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Brodifacoum (BDF) is a potent, long-acting anticoagulant rodenticide that can cause fatal poisoning in humans. The chemical structure of BDF includes 2 chiral carbons, resulting in 2 pairs of diastereomers, BDF-cis (R/S and S/R) and BDF-trans (R/R and S/S). However, the relative potency of these molecules is not known. The purpose of this study was to compare the in vitro and in vivo toxic effects of the 2 BDF diastereomer pairs. In adult Sprague-Dawley rats BDF-cis was significantly more toxic than BDF-trans (LD50 values of 219 versus 316 μg/kg, respectively) while racemic BDF had intermediate potency (266 μg/kg). In adult New Zealand white rabbits, BDF-cis had a longer half-life than BDF-trans which could contribute to its observed increased toxicity. Lastly, BDF-cis (10 μM), but not BDF-trans, damaged cultured SH-SY5Y human neuroblastoma cells by attenuating mitochondrial reductive capacity. Taken together, these data suggest that different toxic manifestations of BDF poisoning in mammals could be attributed, in part, to differences in relative enantiomer concentrations present in racemic formulations of this commercially-available toxicant.

Osteoarthritis (OA) is a painful and debilitating disease. A striking feature of OA is the dramatic increase in vascular endothelial growth factor (VEGF) levels and in new blood vessel formation in the joints, both of which correlate with the severity of OA pain. Our aim was to determine whether anti-VEGF monoclonal antibodies (mAbs) – MF-1 (mAb to VEGFR1) and DC101 (mAb to VEGFR2) – can reduce OA pain and can do so by targeting VEGF signaling pathways such as Flt-1 (VEGFR1) and Flk-1 (VEGFR2). After IACUC approval, OA was induced by partial medial meniscectomy (PMM) in C57/BL6 mice (20 g). ln the first experiment, for validation of VEGFR1 in DRG, the mouse dorsal root ganglion (DRG) was stimulated with NGF for 48 hours to find the relative gene induction for VEGFR1 vs. 18S by RT-PCR. In the second experiment, Biotin-conjugated VEGFA (1 µg/knee joint) was administered in the left knee joint of mice with advanced OA in order to characterization of VEGFR1 and VEGFR2. pVEGFR1/VEGFR2 was detected by immunostaining in DRGs. Finally, MF-1 and DC101 were administered in OA mice by both intrathecal (IT) and intraarticular (IA) injections, and the change in paw withdrawal threshold (PWT) was measured. Retrograde transport of VEGF was confirmed for detection of pVEGFR1/VEGFR2 in the DRG. PMM surgery led to development of OA and mechanical allodynia, with reduced paw withdrawal thresholds (PWT) (P

Discogenic low back pain (DLBP) is extremely common and costly. Effective treatments are lacking due to DLBP's unknown pathogenesis. Currently, there are no in vivo mouse models of DLBP, which restricts research in this field. The aim of this study was to establish a reliable DLBP model in mouse that captures the pathological changes in the disc and allows longitudinal pain testing. The model was generated by puncturing the mouse lumbar discs (L4/5, L5/6, and L6/S1) and removing the nucleus pulposus using a microscalpel under the microscope. Histology, molecular pathways, and pain-related behaviors were examined. Over 12 weeks post-surgery, animals displayed the mechanical, heat, and cold hyperalgesia along with decreased burrowing and rearing. Histology showed progressive disc degeneration with loss of disc height, nucleus pulposus reduction, proteoglycan depletion, and annular fibrotic disorganization. Immunohistochemistry revealed a substantial increase in inflammatory mediators at 2 and 4 weeks. Nerve growth factor was upregulated from 2 weeks to the end of the experiment. Nerve fiber ingrowth was induced in the injured discs after 4 weeks. Disc-puncture also produced an upregulation of neuropeptides in dorsal root ganglia neurons and an activation of glial cells in the spinal cord dorsal horn. These findings indicate that the cellular and structural changes in discs, as well as peripheral and central nervous system plasticity, paralleled persistent, and robust behavioral pain responses. Therefore, this mouse DLBP model could be used to investigate mechanisms underlying discogenic pain, thereby facilitating effective drug screening and development of treatments for DLBP.

Superwarfarins are very long-lasting rodenticides effective in warfarin-resistant rodents at extremely low doses. The consequences of chronic superwarfarin levels in tissues, due to biological half-lives on the order of 20 days, have not been examined. We now characterized the neurological effects of brodifacoum (BDF), one of the most widely used superwarfarins, in adult male Sprague Dawley rats. Dosing curves established the acute oral lethal dose for BDF as 221 ± 14 μg/kg. Measurement of tissue BDF levels showed accumulation throughout the body, including the central nervous system, with levels diminishing over several days. Immunocytochemical staining showed that both astrocyte and microglial activation was increased 4 days after BDF administration, as were levels of carbonylated proteins, and neuronal damage assessed by fluorojade B staining. Direct toxic effects of BDF on neurons and glia were observed using enriched cultures of cerebellar neurons and cortical astrocytes. Proteomic analysis of cerebellar lysates revealed that BDF altered expression of 667 proteins in adult rats. Gene ontology and pathway analysis identified changes in several functional pathways including cell metabolism, mitochondria function, and RNA handling with ribosomal proteins comprising the largest group. In vitro studies using primary astrocytes showed that BDF suppressed de novo protein synthesis. These findings demonstrate that superwarfarin accumulation increases indices of neuroinflammation and neuropathology in adult rodents, suggesting that methods which minimize BDF toxicity may not address delayed neurological sequelae.

Background The impact of local anesthetics on the regulation of glucose homeostasis by protein kinase B (Akt) and 5′-adenosine monophosphate–activated protein kinase (AMPK) is unclear but important because of the implications for both local anesthetic toxicity and its reversal by IV lipid emulsion (ILE). Methods Sprague–Dawley rats received 10 mg/kg bupivacaine over 20 s followed by nothing or 10 ml/kg ILE (or ILE without bupivacaine). At key time points, heart and kidney were excised. Glycogen content and phosphorylation levels of Akt, p70 s6 kinase, s6, insulin receptor substrate-1, glycogen synthase kinase-3β, AMPK, acetyl-CoA carboxylase, and tuberous sclerosis 2 were quantified. Three animals received Wortmannin to irreversibly inhibit phosphoinositide-3-kinase (Pi3k) signaling. Isolated heart studies were conducted with bupivacaine and LY294002—a reversible Pi3K inhibitor. Results Bupivacaine cardiotoxicity rapidly dephosphorylated Akt at S473 to 63 ± 5% of baseline and phosphorylated AMPK to 151 ± 19%. AMPK activation inhibited targets downstream of mammalian target of rapamycin complex 1 via tuberous sclerosis 2. Feedback dephosphorylation of IRS1 to 31 ± 8% of baseline sensitized Akt signaling in hearts resulting in hyperphosphorylation of Akt at T308 and glycogen synthase kinase-3β to 390 ± 64% and 293 ± 50% of baseline, respectively. Glycogen accumulated to 142 ± 7% of baseline. Irreversible inhibition of Pi3k upstream of Akt exacerbated bupivacaine cardiotoxicity, whereas pretreating with a reversible inhibitor delayed the onset of toxicity. ILE rapidly phosphorylated Akt at S473 and T308 to 150 ± 23% and 167 ± 10% of baseline, respectively, but did not interfere with AMPK or targets of mammalian target of rapamycin complex 1. Conclusion Glucose handling by Akt and AMPK is integral to recovery from bupivacaine cardiotoxicity and modulation of these pathways by ILE contributes to lipid resuscitation.

Aims: Acute increases in left ventricular end diastolic pressure (LVEDP) can induce pulmonary edema (PE). The mechanism(s) for this rapid onset edema may involve more than just increased fluid filtration. Lung endothelial cell permeability is regulated by pressure-dependent activation of nitric oxide synthase (NOS). Herein, we demonstrate that pressure-dependent NOS activation contributes to vascular failure and PE in a model of acute heart failure (AHF) caused by hypertension. Methods and results: Male Sprague–Dawley rats were anesthetized and mechanically ventilated. Acute hypertension was induced by norepinephrine (NE) infusion and resulted in an increase in LVEDP and pulmonary artery pressure (Ppa) that were associated with a rapid fall in PaO2, and increases in lung wet/dry ratio and injury scores. Heart failure (HF) lungs showed increased nitrotyrosine content and ROS levels. L-NAME pretreatment mitigated the development of PE and reduced lung ROS concentrations to sham levels. Apocynin (Apo) pretreatment inhibited PE. Addition of tetrahydrobiopterin (BH4) to AHF rats lung lysates and pretreatment of AHF rats with folic acid (FA) prevented ROS production indicating endothelial NOS (eNOS) uncoupling. Conclusion: Pressure-dependent NOS activation leads to acute endothelial hyperpermeability and rapid PE by an increase in NO and ROS in a model of AHF. Acute increases in pulmonary vascular pressure, without NOS activation, was insufficient to cause significant PE. These results suggest a clinically relevant role of endothelial mechanotransduction in the pathogenesis of AHF and further highlights the concept of active barrier failure in AHF. Therapies targetting the prevention or reversal of endothelial hyperpermeability may be a novel therapeutic strategy in AHF.

Purpose. The gravimetric method of weighing surgical sponges is used to quantify intraoperative blood loss. The dry mass minus the wet mass of the gauze equals the volume of blood lost. This method assumes that the density of blood is equivalent to water (1 gm/mL). This study’s purpose was to validate the assumption that the density of blood is equivalent to water and to correlate density with hematocrit. Methods. 50 µL of whole blood was weighed from eighteen rats. A distilled water control was weighed for each blood sample. The averages of the blood and water were compared utilizing a Student’s unpaired, one-tailed t-test. The masses of the blood samples and the hematocrits were compared using a linear regression. Results. The average mass of the eighteen blood samples was 0.0489 g and that of the distilled water controls was 0.0492 g. The t-test showed P=0.2269 and R2=0.03154. The hematocrit values ranged from 24% to 48%. The linear regression R2 value was 0.1767. Conclusions. The R2 value comparing the blood and distilled water masses suggests high correlation between the two populations. Linear regression showed the hematocrit was not proportional to the mass of the blood. The study confirmed that the measured density of blood is similar to water.

Triglyceride micro-emulsions such as Intralipid® have been used to reverse cardiac toxicity induced by a number of drugs but reservations about their broad-spectrum applicability remain because of the poorly understood mechanism of action. Herein we report an integrated mechanism of reversal of bupivacaine toxicity that includes both transient drug scavenging and a cardiotonic effect that couple to accelerate movement of the toxin away from sites of toxicity. We thus propose a multi-modal therapeutic paradigm for colloidal bio-detoxification whereby a micro-emulsion both improves cardiac output and rapidly ferries the drug away from organs subject to toxicity. In vivo and in silico models of toxicity were combined to test the contribution of individual mechanisms and reveal the multi-modal role played by the cardiotonic and scavenging actions of the triglyceride suspension. These results suggest a method to predict which drug toxicities are most amenable to treatment and inform the design of next-generation therapeutics for drug overdose.

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.

OBJECTIVE To determine whether intraosseous infusion of a lipid emulsion reverses cardiac pharmacotoxicity in anaesthetized rats. DESIGN Prospective, randomized animal study. SETTING Academic research laboratory. SUBJECTS Adult, male Sprague-Dawley rats. INTERVENTIONS We assigned 25 male Sprague-Dawley rats into four groups: intraosseous lipid emulsion, intraosseous saline, IV lipid emulsion, and sham/null. Rats were anesthetized with 1.5% isoflurane and 95% oxygen. The left internal carotid artery and both internal jugular veins were cannulated and a flow probe was placed on the right carotid artery. Subsequently, in animals assigned to the intraosseous groups, the greater trochanter of the left proximal femur was exposed and the intraosseous space was cannulated. After surgical recovery, bupivacaine (10 mg/kg) was injected IV over 20 seconds followed 10 seconds later by treatment with one of the following: intraosseous lipid-emulsion (10 mL/kg over 180 s), intraosseous saline (10 mL/kg over 180 s), IV lipid-emulsion (10 mL/kg over 90 s), or no treatment (sham/null). MEASUREMENTS AND MAIN RESULTS Electrocardiogram, aortic blood pressure, and carotid blood flow were recorded continuously. Rats treated with intraosseous lipid emulsion experienced a significantly faster recovery of hemodynamic variables (return of 50% flow; median [CI]: 160 s [105-263 s]) than did rats treated with saline (471 s [283-611 s]; p < 0.05) or animals with no treatment (415 s [340-539 s], p < 0.05), but at a similar rate to animals treated with IV lipid emulsion (176 s [152-217 s], p = not significant). All groups experienced persistent negative chronotropic effects. A compensatory increase in systemic arterial pressure was observed in rats treated with lipid emulsion. CONCLUSION These proof-of-principle data indicate that intraosseous infusion of lipid emulsion rapidly reverses bupivacaine-induced cardiac toxicity in rats. Further studies are warranted to optimize this novel route of lipid emulsion injection in emergency situations when intravascular access is not secured.

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

Background Previous studies indicate epinephrine adversely affects arterial oxygenation when administered in a rat model of local anesthetic overdose. The authors tested whether epinephrine alone exerts similar effects in the intact animal. Methods Anesthetized rats received a single intravenous injection of epinephrine (25, 50, or 100 mcg/kg); matched cohorts were pretreated with phentolamine (100 mcg/kg); n = 5 for each of the six treatment groups. Arterial pressure and blood gases were measured at baseline, 1 and 10 min after epinephrine administration. Pulmonary capillary pressures during epinephrine infusion with normal and increased flows were measured in an isolated lung preparation. Results Epinephrine injection in the intact animal caused hypoxemia, hypercapnia, and acidosis at all doses. Arterial oxygen tension was reduced within 1 min of injection. Hyperlactatemia occurred by 10 min after 50 and 100 mcg/kg. Rate pressure product was decreased by 10 min after 100 mcg/kg epinephrine. Pretreatment with phentolamine attenuated these effects except at 100 mcg/kg epinephrine. In the isolated lung preparation, epinephrine in combination with increased pulmonary flow increased pulmonary capillary pressure and lung water. Conclusions Bolus injection of epinephrine in the intact, anesthetized rat impairs pulmonary oxygen exchange within 1 min of treatment. Effects were blunted by α-adrenergic receptor blockade. Edema occurred in the isolated lung above a threshold pulmonary capillary pressure when epinephrine treatment was coupled with an increase in pulmonary flow. These results potentially argue against using traditional doses of epinephrine for resuscitation, particularly in the anesthetized patient.

The impact of local anesthetics on the regulation of glucose homeostasis by protein kinase B (Akt) and 5'-adenosine monophosphate-activated protein kinase (AMPK) is unclear but important because of the implications for both local anesthetic toxicity and its reversal by IV lipid emulsion (ILE).Sprague-Dawley rats received 10 mg/kg bupivacaine over 20 s followed by nothing or 10 ml/kg ILE (or ILE without bupivacaine). At key time points, heart and kidney were excised. Glycogen content and phosphorylation levels of Akt, p70 s6 kinase, s6, insulin receptor substrate-1, glycogen synthase kinase-3β, AMPK, acetyl-CoA carboxylase, and tuberous sclerosis 2 were quantified. Three animals received Wortmannin to irreversibly inhibit phosphoinositide-3-kinase (Pi3k) signaling. Isolated heart studies were conducted with bupivacaine and LY294002-a reversible Pi3K inhibitor.Bupivacaine cardiotoxicity rapidly dephosphorylated Akt at S473 to 63 ± 5% of baseline and phosphorylated AMPK to 151 ± 19%. AMPK activation inhibited targets downstream of mammalian target of rapamycin complex 1 via tuberous sclerosis 2. Feedback dephosphorylation of IRS1 to 31 ± 8% of baseline sensitized Akt signaling in hearts resulting in hyperphosphorylation of Akt at T308 and glycogen synthase kinase-3β to 390 ± 64% and 293 ± 50% of baseline, respectively. Glycogen accumulated to 142 ± 7% of baseline. Irreversible inhibition of Pi3k upstream of Akt exacerbated bupivacaine cardiotoxicity, whereas pretreating with a reversible inhibitor delayed the onset of toxicity. ILE rapidly phosphorylated Akt at S473 and T308 to 150 ± 23% and 167 ± 10% of baseline, respectively, but did not interfere with AMPK or targets of mammalian target of rapamycin complex 1.Glucose handling by Akt and AMPK is integral to recovery from bupivacaine cardiotoxicity and modulation of these pathways by ILE contributes to lipid resuscitation.

Background The authors tested whether cocaine depresses mitochondrial acylcarnitine exchange and if a drug that enhances glucose metabolism could protect against cocaine-induced cardiac dysfunction. Methods Oxygen consumption with and without cocaine was compared in rat cardiac mitochondria using octanoylcarnitine (lipid) or pyruvate (nonlipid) substrates. Isolated hearts from rats with or without a pioglitazone-supplemented diet were exposed to cocaine. Results The 0.5 mM cocaine inhibited respiration supported by octanoylcarnitine (82 ± 10.4 and 45.7 ± 4.24 ngatomO min⁻¹ · mg⁻¹ · protein ± SEM, for control and cocaine treatment, respectively; P < 0.02) but not pyruvate-supported respiration (281 ± 12.5 and 267 ± 12.7 ngatomO min⁻¹ · mg⁻¹ · protein ± SEM; P = 0.45). Cocaine altered contractility, lusitropy, coronary resistance, and lactate production in isolated heart. These effects were each blunted in pioglitazone-treated hearts. The pioglitazone diet attenuated the drop in the rate-pressure product (P = 0.002), cocaine-induced diastolic dysfunction (P = 0.04), and myocardial vascular resistance (P = 0.05) compared with that of controls. Lactate production was higher in pretreated hearts (P = 0.008) and in ventricular myocytes cultured with pioglitazone (P = 0.0001). Conclusions Cocaine inhibited octanoylcarnitine-supported mitochondrial respiration. A pioglitazone diet significantly attenuated the effects of cocaine on isolated heart. The authors postulate that inhibition of acylcarnitine exchange could contribute to cocaine-induced cardiac dysfunction and that metabolic modulation warrants additional study.

Background Lipid emulsion infusion reverses local anesthetic-induced cardiac toxicity, but the effect of adding epinephrine has not been studied. We compared escalating doses of epinephrine on recovery with lipid infusion in a rat model of bupivacaine overdose. Methods Rats anesthetized with isoflurane received an IV bolus of 20 mg/kg bupivacaine, producing asystole (zero time) in all animals. Ventilation (100% oxygen) and chest compressions were started immediately, and at 3 min the rats received one of six IV treatments (n = 5 for all groups): 5 ml/kg saline followed by infusion for 2 min at 1.0 ml x kg x min, and a second 5 ml/kg bolus at 5 min; or the same bolus and infusion treatment using 30% lipid emulsion plus a single injection of epinephrine at one of five doses: 0 (lipid control), 1, 2.5, 10, or 25 mcg/kg. An electrocardiogram and arterial pressure were monitored continuously, and arterial blood gas was measured at 7.5 and 15 min. Results Epinephrine improved initial return of spontaneous circulation (rate-pressure product > 30% baseline) but only 3 of 5 rats at 10 mcg/kg and 1 of 5 rats at 25 mcg/kg sustained return of spontaneous circulation by 15 min. Lipid alone resulted in slower but more sustained recovery. Epinephrine doses above a threshold near 10 mcg/kg increased lactate, worsened acidosis, and resulted in poor recovery at 15 min, as compared with lipid controls. There was tight correlation of epinephrine dose to serum lactate at 15 min. Conclusions Epinephrine over a threshold dose near 10 mcg/kg impairs lipid resuscitation from bupivacaine overdose, possibly by inducing hyperlactatemia.

Background Lipid emulsion infusion reverses cardiovascular compromise due to local anesthetic overdose in laboratory and clinical settings. The authors compared resuscitation with lipid, epinephrine, and saline control in a rat model of bupivacaine-induced cardiac toxicity to determine whether lipid provides a benefit over epinephrine. Methods Bupivacaine, 20 mg/kg, was infused in rats anesthetized with isoflurane, producing asystole in all subjects. Ventilation with 100% oxygen and chest compressions were begun immediately, along with intravenous treatment with 30% lipid emulsion or saline (5-ml/kg bolus plus continuous infusion at 0.5 ml . kg . min) or epinephrine (30 microg/kg). Chest compressions were continued and boluses were repeated at 2.5 and 5 min until the native rate-pressure product was greater than 20% baseline. Electrocardiogram and arterial pressure were monitored continuously and at 10 min, arterial blood gas, central venous oxygen saturation, and blood lactate were measured. Effect size (Cohen d) was determined for comparisons at 10 min. Results Lipid infusion resulted in higher rate-pressure product (P < 0.001, d = 3.84), pH (P < 0.01, d = 3.78), arterial oxygen tension (P < 0.05, d = 2.8), and central venous oxygen saturation (P < 0.001, d = 4.9) at 10 min than did epinephrine. Epinephrine treatment caused higher lactate (P < 0.01, d = 1.48), persistent ventricular ectopy in all subjects, pulmonary edema in four of five rats, hypoxemia, and a mixed metabolic and respiratory acidosis by 10 min. Conclusions Hemodynamic and metabolic metrics during resuscitation with lipid surpassed those with epinephrine, which were no better than those seen in the saline control group. Further studies are required to optimize the clinical management of systemic local anesthetic toxicity.

Previous studies have demonstrated that the local anesthetic bupivacaine selectively inhibits oxidative metabolism of fatty acids in isolated cardiac mitochondria. In the present investigation, we compare the development of bupivacaine cardiotoxicity during fatty acid and carbohydrate metabolism. Hearts from adult male Sprague-Dawley rats were excised and retrograde perfused with a solution containing fatty acid (oleate or octanoate) or carbohydrate substrates for cardiac metabolism. An infusion of bupivacaine was initiated and sustained until asystole, after which full cardiac recovery was allowed. During fatty acid metabolism, substantially lower bupivacaine doses induced both arrhythmia (60.4+/-11.5 microg oleate and 106.8+/-14.8 octanoate versus 153.4+/-21.4 carbohydrate; P

Objectives Cocaine intoxication leads to over 500,000 emergency department visits annually in the United States and ethanol cointoxication occurs in 34% of those cases. Cardiotoxicity is an ominous complication of cocaine and cocaethylene overdose for which no specific antidote exists. Because infusion of lipid emulsion (Intralipid) can treat lipophilic local anesthetic toxicity and cocaine is an amphipathic local anesthetic, the authors tested whether lipid emulsion could attenuate cocaine cardiotoxicity in vivo. The effects of lipid emulsion were compared with the metabolically inert sulfobutylether-β-cyclodextrin (SBE-β-CD; Captisol) in an isolated heart model of cocaine and cocaethylene toxicity to determine if capture alone could exert similar benefit as lipid emulsion, which exhibits multimodal effects. The authors then tested if cocaine and cocaethylene, like bupivacaine, inhibit lipid-based metabolism in isolated cardiac mitochondria. Methods For whole animal experiments, Sprague-Dawley rats were anesthetized, instrumented, and pretreated with lipid emulsion followed by a continuous infusion of cocaine to assess time of onset of cocaine toxicity. For ex vivo experiments, rat hearts were placed onto a nonrecirculating Langendorff system perfused with Krebs-Henseleit solution. Heart rate, left ventricle maximum developed pressure (LVdevP), left ventricle diastolic pressure, maximum rate of contraction (+dP/dtmax), maximum rate of relaxation (–dP/dtmax), rate-pressure product (RPP = heart rate × LVdevP), and line pressure were monitored continuously during the experiment. A dose response to cocaine (10, 30, 50, and 100 μmol/L) and cocaethylene (10, 30, and 50 μmol/L) was generated in the absence or presence of either 0.25% lipid emulsion or SBE-β-CD. Substrate-specific rates of oxygen consumption were measured in interfibrillar cardiac mitochondria in the presence of cocaine, cocaethylene, ecgonine, and benzoylecgonine. Results Treatment with lipid emulsion delayed onset of hypotension (140 seconds vs. 279 seconds; p = 0.008) and asystole (369 seconds vs. 607 seconds; p = 0.02) in whole animals. Cocaine and cocaethylene induced dose-dependent decreases in RPP, +dP/dtmax, and –dP/dtmaxabs (p

We previously demonstrated in rats that intravenous infusion of a lipid emulsion increases survival in resuscitation from severe bupivacaine cardiac toxicity. The present studies were undertaken to determine if this method is similarly effective in a non-rodent model using a larger animal.Bupivacaine, 10 mg/kg, was administered intravenously over 10 seconds to fasted dogs under isoflurane general anesthesia. Resuscitation included 10 minutes of internal cardiac massage followed with either saline or 20% lipid infusion, administered as a 4-mL/kg bolus followed by continuous infusion at 0.5 mL/kg/min for 10 minutes. Electrocardiogram (EKG), arterial blood pressure (BP), and myocardial pH (pHm) and pO2 (pmO2) were continuously measured.Survival after 10 minutes of unsuccessful cardiac massage was successful for all lipid-treated dogs (n = 6), but with no survivors in the saline controls (n = 6) (P.01). Hemodynamics, PmO2, and pHm were improved during resuscitation with lipid compared with saline treatment in which dogs did not recover.We found that infusing a lipid emulsion during resuscitation from bupivacaine-induced cardiac toxicity substantially improved hemodynamics, pmO2, and pHm and increased survival in dogs.

OBJECTIVE: To assess changes in energy sensing and cell survival pathways both during bupivacaine-induced cardiac pharmacotoxicity and during the accelerated recovery caused by lipid-emulsion. METHODS: Male Sprague-Dawley rats were anesthetized and instrumented to monitor arterial pressures, carotid flows and to deliver drugs to both jugular veins. Animals were separated into 4-conditions: no treatment (control), 10mL/kg lipid emulsion (30% Intralipid, Frensius Kabi, Uppsala, Sweden) over 1 minute, 10mg/kg Bupivacaine over 20s, or 10mL/kg Bupivacaine followed 10 seconds later by 10mL/kg lipid emulsion. Animals were sacrificed at four time-points 0 minutes (for control), 1, 5 & 10 minutes following infusions. Hearts were flash-frozen and proteins extracted in an anti-protease, anti-phosphatase buffer. Following protein quantified for equal loading, the samples were run on a 4-15% Bis-Tris gel, transferred to nitrocellulose paper, stained with phosphorylation-site-specific antibodies in the AMPK and Akt...

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.

Background: Lipid infusion reverses systemic local anesthetic toxicity. The acceptable upper limit for lipid administration is unknown and has direct bearing on clinical management. We hypothesize that high volumes of lipid could have undesirable effects and sought to identify the dose required to kill 50% of the animals (LD50) of large volume lipid administration. Methods: Intravenous lines and electrocardiogram electrodes were placed in anesthetized, male Sprague-Dawley rats. Twenty percent lipid emulsion (20, 40, 60, or 80 mL/kg) or saline (60 or 80 mL/kg), were administered over 30 mins; lipid dosing was assigned by the Dixon "up-and-down" method. Rats were recovered and observed for 48 hrs then euthanized for histologic analysis of major organs. Three additional rats were administered 60 mL/kg lipid emulsion and euthanized at 1, 4, and 24 hrs to identify progression of organ damage. Results: The maximum likelihood estimate for LD50 was 67.72 (SE, 10.69) mL/kg. Triglycerides were elevated immediately after infusion but returned to baseline by 48 hrs when laboratory abnormalities included elevated amylase, aspartate aminotransferase, and serum urea nitrogen for all lipid doses. Histologic diagnosis of myocardium, brain, pancreas, and kidneys was normal at all doses. Microscopic abnormalities in lung and liver were observed at 60 and 80 mL/kg; histopathology in the lung and liver was worse at 1 hr than at 4 and 24 hrs. Conclusions: The LD50 of rapid, high volume lipid infusion is an order of magnitude greater than doses typically used for lipid rescue in humans and supports the safety of lipid infusion at currently recommended doses for toxin-induced cardiac arrest. Lung and liver histopathology was observed at the highest infused volumes.

Lipid emulsion infusion reverses local anesthetic-induced cardiac toxicity, but the effect of adding epinephrine has not been studied. We compared escalating doses of epinephrine on recovery with lipid infusion in a rat model of bupivacaine overdose.Rats anesthetized with isoflurane received an IV bolus of 20 mg/kg bupivacaine, producing asystole (zero time) in all animals. Ventilation (100% oxygen) and chest compressions were started immediately, and at 3 min the rats received one of six IV treatments (n = 5 for all groups): 5 ml/kg saline followed by infusion for 2 min at 1.0 ml x kg x min, and a second 5 ml/kg bolus at 5 min; or the same bolus and infusion treatment using 30% lipid emulsion plus a single injection of epinephrine at one of five doses: 0 (lipid control), 1, 2.5, 10, or 25 mcg/kg. An electrocardiogram and arterial pressure were monitored continuously, and arterial blood gas was measured at 7.5 and 15 min.Epinephrine improved initial return of spontaneous circulation (rate-pressure product30% baseline) but only 3 of 5 rats at 10 mcg/kg and 1 of 5 rats at 25 mcg/kg sustained return of spontaneous circulation by 15 min. Lipid alone resulted in slower but more sustained recovery. Epinephrine doses above a threshold near 10 mcg/kg increased lactate, worsened acidosis, and resulted in poor recovery at 15 min, as compared with lipid controls. There was tight correlation of epinephrine dose to serum lactate at 15 min.Epinephrine over a threshold dose near 10 mcg/kg impairs lipid resuscitation from bupivacaine overdose, possibly by inducing hyperlactatemia.

Lipid emulsion infusion is an emerging antidotal therapy for toxin-induced cardiac arrest. To compare the efficacy of resuscitation from bupivacaine-induced asystole using lipid emulsion infusion vs. vasopressin, alone and with epinephrine.Prospective, randomized, animal study.University research laboratory.Adult, male Sprague-Dawley rats.Instrumented rats were given an intravenous bolus of 20 mg/kg bupivacaine to induce asystole (zero time). Rats (n = 6 for all groups) were ventilated with 100% oxygen, given chest compressions, and randomized to receive 30% lipid emulsion (L, 5 mL/kg bolus then 1.0 mL/kg/min infusion) and vasopressin 0.4 U/kg bolus alone (V) or combined with epinephrine, 30 microg/kg (V + E); boluses (L, V, or V + E) were repeated at 2.5 and 5 minutes for a rate-pressure product (RPP) less than 20% baseline.The arterial blood pressure and electrocardiogram were measured continuously for 10 minutes when blood was drawn for arterial blood gas analysis, lactate content, and central venous oxygen saturation (ScvpO2). Hemodynamic parameters of the L group at 10 minutes (30,615 +/- 4782 mm Hg/min; 151 +/- 19.1 mm Hg; 197 +/- 8.6 min; RPP, systolic blood pressure and heart rate, respectively) exceeded those of the V group (5395 +/- 1310 mm Hg/min; 85.8 +/- 12 mm Hg; 61 +/- 10.8 min) and the V + E group (11,183 +/- 1857 mm Hg/min; 75.5 +/- 12.9 min, RPP and heart rate, respectively; systolic blood pressure was not different). Metrics indicated better tissue perfusion in the L group (7.24 +/- 0.02; 83% +/- 3.5%; 2.2 +/- 0.36 mmol/L; pH, ScvpO2, lactate, respectively) than V (7.13 +/- 0.02; 29.9% +/- 4.4%; 7.5 +/- 0.6 mmol/L) and V + E groups (7.07 +/- 0.03; 26.2% +/- 8.9%; 7.7 +/- 1 mmol/L). Wet-to-dry lung ratios in V (8.3 +/- 0.6) and V + E (8.7 +/- 0.2) were greater than that in the L group (6.2 +/- 05) (mean +/- sem; p0.05 for all shown results).Lipid emulsion in this rat model provides superior hemodynamic and metabolic recovery from bupivacaine-induced cardiac arrest than do vasopressors. Systolic pressure was not a useful metric in the vasopressor groups. Vasopressin was associated with adverse outcomes.

Background Bupivacaine retards myocardial acidosis during ischemia. The authors measured function of rat isolated hearts after prolonged storage to determine whether bupivacaine improves cardiac protection compared with standard cardioplegia alone. Methods After measuring cardiac function on a Langendorff apparatus, hearts were perfused with cardioplegia alone (controls), cardioplegia containing 500 microm bupivacaine, or cardioplegia containing 2 mm lidocaine; were stored at 4 degrees C for 12 h; and were then reperfused. Heart rate and left ventricular developed pressures were measured for 60 min. Maximum positive rate of change in ventricular pressure, oxygen consumption, and lactate dehydrogenase release were also measured. Results All bupivacaine-treated, four of five lidocaine-treated, and no control hearts beat throughout the 60-min recovery period. Mean values of heart rate, left ventricular developed pressure, maximum positive rate of change in ventricular pressure, rate-pressure product, and efficiency in bupivacaine-treated hearts exceeded those of the control group (P < 0.001 at 60 min for all). Mean values of the lidocaine group were intermediate. Oxygen consumption of the control group exceeded the other groups early in recovery, but not at later times. Lactate dehydrogenase release from the bupivacaine group was less than that from the control group (P < 0.001) but did not differ from baseline. Conclusions Adding bupivacaine to a depolarizing cardioplegia solution reduces cell damage and improves cardiac function after prolonged storage. Metabolic inhibition may contribute to this phenomenon, which is not entirely explained by sodium channel blockade.

Infusion of a lipid emulsion has been advocated for treatment of severe bupivacaine cardiac toxicity. The mechanism of lipid rescue is unknown. These studies address the possibility that lipid infusion reduces cardiac bupivacaine content in the context of cardiac toxicity.We compared the effects of a 1% lipid emulsion with standard Krebs buffer after inducing asystole in isolated rat heart with 500 micromol/L bupivacaine. We compared times to first heart beat and recovery of 90% of baseline rate pressure product (RPP = heart rate x [left ventricular systolic pressure - left ventricular diastolic pressure]) between controls and hearts receiving 1% lipid immediately after bupivacaine. We also used minibiopsies to compare control bupivacaine tissue content with hearts getting lipid immediately after an infusion of radiolabeled bupivacaine. We then compared bupivacaine efflux from hearts with and without lipid infusion started 75 seconds after radiolabeled bupivacaine was administered.Infusion of lipid resulted in more rapid return of spontaneous contractions and full recovery of cardiac function. Average (+/- SEM) times to first beat and to 90% recovery of rate pressure product were 44.6 +/- 3.5 versus 63.8 +/- 4.3 seconds (P.01) and 124.7 +/- 12.4 versus 219.8 +/- 25.6 seconds (P.01) for lipid and controls, respectively. Lipid treatment resulted in more rapid loss of bupivacaine from heart tissue (P.0016). Late lipid infusion, 75 seconds after bupivacaine infusion ended, increased the release of bupivacaine measured in effluent for the first 15-second interval compared with controls (183 vs. 121 nmol, n = 5 for both groups, P.008).Lipid emulsion speeds loss of bupivacaine from cardiac tissue while accelerating recovery from bupivacaine-induced asystole. These findings are consistent with the hypothesis that bupivacaine partitions into the emulsion and supports the concept of a "lipid sink." However, the data do not exclude other possible mechanisms of action.

Myocardial tissue oxygen pressure (PmO2 ) and left anterior descending (LAD) artery blood flow were measured in dogs anesthetized with 1.5% isoflurane, and were then compared to brain tissue oxygen pressure (PbO2 ) and middle cerebral artery (MCA) blood flow during normocapnia, hypocapnia, and hypercapnia. A craniotomy was performed and a tissue probe (Codman, Inc.) that measures PO2, PCO2, and pH was inserted into the brain cortex in the MCA region (n = 8). Separately, after a thoracotomy, a probe was inserted into the middle myocardium of the left ventricle, within the distribution of the LAD, in eight dogs. Blood flow probes were placed on the LAD or MCA. Blood flow and tissue gases were measured during normocapnia (PaCO2 = 38 mm Hg), hypocapnia (PaCO2 = 26 mm Hg), and hypercapnia (PaCO2 = 53 mm Hg). Mean arterial pressure, heart rate, arterial gases, and pH were not different between brain and heart measurements. PbO2 was 21 +/- 9 mm Hg (mean +/- SD ), 40 +/- 16 mm Hg, and 47 +/- 11 mm Hg. PmO2 was 35 +/- 12 mm Hg, 40 +/- 14 mm Hg, and 48 +/- 15 mm Hg during hypocapnia, normocapnia, and hypercapnia respectively. During hypercapnia, LAD and MCA flow increased 50% and tissue oxygenation increased 20% ( P < .05). During hypocapnia, MCA flow and PbO2 decreased 50% ( P < .05), but LAD flow and PmO2 did not significantly change. These results indicated that LAD flow and myocardial PO2 were less responsive to hypocapnia than MCA flow and PbO2.

Neurosurgical monitoring devices have recently become available which are capable of measuring cerebral tissue gas tensions and pH. Brain tissue sensors have not been conclusively demonstrated to correlate with other measurements of regional cerebral gas tensions or pH. The present study was undertaken to correlate sensor values for pO2, pCO2 and pH with blood samples taken concurrently from local cerebral veins. Adult mongrel dogs were anesthetized and a craniotomy was performed. A small gyral vein was isolated and cannulated. Adjacent to the venous catheter tip, a Neurotrend brain tissue probe was inserted in an intracortical location. Each subject received a sequence of manipulations in inspired oxygen and end tidal carbon dioxide conditions. Under each experimental condition, samples of arterial and gyral venous blood were obtained and blood gas analysis performed. Concurrent brain probe measurements of tissue pO2, pCO2 and pH were recorded. Statistical analysis determined that local tissue and cerebral venous blood values for pO2, pCO2 and pH were highly correlated (R(s) = 0.62-0.82; p < 0.001). This indicates that there exists a confirmable monotonic relationship between tissue values and conditions in the post-capillary venous bed. Tissue sensors such as the Neurotrend probe can offer reliable trend indications in brain tissue gas tensions and pH.

Background Inhalational anesthetics have been shown to influence T cell functions both in vitro and in vivo, in many cases inducing T cell death, suggesting that exposure to these drugs could modify the course of an autoimmune disease. We tested the hypothesis that in mice immunized to develop experimental autoimmune encephalomyelitis (EAE), a well established model of multiple sclerosis (MS), treatment with the commonly used inhalational anesthetic sevoflurane would attenuate disease symptoms. Methods C57Bl6 female mice were immunized with myelin oligodendrocyte glycoprotein (MOG) peptide residues 35 to 55 to induce a chronic demyelinating disease. At day 10 after immunization, the mice were subjected to 2 h of 2.5% sevoflurane in 100% oxygen, or 100% oxygen, alone. Following treatment, clinical scores were monitored up to 4 weeks, after which brain histology was performed to measure the effects on astrocyte activation and lymphocyte infiltration. Effects of sevoflurane on T cell activation were studied using splenic T cells isolated from MOG peptide-immunized mice, restimulated ex vivo with MOG peptide or with antibodies to CD3 and CD28, and in the presence of different concentrations of sevoflurane. T cell responses were assessed 1 day later by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay for proliferation, lactate dehydrogenase (LDH) release for cell death, and inflammatory activation by production of interleukin (IL)-17 and interferon (IFN)γ. Results Clinical scores in the oxygen-treated group increased until day 28 at which time they showed moderate to severe disease (average clinical score of 2.9). In contrast, disease progression in the sevoflurane-treated group increased to 2.1 at day 25, after which it remained unchanged until the end of the study. Immunohistochemical analysis revealed reduced numbers of infiltrating leukocytes and CD4+ cells in the CNS of the sevoflurane-treated mice, as well as reduced glial cell activation. In splenic T cells, low doses of sevoflurane reduced IFNγ production, cell proliferation, and increased LDH release. Conclusions These results are the first to show attenuation of EAE disease by an inhaled anesthetic and are consistent with previous reports that inhaled anesthetics, including sevoflurane, can suppress T cell activation that, in the context of autoimmune diseases such as MS, could lead to reduced clinical progression.