Levosimendan improves postresuscitation outcomes in a rat model of CPR

Omecamtiv mecarbil treatment improves post-resuscitation cardiac function and neurological outcome in a rat model

Background

Myocardial dysfunction is a major cause of poor outcomes in the post-cardiac arrest period. Omecamtiv mecarbil (OM) is a selective small molecule activator of cardiac myosin that prolongs myocardial systole and increases stroke volume without apparent effects on myocardial oxygen demand. OM administration is safe and improves cardiac function in patients with acute heart failure. Whether OM improves post-resuscitation myocardial dysfunction remains unclear. This study investigated the effect of OM treatment on post-resuscitation myocardial dysfunction and outcomes.

Methods and results

Adult male rats were resuscitated after 9.5 min of asphyxia-induced cardiac arrest. OM and normal saline was continuously intravenously infused after return of spontaneous circulation (ROSC) at 0.25 mg/kg/h for 4 h in the experimental group and control group, respectively (n = 20 in each group). Hemodynamic parameters were measured hourly and monitored for 4 h after cardiac arrest. Recovery of neurological function was evaluated by neurological functioning scores (0–12; favorable: 11–12) for rats 72 h after cardiac arrest. OM treatment prolonged left ventricular ejection time and improved post-resuscitation cardiac output. Post-resuscitation heart rate and left ventricular systolic function (dp/dt₄₀) were not different between groups. Kaplan-Meier analysis showed non-statistically higher 72-h survival in the OM group (72.2% [13/18] and 58.8% [10/17], p = 0.386). The OM group had a higher chance of having favorable neurological outcomes in surviving rats 72 h after cardiac arrest (84.6% [11/13] vs. 40% [4/10], p = 0.026). The percentage of damaged neurons was lower in the OM group in a histology study at 72 h after cardiac arrest (55.5±2.3% vs. 76.2±10.2%, p = 0.004).

Conclusions

OM treatment improved post-resuscitation myocardial dysfunction and neurological outcome in an animal model. These findings support further pre-clinical studies to improve outcomes in post-cardiac arrest care.

CA1 Hippocampal Pyramidal Cells in Rats, Resuscitated From 8 Minutes of Ventricular Fibrillation Cardiac Arrest, Recover After 20 Weeks of Survival: A Retrospective Pilot Study

PURPOSE

The cornu ammonis 1 (CA1) region of the hippocampus is specifically vulnerable to global ischemia. We hypothesized that histopathological outcome in a ventricular fibrillation cardiac arrest (VFCA) rat model depends on the time point of the examination.

METHODS

Male Sprague-Dawley rats were put into VFCA for 8 min, received chest compressions for 2 min, and were defibrillated to achieve return of spontaneous circulation. Animals surviving for 80 min, 14 days and 140 days were compared with controls. Viable neurons were counted in a 500 μm sector of the CA1 region and layer thickness measured. Microglia cells and astrocytes were counted in a 250×300 μm aspect.

RESULTS

Control and 80 min surviving animals had similar numbers of pyramidal neurons in the CA1 region. In 14 days and 140 days survivors neuron numbers and layer thickness were severely diminished compared with controls (P < 0.001). Two-thirds of the 140 days survivors showed significantly more viable neurons than the last third. Microglia was increased in 14 days survivors compared with controls and 140 days survivors, while astrocytes increased in 14 days and 140 days survivors compared with controls (P < 0.001). 140 days survivors had significantly higher astrocyte counts compared with 14 days survivors.

CONCLUSIONS

The amount and type of brain lesions present after global ischemia depend on the survival time. A consistent reduction in pyramidal cells in the CA1 region was present in all animals 14 days after VFCA, but in two-thirds of animals a repopulation of pyramidal cells seems to have taken place after 140 days.

The effect of levosimendan on survival and cardiac performance in an ischemic cardiac arrest model - A blinded randomized placebo-controlled study in swine

BACKGROUND

Survival after out-of-hospital cardiac arrest remains poor. Levosimendan could be a new intervention in this setting. Therefore, we conducted a blinded, placebo controlled randomized study investigating the effects of levosimendan on survival and cardiac performance in an ischemic cardiac arrest model in swine.

METHODS

Twenty-four anesthetised swines underwent experimentally-induced acute myocardial infarction and ventricular fibrillation. At the start of CPR, a bolus dose of levosimendan (12 μg kg^-1) or placebo was given followed by a 24-h infusion (0.2 μg kg^-1 min^-1) after return of spontaneously circulation. Animals were evaluated by risk of death, post-resuscitation hemodynamics and infarction size by magnetic resonance imaging (MRI) up to 32 h post arrest.

RESULTS

Spontaneous circulation was restored in all (12/12) animals in the levosimendan group compared to two thirds (8/12) in the placebo group (P = 0.09). Protocol survival was higher for the levosimendan group (P = 0.02) with an estimated 88% lower risk of death compared to placebo (hazard ratio [95% confidence interval] 0.12 [0.01-0.96], P = 0.046). Cardiac output (CO) recovered 40% faster during the first hour of the intensive care period for the levosimendan group (difference 0.13 [0.01-0.26] L min^-1P = 0.04). The placebo group required higher inotropic support during the intensive care period which masked an even bigger recovery in CO in the levosimendan group (58%). The MRI showed no difference in myocardial scar size or in myocardial area at risk.

CONCLUSIONS

Levosimendan given intra-arrest and during the first 24-h of post-resuscitation care improved survival and cardiac performance in this ischemic cardiac arrest model. Institutional Protocol Number; KERIC 5.2.18-14933.

Reduced long-term memory in a rat model of 8 minutes ventricular fibrillation cardiac arrest: a pilot trial

Background

Evaluating beneficial effects of potential protective therapies following cardiac arrest in rodent models could be enhanced by exploring behavior and cognitive functions. The Morris Water Maze is a well-known cognitive paradigm to test spatial learning and memory.

Results

Behavioral testing with the Morris Water Maze in Sprague–Dawley rats (300 ± 25 g) resuscitated after 8 min of ventricular fibrillation cardiac arrest was carried out 5 and 12 weeks after cardiac arrest (CA) and compared to results of naïve rats (Control).

At 5 weeks, within each group latency time to reach the hidden platform (reflecting spatial learning) decreased equally from day 1 to 4 (CA: 105.6 ± 8.2 vs. 8.9 ± 1.2 s, p < 0.001; Control: 75.5 ± 13.2 vs. 17.1 ± 4.5, p < 0.001) with no differences between groups (p = 0.138). In the probe trial 24 h after the last trial, time spent in the target sector (reflecting memory recall) within each group was significantly longer (CA: 25 ± 1.3; Control: 24.7 ± 2.5 s) than in each of the three other sectors (CA: 7.7 ± 0.7, 14.3 ± 2.5, 8.4 ± 0.8 and Control: 7.8 ± 1.2, 11.7 ± 1.5, 10.3 ± 1.6 s) but with no significantly differences between groups. Seven days later (reflecting memory retention), control group animals remained significantly longer in the target sector compared to every other sector, whereas the cardiac arrest group animals did not. Even 12 weeks after cardiac arrest, the single p values showed that the control animals displayed a trend to perform better than the resuscitated animals.

Conclusions

Memory recall was impaired early after 8 min of ventricular fibrillation cardiac arrest and might be a more valuable tool for cognitive testing than learning recall after global ischemia due to cardiac arrest.

A Rat Model of Ventricular Fibrillation and Resuscitation by Conventional Closed-chest Technique

A rat model of electrically-induced ventricular fibrillation followed by cardiac resuscitation using a closed chest technique that incorporates the basic components of cardiopulmonary resuscitation in humans is herein described. The model was developed in 1988 and has been used in approximately 70 peer-reviewed publications examining a myriad of resuscitation aspects including its physiology and pathophysiology, determinants of resuscitability, pharmacologic interventions, and even the effects of cell therapies. The model featured in this presentation includes: (1) vascular catheterization to measure aortic and right atrial pressures, to measure cardiac output by thermodilution, and to electrically induce ventricular fibrillation; and (2) tracheal intubation for positive pressure ventilation with oxygen enriched gas and assessment of the end-tidal CO2. A typical sequence of intervention entails: (1) electrical induction of ventricular fibrillation, (2) chest compression using a mechanical piston device concomitantly with positive pressure ventilation delivering oxygen-enriched gas, (3) electrical shocks to terminate ventricular fibrillation and reestablish cardiac activity, (4) assessment of post-resuscitation hemodynamic and metabolic function, and (5) assessment of survival and recovery of organ function. A robust inventory of measurements is available that includes - but is not limited to - hemodynamic, metabolic, and tissue measurements. The model has been highly effective in developing new resuscitation concepts and examining novel therapeutic interventions before their testing in larger and translationally more relevant animal models of cardiac arrest and resuscitation.

Effects of levosimendan on hemodynamics, local cerebral blood flow, neuronal injury, and neuroinflammation after asphyctic cardiac arrest in rats

OBJECTIVES

Despite advances in cardiac arrest treatment, high mortality and morbidity rates after successful cardiopulmonary resuscitation are still a major clinical relevant problem. The post cardiac arrest syndrome subsumes myocardial dysfunction, impaired microcirculation, systemic inflammatory response, and neurological impairment. The calcium-sensitizer levosimendan was able to improve myocardial function and initial resuscitation success after experimental cardiac arrest/cardiopulmonary resuscitation. We hypothesized that levosimendan exerts beneficial effects on cerebral blood flow, neuronal injury, neurological outcome, and inflammation 24 hours after experimental cardiac arrest/cardiopulmonary resuscitation.

DESIGN

Laboratory animal study.

SETTING

University animal research laboratory.

SUBJECTS

Sixty-one male Sprague-Dawley rats.

INTERVENTIONS

Animals underwent asphyxial cardiac arrest/cardiopulmonary resuscitation, randomized to groups with levosimendan treatment (bolus 12 µg/kg and infusion for 3 hr [0.3 µg/min/kg]) or vehicle (saline 0.9% bolus and infusion for 3 hr [equivalent fluid volume]). Cardiac index, local cerebral blood flow, and hemodynamic variables were measured for 180 minutes after cardiac arrest/cardiopulmonary resuscitation. Behavioral and neurological evaluations were conducted 24 hours after cardiac arrest/cardiopulmonary resuscitation. Furthermore, neuronal injury, expressed as Fluoro-Jade B-positive cells in the hippocampal formation, cortical and hippocampal inflammatory cytokine gene expression, and blood plasma interleukin-6 values were assessed.

MEASUREMENTS AND MAIN RESULTS

Treatment with levosimendan reduced neuronal injury and improved neurological outcome after 24 hours of reperfusion and resulted in elevated cardiac index and local cerebral blood flow compared with vehicle after cardiac arrest/cardiopulmonary resuscitation. Mean arterial blood pressure was reduced during the early reperfusion period in the levosimendan group. Cortical and hippocampal inflammatory cytokine gene expression and blood plasma interleukin-6 levels were not influenced.

CONCLUSIONS

Levosimendan increased cerebral blood flow after experimental cardiac arrest/cardiopulmonary resuscitation. This effect coincided with reduced neuronal injury and improved neurologic outcome. Findings seem to be independent of inflammatory effects because no effects by levosimendan on cerebral or systemic inflammation could be detected. In summary, levosimendan is a promising agent to improve neurological outcome after cardiac arrest/cardiopulmonary resuscitation.

The role of Levosimendan in cardiopulmonary resuscitation

Although initial resuscitation from cardiac arrest (CA) has increased over the past years, long term survival rates remain dismal. Epinephrine is the vasopressor of choice in the treatment of CA. However, its efficacy has been questioned, as it has no apparent benefits for long-term survival or favorable neurologic outcome. Levosimendan is an inodilator with cardioprotective and neuroprotective effects. Several studies suggest that it is associated with increased rates of return of spontaneous circulation as well as improved post-resuscitation myocardial function and neurological outcome. The purpose of this article is to review the properties of Levosimendan during cardiopulmonary resuscitation (CPR) and also to summarize existing evidence regarding the use of Levosimendan in the treatment of CA.

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.

Levosimendan Does Not Improve Cardiac Output or Blood Pressure in a Rodent Model of Propranolol Toxicity When Administered Using Various Dosing Regimens

Background: Levosimendan (CAS: 141505-33-1) is a myocardial calcium sensitizer that improves myocardial contractility in various forms of heart failure. It produces a moderate improvement in cardiac output (CO) without an improvement in blood pressure (BP) in verapamil and metoprolol poisoned rodents. Aim: To assess the effect of various levosimendan dosing regimens on hemodynamics in a rodent model of propranolol poisoning. Method: Male Wistar rats (350-450 g) were anesthetized, ventilated, and instrumented to record BP, heart rate (HR), and CO. Propranolol was infused continually. When BP dropped to 50% of baseline rats received 1 of 7 treatments: (1) 0.9% saline (control), (2) levosimendan 36 μg/kg loading dose then 0.6 μg/kg per min, (3) levosimendan 0.6 μg/kg per min, (4) epinephrine 0.5 μg/kg per min, (5) levosimendan 70 μg/kg loading dose then 1.2 μg/kg per min, (6) levosimendan 1.2 μg/kg per min, and (7) levosimendan 70 μg/kg loading dose alone. Hemodynamics were recorded every 10 minutes for 70 minutes. Cardiac output, mean arterial pressure, and HR for each group were compared with control. Results: All groups had comparable baseline and maximal toxicity hemodynamics prior to initiation of treatment. Levosimendan did not improve CO or BP with any dosing regimen. Blood pressure tended to be lower than control for all doses of levosimendan. Epinephrine significantly improved BP but not CO compared to all other treatment groups. Survival did not differ between groups. Conclusions: Unlike in verapamil and metoprolol poisoning models, levosimendan did not improve CO or survival in propranolol poisoning. Epinephrine improved BP, but not CO, suggesting that its actions were due to peripheral vasoconstriction.

Levosimendan infusion improves cardiac output but not blood pressure in a rodent model of severe metoprolol toxicity

Levosimendan (Levo) is an inodilator improving cardiac output (CO) and reducing afterload in heart failure. Previously, we reported that Levo improved CO but not blood pressure (BP) in a rodent model of verapamil poisoning. We theorised that Levo-induced vasodilation should not influence BP to a similar degree in metoprolol poisoning. Aim: To assess the effect of Levo on haemodynamics in a rodent model of metoprolol poisoning. Method: Anaesthetized male Wistar rats were infused metoprolol continuously. When the BP dropped to 50% of baseline (time 0) rats received 1 of the 4 treatments: (a) control (0.9% saline bolus + infusion); (b) Levo-l (Levo 36 μm/kg loading dose followed by 0.6 μm/kg/min); (c) Levo-I (Levo infusion only at 0.6 μm/kg/min); and (d) Epi (epinephrine 0.5 μm/kg/min). All groups received comparable fluid volumes. Haemodynamics were recorded every 10 min for 70 min. CO, mean arterial pressure (MAP) and heart rate (HR) of each group were compared to the control. Results: All groups had comparable baseline and time 0 HR, MAP and CO. Levo-L and Levo-I rats showed significantly greater CO at t = 10 min ( p > 0.02 and p > 0.04, respectively). CO was higher at all other time points for both Levo groups. This was not statistically significant. Levo did not improve MAP compared to control. Adrenaline increased MAP but not CO compared to control and Levo groups. Conclusion: Levo did not improve MAP but moderately improved CO compared to control in this model of metoprolol poisoning. The response was similar to that reported previously in verapamil-poisoned rats. The improvement in MAP seen with epinephrine was most likely vasoconstriction mediated.

Vasoactive support in the optimization of post-cardiac arrest hemodynamic status: from pharmacology to clinical practice

As a critical component of post-resuscitation care, prompt optimization of hemodynamic status by means of targeted interventions is vital in order to maximize the likelihood of good outcome. Vasoactive agents play an essential role in the supportive care of post cardiac arrest patients. The administration of these agents is associated with serious side-effects and therefore they should be used in the minimal dose necessary to achieve low-normal mean arterial pressure and adequate systematic perfusion. Careful and frequent serial evaluation of the patient is important primarily to assess volume status and adequacy of circulatory support. Continuous monitoring of blood pressure and laboratory parameters is essential both to accurately titrate therapy and because inotropes and vasopressors have the potential to induce life-threatening side-effects. The clinical efficacy of inotropes and vasopressors has been largely investigated through examination of their impact on hemodynamic end points, and clinical practice has been driven in part by expert opinion, extrapolation from animal studies, and physician preference. Clearly these agents should all be considered as supportive measures to stabilize the patient prior to some form of definitive therapy.

Comparative hemodynamic effects of levosimendan alone and in conjunction with 4-aminopyridine or calcium chloride in a rodent model of severe verapamil poisoning

Levosimendan (Levo) increases sensitivity of troponin-C to calcium, thus increasing myocardial contractility. It is also a vascular K+-ATP channel agonist producing peripheral vasodilation. Previous research with levosimendan revealed an increase in cardiac output (CO) but not blood pressure (BP) in experimental verapamil poisoning. Levosimendan's K+-channel agonist properties may augment verapamil's vasodilatory effects. 4-Aminopyridine (4-AP) is a K+-channel antagonist. It has successfully reversed hypotension in experimental verapamil poisoning. We hypothesized that coadministration of these agents may improve BP and CO in verapamil poisoning. Anesthetized, ventilated, and canulated male Wistar rats were poisoned with verapamil. Animals received one of six treatments, which are as follows: (1) n-saline infusion (control), (2) Levo 6.25 μg/kg loading dose and 36 μg/kg/h infusion, (3) 4-AP 2 mg/kg loading dose and infusion (4-AP), (4) Levo+4-AP, (5) CaCl₂ loading dose and infusion, and (6) Levo+CaCl(2). Hemodynamic parameters were recorded for 60 min. Outcome measures were changes in CO, BP, and heart rate (HR) compared to control. All groups had similar pretoxicity and peak toxicity CO (50% of pretoxicity value), BP (50% or pretoxicity value), and HR. Control group CO, BP, and HR progressively dropped during the verapamil infusion. Levosimendan produced a statistically significant improvement in CO (75% of pretoxicity level) but not BP in comparison to control. 4-AP produced a significant improvement in CO (110% of pretoxicity) and BP (78% of pretoxicity). Levo+4-AP and Levo+CaCl₂ groups improved CO (100% of pretoxicity) and BP (77% and 50% of pretoxicity, respectively), but there was no additive increase in CO or BP in animals compared to 4-AP or CaCl₂ alone. Levosimendan moderately improved CO but not BP in verapamil poisoning. The hypotensive effects of levosimendan were not overcome by coadministration of either 4-AP or CaCl₂. Levosimendan may not be an appropriate agent to use in the treatment of verapamil poisoning.

Part 10: Pediatric basic and advanced life support: 2010 International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science With Treatment Recommendations

Note From the Writing Group: Throughout this article, the reader will notice combinations of superscripted letters and numbers (eg, “Family Presence During ResuscitationPeds-003”). These callouts are hyperlinked to evidence-based worksheets, which were used in the development of this article. An appendix of worksheets, applicable to this article, is located at the end of the text. The worksheets are available in PDF format and are open access.

Increased susceptibility to cardiovascular effects of dihydrocapcaicin in resuscitated rats. Cardiovascular effects of dihydrocapsaicin

Background

Survivors of a cardiac arrest often have persistent cardiovascular derangements following cardiopulmonary resuscitation including decreased cardiac output, arrhythmias and morphological myocardial damage. These cardiovascular derangements may lead to an increased susceptibility towards the external and internal environment of the cardiovascular system as compared to the healthy situation.

Methods

Here we tested the hypothesis that the cardiovascular system in healthy rats and rats resuscitated from a cardiac arrest may be differentially affected by a transient receptor potential vanilloid type 1 agonist, by continuous intravenous infusion of dihydrocapsaicin (DHC).

Results

Compared to baseline, infusion of DHC caused an initial increase in mean arterial blood pressure in both healthy and resuscitated rats of 25% and 10%, respectively. Also, we observed an initial response of tachycardia in both healthy and resuscitated rats of 30% and 20%, respectively. Then, at high levels of DHC infusion (> 2.0 mg/kg/hr) we observed two single episodes of transient bradycardia and hypotension in 33% of the healthy rats, which was consistent with a TRPV1 agonist induced Bezold-Jarisch reflex. In contrast, in resuscitated rats we observed multiple episodes of bradycardia/hypotension in 100% of the rats and at a dose of DHC of 0.65 mg/kg/hr. Notably, this DHC effect could be completely blocked in the resuscitated rats by pre-treatment with atropine, a muscarinic acetylcholine antagonist.

Conclusions

Our results indicate that the susceptibility of the rats towards TRPV1 agonist induced Bezold-Jarisch reflex is increased in those resuscitated from cardiac arrest compared to the healthy situation.

Intravenous infusion of bone marrow mesenchymal stem cells improves brain function after resuscitation from cardiac arrest

OBJECTIVE

Allogeneic bone marrow mesenchymal stem cells were previously shown to improve myocardial function when administered intravenously after resuscitation from cardiac arrest in rats. Coincidental evidence of improved brain function prompted the present study.

DESIGN

Prospective, randomized, controlled study.

SETTING

University-affiliated research institute.

SUBJECTS

Male Sprague-Dawley rats.

INTERVENTIONS

Using an established model in 20 male Sprague-Dawley rats in which 6 mins of untreated cardiac arrest was followed by cardiopulmonary resuscitation, animals were randomized to receive 5 x 10(6) mesenchymal stem cells labeled with PKH26 in phosphate buffer solution or phosphate buffer solution alone as a placebo at 2 hrs after restoration of spontaneous circulation. The stem cells or buffer diluent were injected into a catheter advanced from the jugular vein into the right atrium.

MEASUREMENTS AND MAIN RESULTS

Outcome measurements in addition to 35-day survival included somatosensor testing of capability for removal of an adhesive patch applied to both front paws, testing of motor function using a rotating cylinder, and observational scoring of the severity of neurologic impairment. Labeled mesenchymal stem cells were subsequently identified and counted in 5 microm sections obtained from defined sites in the harvested brain. Immunohistochemistry was used to identify neural cells differentiation of mesenchymal stem cells. Adhesive removal, motor function test, neurologic severity score, and 35-day survival were each significantly improved in comparison with control animals. Labeled mesenchymal stem cells were identified in the hippocampus, cortex, pons, medulla, and cerebellum and expressed protein markers phenotypic neural cells.

CONCLUSIONS

Mesenchymal stem cells injected into the right atrium of rats after resuscitation from cardiac arrest were identified in brains harvested 35 days later. Brain function was significantly improved. Accordingly, venous injection of mesenchymal stem cells after cardiopulmonary resuscitation has promise of minimizing the severity of postresuscitation neurologic impairment.

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.

Improved outcomes of cardiopulmonary resuscitation in rats with myocardial infarction treated with allogenic bone marrow mesenchymal stem cells

OBJECTIVE

We hypothesized that rats in which myocardial infarction had been treated with mesenchymal stem cells (MSCs) would have better outcomes following the global myocardial ischemia of cardiac arrest and cardiopulmonary resuscitation (CPR) compared with rats in which myocardial infarction had been treated with phosphate buffer solution (PBS).

DESIGN

Prospective, randomized controlled study.

SETTING

University-affiliated research institute.

SUBJECTS

Male Sprague-Dawley rats.

INTERVENTIONS

Myocardial infarction was induced in 18 male Sprague-Dawley rats. Four weeks later, animals were randomized to receive 5 x 10 MSCs labeled with red fluorescent dye gel (PKH26) in PBS or a PBS-alone injection into right femoral vein.

MEASUREMENTS AND MAIN RESULTS

Echocardiographically measured myocardial function, including ejection fraction, left ventricular end-diastolic volume, and left ventricular end-systolic volume, was quantitated 2 and 4 weeks after administering MSCs or PBS. Four weeks after MSCs or PBS injection, 6 minutes of ventricular fibrillation (VF) and 6 minutes of CPR were performed before defibrillation. Myocardial function, including cardiac index, left ventricular, dP/dt max (dP/dt max), left ventricular negative dP/dt min (-dP/dt min), and left ventricular diastolic pressure, was measured before inducing VF and hourly following return of spontaneous circulation. Labeled MSCs were observed in 5-mum cryostat sections from each harvested heart. Significant improvements in ejection fraction, left ventricular end-diastolic volume, left ventricular end-systolic volume, cardiac index, dP/dt max, -dP/dt min, and left ventricular diastolic pressure followed injection of MSCs before inducing VF. Following return of spontaneous circulation, myocardial function was significantly better in animals pretreated with MSCs; this was associated with significantly increased duration of postresuscitation survival.

CONCLUSIONS

Myocardial function before and after CPR and duration of survival after CPR were significantly improved in animals in which myocardial infarction was treated with MSCs. MSCs existing in the myocardium resisted a secondary ischemic event and provided better postresuscitation myocardial function.

Mesenchymal stem cells improve outcomes of cardiopulmonary resuscitation in myocardial infarcted rats

We hypothesized that administration of allogeneic bone marrow mesenchymal stem cells (MSCs) by intravenous, intraventricular or intramyocardial injection could improve myocardial function after survival time after cardiopulmonary resuscitation in myocardial infarcted rats. Myocardial infarction was induced by ligation of the left anterior descending artery in 54 rats (6 groups, 9 rats for each group). Left ventricular remodeling was quantitated weekly by ejection fraction (EF) measurement. One month after ligation, animals were randomized to receive injection of either MSCs 5x10(6) labeled with PKH26 in phosphate buffer solution (PBS) or PBS alone as a placebo. MSCs or PBS were administered by injection into the right femoral vein, the left ventricular cavity, or into the infracted anterior ventricular free wall. Four weeks after MSC or PBS injection, ventricular fibrillation (VF) was induced and untreated for 6 min, followed by 6 min of CPR prior to defibrillation. Hemodynamics, including cardiac index (CI), left ventricular dP/dt40 (dP/dt40), left ventricular negative dP/dt (-dP/dt) and left ventricular diastolic pressure (LVDP) were measured at baseline and hourly following return of spontaneous circulation (ROSC). Labeled MSCs were observed in 5 microm sections obtained with a cryostat from each harvested heart. Independently of the site of injection of MSCs, EF, CI, dP/dt40, -dP/dt, and LVDP were significantly improved and sustained before and after CPR in the animals treated with MSCs and were associated with significantly increased survival time when compared with the corresponding PBS treated animals.

Levosimendan improves the initial outcome of cardiopulmonary resuscitation in a swine model of cardiac arrest

BACKGROUND

Cardiac arrest remains the leading cause of death in Western societies. Advanced Life Support guidelines propose epinephrine (adrenaline) for its treatment. The aim of this study was to assess whether a calcium sensitizer agent, such as levosimendan, administered in combination with epinephrine during cardiopulmonary resuscitation, would improve the initial resuscitation success.

METHODS

Ventricular fibrillation was induced in 20 Landrace/Large-White piglets, and left untreated for 8 min. Resuscitation was then attempted with precordial compressions, mechanical ventilation and electrical defibrillation. The animals were randomized into two groups (10 animals each): animals in Group A received saline as placebo (10 ml dilution, bolus) + epinephrine (0.02 mg/kg), and animals in Group B received levosimendan (0.012 mg/kg/10 ml dilution, bolus) + epinephrine (0.02 mg/kg) during cardiopulmonary resuscitation. Electrical defibrillation was attempted after 10 min of ventricular fibrillation.

RESULTS

Four animals in Group A showed restoration of spontaneous circulation and 10 in Group B (P = 0.011). The coronary perfusion pressure, saturation of peripheral oxygenation and brain regional oxygen saturation were significantly higher during cardiopulmonary resuscitation in Group B.

CONCLUSIONS

A calcium sensitizer agent, when administered during cardiopulmonary resuscitation, significantly improves initial resuscitation success and increases coronary perfusion pressure during cardiopulmonary resuscitation.

Clinical review: beyond immediate survival from resuscitation-long-term outcome considerations after cardiac arrest

A substantial body of literature concerning resuscitation from cardiac arrest now exists. However, not surprisingly, the greater part concerns the cardiac arrest event itself and optimising survival and outcome at relatively proximal time points. The aim of this review is to present the evidence base for interventions and therapeutic strategies that might be offered to patients surviving the immediate aftermath of a cardiac arrest, excluding components of resuscitation itself that may lead to benefits in long-term survival. In addition, this paper reviews the data on long-term impact, physical and neuropsychological, on patients and their families, revealing a burden that is often underestimated and underappreciated. As greater numbers of patients survive cardiac arrest, outcome measures more sophisticated than simple survival are required.