The Effects of Levosimendan on Myocardial Function in Ropivacaine Toxicity in Isolated Guinea Pig Heart Preparations

The Coadministration of Levosimendan and Exenatide Offers a Significant Cardioprotective Effect to Isolated Rat Hearts against Ischemia/Reperfusion Injury

(1) Background: The present study aims to investigate the effect of administration of Levosimendan and Exenatide in various concentrations, as well as of the coadministration of those agents in an ischemia–reperfusion injury isolated heart model. (2) Methods: After 30 min of perfusion, the hearts underwent a 30 min period of regional ischemia followed by a 120 min period of reperfusion. All animals were randomly divided into 12 experimental groups of nine animals in each group: (1) Control, (2) Sham, (3) Digox (Negative control, Digoxin 1.67 μg/min), (4) Levo 1 (Levosimendan 0.01 μg/min), (5) Levo 2 (Levosimendan 0.03 μg/mL), (6) Levo 3 (Levosimendan 0.1 μg/min), (7) Levo 4 (Levosimendan 0.3 μg/min), (8) Levo 5 (Levosimendan 1 μg/min), (9) Exen 1 (Exenatide 0.001 μg/min), (10) Exen 2 (Exenatide 0.01 μg/min), (11) Exen 3 (Exenatide 0.1 μg/min) and (12) Combi (Levosimendan 0.1 µg/mL + Exenatide 0.001 μg/min). The hemodynamic parameters were recorded throughout the experiment. Arrhythmias and coronary flow were also evaluated. After every experiment the heart was suitably prepared and infarct size was measured. Markers of myocardial injury were also measured. Finally, oxidative stress was evaluated measuring reactive oxygen species. (3) Results: A dose-dependent improvement of the haemodynamic response was observed after the administration of both Levosimendan and Exenatide. The coadministration of both agents presented an even greater effect, improving the haemodynamic parameters further than the two agents separately. Levosimendan offered an increase of the coronary flow and both agents offered a reduction of arrhythmias. A dose-dependent reduction of the size of myocardial infarction and myocardial injury was observed after administration of Levosimendan and Exenatide. The coadministration of both agents offered a further improving the above parameters. Levosimendan also offered a significant reduction of oxidative stress. (4) Conclusions: The administration of Levosimendan and Exenatide offers a significant benefit by improving the haemodynamic response, increasing the coronary flow and reducing the occurrence of arrhythmias, the size of myocardial injury and myocardial oxidative stress in isolated rat hearts.

In Vitro Negative Inotropic Effect of Low Concentrations of Bupivacaine Relates to Diminished Ca2+ Sensitivity but Not to Ca2+ Handling or β-Adrenoceptor Signaling

BACKGROUND

Systemic toxicity of local anesthetics is predominantly complicated by their myocardial toxicity. Especially long-acting local anesthetics exert a negative inotropic effect that has been described at lower concentrations than defined for blockade of myocardial ion channels. We evaluated the negative inotropic effect of bupivacaine at a concentration described for clinical toxicity testing the hypothesis that negative inotropy is a result of reduced Ca sensitivity rather than blockade of ion channels.

METHODS

We simultaneously measured force development and action potentials in guinea pig right papillary muscles (n = 5 to 7). L-type Ca currents (n = 8 to 16) and Ca transients (n = 10 to 11) were measured in isolated cardiomyocytes. Sensitivity of myofilaments to Ca was assessed in skinned fibers (n = 10). Potential effects of bupivacaine on 3',5'-cyclic adenosine monophosphate concentrations were measured using Förster Resonance Energy Transfer (n = 12 to 14) microscopy.

RESULTS

Bupivacaine reduced force in a concentration-dependent manner from 173 ± 119 µN at baseline to 28 ± 13 µN at 300 µM (mean ± SD). At concentrations giving half-maximum negative inotropic effects (5 µM), the maximum upstroke velocity of action potentials, as a surrogate of sodium channel activity, was unaffected. Maximum positive inotropic effects of isoprenaline were also reduced to 50%. Neither basal nor isoprenaline-induced 3',5'-cyclic adenosine monophosphate accumulation, L-type Ca currents, or Ca transients were affected by 5 µM bupivacaine, but this concentration significantly decreased Ca sensitivity of myofilaments, changing the negative logarithm of the half-maximum effective Ca concentrations from 5.66 to 5.56 -log[M].

CONCLUSIONS

We provide evidence that the negative inotropic effect of bupivacaine may be caused mainly by a reduction in myofilament sensitivity to Ca.

Levosimendan is superior to epinephrine on coronary flow for lipid-base resuscitation of bupivacaine-induced asystole in the isolated rat heart

Background

Successful resuscitation from asystole induced by bupivacaine requires the reestablishment of a sufficient coronary flow (CF) quickly. This study was designed to test whether levosimendan was superior to epinephrine in the reestablishment of crucial coronary flows after bupivacaine-induced asystole.

Methods

The isolated, perfused, nonrecirculating, Langendorff rat heart preparation was used. Bupivacaine 100 μmol/L was perfused into rat hearts to induce asystole, and then for 3 min thereafter. Three experimental groups were assessed after asystole with infusions as follow: (1) a mixture of 2% lipid emulsion and 40 μmol/L bupivacaine (control group), (2) a mixture of 0.15 μg/mL epinephrine combined with 2% lipid emulsion and 40 μmol/L bupivacaine (epinephrine group), and (3) a mixture of 5 μmol/L levosimendan combined with a 2% lipid emulsion and 40 μmol/L bupivacaine mixture (levosimendan group). Coronary flow (CF), the time to recovery (T_recovery), the number of ventricular arrhythmias, and cardiac function parameters were recorded for 40 min after heartbeat recovery.

Results

All hearts in the control, epinephrine and levosimendan groups had heartbeat recovery. The rank order of the mean CF from highest to lowest was the levosimendan group > the epinepgrine group > the control group (P < 0.05). The rank order of T_recovery from shortest to longest was the levosimendan group < the epinephrine group < the control group (P < 0.01). During the recovery phase, isolated rat hearts developed more ventricular arrhythmias in the epinephrine group than in the levosimendan group (P = 0.01).

Conclusion

Levosimendan is superior to epinephrine in producing higher CFs and faster recovery when reversing bupivacaine-induced asystole in the isolated rat hearts.

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

Background

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

Methods

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

Results

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

Conclusions

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

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

Background

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

Methods

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

Results

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

Conclusion

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

Myocardial accumulation of bupivacaine and ropivacaine is associated with reversible effects on mitochondria and reduced myocardial function

BACKGROUND

Mechanisms of local anesthetic cardiac toxicity are still not completely understood. In this study, we analyzed whether concentrations of local anesthetics found in clinical toxicity affect myocardial mitochondrial structure and oxygen consumption.

METHODS

Guinea pig isolated heart Langendorff preparations were exposed to bupivacaine (3.0 and 7.5 μg/mL) and ropivacaine (3.6 and 9.0 μg/mL) for 10 minutes. Heart rate, systolic blood pressure, the first derivative of left ventricular pressure (+dP/dt), electrocardiogram, and coronary flow were recorded. The local anesthetic tissue concentration was measured either immediately after local anesthetic exposure, or after 20- and 60-minute washout periods. In addition, electron microscopy of myocardial mitochondria was performed using a scoring system for structural damage of mitochondria. Cardiomyocyte cell culture was incubated with bupivacaine, and oxygen consumption ratio, extracellular acidification, and relative amounts of PGC-1α mRNA, a regulator of cellular energy metabolism, were determined.

RESULTS

Bupivacaine and ropivacaine induced reversible PR interval and QRS prolongation, and left ventricular pressure and +dP/dt reduction. Myocardial tissue concentration of local anesthetics was 3-fold the arterial concentration. Mitochondria showed a significant concentration-dependent morphological swelling after local anesthetic application. These changes were reversed by a 20-minute washout period for ropivacaine and by a 60-minute washout for bupivacaine. Bupivacaine reduced mitochondrial oxygen consumption and increased PGC-1α expression in neonatal cardiomyocyte cell cultures, whereas fatty acid metabolism remained unaffected.

CONCLUSIONS

Bupivacaine and ropivacaine accumulate in the myocardium. Reversible local anesthetic-induced mitochondrial swelling occurs at concentrations that induce a negative inotropic effect. Bupivacaine reduces cellular metabolism, whereas this reduction is reversible by fatty acids. Interaction with mitochondria may contribute to the negative inotropic effect of local anesthetics.

Midazolam in rabbits terminates dysrhythmias caused by intracerebroventricular ropivacaine

The current study was designed to investigate the mechanisms by which ropivacaine may act within the central nervous system (CNS) to produce cardiotoxicity. Eighty New Zealand rabbits were divided into four groups randomly. In Group 1, 20 rabbits received intracerebroventricular (icv) saline, and then received icv ropivacaine 30 min later. In Group 2, 20 rabbits received icv ropivacaine. Whenever dysrhythmias continued for more than 5 min, 0.1 ml saline was administered into the left cerebral ventricle. Ten minutes later, 0.1 ml midazolam was given into the left lateral ventricle. In Group 3, 20 rabbits received icv ropivacaine, and once the dysrhythmias developed, the inspired isoflurane concentration was increased from 0.75% to 1.50%. In Group 4, 20 animals received an intravenous (iv) phenylephrine infusion until dysrhythmias occurred. In Group 1, the rabbits did not develop dysrhythmias in response to icv saline, whereas dysrhythmias did develop in these animals after icv ropivacaine. In Group 2, icv saline had no effect on the dysrhythmias; however, icv midazolam terminated cardiac dysrhythmias. In Group 3, an increase in the concentration of the inspired isoflurane had no effect on dysrhythmias. In Group 4, icv midazolam had no effect on dysrhythmias in response to iv phenylephrine. Ropivacaine administered directly into the CNS is capable of producing cardiac dysrhythmias; midazolam terminated dysrhythmias presumably by potentiation of γ-aminobutyric acid (GABA) receptor activity. Our results suggest that ropivacaine produces some of its cardiotoxicity not only by the direct cardiotoxicity of the drug, but also by the CNS effects of ropivacaine.

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.