G-protein-coupled receptor 40 is expressed in rodent hearts. GW1100 abolished lipid emulsion-induced cardioprotection against ischemia/reperfusion in mice because rate pressure product and left ventricular developed pressure were lower than lipid emulsion alone (rate pressure product: 2,186 ± 1,783 [n = 7] vs. 11,607 ± 4,347 [n = 8]; left ventricular developed pressure: 22.6 ± 10.4 vs. 63.8 ± 20; P < 0.0001). Lipid emulsion + GW1100 also demonstrated reduced LV dP/dtmax and LV dP/dtmin (dP/dtmax = 749 ± 386 vs. 2,098 ± 792, P < 0.001; dP/dtmin = -443 ± 262 vs. -1,447 ± 546, P < 0.001). In bupivacaine-induced cardiotoxicity rat model, GW1100 pretreatment had no significant effect on heart rate (HR) and ejection fraction after 30 min (HR: 302 ± 17 vs. 312 ± 38; ejection fraction: 69 ± 3% vs. 73 ± 4%). GW1100 pretreatment, however, prevented lipid-rescue, with no recovery after 10 min. In the control group, lipid emulsion improved HR (215 ± 16 at 10 min) and fully rescued left ventricle function at 10 min (ejection fraction = 67 ± 8%, fractional shortening = 38 ± 6%).

CONCLUSIONS

G-protein-coupled receptor 40 is expressed in the rodent heart and is involved in cardioprotection mediated by lipid emulsion against ischemia/reperfusion injury and bupivacaine-induced cardiotoxicity.

Lipid Emulsion for Treating Local Anesthetic Systemic Toxicity

Lipid emulsion has been shown to be an effective treatment for systemic toxicity induced by local anesthetics, which is reflected in case reports. A systemic review and meta-analysis confirm the efficacy of this treatment. Investigators have suggested mechanisms associated with the lipid emulsion-mediated recovery of cardiovascular collapse caused by local anesthetic systemic toxicity; these mechanisms include lipid sink, a widely accepted theory in which highly soluble local anesthetics (particularly bupivacaine) are absorbed into the lipid phase of plasma from tissues (e.g., the heart) affected by local-anesthetic-induced toxicity; enhanced redistribution (lipid shuttle); fatty acid supply; reversal of mitochondrial dysfunction; inotropic effects; glycogen synthase kinase-3β phosphorylation associated with inhibition of the mitochondrial permeability transition pore opening; inhibition of nitric oxide release; and reversal of cardiac sodium channel blockade. The current review includes the following: 1) an introduction, 2) a list of the proposed mechanisms, 3) a discussion of the best lipid emulsion treatment for reversal of local anesthetic toxicity, 4) a description of the effect of epinephrine on lipid emulsion-mediated resuscitation, 5) a description of the recommended lipid emulsion treatment, and 6) a conclusion.

Levosimendan combined with epinephrine improves rescue outcomes in a rat model of lipid-based resuscitation from bupivacaine-induced cardiac arrest

Background

The effectiveness of a combination of a lipid emulsion with epinephrine in reversing local anesthetic-induced cardiac arrest has been confirmed. The combination of a lipid emulsion with levosimendan, was shown to be superior to administration of a lipid emulsion alone with regard to successful resuscitation. In this study, we compared the reversal effects of levosimendan, epinephrine, and a combination of the two agents in lipid-based resuscitation in a rat model of bupivacaine-induced cardiac arrest.

Methods

Fifty-four adult male Sprague-Dawley rats were subjected to bupivacaine (15 mg·kg⁻¹) –induced asystole and were then randomly divided into 3 groups. A lipid emulsion was used as the basic treatment, and administration of drug combinations varied in each group as follows: (1) levosimendan combined with epinephrine (LiEL); (2) epinephrine (LiE); and (3) levosimendan (LiL). The resuscitation outcomes were recorded and included the rate of return of spontaneous circulation (ROSC) and survival at 40 min, time to first heartbeat, time to ROSC, and cumulative dose of epinephrine. We calculated the wet-to-dry ratio of the lung, blood gas values at 40 min and bupivacaine concentration of cardiac tissue and plasma.

Results

The rates of ROSC in LiEL and LiE groups were higher than LiL group (P < 0.001; LiEL vs LiL, P = 0.001; LiE vs LiL, P = 0.007). The survival rate in LiEL group was higher than LiE group (P = 0.003; LiEL vs LiE, P = 0.008; LiEL vs LiL, P = 0.001). The time to first heart beat in LiEL group was shorter than LiE, LiL groups. (P < 0.001; LiE vs LiEL, P = 0.001; LiL vs LiEL, P < 0.001). The time to ROSC in LiEL group was shorter than LiE, LiL groups (P < 0.001; LiEL vs LiE, P < 0.001; LiEL vs LiL, P < 0.001). The result was similar for the bupivacaine concentration of cardiac tissue and plasma (cardiac tissue: P = 0.002; plasma: P = 0.011). Furthermore, there were significant differences in the blood-gas values at 40 min, wet-to-dry lung weight ratio, and ratio of damaged alveoli among groups. The LiEL group had the best result for all parameters (P < 0.01, P = 0.008, P < 0.001, respectively). Additionally, significantly less epinephrine was used in the LiEL group (P < 0.001).

Conclusions

Levosimendan combined with epinephrine may be superior to either drug alone for lipid-based resuscitation in a rat model of bupivacaine-induced cardiac arrest. The drug combination was associated with a higher survival rate as well as decreased epinephrine consumption and lung damage.

Electroacupuncture pretreatment induces rapid tolerance to bupivacaine cardiotoxicity in rats

BACKGROUND

Evidence suggests that electroacupuncture (EA) protects against arrhythmia and myocardial injury induced by myocardial ischaemia-reperfusion. However, to our knowledge, it remains unknown whether EA could alleviate bupivacaine-induced cardiotoxicity. Therefore, we aimed to explore the effect of EA pretreatment on bupivacaine-induced cardiac arrest and outcomes of cardiopulmonary resuscitation (CPR) in rats.

METHODS

24 adult male Sprague-Dawley rats were randomly divided into two groups: EA (n=12), and minimal acupuncture (MA) (n=12). Rats in both groups were needled at bilateral PC6, ST36, and ST40. Needles in the EA group were electrically stimulated for 60 min. ECG and invasive arterial blood pressure measurements were recorded. Two hours after EA or MA, 10 mg/kg bupivacaine was infused intravenously at a rate of 5 mg/kg/min in all rats. Rats suffering cardiac arrest were immediately subjected to CPR. At the end of the experiment, arterial blood samples were taken from surviving rats for blood gas analysis.

RESULTS

The time from bupivacaine infusion until 20% prolongation of the QRS and QT interval, and the time to cardiac arrest, were notably increased among the rats pretreated with EA. Moreover, EA pretreatment significantly improved mean arterial pressure and heart rate at all monitored points after bupivacaine infusion. The proportion of animals surviving was higher in the EA group (9/12) than the MA group (3/12) at the end of experiment (p=0.039).

CONCLUSIONS

Tolerance to bupivacaine-induced cardiotoxicity appeared to be increased following EA pre-treatment. The mechanism of action underlying the effects of EA on bupivacaine-induced cardiotoxicity requires further investigation.

Systematic review of the effect of intravenous lipid emulsion therapy for local anesthetic toxicity

BACKGROUND

Following national and regional recommendations, intravenous lipid emulsion (ILE) has become established in clinical practice as a treatment for acute local anesthetic (LA) toxicity, although evidence of efficacy is limited to animal studies and human case reports. A collaborative lipid emulsion workgroup was therefore established by the American Academy of Clinical Toxicology to review the evidence on the effect of ILE for LA toxicity.

METHODS

We performed a systematic review of the literature published through 15 December 2014. Relevant articles were determined based on pre-defined inclusion and exclusion criteria. Pre-treatment experiments, pharmacokinetic studies not involving toxicity and studies that did not address antidotal use of ILE were excluded.

RESULTS

We included 113 studies and reports. Of these, 76 were human and 38 animal studies. One publication included both a human case report and an animal study. Human studies included one randomized controlled crossover trial involving 16 healthy volunteers. The subclinical LA toxicity design did not show a difference in the effects of ILE versus saline. There was one case series and 73 case reports of ILE use in the context of toxicity (83 patients) including CNS depression or agitation (n = 45, 54%), seizures (n = 49, 59%), hypotension, hypertension, EKG changes, arrhythmias (n = 39, 47%), cardiac arrest (n = 18, 22%), cardiopulmonary resuscitation, and/or requirement for endotracheal intubation and/or mechanical ventilation (n = 35, 42%). There were 81 (98%) survivors including 63 (76%) with no reported sequelae from the LA poisoning or ILE, although the presence or absence of sequelae was not reported in 15 (18%) cases. Animal studies included 29 randomized controlled studies, three observational studies, five case series, and one case report; bupivacaine was used in 29 of these reports (76%). Of 14 controlled experiments in animals, eight showed improved survival or time to return of spontaneous circulation and five no benefit of ILE versus saline or non-ILE treatments. Combining ILE with epinephrine improved survival in five of the six controlled animal experiments that studied this intervention. The studies were heterogeneous in the formulations and doses of ILE used as well as the doses of LA. The body of the literature identified by this systematic review yielded only a very low quality of evidence.

CONCLUSION

ILE appears to be effective for reversal of cardiovascular or neurological features in some cases of LA toxicity, but there is currently no convincing evidence showing that ILE is more effective than vasopressors or to indicate which treatment should be instituted as first line therapy in severe LA toxicity.

Miniature Swine for Preclinical Modeling of Complexities of Human Disease for Translational Scientific Discovery and Accelerated Development of Therapies and Medical Devices

Noncommunicable diseases, including cardiovascular disease, diabetes, chronic respiratory disease, and cancer, are the leading cause of death in the world. The cost, both monetary and time, of developing therapies to prevent, treat, or manage these diseases has become unsustainable. A contributing factor is inefficient and ineffective preclinical research, in which the animal models utilized do not replicate the complex physiology that influences disease. An ideal preclinical animal model is one that responds similarly to intrinsic and extrinsic influences, providing high translatability and concordance of preclinical findings to humans. The overwhelming genetic, anatomical, physiological, and pathophysiological similarities to humans make miniature swine an ideal model for preclinical studies of human disease. Additionally, recent development of precision gene-editing tools for creation of novel genetic swine models allows the modeling of highly complex pathophysiology and comorbidities. As such, the utilization of swine models in early research allows for the evaluation of novel drug and technology efficacy while encouraging redesign and refinement before committing to clinical testing. This review highlights the appropriateness of the miniature swine for modeling complex physiologic systems, presenting it as a highly translational preclinical platform to validate efficacy and safety of therapies and devices.

The possible role of intravenous lipid emulsion in the treatment of chemical warfare agent poisoning

Organophosphates (OPs) are cholinesterase inhibitors that lead to a characteristic toxidrome of hypersecretion, miosis, dyspnea, respiratory insufficiency, convulsions and, without proper and early antidotal treatment, death. Most of these compounds are highly lipophilic. Sulfur mustard is a toxic lipophilic alkylating agent, exerting its damage through alkylation of cellular macromolecules (e.g., DNA, proteins) and intense activation of pro-inflammatory pathways. Currently approved antidotes against OPs include the peripheral anticholinergic drug atropine and an oxime that reactivates the inhibited cholinesterase. Benzodiazepines are used to stop organophosphate-induced seizures. Despite these approved drugs, efforts have been made to introduce other medical countermeasures in order to attenuate both the short-term and long-term clinical effects following exposure. Currently, there is no antidote against sulfur mustard poisoning. Intravenous lipid emulsions are used as a source of calories in parenteral nutrition. In recent years, efficacy of lipid emulsions has been shown in the treatment of poisoning by fat-soluble compounds in animal models as well as clinically in humans. In this review we discuss the usefulness of intravenous lipid emulsions as an adjunct to the in-hospital treatment of chemical warfare agent poisoning.

Hemodynamic changes with high infusion rates of lipid emulsion. Experimental study in swine

PURPOSE

To evaluate hemodynamic changes caused by sole intravenous infusion of lipid emulsion with doses recommended for treatment of drug-related toxicity.

METHODS

Large White pigs underwent general anesthesia, tracheal intubation was performed, and mechanical ventilation was instituted. Hemodynamic variables were recorded using invasive blood pressure and pulmonary artery catheterization. Baseline hemodynamic measurements were obtained after a 30-minute stabilization period. An intravenous bolus injection of 20% lipid emulsion at 1.5 ml/kg was administered. Additional hemodynamic measurements were made after 1 minute, followed by a continuous intravenous lipid infusion of 0.25 ml/kg/min. Further measurements were carried out at 10, 20 and 30 minutes, when the infusion was doubled to 0.5 ml/kg/min. Assessment of hemodynamic changes were then made at 40, 50 and 60 minutes.

RESULTS

Lipid infusion did not influence cardiac output or heart rate, but caused an increase in arterial blood pressure, mainly pulmonary blood pressure due to increased vascular resistance. Ventricular systolic stroke work consequently increased with greater repercussions on the right ventricle.

CONCLUSION

In doses used for drug-related toxicity, lipid emulsion cause significant hemodynamic changes with hypertension, particularly in the pulmonary circulation and increase in vascular resistance, which is a factor to consider prior to use of these solutions.

Hypersensitivity reactions to intravenous lipid emulsion in swine: relevance for lipid resuscitation studies

BACKGROUND

Reports in the recent experimental literature have provided contradicting results in different animal species regarding the efficacy of IV lipid emulsion (ILE) in the reversal of cardiovascular and central nervous system symptoms of local anesthetic and other lipophilic drug overdoses. In particular, ILE seemed to be effective in rats, rabbits, dogs, and humans, but not in swine, for which it not only failed to reverse the adverse effects of anesthetics, but the animals also developed a generalized cutaneous mottling or a dusky appearance immediately after ILE, suggestive of another type of toxicity. The latter symptoms arise in complement (C) activation-related pseudoallergy, a hypersensitivity reaction to particulate drugs and agents.

METHODS

Ten Yorkshire swine (15-20 kg) were sedated with ketamine and anesthetized with isoflurane. ILE 1.5 and 5 mL/kg 20% was administered via the ear vein while pulmonary arterial pressure, systemic arterial blood pressure, electrocardiogram, and end-tidal CO2 were recorded continuously. Thromboxane was measured in blood collected at baseline and 2 and 10 minutes after injections. Complement activation by lipid emulsion was also assessed in vitro with soluble terminal complement complex (SC5b-9) and sheep red blood cell assays.

RESULTS

Significant increases were observed in the pulmonary pressure (median [interquartile range]) within minutes after the administration of ILE, both at doses 1.5 and 5 mL/kg (15 [12-16.5] to 18.5 [16-20] mm Hg, P = 0.0058 and 15.5 [13-17.25] to 39.5 [30.5-48.5], respectively). The systemic arterial blood pressure increased, and the heart rate decreased after both injections. Thromboxane B2 concentration (median [interquartile range]) in the blood plasma increased from a baseline of 617.3 [412.4-920] to 1132 [597.9-1417] pg/mL (P = 0.0055) and from 1276 [1200-2581] to 4046 [2946-8442] pg/mL (P = 0.0017) after the administration of 1.5 and 5 mL/kg ILE, respectively. Intralipid did not cause in vitro complement activation in human serum.

CONCLUSIONS

ILE causes clinically significant hemodynamic changes in pigs, in concert with significant increases in the plasma thromboxane concentration. However, the in vitro tests did not confirm involvement of the complement system in human sera, leaving the underlying mechanism of these findings in doubt. Nonetheless, the observed hemodynamic and biochemical effects of ILE serve as a caveat that the pig is not an ideal model for the study of interventions involving ILE.

The effect of fat emulsion on hemodynamics following treatment with propranolol and clonidine in anesthetized rats

OBJECTIVES

There is evidence indicating that intravenous fatty emulsion (IFE) is beneficial in restoring circulatory function in certain types of drug overdose. The authors investigated the hemodynamic effects of IFE compared to epinephrine in rats treated with propranolol and clonidine.

METHODS

Anesthetized male Sprague-Dawley rats were instrumented for measurement of hemodynamics. Rats were randomly assigned to one of six groups (n = 6-8), and each received a clonidine infusion (150 μg/kg) or an equivalent volume of normal saline (0.9% NaCl) over 1 hour. Each rat then received normal saline (1.0 mL/kg) or propranolol (15 to 20 mg/kg). Thereafter, each rat received a dose of IFE (20% solution; 1.0 mL/kg) or epinephrine (2.0 μg/kg) or an equivalent volume of normal saline (1.0 mL/kg).

RESULTS

Propranolol alone or with clonidine significantly (p < 0.05) reduced a number of hemodynamic parameters (mean arterial pressure, 37% to 70%; heart rate, 30% to 51%; cardiac contractility [dP/dtmax], 50% to 67%; and abdominal aortic blood flow, 50% to 83%), while increasing PR intervals (65% to 85%) and QTc intervals (26% to 64%). Saline and epinephrine treatment after propranolol and clonidine combined resulted in no survivors in saline and two out of six in epinephrine group. IFE resulted in significant survival (seven out of eight) for 30 minutes in rats treated with propranolol alone, and propranolol combined with clonidine (seven out of eight).

CONCLUSIONS

These data demonstrate that IFE is effective for resuscitating rats overdosed on propranolol combined with clonidine. The effect of IFF is unlikely due to a direct positive inotropic or chronotropic action on the myocardium. IFE is also more effective than epinephrine treatment in this paradigm.

Age and bupivacaine plasma concentrations following radical cystectomy

PURPOSE

Continuous epidural analgesia with bupivacaine for postoperative analgesia can increase its plasma concentrations. Whether this effect can be aggravated with increasing age is unknown. Therefore, bupivacaine concentrations were prospectively monitored in patients undergoing radical cystectomies.

METHODS

We analyzed plasma concentrations of bupivacaine in 38 consecutive patients scheduled for radical cystectomy. All patients received general and epidural anesthesia (10 ml bupivacaine 0.5% followed by bupivacaine 0.375% every 90 min) and postoperative continuous epidural analgesia (bupivacaine 0.25% with sufentanil 0.5 μg/ml). For 4 subsequent days, bupivacaine plasma concentrations were measured and the correlation of bupivacaine plasma concentrations with the patient's age were analyzed. Data (mean ± SD) were analyzed by 2-way ANOVA with post hoc analysis or regression analysis.

RESULTS

The median age of the patients was 70 years (range 41-86). Postoperatively, bupivacaine plasma concentrations increased significantly. No correlation of plasma concentrations and age could be found. Maximal bupivacaine concentrations of the younger patients were not different from the older patients. No neurological or cardiovascular symptoms of bupivacaine intoxication were found.

CONCLUSION

In conclusion, continuous epidural administration of bupivacaine leads to increasing plasma concentrations. No age dependent differences in bupivacaine plasma concentrations could be found. Therefore, in our patients with intact liver function, we did not find a reason for an age-related restriction in the use of continuous epidural analgesia.

The effects of levosimendan and dobutamine in experimental bupivacaine-induced cardiotoxicity

Background

Accidental intravenous exposure to bupivacaine is highly cardiotoxic and may lead to death. Positive inotropic agents are usually utilized in resuscitative efforts. We have compared the efficacy of levosimendan, a novel inotropic agent, with dobutamine and their combination in a rat model of bupivacaine intoxication.

Methods

Twenty-eight male Wistar albino rats weighing between 250-300 g were divided into these four groups: control (C), levosimendan (L), dobutamine (D) and dobutamine+levosimendan (D+L). Bupivacaine was administered at a dose of 3 mg/kg/min until cardiac arrest occurred or for 120 min. ECG, heart rate, blood pressure, arterial blood gases, and end tidal CO₂ levels were monitored. Levosimendan was administered as a bolus of 12 μg/kg for 10 min and continued as an infusion at 0.3 μg/kg/min. Dobutamine was infused at a dose of 3 μg/kg/min. The time required for a 50% and 75% decrease in heart rate and blood pressure with a total time to cardiac arrest and bupivacaine dose for obtaining cardiac arrest were analyzed.

Results

Time periods for heart rate reductions of 50% and 75% were significantly longer in groups L (903, 1198 s), D (984, 1542 s) and L+D (1705, 3152 s) compared with the control group (345, 538 s p < 0.001). Median times to mean blood pressure reductions of 50% and 75% were 399 - 504 s in the control group, 1005 -1204 s in group L, 685 - 1009 s in group D and 1544- 2982 s in group L+D, and the difference was significant compared with the control group. Median time duration to asystole was 703 s in the control group compared with 1385 s in group L, 1789 s in group D and 3557 s in group L+D. Time to cardiac arrest was significantly higher in all 3 study groups. It was also significantly higher in the L+D group compared with both groups L and D separately.

Conclusion

A combination of dobutamine with levosimendan significantly increased survival times in this bupivacaine-induced toxicity rat model compared with the control, levosimendan, and dobutamine groups.

Insulin/glucose infusion successfully resuscitates bupivacaine-induced sudden-onset circulatory collapse in dogs

PURPOSE

In previous studies, insulin reversed the cardiac toxicity gradually induced by a continuous infusion of bupivacaine. In this randomized controlled study, we intended to simulate a more relevant clinical situation by injecting bupivacaine rapidly as a bolus to induce sudden-onset circulatory collapse in dogs. We then evaluated the insulin effect.

METHODS

Bupivacaine (10 mg.kg(-1) iv) was rapidly administered intravenously to 12 dogs. At the onset of circulatory collapse (defined as a mean arterial pressure [MAP] of 30 mmHg), external chest compression was initiated. Insulin (2 U.kg(-1) iv) was given to the insulin-glucose (IG) group (n = 6) and the same volume of 0.9% saline was given to the control (C) group (n = 6). The primary outcome was successful resuscitation defined as both MAP ≥ 60 mmHg and sinus rhythm on an electrocardiogram that lasted ≥ 60 sec. Hemodynamic and blood variables were measured, including cardiac output and electrocardiogram intervals.

RESULTS

All IG dogs were successfully resuscitated within 15 (3) min, whereas none of the control dogs were resuscitated (P = 0.002). After circulatory collapse, the average MAP was higher in group IG than in group C (P = 0.006).

CONCLUSION

Insulin effectively reversed the sudden-onset circulatory collapse in dogs caused by an intravenous bolus injection of bupivacaine.

Fatty-acid oxidation and calcium homeostasis are involved in the rescue of bupivacaine-induced cardiotoxicity by lipid emulsion in rats

OBJECTIVES

Lipid emulsion has been shown to be effective in resuscitating bupivacaine-induced cardiac arrest but its mechanism of action is not clear. Here we investigated whether fatty-acid oxidation is required for rescue of bupivacaine-induced cardiotoxicity by lipid emulsion in rats. We also compared the mitochondrial function and calcium threshold for triggering of mitochondrial permeability transition pore opening in bupivacaine-induced cardiac arrest before and after resuscitation with lipid emulsion.

DESIGN

Prospective, randomized animal study.

SETTING

University research laboratory.

SUBJECTS

Adult male Sprague-Dawley rats.

INTERVENTIONS

Asystole was achieved with a single dose of bupivacaine (10 mg/kg over 20 secs, intravenously) and 20% lipid emulsion infusion (5 mL/kg bolus, and 0.5 mL/kg/min maintenance), and cardiac massage started immediately. The rats in CVT-4325 (CVT) group were pretreated with a single dose of fatty-acid oxidation inhibitor CVT (0.5, 0.25, 0.125, or 0.0625 mg/kg bolus intravenously) 5 mins prior to inducing asystole by bupivacaine overdose. Heart rate, ejection fraction, fractional shortening, the threshold for opening of mitochondrial permeability transition pore, oxygen consumption, and membrane potential were measured. The values are mean ± SEM.

MEASUREMENTS AND MAIN RESULTS

Administration of bupivacaine resulted in asystole. Lipid Emulsion infusion improved the cardiac function gradually as the ejection fraction was fully recovered within 5 mins (ejection fraction=64±4% and fractional shortening=36±3%, n=6) and heart rate increased to 239±9 beats/min (71% recovery, n=6) within 10 mins. Lipid emulsion was only able to rescue rats pretreated with low dose of CVT (0.0625 mg/kg; heart rate~181±11 beats/min at 10 mins, recovery of 56%; ejection fraction=50±1%; fractional shortening=26±0.6% at 5 mins, n=3), but was unable to resuscitate rats pretreated with higher doses of CVT (0.5, 0.25, or 0.125 mg/kg). The calcium-retention capacity in response to Ca²⁺ overload was significantly higher in cardiac mitochondria isolated from rats resuscitated with 20% lipid emulsion compared to the group that did not receive Lipid Emulsion after bupivacaine overdose (330±42 nmol/mg vs. 180±8.2 nmol/mg of mitochondrial protein, p<.05, n=3 in each group). The mitochondrial oxidative rate and membrane potential were similar in the bupivacaine group before and after resuscitation with lipid emulsion infusion.

CONCLUSIONS

Fatty-acid oxidation is required for successful rescue of bupivacaine-induced cardiotoxicity by lipid emulsion. This rescue action is associated with inhibition of mitochondrial permeability transition pore opening.

The Use of IV Lipid Emulsion for Lipophilic Drug Toxicities

IV lipid emulsion (ILE) therapy is emerging as a potential antidote for lipophilic drug toxicities in both human and veterinary medicine. ILE has already gained acceptance in human medicine as a treatment of local anesthetic systemic toxicity, but its mechanism of action, safety margins, and standardized dosing information remains undetermined at this time. Experimental and anecdotal use of ILE in the human and veterinary literature, theorized mechanisms of action, current dosing recommendations, potential adverse effects, and indications for use in human and veterinary emergency medicine are reviewed herein.

Intravenous Lipid Emulsion for the Treatment of Drug Toxicity

Intravenous lipid emulsion (ILE) has emerged as a powerful antidote for the treatment of drug toxicity in the past decade. Initial efficacy of ILE was shown in the setting of local anesthetic systemic toxicity (LAST), but recent case reports suggest its consideration in a variety of other drug toxicities. In this review, we will summarize the experimental evidence as well as the clinical experience in using ILE as an antidote. Specifically, we will look at the evidence for using ILE in LAST as well as toxicity due to beta-blockers, calcium-channel blockers, and tricyclic antidepressants. We will also review the current dosing recommendations as well as potential side effects of ILE as an antidote.

Anesthesia advanced circulatory life support

PURPOSE

The constellation of advanced cardiac life support (ACLS) events, such as gas embolism, local anesthetic overdose, and spinal bradycardia, in the perioperative setting differs from events in the pre-hospital arena. As a result, modification of traditional ACLS protocols allows for more specific etiology-based resuscitation.

PRINCIPAL FINDINGS

Perioperative arrests are both uncommon and heterogeneous and have not been described or studied to the same extent as cardiac arrest in the community. These crises are usually witnessed, frequently anticipated, and involve a rescuer physician with knowledge of the patient's comorbidities and coexisting anesthetic or surgically related pathophysiology. When the health care provider identifies the probable cause of arrest, the practitioner has the ability to initiate medical management rapidly.

CONCLUSIONS

Recommendations for management must be predicated on expert opinion and physiological understanding rather than on the standards currently being used in the generation of ACLS protocols in the community. Adapting ACLS algorithms and considering the differential diagnoses of these perioperative events may prevent cardiac arrest.

Effect of intravenous lipid emulsion on bupivacaine plasma concentration in humans

Intravenous lipid emulsion is the recommended treatment for severe local anaesthetic intoxication. Lipid emulsion may entrap lipid soluble drugs by functioning as a 'lipid sink', but its effect on bupivacaine pharmacokinetics remains unknown. In this randomised, double-blind, crossover study, eight healthy male volunteers were infused bupivacaine 0.5mg.kg(-1) intravenously over 20 min, followed by an infusion of either intravenous lipid emulsion or Hartmann's solution for 30 min. At 20 and 30 min after the start of the infusion, the total plasma bupivacaine concentration was lower while receiving lipid emulsion than Hartmann's solution (mean difference 111 (95% CI 55-167) μg.l(-1) and 75 (95% CI 26-124 μg.l(-1) at 20 and 30 min, respectively; p<0.02). However, there were no differences in un-entrapped (non-lipid bound) or free (non-protein bound) bupivacaine plasma concentrations during the infusion. Intravenous lipid emulsion infusion reduced the context-sensitive half-life of total plasma bupivacaine from 45 (95% CI 32-76)min to 25 (95% CI 20-33)min; p=0.01. We observed no significant adverse effects of lipid emulsion. In conclusion, lipid emulsion may slightly increase the rate of bupivacaine tissue distribution. No 'lipid sink' effect was observed with the non-toxic dose of bupivacaine used.

Resuscitation strategies from bupivacaine-induced cardiac arrest

OBJECTIVES

Local anesthetic (LA) intoxication with cardiovascular arrest is a potential fatal complication of regional anesthesia. Lipid resuscitation has been recommended for the treatment of LA-induced cardiac arrest. Aim of the study was to compare four different rescue regimens using epinephrine and/or lipid emulsion and vasopressin to treat cardiac arrest caused by bupivacaine intoxication.

METHODS

Twenty-eight piglets were randomized into four groups (4 × 7), anesthetized with sevoflurane, intubated, and ventilated. Bupivacaine was infused with a syringe driver via central venous catheter at a rate of 1 mg·kg(-1)·min(-1) until circulatory arrest. Bupivacaine infusion and sevoflurane were then stopped, chest compression was started, and the pigs were ventilated with 100% oxygen. After 1 min, epinephrine 10 μg·kg(-1) (group 1), Intralipid(®) 20% 4 ml·kg(-1) (group 2), epinephrine 10 μg·kg(-1) + Intralipid(®) 4 ml·kg(-1) (group 3) or 2 IU vasopressin + Intralipid(®) 4 ml·kg(-1) (group 4) were administered. Secondary epinephrine doses were given after 5 min if required.

RESULTS

Survival was 71%, 29%, 86%, and 57% in groups 1, 2, 3, and 4. Return of spontaneous circulation was regained only by initial administration of epinephrine alone or in combination with Intralipid(®). Piglets receiving the combination therapy survived without further epinephrine support. In contrast, in groups 2 and 4, return of spontaneous circulation was only achieved after secondary epinephrine rescue.

CONCLUSIONS

In cardiac arrest caused by bupivacaine intoxication, first-line rescue with epinephrine and epinephrine + Intralipid(®) was more effective with regard to survival than Intralipid(®) alone and vasopressin + Intralipid(®) in this pig model.

Use of intravenous lipid emulsions for treating certain poisoning cases in small animals

Intravenous lipid emulsion (ILE) infusions have become an emerging treatment modality in managing intoxications of veterinary patients. The advantages of ILE include an apparent wide margin of safety, relatively low cost, long shelf-life, and ease of administration. Based on limited case and anecdotal reports, ILEs have shown promise in the management of toxicoses from a variety of lipophilic agents, including drugs and pesticides. More studies are needed to determine optimum dosing regimens and identify potential adverse effects from the antidotal use of ILE in veterinary medicine.

Comparison of epinephrine vs lipid rescue to treat severe local anesthetic toxicity - an experimental study in piglets

OBJECTIVES

Local anesthetic (LA) intoxication with severe hemodynamic compromise is a potential catastrophic event. Lipid resuscitation has been recommended for the treatment of LA-induced cardiac arrest. However, there are no data about effectiveness of Intralipid for the treatment of severe cardiovascular compromise prior to cardiac arrest. Aim of this study was to compare effectiveness of epinephrine and Intralipid for the treatment of severe hemodynamic compromise owing to bupivacaine intoxication.

METHODS

  Piglets were anesthetized with sevoflurane, intubated, and ventilated. Bupivacaine was infused with a syringe driver via a central venous catheter at a rate of 1 mg·kg(-1) ·min(-1) until invasively measured mean arterial pressure (MAP) dropped to 50% of the initial value. Bupivacaine infusion was then stopped, and epinephrine 3 μg·kg(-1) (group 1), Intralipid(®) 20% 2 ml·kg(-1) (group 2), or Intralipid 20% 4 ml·kg(-1) (group 3) was immediately administered. Survival, hemodynamic course, and ET(CO2) were recorded.

RESULTS

  Twenty-one piglets (3 × 7), with median age of 26 days (19-43) and weighing 4.9 kg (4.3-5.8), were investigated. All animals in group 1 (100%) but only four of seven (57%) piglets in group 2 and group 3, respectively, survived. Normalization of hemodynamic parameters (HR, MAP) and ET(CO2) was fastest in group 1 with all piglets achieving HR and MAP values at or above baseline within 1 min.

CONCLUSION

  For the treatment of severe hemodynamic compromise owing to bupivacaine intoxication in piglets, first-line rescue with epinephrine was more effective than Intralipid with regard to survival as well as normalization of hemodynamic parameters and ET(CO2) .

Local anesthetic systemic toxicity: prevention and treatment

Anesthesia is a sine qua non for most surgeries. Like any medical advance, progress in regional anesthesia has not come without its share of complications, including a spectrum extending from localized nerve injury to systemic cardiovascular toxicity and death. This article discusses the mechanisms and clinical presentation, prevention, treatment, and future trends of local anesthetic systemic toxicity. The adverse effects of lipid emulsion therapy are also included.

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.

[Bupivacaine toxicity and propofol anesthesia : animal study on intravascular bupivacaine injection]

BACKGROUND

Several reports have confirmed the efficacy of Intralipid® (containing soya bean oil, egg phospholipids, glycerin and water) in the therapy of systemic local anesthetic intoxication. Pretreatment with Intralipid® shifted the dose-response to bupivacaine-induced asystole in rats. Whether intravenous anesthesia with propofol in the widely used medium chain triglyceride lipid emulsion increases the therapeutic range of systemically administered bupivacaine or not is unknown and was investigated in this study.

METHODS

A total of 30 piglets aged 2-6 weeks and weighing 4.5-6.5 kg were randomized into 2 groups and anesthetized with sevoflurane (group S) alone or with propofol 10 mg/kg body weight (BW)/h plus sevoflurane (group PS). After 60 min of steady state anesthesia arterial blood was sampled for assessment of blood gases, acid-base state and triglyceride plasma concentrations. Thereafter bupivacaine 0.125% was continuously infused by an infusion syringe pump through a central venous line at a rate of 4 mg/kg BW/min until invasively measured mean arterial pressure (MAP) was reduced by 50% of initial value. The bupivacaine infusion was stopped, blood for assessment of bupivacaine plasma concentration was drawn and the spontaneous hemodynamic course was observed. Resuscitation was not attempted. Results are presented as median and range. The Mann-Whitney U-test was used to assess differences between the two groups for triglyceride as well as for bupivacaine plasma concentrations measured at MAP 50%. A p-value≤0.05 was considered to be significant.

RESULTS

Baseline conditions (arterial blood pH, plasma protein and triglyceride plasma concentrations) did not differ significantly between the two groups. After 1 h of anesthesia, triglyceride plasma concentrations were significantly increased in group PS (median 0.69 mmol/l) compared to the corresponding baseline values (median 0.14 mmol/l; p<0.001) and to the 1 h values of group S (median 0.16 mmol/l; p<0.001). The total amount of bupivacaine administered was 9 mg/kg BW in both groups (6-13 mg/kg BW in group S, 5-13 mg/kg BW in group PS). Resulting bupivacaine plasma concentrations were 180 μmol/l (83-686 μmol/l) in group S and 185 μmol/l (130-465 μmol/l) in group PS. However, the total amount of bupivacaine administered and bupivacaine plasma concentrations at MAP 50% did not reveal statistically significant differences between the two groups but a huge variability of both parameters within each group was observed. None of the 30 piglets spontaneously recovered and they died from pulseless electrical activity or from asystolic cardiac arrest. The time from MAP 50% until cardiac arrest demonstrated a large variability but did not reveal significant differences between the two groups. The time to cardiac arrest was similar in both groups.

CONCLUSION

Medium/long chain triglyceride lipid emulsion (50:50) as widely used in propofol solutions did not increase therapeutic safety in cases of intravascular bupivacaine administration in this piglet model.