Long-chain triglycerides improve recovery from myocardial stunning in conscious dogs

The effect of intravenous lipid emulsion (ILE) on the pharmacokinetic/toxicokinetic dispositions of ivermectin and carprofen in rabbits

Intravenous lipid emulsion (ILE) has been widely used as an effective antidote in both veterinary and human medicine for the treatment of acute intoxications caused by drugs and pesticides with high lipid solubility. This study was conducted to investigate the effect of ILE co-administration on the kinetic dispositions of ivermectin (IVM) and carprofen (CRP) following intravenous bolus administration at subtoxic doses in rabbits.Twenty-four male New Zealand rabbits weighing 2.78 ± 0.2 kg were used in this study. Rabbits were divided into four groups (Group 1: IVM and Group 2: IVM + ILE or Group 3: CRP and Group 4: CRP + ILE), each group consisting of 6 animals. In the IVM study, Group 1 received IVM (0.6 mg/kg) alone while Group 2 received IVM (0.6 mg/kg) and ILE (2.5 ml/kg). In the CRP study, Group 3 received CRP (12 mg/kg) alone while Group 4 received CRP (12 mg/kg) and ILE (2.5 ml/kg). In both drug groups, ILE was administered 3 times as an i.v. bolus at the 10th min and repeated 4th and 8th h after the drug administration. Blood samples were collected from the auricular vein at various times after drug administration. The drug concentrations in plasma samples were determined by high-pressure liquid chromatography. Kinetic parameters were calculated using a non-compartmental model for both CRP and IVM.The C0 and area under the concentration-time curve from zero up to ∞ (AUC0-∞) values were significantly greater with ILE co-administration (2136 ng/ml and 360.84 ng.d/ml) compared to the IVM alone (1340.63 ng/ml and 206 ng.d/ml), respectively. Moreover, the volume of distribution (Vdss) and clearance (Cl) of IVM were reduced by approximately 42% and 46% with ILE co-administration compared to IVM alone resulting in a reduction of the distribution and slower elimination, respectively. Similar differences in C0, and Vdss values were also observed in CRP with ILE co-administration compared to CRP alone. ILE co-administration changed significantly the kinetic profile of both IVM and CRP in rabbits, supporting the lipid sink theory in which highly lipid-soluble compounds are absorbed into the lipid phase of plasma from peripheral organs such as the heart and brain affected by the acute toxicity of the compounds.

Lipid emulsions in the treatment of intoxications by local anesthesics and other drugs. Review of mechanisms of action and recommendations for use

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

Successful treatment of ivermectin overdose in a bearded dragon (Pogona vitticeps) using gastric lavage and intravenous lipid emulsion

OBJECTIVE

To describe the clinical signs and outcome following ivermectin overdose in a bearded dragon. This case also describes the novel use of intravenous lipid emulsion (ILE) as a rescue therapy in reptiles, as well as the use of aggressive gastrointestinal decontamination.

CASE SUMMARY

A 4-year-old female intact bearded dragon (Pogona vitticeps) (0.6 kg) was admitted to the ICU at a specialty hospital following accidental overdose of 40 mg (66.7 mg/kg) of ivermectin enterally. The patient was physically inverted to allow passive reflux of the medication, then sedated for gastric lavage. A 20% ILE was administered intravenously due to the high risk for fatality. Additional treatments included 2 doses of activated charcoal, as well as SC fluids, enteral nutrition, and sucralfate. The patient was profoundly sedate until day 4 when mild improvements in mentation were noted. The patient started ambulating on its own on day 6 and was discharged from the hospital on day 13. The patient was alive 720 days postdischarge.

NEW OR UNIQUE INFORMATION PROVIDED

This is the first case report describing the events following ivermectin overdose and the use of ILE therapy and activated charcoal in a bearded dragon. These therapies were tolerated with no adverse effects noted in this patient. This report provides evidence that complete recovery from ivermectin overdose is possible.

Lipid emulsions in the treatment of intoxications by local anesthesics and other drugs. Review of mechanisms of action and recommendations for use

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

Supplement of Lipid Emulsion to Epinephrine Improves Resuscitation Outcomes of Asphyxia-Induced Cardiac Arrest in Aged Rats

Objective

The goal of the study was to investigate the efficacy of lipid supplement to epinephrine-based therapy in resuscitation of asphyxia-induced cardiac arrest in aged rats.

Methods

The study included two parts: in experiment A, rats underwent asphyxial cardiac arrest and cardiopulmonary resuscitation, randomized to receive epinephrine and normal saline (control group, n=22), epinephrine and intralipid 20% (long-chain triglycerides (LCT) group, n=22) or epinephrine and lipovenoes 20% (LCT/medium-chain triglcerides (MCT) group, n=22). Return of spontaneous circulation, recurrence of asystole after resuscitation, hemodynamic metrics, arterial blood gas values, neurological assessment score and indexes of pulmonary transudation were recorded. In experiment B, rats using the same model and resuscitation protocol were randomly divided into 21 groups: Control ₀, Control ₂₀, Control ₄₀, Control ₆₀, Control ₈₀, Control ₁₀₀, Control ₁₂₀, LCT ₀, LCT ₂₀, LCT ₄₀, LCT ₆₀, LCT ₈₀, LCT ₁₀₀, LCT ₁₂₀, LCT/MCT ₀, LCT/MCT ₂₀, LCT/MCT ₄₀, LCT/MCT ₆₀, LCT/MCT ₈₀, LCT/MCT ₁₀₀ and LCT ₁₂₀ (n=10, the subscripts represent respective endpoint of observation in minutes). Myocardial bioenergetics were determined.

Results

In experiment A, the LCT and LCT/MCT groups had a shorter time to return of spontaneous circulation (ROSC) (P=0.001and P<0.001, respectively) and higher survival rate (P=0.033 and P=0.014, respectively) compared with the Control group. The LCT/MCT group had higher MAP (P<0.001 and P=0.001, respectively), HR (P<0.001 and P=0.004, respectively) and RPP (P<0.001 and P<0.001, respectively) compared with the Control and LCT groups, respectively. In experiment B, the LCT/MCT group had a higher energy charge compared with the control group at 20 (P<0.001) and 40 (P<0.001) minutes. The LCT group had higher energy charge compared with the Control group at 40 (P<0.001) and 60 (P<0.001) minutes.

Conclusion

The supplement of lipid emulsion to epinephrine improves resuscitation outcomes of asphyxia-induced cardiac arrest than epinephrine alone in our in vivo model of aged rat. LCT/MCT emulsion may be superior to LCT emulsion in epinephrine-based resuscitation.

Literature review of the evidence regarding intravenous lipid administration in drug-induced cardiotoxicity

Introduction: Intravenous lipid emulsion (ILE) administration is capable of reversing the acute cardiac and neurological toxicity caused by local anesthetic agents. In recent years, ILE has also been explored as a potential antidote for cardiotoxicity caused by non-anesthetic agents too. Areas covered: The potential mechanisms, safety, and efficacy of this approach are considered. Data were sought from published reports listed in PubMed and EMBASE, and abstracts of meetings of the North American Congress of Clinical Toxicology and European Association of Poisons Centres and Clinical Toxicologists. There were reports involving 298 patients where ILE has been administered for severe drug toxicity. Clinical improvement was observed in 57 of 59 patients with local anesthetic toxicity (96.6%); there were 239 patients where toxicity was due to non-anesthetic agents, and ILE apparently improved clinical outcome in 215 (72.1%). Expert opinion: Response rates were similar between ILE treated toxicity caused by lipid soluble and non-lipid soluble drugs. Potential adverse effects of ILE include interference with laboratory assays, acute pancreatitis, and adult respiratory distress syndrome, although the rate of occurrence is difficult to ascertain.

The Mechanisms Underlying Lipid Resuscitation Therapy

The experimental use of lipid emulsion for local anesthetic toxicity was originally identified in 1998. It was then translated to clinical practice in 2006 and expanded to drugs other than local anesthetics in 2008. Our understanding of lipid resuscitation therapy has progressed considerably since the previous update from the American Society of Regional Anesthesia and Pain Medicine, and the scientific evidence has coalesced around specific discrete mechanisms. Intravenous lipid emulsion therapy provides a multimodal resuscitation benefit that includes both scavenging (eg, the lipid shuttle) and nonscavenging components. The intravascular lipid compartment scavenges drug from organs susceptible to toxicity and accelerates redistribution to organs where drug (eg, bupivacaine) is stored, detoxified, and later excreted. In addition, lipid exerts nonscavenging effects that include postconditioning (via activation of prosurvival kinases) along with cardiotonic and vasoconstrictive benefits. These effects protect tissue from ischemic damage and increase tissue perfusion during recovery from toxicity. Other mechanisms have diminished in favor based on lack of evidence; these include direct effects on channel currents (eg, calcium) and mass-effect overpowering a block in mitochondrial metabolism. In this narrative review, we discuss these proposed mechanisms and address questions left to answer in the field. Further work is needed, but the field has made considerable strides towards understanding the mechanisms.

ω-3 Polyunsaturated Fatty Acid Postconditioning Protects the Isolated Perfused Rat Heart from Ischemia-Reperfusion Injury

AIMS

This study aimed to evaluate the cardioprotective effects of ω-3 polyunsaturated fatty acids (PUFAs) postconditioning against ischemia-reperfusion (I/R) injury.

METHODS

Sixty Sprague-Dawley rats were randomly divided into 4 groups (n = 15 for each) and used to generate the Langendorff isolated perfused rat heart model. The sham group received a continuous perfusion of 150 min. The remaining three I/R-treated groups sequentially received a 30-min perfusion, a 30-min cardioplegia, and a 90-min reperfusion. The I/R-ischemic preconditioning (IP) group additionally received three cycles of 20-s reperfusion and 20-s coronary reocclusion preceded the 90 min of reperfusion. The I/R-ω group were perfused with ω-3 PUFAs for 15 min before the 90 min of reperfusion. The myocardial infarct size, the degree of mitochondrial damage, the antioxidant capacity of the myocardium, and the cardiac functions during reperfusion were compared among groups.

RESULTS

Compared with the I/R group, the I/R-ω group had significantly reduced myocardial infarct size, reduced levels of lactate dehydrogenase and malondialdehyde, elevated superoxide dismutase level, and elevated rising (+dp/dtmax) and descending (-dp/dtmax) rate of left ventricular pressure. The I/R-ω group had a significantly lower rate of mitochondrial damage in myocardial tissue compared with the I/R and I/R-IP groups.

CONCLUSION

ω-3 PUFA postconditioning possesses good cardioprotective effects and may be developed into a therapeutic strategy for myocardial I/R injury.

Postconditioning with Intralipid emulsion protects against reperfusion injury in post-infarct remodeled rat hearts by activation of ROS-Akt/Erk signaling

The clinically used lipid emulsion Intralipid (ILE) reduces ischemia reperfusion injury in healthy rodent hearts. We tested whether ILE is cardioprotective in postinfarct remodeled hearts. Post-infarct remodeled and sham Sprague-Dawley rat hearts were perfused in working mode and subjected to ischemia (15 minutes) and reperfusion (30 minutes). Left ventricular (LV) work was measured in hearts that were untreated or that received ILE (1%) postconditioning administered at the onset of reperfusion, or the reactive oxygen species (ROS) scavenger N-(2-mercaptopropionyl)-glycine (10 μM) alone or in combination with ILE. Mitochondrial O₂ consumption was measured in LV muscle fibers. Acetyl CoA production was calculated from the oxidation of [U-¹⁴C]glucose and [9,10-³H]palmitate. ROS production was assessed by loss of aconitase activity as well as by release of hydrogen peroxide. Phosphorylation of Akt, Erk1/2, and STAT3 were used to evaluate protection signaling. Remodeled hearts exhibited LV dysfunction and signs of hypertrophy consistent with significant postinfarct remodeling. ILE postconditioning enhanced the recovery of postischemic LV function in remodeled hearts, preserved energy metabolism in mitochondria, accelerated palmitate oxidation and acetyl CoA production, and activated Akt/Erk/STAT3 in a ROS-dependent manner. Protection by ILE postconditioning evolved rapidly within the first minutes of reperfusion without evidence of additional cardiotonic effects due to provision of supplementary energy substrates potentially released from ILE during reperfusion. ILE represents a novel and clinically feasible cardioprotective strategy that is highly effective in remodeled hearts. Our data provide a rationale for the clinical evaluation of ILE postconditioning where ILE is administered as a bolus at the onset of reperfusion.

Review of management in cardiotoxic overdose and efficacy of delayed intralipid use

We present the case of a 51-year-old woman admitted to our intensive care unit following an intentional overdose of a calcium channel antagonist and a beta blocker. The resultant hypotension was reversed with glucagon, noradrenaline, calcium and high-dose insulin. Despite these interventions, she remained vasoplegic and received a delayed, standard dose of intralipid. Subsequently, the vasoplegia resolved rapidly, and the vasopressor was stopped. Here, we review the management of overdose of calcium channel and beta-adrenergic receptor blockers, concentrating on the pharmacology of lipid emulsion therapy. There remain some unanswered questions about lipid emulsion therapy: treatment with lipid therapy is usually advocated as soon as possible; this case report suggests that it remains efficacious even if its administration were delayed.

Intravenous Lipid Emulsion as an Antidote for the Treatment of Acute Poisoning: A Bibliometric Analysis of Human and Animal Studies

In recent years, there has been increasing interest in the role of intravenous lipid formulations as potential antidotes in patients with severe cardiotoxicity caused by drug toxicity. The aim of this study was to conduct a comprehensive bibliometric analysis of all human and animal studies featuring lipid emulsion as an antidote for the treatment of acute poisoning. The Scopus database search was performed on 5 February 2016 to analyse the research output related to intravenous lipid emulsion as an antidote for the treatment of acute poisoning. Research indicators used for analysis included total number of articles, date (year) of publication, total citations, value of the h-index, document types, countries of publication, journal names, collaboration patterns and institutions. A total of 594 articles were retrieved from Scopus database for the period of 1955-2015. The percentage share of global intravenous lipid emulsion research output showed that research output was 85.86% in 2006-2015 with yearly average growth in this field of 51 articles per year. The USA, United Kingdom (UK), France, Canada, New Zealand, Germany, Australia, China, Turkey and Japan accounted for 449 (75.6%) of all the publications. The total number of citations for all documents was 9,333, with an average of 15.7 citations per document. The h-index of the retrieved documents for lipid emulsion research as antidote for the treatment of acute poisoning was 49. The USA and the UK achieved the highest h-indices, 34 and 14, respectively. New Zealand produced the greatest number of documents with international collaboration (51.9%) followed by Australia (50%) and Canada (41.4%) out of the total number of publications for each country. In summary, we found an increase in the number of publications in the field of lipid emulsion after 2006. The results of this study demonstrate that the majority of publications in the field of lipid emulsion were published by high-income countries. Researchers from institutions in the USA led scientific production on lipid emulsion research. There is an obvious need to promote a deeper engagement through international collaborative research projects and funding mechanisms.

Intralipid™ administration attenuates the hypotensive effects of acute intravenous amiodarone overdose in a swine model

PURPOSE

To investigate whether a lipid emulsion could counteract the hypotensive effects of amiodarone overdose after an acute intravenous administration and improve 4 h survival in an established model of swine cardiovascular research.

METHODS

Twenty pigs were intubated and instrumented to measure aortic pressures and central venous pressures (CVP). After allowing the animals to stabilize for 60 minutes, amiodarone overdose (1 mg/kg/min) was initiated for a maximum of 20 minutes. Afterwards, the animals were randomized into 2 groups. Group A (n = 10) received 0.9% Normal Saline (NS) and Group B (n = 10) received 20% Intralipid® (ILE). A bolus dose of 2 ml/kg in over 2 min time was initially administered in both groups followed by a 45 min infusion (0.2 ml/kg/min) of either NS or ILE.

RESULTS

All animals survived the overdose and all animals survived the monitoring period of 4 hours. Systolic aortic pressure (SpthAorta) (6.90 vs 14.10 mmHg, P = .006) and mean arterial pressure (MAP) (6.10 vs 14.90 mmHg, P = .001) were higher in the ILE group 2 min after the bolus ILE infusion. This difference was maintained for 15 min after ILE infusion for both SpthAorta (7.85 vs 13.15 mmHg, P = .044) and MAP (7.85 vs 13.15 mmHg, P = .042). Animals that received ILE had higher CVP (11.6 vs 15.7 mmHg, P = .046), an effect which was attenuated 2 and 4 hours post administration. Animals receiving ILE were more acidotic (7.21 vs 7.38, P = .048) in the monitoring period compared to animals receiving NS.

CONCLUSIONS

Intralipid attenuated the hypotensive effects of amiodarone toxicity for a period of 15 minutes compared to animals receiving NS.

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.

Electrophysiological, haemodynamic, and mitochondrial alterations induced by levobupivacaine during myocardial ischemia in a pig model: protection by lipid emulsions?

Accidental intravascular or high-dose injection of local anesthetics (LA) can result in serious, potentially life-threatening complications. Indeed, adequate supportive measures and the administration of lipid emulsions are required in such complications. The study's objectives were threefold: (i) evaluate the myocardial toxicity of levobupivacaine when administered intravenously; (ii) investigate levobupivacaine toxicity on cardiomyocytes mitochondrial functions and cellular structure; (iii) assess the protective effects of a lipid emulsion in the presence or absence of myocardial ischemia. Domestic pigs randomized into two groups of 24 animals each, with either preserved coronary circulation or experimental myocardial ischemia. Six animals from each group received either: (i) single IV injection of saline, (ii) lipid emulsion (Intralipid(®) ), (iii) levobupivacaine, (iv) combination levobupivacaine-Intralipid(®) . Serially measured endpoints included: heart rate, duration of the monophasic action potentials (dMAP), mean arterial pressure, and peak of the time derivative of left ventricular pressure (LV dP/dtmax ). In addition, the following cardiomyocytes mitochondrial functions were measured: reactive oxygen species (ROS) production, oxidative phosphorylation, and calcium retention capacity (CRC) as well as the consequences of ROS production on lipids, proteins, and DNA. IV injection of levobupivacaine induced sinus bradycardia and reduced dMAP and LV dP/dtmax . At the mitochondrial level, oxygen consumption and CRC were decreased. In contrast, ROS production was increased leading to enhanced lipid peroxidation and structural alterations of proteins and DNA. Myocardial ischemia was associated with global worsening of all changes. Intralipid(®) quickly improved haemodynamics. However, beneficial effects of Intralipid(®) were less clear after myocardial ischemia.

The effects of intravenous lipid emulsion on prolongation of survival in a rat model of calcium channel blocker toxicity

CONTEXT

Intravenous lipid emulsion (ILE) has been shown to ameliorate the toxicity of lipid-soluble agents in animal studies and clinical cases.

OBJECTIVES

To investigate the therapeutic effects of ILE in a rat model of toxicity from calcium channel blockers (CCBs), including diltiazem and nicardipine.

METHODS

Two sets of experiments of CCB poisoning were conducted. In the first set, 14 male Sprague-Dawley rats were sedated and treated with ILE or normal saline (NS), followed by continuous intravenous infusion of diltiazem (20 mg/kg/h). In the second experiment, the study protocol was the same except the infusion of nicardipine (20 mg/kg/h). The total dose of infused drug and the duration of survival were measured. In addition, mean arterial pressure and heart rate were monitored.

RESULTS

Survival was prolonged in the ILE group (48.4 ± 11.3 vs. 25.0 ± 3.7 min; p = 0.002). Furthermore, the cumulative mean lethal dose of diltiazem was higher in the ILE group (16.1 ± 3.8 mg/kg) than in the NS group (8.3 ± 1.1 mg/kg) (p = 0.002). With nicardipine poisoning, survival was also prolonged in the ILE group (71.0 ± 8.3 min vs. 30.6 ± 6.1 min; p = 0.002). The cumulative mean lethal dose was higher in the ILE group than in the NS group (23.7 ± 2.8 mg/kg vs. 10.2 ± 2.0 mg/kg; p = 0.002).

CONCLUSIONS

ILE pretreatment prolonged survival and increased the lethal dose in a rat model of CCB poisoning using diltiazem and nicardipine.

Lipid emulsion rapidly restores contractility in stunned mouse cardiomyocytes: a comparison with therapeutic hypothermia

OBJECTIVES

Cooling following cardiac arrest can improve survival significantly. However, delays in achieving target temperature may decrease the overall benefits of cooling. Here, we test whether lipid emulsion, a clinically approved drug reported to exert cardioprotection, can rescue heart contractility in the setting of delayed cooling in stunned mouse cardiomyocytes.

DESIGN

Cell culture study.

SETTING

Academic research laboratory.

SUBJECTS

Cardiomyocytes isolated from 1- to 2-day-old C57BL6 mice.

INTERVENTIONS

Cardiomyocytes were exposed to 30 minutes of ischemia followed by 90 minutes of reperfusion and 10 minutes of isoproterenol with nine interventions: 1) no additional treatment; 2) intraischemic cooling at 32 °C initiated 10 minutes prior to reperfusion; 3) delayed cooling started 20 minutes after reperfusion; 4) lipid emulsion + delayed cooling; 5) lipid emulsion (0.25%) administered at reperfusion; 6) lipid emulsion + intraischemic cooling; 7) delayed lipid emulsion; 8) lipid emulsion + delayed cooling + Akt inhibitor (API-2, 10 µM); and 9) lipid emulsion + delayed cooling + Erk inhibitor (U0126, 10 µM). Inhibitors were given to cells 1 hour prior to ischemia.

MEASUREMENTS AND MAIN RESULTS

Contractility was recorded by real-time phase-contrast imaging and analyzed with pulse image velocimetry in MATLAB (Mathworks, Natick, MA). Ischemia diminished cell contraction. The cardioprotective effect of cooling was diminished when delayed but was rescued by lipid emulsion. Further, lipid emulsion on its own improved recovery of the contractility to a greater extent as intraischemic cooling. However, cotreatment of lipid emulsion and intraischemic cooling did not further improve the recovery compared to either treatment alone. Furthermore, Akt and Erk inhibitors blocked lipid emulsion-induced protection.

CONCLUSIONS

Lipid emulsion improved contractility and rescued contractility in the context of delayed cooling. This protective effect required Akt and Erk signaling. Lipid emulsion might serve as a treatment or adjunct to cooling in ameliorating myocardial ischemia/reperfusion injury.

An in vitro analysis of the effects of intravenous lipid emulsion on free and total local anaesthetic concentrations in human blood and plasma

Background. Intravenous lipid emulsion (ILE) is recommended as a “rescue” treatment for local anaesthetic (LA) toxicity. A purported mechanism of action suggests that lipophilic LAs are sequestered into an intravascular “lipid-sink,” thus reducing free drug concentration. There is limited data available correlating the effects of ILE on LAs. Aims. To compare the in vitro effect of ILE on LA concentrations in human blood/plasma and to correlate this reduction to LA lipophilicity. Method. One of four LAs (bupivacaine-most lipophilic-4 mg/L, ropivacaine-6 mg/L, lignocaine-14 mg/L, and prilocaine-least lipophilic-7 mg/L) was spiked into plasma or whole blood. ILE or control-buffer was added. Plasma was centrifuged to separate ILE and total-LA concentration assayed from the lipid-free fraction. Whole blood underwent equilibrium dialysis and free-LA concentration was measured. Percent reduction in LA concentration from control was compared between the LAs and correlated with lipophilicity. Results. ILE caused a significant reduction in total and free bupivacaine concentration compared with the other LAs. Ropivacaine had the least reduction in concentration, despite a lipophilicity similar to bupivacaine. The reduction in LA concentration correlated to increasing lipophilicity when ropivacaine was excluded from analysis. Conclusion. In this first in vitro model assessing both free- and total-LA concentrations exposed to ILE in human blood/plasma, ILE effect was linearly correlated with increasing lipophilicity for all but ropivacaine.

Intravenous lipid emulsion alters the hemodynamic response to epinephrine in a rat model

Intravenous lipid emulsion (ILE) is an adjunctive antidote used in selected critically ill poisoned patients. These patients may also require administration of advanced cardiac life support (ACLS) drugs. Limited data is available to describe interactions of ILE with standard ACLS drugs, specifically epinephrine. Twenty rats with intra-arterial and intravenous access were sedated with isoflurane and split into ILE or normal saline (NS) pretreatment groups. All received epinephrine 15 μm/kg intravenously (IV). Continuous mean arterial pressure (MAP) and heart rate (HR) were monitored until both indices returned to baseline. Standardized t tests were used to compare peak MAP, time to peak MAP, maximum change in HR, time to maximum change in HR, and time to return to baseline MAP/HR. There was a significant difference (p = 0.023) in time to peak MAP in the ILE group (54 s, 95 % CI 44-64) versus the NS group (40 s, 95 % CI 32-48) and a significant difference (p = 0.004) in time to return to baseline MAP in ILE group (171 s, 95 % CI 148-194) versus NS group (130 s, 95 % CI 113-147). There were no significant differences in the peak change in MAP, peak change in HR, time to minimum HR, or time to return to baseline HR between groups. ILE-pretreated rats had a significant difference in MAP response to epinephrine; ILE delayed the peak effect and prolonged the duration of effect of epinephrine on MAP, but did not alter the peak increase in MAP or the HR response.

Resuscitation with lipid emulsion: dose-dependent recovery from cardiac pharmacotoxicity requires a cardiotonic effect

BACKGROUND

Recent publications have questioned the validity of the "lipid sink" theory of lipid resuscitation while others have identified sink-independent effects and posed alternative mechanisms such as hemodilution. To address these issues, the authors tested the dose-dependent response to intravenous lipid emulsion during reversal of bupivacaine-induced cardiovascular toxicity in vivo. Subsequently, the authors modeled the relative contribution of volume resuscitation, drug sequestration, inotropy and combined drug sequestration, and inotropy to this response with the use of an in silico model.

METHODS

Rats were surgically prepared to monitor cardiovascular metrics and deliver drugs. After catheterization and instrumentation, animals received a nonlethal dose of bupivacaine to produce transient cardiovascular toxicity, then were randomized to receive one of the four treatments: 30% intravenous lipid emulsion, 20% intravenous lipid emulsion, intravenous saline, or no treatment (n = 7 per condition; 28 total animals). Recovery responses were compared with the predictions of a pharmacokinetic-pharmacodynamic model parameterized using previously published laboratory data.

RESULTS

Rats treated with lipid emulsions recovered faster than did rats treated with saline or no treatment. Intravenous lipid emulsion of 30% elicited the fastest hemodynamic recovery followed in order by 20% intravenous lipid emulsion, saline, and no treatment. An increase in arterial blood pressure underlay the recovery in both lipid emulsion-treated groups. Heart rates remained depressed in all four groups throughout the observation period. Model predictions mirrored the experimental recovery, and the model that combined volume, sequestration, and inotropy predicted in vivo results most accurately.

CONCLUSION

Intravenous lipid emulsion accelerates cardiovascular recovery from bupivacaine toxicity in a dose-dependent manner, which is driven by a cardiotonic response that complements the previously reported sequestration effect.

The mechanism of Intralipid®-mediated cardioprotection complex IV inhibition by the active metabolite, palmitoylcarnitine, generates reactive oxygen species and activates reperfusion injury salvage kinases

BACKGROUND

Intralipid® administration at reperfusion elicits protection against myocardial ischemia-reperfusion injury. However, the underlying mechanisms are not fully understood.

METHODS

Sprague-Dawley rat hearts were exposed to 15 min of ischemia and 30 min of reperfusion in the absence or presence of Intralipid® 1% administered at the onset of reperfusion. In separate experiments, the reactive oxygen species (ROS) scavenger N-(2-mercaptopropionyl)-glycine was added either alone or with Intralipid®. Left ventricular work and activation of Akt, STAT3, and ERK1/2 were used to evaluate cardioprotection. ROS production was assessed by measuring the loss of aconitase activity and the release of hydrogen peroxide using Amplex Red. Electron transport chain complex activities and proton leak were measured by high-resolution respirometry in permeabilized cardiac fibers. Titration experiments using the fatty acid intermediates of Intralipid® palmitoyl-, oleoyl- and linoleoylcarnitine served to determine concentration-dependent inhibition of complex IV activity and mitochondrial ROS release.

RESULTS

Intralipid® enhanced postischemic recovery and activated Akt and Erk1/2, effects that were abolished by the ROS scavenger N-(2-mercaptopropionyl)glycine. Palmitoylcarnitine and linoleoylcarnitine, but not oleoylcarnitine concentration-dependently inhibited complex IV. Only palmitoylcarnitine reached high tissue concentrations during early reperfusion and generated significant ROS by complex IV inhibition. Palmitoylcarnitine (1 µM), administered at reperfusion, also fully mimicked Intralipid®-mediated protection in an N-(2-mercaptopropionyl)-glycine -dependent manner.

CONCLUSIONS

Our data describe a new mechanism of postconditioning cardioprotection by the clinically available fat emulsion, Intralipid®. Protection is elicited by the fatty acid intermediate palmitoylcarnitine, and involves inhibition of complex IV, an increase in ROS production and activation of the RISK pathway.

Rapid cardiotonic effects of lipid emulsion infusion*

OBJECTIVES

Bolus infusion of lipid emulsion can reverse cardiac pharmacotoxicity caused by local anesthetics and other lipophilic drugs. The mechanisms of this effect are not completely elucidated. The authors test the hypothesis that lipid emulsion infusion exerts direct, positive inotropic effects.

DESIGN

Prospective, randomized animal study.

SETTING

University research laboratory.

SUBJECTS

Adult male Sprague-Dawley rats.

INTERVENTIONS

Rats anesthetized with isoflurane were given intravenous infusions (9 mL/kg over 1 min) of either 20% soybean oil-based emulsion or saline.

MEASUREMENTS AND MAIN RESULTS

Arterial pressure and aortic flow were measured continuously in intact animals. Lipid infusion increased aortic flow and arterial pressure faster and to a greater degree than did the same volume of saline infusion. Isolated rat hearts were studied using an isovolumetric, constant flow, nonrecirculating system. Left ventricular pressure was monitored. The infusion of lipid emulsion in the isolated heart dose-dependently increased rate pressure product, dP/dt, -dP/dt, and myocardial oxygen demand.

CONCLUSIONS

Lipid emulsion exerts rapid, positive inotropic and positive lusitropic effects in both intact animal and isolated heart models. We hypothesize that this inotropy and the resulting increase in tissue blood flow contribute to the phenomenon of lipid reversal of cardiac toxicity caused by drug overdose.

Lipid infusion in the management of poisoning: a report of 6 canine cases

Intravenous administration of lipid is a relatively new treatment in the management of toxicity from lipophilic compounds. It is used in human medicine in the treatment of toxicity from lipophilic local anaesthetics and cardiotoxic drugs and can result in dramatic improvement in clinical status. We present six cases of poisoning in dogs successfully treated with lipid infusion after ingestion of ivermectin (3), moxidectin (2) and baclofen (1). The dogs ranged in age from eight weeks to 14 years, and weighed 4-30 kg. Intravenous lipid therapy was started between six and eight hours and 22 hours after ingestion, and all the dogs responded well. In four dogs, there was clinical improvement within one hour; one had improved within two hours and the other within 4.5 hours of lipid administration. The only adverse effect of lipid infusion reported was mild swelling and pain after extravasation in one case which resolved with conservative management. All the dogs were discharged within 24-52 hours after exposure (7-46 hours after the start of lipid administration), and none developed any apparent sequelae.

Intravenous lipid administration for drug-induced toxicity: a critical review of the existing data

Following the discovery that administration of intravenous lipid emulsion (ILE) may reverse the cardiac and neurological toxicity of certain local anesthetic agents, ILE's potential role has recently been explored in the setting of toxicity attributed to a variety of different drugs. The potential mechanisms, safety and efficacy of this approach are considered in this review. Data are reviewed from 76 published reports involving ILE administration for severe drug toxicity, including 55 where toxicity was due to nonanesthetic agents. ILE was reported to exert a positive therapeutic effect in only a proportion of the reported cases, with greatest evidence of efficacy concerning local anesthetic agents. Administration has typically involved bolus administration followed by continuous maintenance infusion, and a number of different mechanisms are proposed, from preferential partitioning of the drug from cardiac tissue to the circulating lipid fraction and direct inotropic effects related to carnitine pathways and fatty acid oxidative metabolism. No major adverse effects have been encountered, but too few data exist to adequately address the safety profile of ILE.

Use of intravenous lipid therapy in three cases of feline permethrin toxicosis

OBJECTIVE

To describe the use of intravenous lipid emulsion (IVLE) as an adjunctive therapy in 3 cats with permethrin toxicosis.

CASE SERIES SUMMARY

Three cats with permethrin toxicosis were treated with IVLE in addition to the current accepted treatment regime. All 3 cats demonstrated a subjective rapid clinical improvement after the administration of IVLE, with no adverse reactions observed.

NEW OR UNIQUE INFORMATION PROVIDED

This is the first reported use of IVLE for feline permethrin toxicosis, with encouraging results. A possible reduction in costs associated with treatment may contribute to a reduction in euthanasia. Further investigation of the use of IVLEs in permethrin toxicosis is warranted.

Infarct-remodelled hearts with limited oxidative capacity boost fatty acid oxidation after conditioning against ischaemia/reperfusion injury

AIMS

Infarct-remodelled hearts are less amenable to protection against ischaemia/reperfusion. Understanding preservation of energy metabolism in diseased vs. healthy hearts may help to develop anti-ischaemic strategies effective also in jeopardized myocardium.

METHODS AND RESULTS

Isolated infarct-remodelled/sham Sprague-Dawley rat hearts were perfused in the working mode and subjected to 15 min of ischaemia and 30 min of reperfusion. Protection of post-ischaemic ventricular work was achieved by pharmacological conditioning with sevoflurane. Oxidative metabolism was measured by substrate flux in fatty acid and glucose oxidation using [(3)H]palmitate and [(14)C]glucose. Mitochondrial oxygen consumption was measured in saponin-permeabilized left ventricular muscle fibres. Activity assays of citric acid synthase, hydroxyacyl-CoA dehydrogenase, and pyruvate dehydrogenase and mass spectrometry for acylcarnitine profiling were also performed. Six weeks after coronary artery ligation, the hearts exhibited macroscopic and molecular signs of hypertrophy consistent with remodelling and limited respiratory chain and citric acid cycle capacity. Unprotected remodelled hearts showed a marked decline in palmitate oxidation and acetyl-CoA energy production after ischaemia/reperfusion, which normalized in sevoflurane-protected remodelled hearts. Protected remodelled hearts also showed higher β-oxidation flux as determined by increased oxygen consumption with palmitoylcarnitine/malate in isolated fibres and a lower ratio of C16:1+C16OH/C14 carnitine species, indicative of a higher long-chain hydroxyacyl-CoA dehydrogenase activity. Remodelled hearts exhibited higher PPARα-PGC-1α but defective HIF-1α signalling, and conditioning enabled them to mobilize fatty acids from endogenous triglyceride stores, which closely correlated with improved recovery.

CONCLUSIONS

Protected infarct-remodelled hearts secure post-ischaemic energy production by activation of β-oxidation and mobilization of fatty acids from endogenous triglyceride stores.

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.

Partition constant and volume of distribution as predictors of clinical efficacy of lipid rescue for toxicological emergencies

CONTEXT

Lipid infusion is useful in reversing cardiac toxicity of local anesthetics, and recent reports indicate it may be useful in resuscitation from toxicity induced by a variety of other drugs. While the mechanism behind the utility of lipid rescue remains to be fully elucidated, the predominant effect appears to be creation of a "lipid sink".

OBJECTIVE

Determine whether the extraction of drugs by lipid, and hence the clinical efficacy of lipid rescue in toxicological emergencies can be predicted by specific drug properties.

MATERIALS AND METHODS

Each drug investigated was added individually to human drug-free serum. Intralipid® was added to this drug-containing serum, shaken and then incubated at 37°C. The lipid was removed by ultracentrifugation and the concentration of drug remaining in the serum was measured by high-pressure liquid chromatography.

RESULTS

In this in vitro model, the ability of lipid emulsion to bind a drug was largely dependent upon the drug's lipid partition constant. Additionally, using a multiple linear regression model, the prediction of binding could be improved by combining the lipid partition constant with the volume of distribution together accounting for approximately 88% of the variation in the decrease in serum drug concentration with the administration of lipid emulsion.

CONCLUSIONS

The lipid partition constant and volume of distribution can likely be used to predict the efficacy of lipid infusion in reversing the cardiac toxicity induced by anesthetics or other medications.

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.

Serum verapamil concentrations before and after Intralipid® therapy during treatment of an overdose

CONTEXT. Intralipid® infusion is useful in reversing cardiac and central nervous system toxicity of local anesthetic drugs, and recent reports suggest utility in other drug overdoses. CASE DETAILS. A 47-year-old man presented to the emergency department with hypotension and complete heart block 3 h after a sustained-release verapamil overdose. He was given supportive care including calcium and hyperinsulinemia/euglycemia therapy. Nineteen and 29 h post-ingestion, Intralipid® was administered as a bolus, followed by an infusion. OBJECTIVE. The objective of this study was to determine the serum verapamil concentrations before and after Intralipid® administration and to ascertain its clinical effects. DISCUSSION. It was found that administration of Intralipid® was followed by a decrease in verapamil concentration once the lipid had been removed from the sample, demonstrating that Intralipid® was effective in sequestering verapamil, effectively removing it from the serum, and supporting its use in the treatment of verapamil overdose. Intralipid® administration was associated with an increase in the patient's blood pressure, but because other vasoactive drugs were given at the same time, it was difficult to determine its relative contribution to clinical improvement.

Complications of peripheral nerve blocks

Complications of peripheral nerve blocks are fortunately rare, but can be devastating for both the patient and the anaesthesiologist. This review will concentrate on current knowledge about peripheral nerve injury secondary to nerve blocks, complications from continuous peripheral nerve catheter techniques, and local anaesthetic systemic toxicity.

Intravenous lipid emulsion in clinical toxicology

Intravenous lipid emulsion is an established, effective treatment for local anesthetic-induced cardiovascular collapse. The predominant theory for its mechanism of action is that by creating an expanded, intravascular lipid phase, equilibria are established that drive the offending drug from target tissues into the newly formed 'lipid sink'. Based on this hypothesis, lipid emulsion has been considered a candidate for generic reversal of toxicity caused by overdose of any lipophilic drug. Recent case reports of successful resuscitation suggest the efficacy of lipid emulsion infusion for treating non-local anesthetic overdoses across a wide spectrum of drugs: beta blockers, calcium channel blockers, parasiticides, herbicides and several varieties of psychotropic agents. Lipid emulsion therapy is gaining acceptance in emergency rooms and other critical care settings as a possible treatment for lipophilic drug toxicity. While protocols exist for administration of lipid emulsion in the setting of local anesthetic toxicity, no optimal regimen has been established for treatment of acute non-local anesthetic poisonings. Future studies will shape the evolving recommendations for lipid emulsion in the setting of non-local anesthetic drug overdose.

Intralipid infusion diminishes return of spontaneous circulation after hypoxic cardiac arrest in rabbits

BACKGROUND

Infusion of lipid emulsion has been shown to reverse lipophilic drug-induced cardiovascular collapse in laboratory models and humans. The effect of high dose lipid in nondrug-induced cardiac arrest is, however, uncertain. In a rabbit model of asphyxial pulseless electrical activity (PEA) we compared lipid augmented with standard advanced cardiac life support (ACLS) resuscitation.

METHOD

Adult New Zealand White rabbits underwent hypoxic PEA via tracheal clamping. After 2 min of cardiac arrest, basic life support cardiopulmonary resuscitation was commenced and 3 mL/kg 20% Intralipid or 3 mL/kg 0.9% saline solution infused. Adrenaline (100 microg/kg) was administered at 4 and 5 min. Return of spontaneous circulation (ROSC), hemodynamic metrics, and survival to 50 min were recorded.

RESULTS

Seven of 11 saline-treated rabbits developed ROSC versus 1 of 12 Intralipid-treated animals; P = 0.009. No significant difference in survival to 50 min was observed (3/11 saline vs 0/12 Intralipid; P = 0.211).

CONCLUSION

In this model of hypoxia-induced PEA, standard ACLS resulted in greater coronary perfusion pressure and increased ROSC compared with ACLS plus lipid infusion. Lipid emulsion may be contraindicated in cardiac arrest complicated by significant hypoxia.

Glucose-insulin therapy, plasma substrate levels and cardiac recovery after cardiac ischemic events

Introduction

The potential usefulness of glucose-insulin therapy relies to a large extent on the premise that it prevents hyperglycemia and hyperlipidemia following cardiac ischemic events.

Methods

In this review we evaluate the literature concerning plasma glucose and free fatty acids levels during and following cardiac ischemic events.

Results

The data indicate that hyperlipidemia and hyperglycemia most likely occur during acute coronary ischemic syndromes in the conscious state (e.g. acute myocardial infarction) and less so during reperfusion following CABG reperfusion. This is in accordance with observations that glucose-insulin therapy during early reperfusion post CABG may actually cause hypolipidemia, because substantial hyperlipidemia does not appear to occur during that stage of cardiac surgery.

Discussion

Considering recent data indicating that hypolipidemia may be detrimental for cardiac function, we propose that free fatty acid levels during reperfusion post CABG with the adjunct glucose-insulin therapy need to be closely monitored.

Conclusion

From a clinical point of view, a strategy directed at monitoring and thereafter maintaining plasma substrate levels in the normal range for both glucose (4–6 mM) and FFA (0.2–0.6 mM) as well as stimulation of glucose oxidation, promises to be the most optimal metabolic reperfusion treatment following cardiac ischemic episodes. Future (preclinical and subsequently clinical) investigations are required to investigate whether the combination of glucose-insulin therapy with concomitant lipid administration may be beneficial in the setting of reperfusion post CABG.

Intralipid infusion ameliorates propranolol-induced hypotension in rabbits

OBJECTIVE

Recent case reports of successful amelioration of lipid-soluble drug toxidromes with Intralipid infusion have prompted interest in the scope of lipid emulsions as antidotal therapy. Propranolol is a highly lipid-soluble, nonselective beta-blocker with additional local-anaesthetic properties. We explored the hypothesis that propranolol toxicity may be similarly attenuated by Intralipid infusion in a rabbit model.

METHODS

Twenty sedated, invasively monitored, and mechanically ventilated New Zealand White rabbits underwent propranolol infusion at 4.2 mg/min to a target mean arterial pressure (MAP) of 60% baseline MAP. Animals subsequently received 6 ml/kg 20% Intralipid, or 6 ml/kg 0.9% saline solution over a 4-minute period. Pulse rate and MAP were recorded at 2.5-minute intervals to 15 minutes.

RESULTS

MAP was greatest in the Intralipid group (median 69 mmHg, interquartile range [IQR] 17.5 mmHg Intralipid vs. median 53 mmHg, IQR 12.75 mmHg saline; p=0.029) at 15 minutes. No difference was observed in first derivative of MAP, or pulse rate between groups.

CONCLUSIONS

Propranolol-induced hypotension is ameliorated by Intralipid infusion in this intact rabbit model. The mechanism of action remains to be elucidated.