Andrographolide attenuates bupivacaine-induced cytotoxicity in SH-SY5Y cells through preserving Akt/mTOR activity.

Background: Bupivacaine (Bup) is the most commonly used local anesthetic. However, Bup induces cytotoxicity, especially in older patients. Recent reports have indicated that andrographolide (Andro) exhibits protective effects on human neurons. Nevertheless, whether Andro can inhibit Bup-induced cytotoxicity remains unclear. As such, we investigated the effect of Andro on Bup-induced cytotoxicity of SH-SY5Y cells in the present study. Methods: Western blotting was used to examine expression of Bax, Bcl2, active caspase 3, p-Akt, and p-mTOR in SH-SY5Y cells. In addition, ELISA was used to detect levels of total glutathione and reactive oxygen species in cells. Results: We found that Andro attenuated Bup-induced cytotoxicity of SH-SY5Y cells. In addition, Andro inhibited Bup-induced apoptosis via downregulating the expression of Bax and active caspase 3 and upregulating the proteins Bcl2, p-Akt, and p-mTOR in SH-SY5Y cells. Moreover, Andro alleviated Bup-induced oxidative damage in SH-SY5Y cells via downregulating the level of reactive oxygen species and upregulating of the level of total glutathione. More significantly, inhibition of Akt abolished the protective effect of Andro in Bup-treated SH-SY5Y cells. Conclusion: Our findings indicated that Andro played a neuroprotective role via preserving Akt/mTOR activity and increasing antioxidative status in Bup-treated SH-SY5Y cells. Therefore, Andro may be a potential agent for the treatment of human cytotoxicity induced by Bup.

Tetramethylpyrazine attenuated bupivacaine-induced neurotoxicity in SH-SY5Y cells through regulating apoptosis, autophagy and oxidative damage.

Background: Bupivacaine (BUP) acts as a local anesthetic, which is extensively used for clinical patients but could generate neurotoxicity in neurons. Tetramethylpyrazine (TET) exhibits strong neuron protective effects against neurotoxicity. Hence, we investigate the effect of TET on BUP-induced neurotoxicity in SH-SY5Y cells. Methods: CCK-8 assay was used to detect cell proliferation in SH-SY5Y cells. In addition, Western blotting was used to examine Bax, Bcl-2, active caspase 3, LC3II, Beclin 1 and p-62 protein levels in cells. Moreover, ELISA assay was used to detect the levels of total glutathione (GS), superoxide dismutase (SOD) and malondialdehyde (MDA) in cells. Results: In this study, we found that TET attenuated the neurotoxicity of BUP on SH-SY5Y cells. Meanwhile, TET alleviated BUP-induced apoptosis in SH-SY5Y cell via decreasing the expressions of active caspase-3 and Bax and increasing the expression of Bcl-2. In addition, monodansylcadaverine staining assay and Western blotting results confirmed that TET induced autophagy in SH-SY5Y cells via increasing the LC3II/I and Beclin 1 levels. Furthermore, TET attenuated BUP-induced oxidative damage in SH-SY5Y cells via upregulation of the levels of total GS and SOD and downregulation of the level of MDA. Interesting, the protective effects of TET against BUP-induced neurotoxicity in SH-SY5Y cells were reversed by autophagy inhibitor 3-methyladenine (3MA). Conclusion: These data indicated that TET may play a neuroprotective role via inhibiting apoptosis and inducing autophagy in SH-SY5Y cells. Therefore, TET may be a potential agent for the treatment of human neurotoxicity induced by BUP.

Monosialoganglioside protects against bupivacaine-induced neurotoxicity caused by endoplasmic reticulum stress in rats.

BACKGROUND: Local anesthetics in spinal anesthesia have neurotoxic effects, resulting in severe neurological complications. Intrathecal monosialoganglioside (GM1) administration has a therapeutic effect on bupivacaine-induced neurotoxicity. The aim of this study was to determine the underlying mechanisms of bupivacaine-induced neurotoxicity and the potential neuroprotective role of GM1. MATERIALS AND METHODS: A rat spinal cord neurotoxicity model was established by injecting bupivacaine (5%, 0.12 µL/g) intrathecally. The protective effect of GM1 (30 mg/kg) was evaluated by pretreating the animals with it prior to the bupivacaine regimen. The neurological and locomotor functions were assessed using standard tests. The histomorphological changes, neuron degeneration and apoptosis, and endoplasmic reticulum stress (ERS) relevant markers were analyzed using immunofluorescence, quantitative real-time PCR, and Western blotting. RESULTS: Bupivacaine resulted in significant neurotoxicity in the form of aberrant neurolocomoter functions and spinal cord histomorphology and neuronal apoptosis. Furthermore, the ERS specific markers were significantly upregulated during bupivacaine-induced neurotoxicity. These neurotoxic effects were ameliorated by GM1. CONCLUSION: Pretreatment with GM1 protects against bupivacaine-induced neurotoxicity via the inhibition of the GRP78/PERK/eIF2α/ATF4-mediated ERS.

Lipid resuscitation in acute poisoning: after a decade of publications, what have we really learned?

PURPOSE OF REVIEW: The decision to provide intravenous lipid emulsion (ILE) therapy as a treatment modality for the reversal of various drug toxicity was discovered in the last decade. Numerous publications, in both humans and animals attest to its clinical use, but current supporting evidence is inconsistent. RECENT FINDINGS: A recent systematic review reported evidence for benefit of ILE in bupivacaine toxicity. Human randomized trials, large observational studies as well as animal models of orogastric poisoning failed to report a clear benefit of ILE for nonlocal anesthetics poisoning. SUMMARY: ILE can be used to resuscitate local anesthetics especially bupivacaine. The impact of ILE on oral overdoses is controversial and clear evidence on benefit is lacking. A thorough risk benefit assessment with consideration of alternative options is warranted to minimize the risk of adverse effects. Evidence supports using bolus doses of ILE, while infusion rates are still debatable.

Modification of Bupivacaine-Induced Myotoxicity with Dantrolene and Caffeine In Vitro.

BACKGROUND: Local anesthetics, especially bupivacaine, have myotoxic effects in clinically used concentrations and context. Detailed mechanisms of these effects are unknown, but an increase in intracellular calcium levels is suspected to be the most important trigger. Dantrolene and caffeine modify cellular calcium release from the sarcoplasmic reticulum. The aim of our study was to investigate the effect of dantrolene and caffeine on bupivacaine-induced myotoxicity in vitro. METHODS: A cell culture model of primary muscle cells of BALB/c AnNCrl mice was established. Cells were incubated simultaneously with increasing concentrations of bupivacaine, dantrolene, and caffeine. The fraction of dead cells was calculated after staining with propidium iodide and analysis by flow cytometry. The half-maximal inhibitory concentration of bupivacaine was calculated for each concentration. Group differences were determined by using 1-way analysis of variances with subsequent post hoc 1-way Dunnett t test. RESULTS: Both dantrolene and caffeine alone had no effect on muscle cell survival. Increasing concentrations of bupivacaine caused increasing cell death. Dantrolene dose-dependently reduced the fraction of necrotic cells, whereas caffeine dose-dependently increased the fraction of dead cells. CONCLUSIONS: Dantrolene attenuated, and caffeine enhanced, bupivacaine-induced myotoxicity, presumably by modifying sarcoplasmic calcium release. This indicates that intracellular calcium release is an important factor for local anesthetic-induced cell death.

Lipid Emulsion Inhibits Vasodilation Induced by a Toxic Dose of Bupivacaine via Attenuated Dephosphorylation of Myosin Phosphatase Target Subunit 1 in Isolated Rat Aorta.

Lipid emulsions are widely used for the treatment of systemic toxicity that arises from local anesthetics. The goal of this in vitro study was to examine the cellular mechanism associated with the lipid emulsion-mediated attenuation of vasodilation induced by a toxic dose of bupivacaine in isolated endothelium-denuded rat aorta. The effects of lipid emulsion on vasodilation induced by bupivacaine, mepivacaine, and verapamil were assessed in isolated aorta precontracted with phenylephrine, the Rho kinase stimulant NaF, and the protein kinase C activator phorbol 12,13-dibutyrate (PDBu). The effects of Rho kinase inhibitor Y-27632 on contraction induced by phenylephrine or NaF were assessed. The effects of bupivacaine on intracellular calcium concentrations ([Ca(2+)]i) and tension induced by NaF were simultaneously measured. The effects of bupivacaine alone and lipid emulsion plus bupivacaine on myosin phosphatase target subunit 1 (MYPT1) phosphorylation induced by NaF were examined in rat aortic vascular smooth muscle cells. In precontracted aorta, the lipid emulsion attenuated bupivacaine-induced vasodilation but had no effect on mepivacaine-induced vasodilation. Y-27632 attenuated contraction induced by either phenylephrine or NaF. The lipid emulsion attenuated verapamil-induced vasodilation. Compared with phenylephrine-induced precontracted aorta, bupivacaine-induced vasodilation was slightly attenuated in NaF-induced precontracted aorta. The magnitude of the bupivacaine-induced vasodilation was higher than that of a bupivacaine-induced decrease in [Ca(2+)]i. Bupivacaine attenuated NaF-induced MYPT1 phosphorylation, whereas lipid emulsion pretreatment attenuated the bupivacaine-induced inhibition of MYPT1 phosphorylation induced by NaF. Taken together, these results suggest that lipid emulsions attenuate bupivacaine-induced vasodilation via the attenuation of inhibition of MYPT1 phosphorylation evoked by NaF.

Pre-treatment of bupivacaine-induced cardiovascular depression using different lipid formulations of propofol.

BACKGROUND: Pre-treatment with lipid emulsions has been shown to increase lethal doses of bupivacaine, and the lipid content of propofol may alleviate bupivacaine-induced cardiotoxicity. The aim of this study is to investigate the effects of propofol in intralipid or medialipid emulsions on bupivacaine-induced cardiotoxicity. METHODS: Rats were anaesthetised with ketamine and were given 0.5 mg/kg/min propofol in intralipid (Group P), propofol in medialipid (Group L), or saline (Group C) over 20 min. Thereafter, 2 mg/kg/min bupivacaine 0.5% was infused. We recorded time to first dysrhythmia occurrence, respective times to 25% and 50% reduction of the heart rate (HR) and mean arterial pressure, and time to asystole and total amount of bupivacaine consumption. Blood and tissue samples were collected following asystole. RESULTS: The time to first dysrhythmia occurrence, time to 25% and 50% reductions in HR, and time to asystole were longer in Group P than the other groups. The cumulative bupivacaine dose given at those time points was higher in Group P. Plasma bupivacaine levels were significantly lower in Group P than in Group C. Bupivacaine levels in the brain and heart were significantly lower in Group P and Group L than in Group C. CONCLUSION: We conclude that pre-treatment with propofol in intralipid, compared with propofol in medialipid or saline, delayed the onset of bupivacaine-induced cardiotoxic effects as well as reduced plasma bupivacaine levels. Further studies are needed to explore tissue bupivacaine levels of propofol in medialipid and adapt these results to clinical practice.

Effect of long-chain triglyceride lipid emulsion on bupivacaine-induced changes in electrophysiological parameters of rabbit Purkinje cells.

Lipid emulsions are used in the reversal of local anesthetic toxicity. The aim of this study was to investigate the cellular electrophysiological effects of long-chain triglyceride lipid emulsion (LCTE) on cardiac action potential characteristics and conduction disturbances induced by bupivacaine. Purkinje fibers were dissected from the left ventricle of New Zealand white rabbit hearts and superfused with either Tyrode's solution during 30 min (control group), with bupivacaine 10(-6) M, 10(-5) M, and 5.10(-5) M alone, or in the presence of LCTE 0.5%, in addition, LCTE at 0.1%, 0.5%, and 1% was perfused alone. Electrophysiological parameters were recorded using the conventional microelectrode technique (37 °C, 1 Hz frequency). Bupivacaine 5.10(-5) M-induced conduction blocks (8/8 preparations): LCTE 0.5% suppressed the bupivacaine 5.10(-5) M-induced conduction blocks (1/8 preparations). Exposure to bupivacaine 10(-6) M, 10(-5) M, and 5.10(-5) M resulted in a significant decrease in the maximal rate of depolarization (Vmax) (respectively, 25%, 55%, 75%; P < 0.002 vs. control group). In the presence of LCTE 0.5%, bupivacaine 10(-6) M did not significantly decreased Vmax (13%; P = 0.10 vs. control group). The decrease in Vmax resulting from bupivacaine 10(-5) M alone was significantly less in the presence of LCTE 0.5% (P < 0.01 vs. bupivacaine 10(-5) M alone). Exposure to bupivacaine 10(-6) M, 10(-5) M, and 5.10(-5) M alone or in the presence of LCTE 0.5% resulted in a significant decrease in action potential duration measured at 50% and 90% repolarization (APD50 and APD90; P < 0.01 vs. control group). LCTE inhibited the Purkinje fibers conduction blocks induced by bupivacaine. Moreover, LCTE 0.5% attenuates the decrease in Vmax induced by bupivacaine 10(-6) M and 10(-5) M.

Bupivacaine-induced apoptosis independently of WDR35 expression in mouse neuroblastoma Neuro2a cells.

BACKGROUND: Bupivacaine-induced neurotoxicity has been shown to occur through apoptosis. Recently, bupivacaine was shown to elicit reactive oxygen species (ROS) production and induce apoptosis accompanied by activation of p38 mitogen-activated protein kinase (MAPK) in a human neuroblastoma cell line. We have reported that WDR35, a WD40-repeat protein, may mediate apoptosis through caspase-3 activation. The present study was undertaken to test whether bupivacaine induces apoptosis in mouse neuroblastoma Neuro2a cells and to determine whether ROS, p38 MAPK, and WDR35 are involved. RESULTS: Our results showed that bupivacaine induced ROS generation and p38 MAPK activation in Neuro2a cells, resulting in apoptosis. Bupivacaine also increased WDR35 expression in a dose- and time-dependent manner. Hydrogen peroxide (H(2)O(2)) also increased WDR35 expression in Neuro2a cells. Antioxidant (EUK-8) and p38 MAPK inhibitor (SB202190) treatment attenuated the increase in caspase-3 activity, cell death and WDR35 expression induced by bupivacaine or H(2)O(2). Although transfection of Neuro2a cells with WDR35 siRNA attenuated the bupivacaine- or H(2)O(2)-induced increase in expression of WDR35 mRNA and protein, in contrast to our previous studies, it did not inhibit the increase in caspase-3 activity in bupivacaine- or H(2)O(2)-treated cells. CONCLUSIONS: In summary, our results indicated that bupivacaine induced apoptosis in Neuro2a cells. Bupivacaine induced ROS generation and p38 MAPK activation, resulting in an increase in WDR35 expression, in these cells. However, the increase in WDR35 expression may not be essential for the bupivacaine-induced apoptosis in Neuro2a cells. These results may suggest the existence of another mechanism of bupivacaine-induced apoptosis independent from WDR35 expression in Neuro2a cells.

Effect of intravenous lipid emulsion on bupivacaine plasma concentration in humans.

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

Hyaluronidase shortens levobupivacaine lumbosacral epidural anaesthesia in dogs.

OBJECTIVES: The aim of this study was to evaluate the effects of hyaluronidase added to levobupivacaine in lumbosacral epidural blockade in dogs. METHODS: Six adult mixed breed dogs (two males and four females) weighing 7 to 14 kg (10.5 ±1.5 kg) and aged two to five years were used. Each dog received both treatments in random order: levobupivacaine alone (LBA; n=6) or levobupivacaine plus hyaluronidase (LBH; n=6) administered in the lumbosacral epidural space. Systemic effects, spread and duration of anaesthesia and motor block were determined before treatment and at predetermined intervals. RESULTS: The duration of local anaesthesia was 90 ±10 minutes (P=0.001) for LBH treatment and 150 ±15 minutes for LBA treatment. In the LBH treatment, anaesthesia reached the T12 to T13 dermatome and in the LBA treatment it reached the T11 to T12 dermatome in all animals in 5 and 15 minutes, respectively. Complete motor blockade was 75 ±12 minutes (P=0.01) and 120 ±15 minutes for LBH and LBA treatments, respectively. CLINICAL SIGNIFICANCE: Hyaluronidase added to levobupivacaine significantly shortens the duration of epidural anaesthesia with the same dermatome spread into the epidural space in dogs.

Lipid emulsion reverses Levobupivacaine-induced responses in isolated rat aortic vessels.

BACKGROUND: The goal of this in vitro study was to investigate the effects of lipid emulsion (LE) on local anesthetic levobupivacaine-induced responses in isolated rat aorta and to determine whether the effect of LE is related to the lipid solubility of local anesthetics. METHODS: Isolated rat aortic rings were suspended for isometric tension recording. The effects of LE were determined during levobupivacaine-, ropivacaine-, and mepivacaine-induced responses. Endothelial nitric oxide synthase and caveolin-1 phosphorylation was measured in human umbilical vein endothelial cells treated with levobupivacaine alone and with the addition of LE. RESULTS: Levobupivacaine produced vasoconstriction at lower, and vasodilation at higher, concentrations, and both were significantly reversed by treatment with LE. Levobupivacaine and ropivacaine inhibited the high potassium chloride-mediated contraction, which was restored by LE. The magnitude of LE-mediated reversal was greater with levobupivacaine treatment than with ropivacaine, whereas this reversal was not observed in mepivacaine-induced responses. In LE-pretreated rings, low-dose levobupivacaine- and ropivacaine-induced contraction was attenuated, whereas low-dose mepivacaine-induced contraction was not significantly altered. Treatment with LE also inhibited the phosphorylation of endothelial nitric oxide synthase induced by levobupivacaine in human umbilical vein endothelial cells. CONCLUSIONS: These results indicate that reversal of levobupivacaine-induced vasodilation by LE is mediated mainly through the attenuation of levobupivacaine-mediated inhibition of L-type calcium channel-dependent contraction and, in part, by inhibition of levobupivacaine-induced nitric oxide release. LE-mediated reversal of responses induced by local anesthetics may be related to their lipid solubility.

Lipid emulsion reverses bupivacaine-induced asystole in isolated rat hearts: concentration-response and time-response relationships.

BACKGROUND: The concentration-response and time-response relationships of lipid emulsions used to reverse bupivacaine-induced asystole are poorly defined. METHODS: Concentration response across a range of lipid concentrations (0-16%) to reverse bupivacaine-induced asystole were observed using isolated rat heart Langendorff preparation. Cardiac function parameters were recorded during infusion. Concentrations of bupivacaine in myocardial tissue were measured by liquid chromatography and tandem mass spectrometry at the end of the experiment. RESULTS: Although all lipid-treated hearts recovered (cardiac recovery was defined as a rate-pressure product more than 10% baseline), no nonlipid-treated hearts (control group) did so. The ratio of the maximum rate pressure product during recovery to baseline value demonstrated a concentration-dependent relationship among lipid groups, with 0.25, 0.5, 1, 2, 4, 8, and 16%. Mean ± SD values for each corresponding group were 22 ± 4, 24 ± 5, 29 ± 6, 52 ± 11, 73 ± 18, 119 ± 22, and 112 ± 10%, respectively (n = 6, P < 0.01). Rate-pressure product in lipid groups with 4-16% concentrations was lower at 15-40 min than at 1 min, showing a decreasing tendency during recovery phase (P < 0.01). The concentration of myocardial bupivacaine in all lipid-treated groups was significantly lower than in the control group (P < 0.01). It was also lower in lipid groups with 2-16% concentrations than in those with concentrations at 0.25-1% (P < 0.05), with the 16% group lower than groups with 2-8% concentrations (P < 0.001). CONCLUSION: Lipid application in bupivacaine-induced asystole displays a concentration-dependent and time-response relationship in isolated rat hearts.

Reversal of bupivacaine-induced cardiac electrophysiologic changes by two lipid emulsions in anesthetized and mechanically ventilated piglets.

BACKGROUND: Accidental IV administration of bupivacaine can compromise cardiovascular function by inducing lethal arrhythmias whose hemodynamic consequences may be alleviated by lipid emulsions. However, little is known about the electrophysiologic effects of lipid emulsions. In this study, we assessed whether 2 different lipid emulsions can reverse cardiac electrophysiologic impairment induced by the IV administration of bupivacaine in anesthetized and mechanically ventilated piglets. METHODS: Bupivacaine (4 mg . kg(-1)) was injected over a 30-second period in 26 piglets. Thirty seconds after the end of bupivacaine injection, 1.5 mL . kg(-1) saline solution for the control group, and long-chain triglyceride emulsion (LCT group) or a mixture of long-chain and medium-chain triglyceride emulsion (LCT/MCT group) were infused over 1 minute. Cardiac conduction variables and hemodynamic variables were monitored for 30 minutes after injection. RESULTS: Bupivacaine induced similar electrophysiologic and hemodynamic changes. After 3 minutes, His ventricle intervals (median and interquartiles) were 100 (85-105), 45 (35-55), and 53 (48-73) milliseconds in the control, LCT, and LCT/MCT groups, respectively (P < 0.001 between control and both lipid emulsion groups). Lipid emulsions also reversed the effects on QRS duration, atrial-His, and PQ (the onset of the P wave to the Q wave of the QRS complex) intervals. LCT/MCT emulsion restored the decrease in maximal first derivative of left ventricular pressure (P < 0.01 after 3 minutes versus control group). CONCLUSIONS: LCT and LCT/MCT emulsions reversed the lengthening of His ventricle, QRS, atrial-His, and PQ intervals induced by the IV injection of 4 mg . kg(-1) bupivacaine.

The effect of levosimendan on bupivacaine-induced severe myocardial depression in anesthetized pigs.

BACKGROUND AND OBJECTIVES: Levosimendan, an inodilator without proarrhythmogenic properties, has been shown to reverse ropivacaine-induced negative inotropy in isolated heart preparations. In this randomized and blinded study, we investigated whether levosimendan is able to reverse rapidly bupivacaine-induced myocardial depression in pigs. METHODS: Twenty invasively monitored pigs anesthetized with isoflurane 1% received bupivacaine 2 mg/kg per minute into a central vein until mean arterial pressure decreased to 55% of baseline. Thereafter, levosimendan 80 microg/kg for 10 mins, followed by 0.7 microg/kg per minute during the next 50 mins (L-SIM) or corresponding amounts of placebo were administered intravenously. Simultaneously, Ringer's acetate was infused intravenously, 20 mL/kg for 10 mins, followed by 20 mL/kg for 50 mins. RESULTS: Two pigs in each group developed cardiac arrest immediately after bupivacaine and could not be resuscitated. Bupivacaine induced widening of the QRS complex in the electrocardiogram and bradycardia.In the remaining 16 pigs, 3 (2 in L-SIM group and 1 in placebo group) needed short-lasting manual cardiac compression and 1 dose of epinephrine. Cardiac output, ejection fraction, and stroke power/end-diastolic volume recovered initially very rapidly in the L-SIM group.However, there was no time x group effect difference in the overall recovery in the various parameters between the 2 groups, except in heart rate which was higher (P G 0.05) when levosimendan was administered.During the 50-min levosimendan infusion, mean arterial pressure and systemic vascular resistance stayed slightly lower in comparison with placebo infusion, but the difference was not statistically significant. CONCLUSIONS: Levosimendan together with the infusion of Ringer's solution rapidly reversed the cardiac depression, but there was no difference in overall cardiovascular recovery in comparison to treatment with Ringer's solution alone. Levosimendan-induced increase in heart rate possibly facilitated the recovery from bupivacaine intoxication.

Epinephrine impairs lipid resuscitation from bupivacaine overdose: a threshold effect.

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.