Postresuscitation Myocardial Dysfunction Research Articles

Adverse postresuscitation myocardial effects elicited by buffer-induced alkalemia ameliorated by NHE-1 inhibition in a rat model of ventricular fibrillation.

Major myocardial abnormalities occur during cardiac arrest and resuscitation including intracellular acidosis-partly caused by CO2 accumulation-and activation of the Na+-H+ exchanger isoform-1 (NHE-1). We hypothesized that a favorable interaction may result from NHE-1 inhibition during cardiac resuscitation followed by administration of a CO2-consuming buffer upon return of spontaneous circulation (ROSC). Ventricular fibrillation was electrically induced in 24 male rats and left untreated for 8 min followed by defibrillation after 8 min of cardiopulmonary resuscitation (CPR). Rats were randomized 1:1:1 to the NHE-1 inhibitor zoniporide or vehicle during CPR and disodium carbonate/sodium bicarbonate buffer or normal saline (30 ml/kg) after ROSC. Survival at 240 min declined from 100% with Zoniporide/Saline to 50% with Zoniporide/Buffer and 25% with Vehicle/Buffer (P = 0.004), explained by worsening postresuscitation myocardial dysfunction. Marked alkalemia occurred after buffer administration along with lactatemia that was maximal after Vehicle/Buffer, attenuated by Zoniporide/Buffer, and minimal with Zoniporide/Saline [13.3 ± 4.8 (SD), 9.2 ± 4.6, and 2.7 ± 1.0 mmol/l; P ≤ 0.001]. We attributed the intense postresuscitation lactatemia to enhanced glycolysis consequent to severe buffer-induced alkalemia transmitted intracellularly by an active NHE-1. We attributed the worsened postresuscitation myocardial dysfunction also to severe alkalemia intensifying Na+ entry via NHE-1 with consequent Ca2+ overload injuring mitochondria, evidenced by increased plasma cytochrome c Both buffer-induced effects were ameliorated by zoniporide. Accordingly, buffer-induced alkalemia after ROSC worsened myocardial function and survival, likely through enhancing NHE-1 activity. Zoniporide attenuated these effects and uncovered a complex postresuscitation acid-base physiology whereby blood pH drives NHE-1 activity and compromises mitochondrial function and integrity along with myocardial function and survival.

CHANGES IN SUBLINGUAL MICROCIRCULATION IS CLOSELY RELATED WITH THAT OF BULBAR CONJUNCTIVAL MICROCIRCULATION IN A RAT MODEL OF CARDIAC ARREST.

Following successful resuscitation, a significantly impaired microcirculation has been identified. The severity of the impairment of microcirculation is closely related to that of vital organ dysfunction. Sublingual microcirculation is a traditional site for the measurement of tissue perfusion. In the present study, we investigated the bulbar conjunctival microcirculatory alterations following CPR and its relationship with the changes of sublingual microcirculation in a rat model of cardiac arrest.Male Sprague-Dawley rats (450-550 g) were utilized. Ventricular fibrillation was induced and untreated for 8 min followed by 8 min of CPR. Sublingual and bulbar conjunctival microcirculatory blood flow was visualized by a sidestream dark-field imaging device at baseline, 30 min, 1, 2, 4, and 8 h post-resuscitation. Both perfused vessel density (PVD) and microcirculatory flow index (MFI) were recorded.The post-resuscitation PVD and MFI were significantly decreased in both sublingual and bulbar conjunctival sites. Sublingual PVD decreased from baseline of 5.9 ± 0.3 to 3.1 ± 0.4 n/mm at 30 min post-resuscitation and MFI from 3.0 ± 0.0 to 1.5 ± 0.3 (both P < 0.05 vs. baseline). Bulbar conjunctival PVD was significantly reduced from baseline of 6.5 ± 0.6 to 3.9 ± 0.5 n/mm at 30 min post-resuscitation and MFI from 3.0 ± 0.0 to 1.2 ± 0.4 (both P < 0.05 vs. baseline). PVD, MFI, and cardiac function did not change significantly from the 30-min measurements in the surviving rats throughout the remainder of the study (both P > 0.05 vs. 30-min post-resuscitation). The decreases in sublingual microcirculatory blood flow were closely correlated with the reductions of bulbar conjunctival microcirculatory blood flow (PVD: r = 0.87, P < 0.05; MFI: r = 0.92, P < 0.05). Myocardial function was significantly impaired in all animals after resuscitation when compared with baseline values (P < 0.05). The impairments of both sublingual and bulbar conjunctival microcirculation were significantly correlated with the impairment of myocardial function.In the rat model of cardiac arrest, the changes in sublingual microcirculatory blood flow are closely correlated with that of bulbar conjunctival microcirculatory blood flow after successful resuscitation. The changes are correlated with the severity of post-resuscitation myocardial dysfunction. Our study testified sublingual site could be substituted by bulbar conjunctival at least in the rat model of cardiac arrest. The measurement of conjunctival microcirculation may provide an accessible and convenient option as sublingual site for monitoring microcirculation in humans.

The effects of sevoflurane on myocardial damage after cardiopulmonary resuscitation in rats

Objective To investigate the effects of sevoflurane on myocardial damage after cardiopulmonary resuscitation in rats. Methods The cardiac arrest model was established by asphyxia. Thirth-six male Wistar rats were assigned to three groups randomly(random number). Rats in the sham group were anesthetized with intubation, without induced cardiac arrest. Rats in the sevo group inhaled 1minimal alveolar concentration(MAC) of sevoflurane during CPR. Rats in the control group received the standard CPR. At 4 h and 24 h after ROSC , half the rats of every group received the echocardiography examination. At 4 h after ROSC, the rest of rats in every group were sacrificed with overdose anesthetics, the hearts were removed and mitochondria was isolated promptly. Determination of the status of mitochondrial permeability transition pore(MPTP) using the spectrophotometer. The level of cytosolic cytochrome C was measured by Western blot. Results After ROSC, the left ventricular posterior wall during diastolic(LVPWd) became thick and the cardiac output was decreased dramatically. At 4 h after ROSC, the mice of the sevo group had a slighter thickness of LVPWd (mm)(1.95±0.14)vs.(2.32±0.34), P<0.05 and an enhanced cardiac output(mL/min)(46.94±3.61)vs.(38.77±6.63), P<0.05 than the control group. The mitochondria swelling was triggered by the addition of CaCl2,the sevo group showed an slighter decrease in the absorbance of light compared with the control group(0.048±0.007)vs.(0.069±0.011), P<0.01. After ROSC, cytochrome C was released to cytosol, and the sevo group had a lower level of this protein than the control group(1.02±0.22)vs.(1.59±0.31), P<0.05. Conclusions After ROSC, sevoflurane can alleviate myocardial dysfunction, attenuate the MPTP opening and decrease the level of cytosolic cytochrome C. Key words: Cardiac arrest; Cardio-pulmonary resuscitation; Asphyxia; Sevoflurane; Post-resuscitation myocardial dysfunction; Mitochondrial permeability transition pore

Effects of Oxygen Concentrations on Postresuscitation Myocardial Oxidative Stress and Myocardial Function in a Rat Model of Cardiopulmonary Resuscitation.

Lipid peroxidation induced by free-radical species plays a prominent role in myocardial injury following ischemia and reperfusion. However, there is a lack of data in different oxygen concentrations on myocardial lipid peroxidation during the early phase of reperfusion. In this study, we investigated whether ventilation with medium or normal concentration of oxygen would decrease the severity of myocardial lipid peroxidation and postresuscitation myocardial dysfunction. Prospective, randomized, controlled experimental study. University-affiliated animal research institution. Sixty-three healthy male Sprague-Dawley rats. Animals were randomized into three groups: 1) 100% group, 2) 50% group, and 3) 21% group. Ventricular fibrillation was induced and untreated for 8 minutes, and defibrillation was attempted after 8 minutes of cardiopulmonary resuscitation. Ventilation with 100%, 50%, or 21% oxygen was initiated in all groups during cardiopulmonary resuscitation and 1 hour following the return of spontaneous circulation. Normoxic ventilation was maintained thereafter. Myocardial function, including ejection fraction and myocardial performance index, were measured at baseline, 4, or 72 hours after resuscitation. Blood samples were drawn at baseline, 15 minutes, 1, 4, or 72 hours after resuscitation for the measurements of blood gas or biomarkers. Significantly better myocardial function and longer duration of survival were observed in the 50% group. Compared with the 21% and 100% groups, a mild hyperoxia and greater oxygen extraction with lower 8-iso-prostaglandin F2α were observed in the 50% group. Pearson correlation analysis confirmed that 8-iso-prostaglandin F2α was positively correlated with myocardial performance index at 4 hours postresuscitation. In a rat model of cardiac arrest and resuscitation, ventilation with 50% inspired oxygen during early postischemic reperfusion phase contributed to a decreased lipid peroxidation and a better myocardial function and duration of survival.

Abstract 10770: Curcumin Mitigates the Severity of Post-Resuscitation Myocardial Dysfunction Caused by Epinephrine in a Rat Cardiac Arrest Model

Introduction: Epinephrine significantly increases the severity of post-resuscitation myocardial dysfunction (PRMD) and reduces the duration of survival. The cardioprotective effect of curcumin against catecholamine-induced cardiotoxicity has been established. In the present study, we investigated the effects of curcumin on PRMD caused by epinephrine in a rat model of cardiac arrest. Hypothesis: Curcumin reduces the severity of PRMD caused by epinephrine. Methods: Twenty-four male Sprague-Dawley rats weighing between 450-550g were randomized into three groups: 1) Placebo group; 2) Epinephrine (20ug/kg) group; 3) Curcumin (100 mg/kg) pretreatment + epinephrine (20ug/kg) group. Ventricular fibrillation (VF) was then induced. After 8 mins of VF, CPR was initiated for 8 mins, and defibrillation was then attempted. Myocardial function was measured by echocardiography at baseline and hourly for 4 hours following successful resuscitation. Results: All animals except for two in the placebo group were resuscitated. Post-resuscitation myocardial function was significantly impaired in all animals. Significantly worse myocardial function was observed in the Epinephrine group in comparison with the two other groups (Figure). However, myocardial function was significantly better in the animals treated with curcumin when compared with those in the two other groups (Figure). Conclusion: In a rat cardiac arrest model, curcumin reduced the severity of PRMD caused by epinephrine.

Abstract 11029: Netrin-1 Alleviates Post-Resuscitation Myocardial Dysfunction in a Rat Model of Cardiac Arrest

Introduction: Post-resuscitation myocardial dysfunction has been recognized as one of the major causes of fatal outcomes after initial successful cardiopulmonary resuscitation (CPR). Previous research demonstrated that Netrin-1 improved post ischemic injury cardiac function via preservation of mitochondrial integrity. In the present study, we investigated the role of netrin-1 after cardiac arrest. Hypothesis: We hypothesized that the netrin-1 alleviated post-resuscitation myocardial dysfunction in a rat model of cardiac arrest. Methods: A total of sixteen male Sprague-Dawley rats (450-550 g) were randomized to two groups as follows: (1) Control group (C group); (2) Netrin-1 group (N group). Ventricular fibrillation was induced and untreated for 8 mins followed by 8 mins of CPR. Netrin-1 or saline were given at the onset of precordial compression. Ejection fraction (EF) was measured by echocardiography at baseline, 1,2,3 and 4 hours after ROSC. Results: Eight rats were resuscitated in the netrin-1 group and 7 rats were resuscitated in the saline group. In both groups, EF decreased after resuscitation when compared to the baseline (#p &lt; 0.05). In the netrin-1 group, EF decreased from ( 68.1±3.4)% at baseline to (51.1±5.0)% at 1 hour post-resuscitation. In the saline group, EF decreased from (67.7±2.1)% at baseline to (44.5±5.3)% at 1 hr post-resuscitation. EF was better in the netrin-1 group than in the saline group at 2, 3 and 4 hours post-resuscitation (*p &lt; 0.05) ( Figure 1). Conclusion: Netrin-1 alleviates post-resuscitation myocardial dysfunction in a rat model of cardiac arrest.

Abstract 18992: Kappa Opioid Receptor Improves Postresuscitation Myocardial Dysfunction via Activation of Grk3 and Phosphorylation of Erk

Objective: To investigate the signaling pathway of kappa opioid receptor (κ-OR) on postresuscitation myocardial protection. Method: A total of 120 male SD rats were randomized into control group (n=40), κ-OR agonist group (n=40) and κ-OR inhibitor group (n=40). Asphyxia-induced cardiac arrest was performed by turning-off the ventilator and clamping the endotracheal tube. Cardiac arrest was started when systolic blood pressure dropped below 25mmHg. CPR with chest compression and mechanical ventilation were started 6mins after cardiac arrest. Normal saline (1ml/kg), U50488H (ΚOR agonist, 1mg/kg) or GNTI(ΚOR inhibitor, 0.5mg/kg) was injected from on set of CPR in each group. The baseline blood gas, HR, SBP, DBP, MAP, dP/dtmax and -dP/dtmax were measured. The rat hearts were harvested at 1h, 2h, 6h, 12h and 24h post resuscitation (PR). The expression of both total κ-OR and phosphorylated κ-OR in myocaridum were determined, the likely signaling pathway molecules of G protein receptor kinase 3(GRK3) and ERK1/2 were detected. Results: The postresuscitation myocardial function, include HR, SAP, MAP, dP/dtmax and -dP/dtmax were improved in κ-OR agonist group compared to κ-OR inhibitor and control group, specifically after PR2h(p&lt;0.01).Both phosphorylated κ-OR and GRK3 protein impression were significantly increased in κ-OR agonist group, in comparison to κ-OR inhibitor group and control group (p&lt;0.01). Positive linear correlation was observed between κ-OR and GRK3. The ERK1/2 mRNA and protein expression were significantly increased in κ-OR agonist group and significantly decreased in κ-OR inhibitor group, in comparison to control group(p&lt;0.05). Conclusion: The activation of κ-OR improves postresuscitation myocardial dysfunction. The protective effects of κ-OR may via activation of GRK3 and ERK1/2 signaling pathway.

Abstract 10773: Curcumin Improves the Outcomes of Cardiopulmonary Resuscitation in a Rat Model of Cardiac Arrest

Introduction: Curcumin has been proven to provide potent protection of vital organs against regional ischemia reperfusion injury. In this study, we investigated the effects of curcumin on the outcomes of CPR in a rat model of cardiac arrest. Hypothesis: Curcumin reduces the severity of post-CPR myocardial dysfunction and prolong the duration of survival. Method: Sixteen male Sprague-Dawley rats weighing between 450-550g were randomized into two groups: 1) Placebo; 2) Curcumin (100 mg/kg) pre-treatment. Ventricular fibrillation (VF) was induced. After 8 mins of VF, CPR was initiated for 8 mins and defibrillation was then attempted. Myocardial function was measured by echocardiography at baseline and hourly for 4 hours following successful resuscitation. The duration of survival was observed for total 72 hours. Result: Six animals in the placebo group and seven in the curcumin group were successfully resuscitated. Post-resuscitation myocardial function was significantly impaired in all animals. However, myocardial function gradually improved 4 hours after resuscitation and was significantly better in the animals pre-treated with curcumin (Figure). Significantly shorter duration of survival of 40±29 hours was observed in the placebo group. Conclusion: In a rat model of cardiac arrest, curcuminim proves post-resuscitation myocardial dysfunction and prolongs the duration of survival.

Abstract 12914: The Effect of Isosorbidemononitrate on Myocardium in a Swine Model of Cardiac Arrest

Introduction: To investigate the protective effect of isosorbidemononitrate (IM) on myocardial injury after the return of spontaneous circulation (ROSC) in a swine model of ventricular fibrillation cardiac arrest (VFCA). Methods: Ventricular fibrillation was induced and untreated for 8 minutes in twenty domestic pigs. Defibrillation was attempted after 2 minutes of CPR. The animals were randomized into two groups: IM group (n=10) and saline control group (SA group, n=10). IM (2μg/kg/min) or the same volume of saline was administered for 6 hrs post-resuscitation. Post resuscitation myocardial function was evaluated using pulse-induced contour cardiac output (PiCCO) at 1, 6 and 24 hrs after ROSC. Serum troponin I was tested using the enzyme-linked immunosorbent assay (ELISA) at the same time points during 24 hours post-resuscitation. Echocardiography and transmission electron microscopy were performed at 72 hrs after ROSC. The duration of survival was monitored in all animals. Results: Significantly greater ejection fraction (EF) and cardiac output (CO) in the IM group at 1, 6 and 24 hrs after ROSC (Fig.1). Troponin I in the IM group was significantly lower than that in the SA group at 6 and 24 hrs after ROSC. Better cardiac function (Table 1) and less ultrastructural deterioration were observed in the MI group at 72 hrs after resuscitation. However, there is no significant difference in the duration of survival between the two groups. Conclusions: In a swine model of cardiac arrest, isosorbidemononitrate attenuated post-resuscitation myocardial dysfunction.

Combining Epinephrine and Esmolol Attenuates Excessive Autophagy and Mitophagy in Rat Cardiomyocytes After Cardiac Arrest.

Recent experimental and clinical studies have indicated that the β-adrenergic effect of epinephrine significantly increases the severity of postresuscitation myocardial dysfunction. The aim of this study was to investigate whether the short-acting β1-selective adrenergic blocking agent, esmolol, would impact postresuscitation autophagy and mitophagy in cardiomyocytes in a rat cardiac arrest (CA) model. CA was induced in Sprague Dawley rats by epicardial ventricular fibrillation for 5 minutes. After successful resuscitation, the surviving rats were randomly divided into 2 groups that received femoral venous injections of epinephrine combined with either esmolol (EE group) or epinephrine (E group). Arterial blood samples were obtained at times 0, 30, and 180 minutes after return of spontaneous circulation. Surviving rats were euthanatized at 12 or 24 hours after return of spontaneous circulation, and the hearts were removed for histochemical analysis, electron microscopy, Western blotting, and TUNEL experiment. Relative to the E group, the EE group had reduced N-Methyl-D-Aspartate receptors expression and reduced arterial lactate levels (P < 0.05), suggesting that epinephrine/esmolol can attenuate postresuscitation antioxidation and apoptosis. This protective effect also correlated with a reduction of excessive autophagy and mitophagy in the cardiomyocytes, as evidenced by a reduction in Beclin-1 and Parkin expression (P < 0.05). Esmolol significantly alleviates postresuscitational autophagy, including mitophagy, and cardiomyocyte apoptosis in a rat CA model.

The optimal hemodynamics management of post-cardiac arrest shock.

Patients resuscitated from cardiac arrest develop a pathophysiological state named "post-cardiac arrest syndrome." Post-resuscitation myocardial dysfunction is a common feature of this syndrome, and many patients eventually die from cardiovascular failure. Cardiogenic shock accounts for most deaths in the first 3 days, when post-resuscitation myocardial dysfunction peaks. Thus, identification and treatment of cardiovascular failure is one of the key therapeutic goals during hospitalization of post-cardiac arrest patients. Patients with hemodynamic instability may require advanced cardiac output monitoring. Inotropes and vasopressors should be considered if hemodynamic goals are not achieved despite optimized preload. If these measures fail to restore adequate organ perfusion, a mechanical circulatory assistance device may be considered. Adequate organ perfusion should be ensured in the absence of definitive data on the optimal target pressure goals. Hemodynamic goals should also take into account targeted temperature management and its effect on the cardiovascular function.

Shen-Fu Injection (参附注射液) alleviates post-resuscitation myocardial dysfunction by up-regulating expression of sarcoplasmic reticulum Ca2+-ATPase

To compare the effect of Shen-Fu Injection (SFI) and epinephrine on the expression of sarcoplasmic reticulum Ca(2+) ATPase 2a (SERCA2a) in a pig model with post-resuscitation myocardial dysfunction. Ventricular fibrillation (VF) was electrically induced in Wu-zhi-shan miniature pigs. After 8 min of untreated VF and 2 min of cardiopulmonary resuscitation (CPR), all animals were randomly administered a bolus injection of saline placebo (SA group, n=10), SFI (0.8 mg/kg, SFI group, n=10) or epinephrine (20 μg/kg, EPI group, n=10). After 4 min of CPR, a 100-J shock was delivered. If the defibrillation attempt failed to attain restoration of spontaneous circulation (ROSC), manual chest compressions were rapidly resumed for a further 2 min followed by a second defibrillation attempt. Hemodynamic variables were recorded, and plasma concentrations of catecholamines were measured. Adenylate cyclase (AC), cyclic adenosine monophosphate (cAMP) and the expressions of β1-adrenoceptor (AR) and SERCA 2a were determined. Cardiac output, left ventricular dp/dtmax and negative dp/dtmax were significantly higher in the SFI group than in the SA and EPI groups at 4 and 6 h after ROSC. The expression of β1-AR and SERCA2a at 24 h after ROSC were significantly higher in the SFI group than in the SA and EPI groups (P<0.05 or P<0.01). The administration of epinephrine during CPR decreased the expression of SERCA2a and aggravated postresuscitation myocardial function (P<0.01). SFI attenuated post-resuscitation myocardial dysfunction, and the mechanism might be related to the up-regulation of SERCA2a expression.

The effects of phosphodiesterase-5 inhibitor sildenafil against post-resuscitation myocardial and intestinal microcirculatory dysfunction by attenuating apoptosis and regulating microRNAs expression: essential role of nitric oxide syntheses signaling.

BackgroundRecent experimental and clinical studies have indicated the cardioprotective role of sildenafil during ischemia/reperfusion (I/R) injury. Sildenafil has been shown to attenuate postresuscitation myocardial dysfunction in piget models of ventricular fibrillation. This study was designed to investigate if administration of sildenafil will attenuate post-resuscitation myocardial dysfunction by attenuating apoptosis and regulating miRNA expressions, furthermore, ameliorating the severity of post-microcirculatory dysfunction.MethodsTwenty-four male pigs (weighing 30 ± 2 kg) were randomly divided into groups, sildenafil pretreatment (n = 8), saline (n = 8) and sham operation (sham, n = 8). Sildenafil pretreatment consisted of 0.5 mg/kg sildenafil, administered once intraperitoneally 30 min prior to ventricular fibrillation (VF). Eight minutes of untreated VF was followed by defibrillation in anesthetized, closed-chest pigs. Hemodynamic status and blood samples were obtained at 0 min, 0.5, 1, 2, 4 and 6 h after return of spontaneous circulation (ROSC). Surviving pigs were euthanatized at 24 h after ROSC, and hearts were removed for analysis by electron microscopy, western blotting, quantitative real-time polymerase chain reaction (PCR), and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay. Intestinal microcirculatory blood flow was visualized by a sidestream dark-field imaging device at baseline and 0.5, 1, 2, 4, and 6 h after ROSC.ResultsCompared with the saline group, the sildenafil group had a higher 24-hour survival (7/8 versus 3/8 survivors, p < 0.05) and a better outcome in hemodynamic parameters. The protective effect of sildenafil also correlated with reduced cardiomyocyte apoptosis, as evidenced by reduced TUNEL-positive cells, increased anti-apoptotic Bcl-2/Bax ratio and inhibited caspase-3 activity in myocardium. Additionally, sildenafil treatment inhibited the increases in the microRNA-1 levels and alleviated the decreases in the microRNA-133a levels which negatively regulates pro-apoptotic genes. At 6 h after ROSC, post-resuscitation perfused vessel density and microcirculatory flow index were significantly lower in the saline group than in the sildenafil group.ConclusionsThe major findings of this study are as follows: (1) sildenafil improved post-resuscitation perfusion of the heart, and thus reduced cardiac myocyte apoptosis and improved cardiac function; (2) sildenafil treatment inhibited the increases in the microRNA-1 levels, but alleviated the decreases in the microRNA-133a levels.

Effects of Shenfu injection on the expression of transcription factors T-bet / GATA-3 in pigs with post-resuscitation myocardial dysfunction

To examine whether Shenfu injection (SFI) reduces post-resuscitation myocardial dysfunction in a pig model by modulating expression imbalance of transcription factors of regulatory T cell, namely GATA-3 and T-bet. Thirty pigs were randomly divided into sham group (n = 6) and cardiopulmonary resuscitation (CPR) group (n = 24) according to the random number table method, and the pigs in the CPR group were randomly subdivided into normal saline (NS) group, epinephrine (EP) group, and SFI group (n = 8 per group). After 8 minutes of untreated ventricular fibrillation (VF) followed by 2 minutes of CPR, animals in three groups respectively received central venous injection of either 20 mL SFI (1.0 mL/kg, SFI group), EP (0.02 mg/kg, EP group) or NS (NS group). Blood samples were obtained before VF and 0.5, 2, 6 hours after restoration of spontaneous circulation (ROSC), and the parameters of hemodynamics and oxygen metabolism were determined. Surviving pigs were sacrificed at 24 hours after ROSC, the pathological changes in myocardium were observed, the levels of interleukin-4 (IL-4), tumor necrosis factor-α (TNF-α) and γ-interferon (IFN-γ) were measured by enzyme linked immunosorbent assay (ELISA), and expressions of protein and mRNA of GATA-3 and T-bet were determined by Western Blot and quantitative real-time polymerase chain reaction (RT-qPCR), respectively. Six pigs of three resuscitation groups were successfully resuscitated. The CPR time, number of defibrillation, defibrillation energy, and ROSC time were significantly decreased in the EP and SFI groups compared with those in the NS group. Compared with the sham group, the parameters of left ventricular systolic function and oxygen metabolism were significantly decreased, myofibril organelles were extensively damaged, and progressive and severe deterioration of the myocardium was found, and mitochondrial structure was not recognizable in the NS group; the level of IL-4 in myocardium were markedly decreased, while that of TNF-α, IFN-γ and IFN-γ/ IL-4 [reflecting helper T cell 1/2 (Th1/Th2)] were significantly increased. Protein and mRNA expressions of GATA-3 were markedly reduced in the myocardium of pigs in the NS group compared with that of the sham group at 24 hours after ROSC, while T-bet was significantly increased. Compared with the NS group, animals treated with SFI had minimal myocardial intracellular damage, with decreased heart rate (HR, bpm: 90.33 ± 3.79 vs. 106.83 ± 5.36) and increased mean arterial pressure (MAP), cardiac output (CO), oxygen delivery (DO₂), and oxygen consumption (VO₂) at 6 hours after ROSC [MAP (mmHg, 1 mmHg = 0.133 kPa): 107.67 ± 1.96 vs. 86.83 ± 1.85, CO (L/min): 2.47 ± 0.08 vs. 2.09 ± 0.04, DO₂ (mL/min): 364.31 ± 4.21 vs. 272.33 ± 3.29, VO₂(mL/min): 95.00±2.22 vs. 82.50 ±2 .28, all P < 0.05]. Compared with the NS groups at 24 hours after ROSC, level of IL-4 was markedly increased in myocardial cells (ng/L: 33.80 ± 3.06 vs. 16.15 ± 1.34, P < 0.05), while the levels of TNF-α, IFN-γ and IFN-γ/IL-4 were lowered significantly [TNF-α (ng/L): 18.16 ± 0.71 vs. 29.64 ± 1.89, IFN-γ (ng/L): 373.75 ± 18.36 vs. 512.86 ± 27.86, IFN-γ/IL-4: 16.15 ± 1.34 vs. 33.80 ± 3.06, all P < 0.05], and myocardial T-bet protein and mRNA expressions were reduced [T-bet protein (gray value): 0.41 ± 0.07 vs. 0.59 ± 0.11, T-bet mRNA (2(-ΔΔCt)): 4.37 ± 0.21 vs. 7.57 ± 0.55, both P < 0.05], furthermore, myocardial GATA-3 protein and mRNA expressions were significantly up-regulated in SFI group [GATA-3 protein (gray value): 0.25 ± 0.07 vs. 0.16 ± 0.07, GATA-3 mRNA (2(-ΔΔCt)): 0.63 ± 0.07 vs. 0.34 ± 0.05, both P < 0.05]. The parameters in SFI group were significantly improved compared with those of the EP group. Myocardial immune dysfunction is induced by Th1/Th2 imbalance following myocardial injury subsequent to CPR in pigs. SFI can attenuate myocardial injury and regulate myocardial immune disorders, protect post-resuscitation myocardial injury by modulating expression imbalance of transcription factors GATA-3 and T-bet.

Inhibition of nitric oxide synthases, but not inducible nitric oxide synthase, selectively worsens left ventricular function after successful resuscitation from cardiac arrest in swine.

Nitric oxide (NO) is a critical regulator of vascular tone and signal transduction in the cardiovascular system. NO is synthesized by three unique enzymes (nitric oxide synthases [NOS]): endothelial and neuronal NOS, both constitutively expressed, and inducible NOS (iNOS), which is induced by proinflammatory stimuli and subsequently produces a burst of NO. NO has been implicated as both an injurious and a beneficial mediator after cardiac arrest and resuscitation. A previous study in swine found that iNOS expression is absent in the myocardium prior to cardiac arrest and that it increases after 10 minutes of untreated ventricular fibrillation (VF), decreases somewhat during the early postresuscitation period, and then steadily increases up to 6 hours postresuscitation. Because this time course of iNOS expression mirrors that of postresuscitation myocardial dysfunction, this study was designed to test the hypothesis that selective inhibition of iNOS improves postresuscitation outcomes in swine. Thirty-two domestic swine of either sex were randomly assigned to receive one of the following treatments 15 minutes after return of spontaneous circulation (ROSC): (1) N(G) -nitro-l-arginine methyl ester (l-NAME), a global NO inhibitor; (2) aminoguanidine (AG), a selective iNOS inhibitor; or (3) saline as control. After 10 minutes of untreated VF, swine received a standard resuscitation protocol. Twenty-four-hour survival, neurological status, left ventricular (LV) function, and hemodynamic measurements were obtained. Return of spontaneous circulation occurred in 28 of 32 animals (88%). Only successfully resuscitated animals were assigned to treatment groups and completed the study. There were no differences in survival or neurological outcomes between groups. There were also no differences in LV function or hemodynamic variables found between the control group and the AG group. Global inhibition of NOS with l-NAME post-ROSC increased aortic pressure and transiently decreased pulse pressure. Treatment with l-NAME also increased LV end diastolic pressure and decreased cardiac output within 30 minutes post-ROSC, which was sustained throughout the 4-hour measurements, compared to both the control and the AG groups. In addition, LV ejection fraction recovered to baseline measurements in both the control and AG groups, but failed to recover in the l-NAME group. Global inhibition of NOS after cardiac arrest and resuscitation markedly worsens hemodynamic variables. Selective inhibition of iNOS after cardiac arrest and resuscitation does not prevent postresuscitation myocardial stunning. There were no significant differences in neurological outcome or survival between treatment groups.

Remote ischemic pre- and postconditioning improve postresuscitation myocardial and cerebral function in a rat model of cardiac arrest and resuscitation.

Cardiac arrest and resuscitation are models of whole body ischemia reperfusion injury. Postresuscitation myocardial and cerebral dysfunction are major causes of high mortality and morbidity. Remote ischemic postconditioning has been proven to provide potent protection of the heart and brain against ischemia reperfusion injury. In this study, we investigated the effects of remote ischemic postconditioning on postresuscitation myocardial and cerebral function in a rat model of cardiac arrest and resuscitation. Prospective, randomized, controlled experimental study. University-affiliated animal research institution. Twenty-eight healthy male Sprague-Dawley rats. The animals were randomized into four groups: 1) remote ischemic preconditioning initiated 40 minutes before induction of ventricular fibrillation, 2) remote ischemic postconditioning initiated coincident with the start of cardiopulmonary resuscitation, 3) remote ischemic postconditioning initiated 5 minutes after successful resuscitation, and 4) control. Remote ischemic pre- and postconditioning was induced by four cycles of 5 minutes of limb ischemia, followed by 5 minutes of reperfusion. Ventricular fibrillation was induced and untreated for 6 minutes while defibrillation was attempted after 8 minutes of cardiopulmonary resuscitation. The animals were then monitored for 4 hours and observed for an additional 68 hours after resuscitation. Hemodynamic measurements and myocardial function, including cardiac output, left ventricular ejection fraction, and myocardial performance index, were measured at baseline and hourly for 4 hours after resuscitation. Postresuscitation cerebral function was evaluated by neurologic deficit score at 24-hour intervals for a total of 72 hours. Consequently, significantly better myocardial and cerebral function with a longer duration of survival were observed in the three groups treated with remote ischemic pre- and postconditioning. In a rat model of cardiac arrest and resuscitation, remote ischemic pre-and postconditioning attenuated postresuscitation myocardial and cerebral dysfunction and improved the duration of survival.

The protective effects of a phosphodiesterase 5 inhibitor, sildenafil, on postresuscitation cardiac dysfunction of cardiac arrest: metabolic evidence from microdialysis.

IntroductionRecent experimental and clinical studies have indicated the cardioprotective role of sildenafil during ischemia/reperfusion injury. The aim of this study was to determine, by obtaining metabolic evidence from microdialysis, if sildenafil could reduce the severity of postresuscitation myocardial dysfunction and lead to cardioprotection through beneficial effects on energy metabolism.MethodsTwenty-four male piglets were randomly divided into three groups: sildenafil (n = 8), saline (SA; n = 8) and sham operation (n = 8). Sildenafil pretreatment consisted of 0.5 mg/kg sildenafil administered once intraperitoneally 30 minutes prior to ventricular fibrillation (VF). The myocardial interstitial fluid (ISF) concentrations of glucose, lactate, pyruvate, glutamate and glycerol were determined by microdialysis before VF. Afterward, the piglets were subjected to 8 minutes of untreated VF followed by 15 minutes of open-chest cardiopulmonary resuscitation. ISF was collected continuously, and the experiment was terminated 24 hours after resuscitation.ResultsAfter 8 minutes of untreated VF, the sildenafil group exhibited higher glucose and pyruvate concentrations of ISF and lower lactate and glutamate levels in comparison with the SA group, and these data reached statistical significance (P < 0.05). Advanced cardiac life support was delivered to both groups, with a 24-hour survival rate showing a promising trend in the sildenafil group (7 of 8 versus 3 of 8 survivors, P < 0.05). Compared with the SA group, the sildenafil group had a better outcome in terms of hemodynamic and oxygen metabolism parameters (P < 0.05). Myocardial tissue analysis revealed a dramatic increase in the contents of ATP, ADP and phosphocreatine in the sildenafil group versus the SA group at 24 hours after return of spontaneous circulation (ROSC; P = 0.03, P = 0.02 and P = 0.02, respectively). Furthermore, 24 hours after ROSC, the sildenafil group had marked elevations in activity of left ventricular Na+-K+-ATPase and Ca2+-ATPase compared with the SA group (P = 0.03, P = 0.04, respectively).ConclusionsSildenafil could reduce the severity of postresuscitation myocardial dysfunction, and it produced better clearance of metabolic waste in the ISF. This work might provide insights into the development of a novel strategy to treat postresuscitation myocardial dysfunction.Electronic supplementary materialThe online version of this article (doi:10.1186/s13054-014-0641-7) contains supplementary material, which is available to authorized users.

Abstract 127: Severity of Postresuscitation Myocardial Dysfunction Is Dependent on the Duration of Untreated Cardiac Arrest

Introduction: The duration of untreated ventricular fibrillation (VF) is one of the major determinant for outcome of cardiac arrest (CA). We investigated the relationship between different durations of untreated VF and post-resuscitation myocardial dysfunction and survival in a pig model. Methods: An established model of myocardial infarction followed by CA and CPR was used. Twenty pigs(35-43 Kg) were subjected to 3 different untreated VF intervals, prior to mechanical CPR and defibrillation: 8-10 min; 12-13 min; or 14-15 min. Arterial and central venous pressures were invasively monitored. Ejection fraction (EF) was echocardiographically assessed together with termodilution cardiac output (CO) and high sensitivity cardiac troponin T (hs-cTnT) assay. Ninety six hr survival was evaluated. Results: All the animals were resuscitated, except for 2 in the 14-15 min VF duration (Table). More than 80% of animals survived when the duration of VF was below 13 min, compared to only 17% after 14-15 min (Fig A). The duration of untreated VF correlated with the number of defibrillations required prior to resuscitation (r=0.60, p=0.01, Table). Longer durations of VF were characterized by higher post-resuscitation heart rate and right atrium pressure and by lower post-resuscitation CO and EF (p&lt;0.01, Table). Ninety six hr EF recovered in all animals except in the pig that survived after 14-15 min VF. EF correlated with the number of defibrillation delivered (Fig B) and with hs-cTnT release (r=-0.84, p&lt;0.0001). Conclusions: In this model, post-resuscitation myocardial dysfunction and survival were affected by the duration of untreated VF in a time-dependent manner.

Abstract 11100: Effect of Different Oxygen Concentrations on Post Resuscitation Myocardial Oxidative Stress and Myocardial Function in a Rat Model of CPR

Background: Lipid peroxidation induced by oxygen free radicals plays a prominent role in myocardial injury after global ischemia. The present study investigated whether ventilation with lower concentration of inspired oxygen would decrease the severity of myocardial lipid peroxidation and post resuscitation myocardial dysfunction. Methods: Ventricular fibrillation was induced and untreated for 8 mins in 46 male Sprague-Dawley rats. Defibrillation was attempted after 8 mins of CPR. The animals were randomized into 3 groups: mechanical ventilation with 100% O2, 50% O2 or 21% O2 during CPR and one hr following return of spontaneous circulation. Normoxic ventilation was maintained thereafter. The level of 8-iso-Prostaglandin F2α (8-iso-PGF2α) in myocardium was evaluated using the enzyme-linked immunosorbent assay (ELISA). Blood gases, post resuscitation myocardial function and the duration of survival were monitored in all animals. Results: Compared with the 100% and 21% groups, the 50% group showed a lower 8-iso-PGF2α level at 4 hrs post resuscitation (Table). Significantly greater oxygen extraction rate, lower lactate, better myocardial ejection fraction and myocardial performance index were observed in the 50% group (Table). A significantly shorter duration of survival was observed in the 21% group when compared with the other two groups (Table). There was a trend in the 50% group towards an increased duration of survival when compared with the 100% group. Conclusions: In a rat cardiac arrest model, ventilation with 50% inspired oxygen during early post-ischemic reperfusion contributed to a decreased lipid peroxidation, a better oxygenation, myocardial function and duration of survival.

Abstract 307: The Velocity of Increasing End-Tidal CO 2 Immediately Following Resuscitation Is Associated with Postresuscitation Myocardial Function

Introduction: End-tidal CO2 (ETCO2) serves as a sensitive indicator of hemodynamic efficacy during CPR and therefore predicts the success of resuscitation. In the present study, we investigated the relationship between the velocity of increasing ETCO2 immediately after successful resuscitation and post resuscitation myocardial function. Hypothesis: The velocity of increasing ETCO2 immediately following resuscitation is associated with the severity of post resuscitation myocardial dysfunction. Methods: Twenty rats were randomly assigned to one of two groups: (1) short duration of cardiac arrest (CA) (n = 10): ventricular fibrillation (VF) was untreated for 4 mins prior to 6 mins of CPR; (2) long duration of CA (n = 10): VF was untreated for 8 mins followed by 8 mins of CPR. After successful resuscitation, the first 20 secs of ETCO2 were analyzed. The velocity of ETCO2 changes was defined as the difference of the maximum and minimum ETCO2 value divided by the duration between the two ETCO2 values. Ejection fraction (EF) was measured by echocardiography at 8 hrs after resuscitation. Results: Increasing ETCO2 immediately following successful resuscitation was observed in all rats. However, the velocity of ETCO2 increasing in the group of short duration of CA was significantly faster than the group of long duration. This was associated with significantly greater EF at 8 hrs after resuscitation (Table). A close correlation between the velocity of increasing ETCO2 and EF was demonstrated (r=0.70, p&lt;0.01) (Figure). Conclusion: The velocity of increasing ETCO2 immediately following resuscitation is associated with post resuscitation myocardial function.