Individualized Biventricular Epicardial Augmentation Technology in a Drug-Induced Porcine Failing Heart Model.

For treatment of advanced heart failure, current strategies include cardiac transplantation or blood-contacting pump technology associated with complications, including stroke and bleeding. This study investigated an individualized biventricular epicardial augmentation technology in a drug-induced porcine failing heart model. A total of 11 pigs were used, for the assessment of hemodynamics and cardiac function under various conditions of support pressures and support durations (n = 4), to assess device positioning and function by in vivo computer tomographic imaging (n = 3) and to investigate a minimally invasive implantation on the beating heart (n = 4). Support pressures of 20-80 mm Hg gradually augmented cardiac function parameters in this animal model as indicated by increased left ventricular stroke volume, end-systolic pressures, and decreased end-diastolic pressures. Strong evidence was found regarding the necessity of mechanical synchronization of support end with the isovolumetric relaxation phase of the heart. In addition, the customized, self-expandable implant enabled a marker-guided minimally invasive implantation through a 4 cm skin incision using fluoroscopy. Correct positioning was confirmed in computer tomographic images. Continued long-term survival investigations will deliver preclinical evidence for further development of this concept.

Hyperoxia or Therapeutic Hypothermia During Resuscitation from Non-Lethal Hemorrhagic Shock in Swine.

We previously demonstrated beneficial effects of 22 h of hyperoxia following near-lethal porcine hemorrhagic shock, whereas therapeutic hypothermia was detrimental. Therefore, we investigated whether shorter exposure to hyperoxia (12 h) would still improve organ function, and whether 12 h of hypothermia with subsequent rewarming could avoid deleterious effects after less severe hemorrhagic shock.Twenty-seven anesthetized and surgically instrumented pigs underwent 3 h of hemorrhagic shock by removal of 30% of the blood volume and titration of the mean arterial blood pressure (MAP) to 40 mm Hg. Post-shock, pigs were randomly assigned to control, hyperoxia (FIO2 100% for 12 h) or hypothermia group (34°C core temperature for 12 h with subsequent rewarming). Before, at the end of shock, after 12 and 23 h of resuscitation, data sets comprising hemodynamics, blood gases, and parameters of inflammation and organ function were acquired. Postmortem, kidney samples were collected for immunohistochemistry and western blotting.Hyperoxia exerted neither beneficial nor detrimental effects. In contrast, mortality in the hypothermia group was significantly higher compared with controls (67% vs. 11%). Hypothermia impaired circulation (MAP 64 (57;89) mm Hg vs. 104 (98; 114) mm Hg) resulting in metabolic acidosis (lactate 11.0 (6.6;13.6) mmol L vs. 1.0 (0.8;1.5) mmol L) and reduced creatinine clearance (26 (9;61) mL min vs. 77 (52;80) mL min) compared to the control group after 12 h of resuscitation. Impaired kidney function coincided with increased renal 3-nitrotyrosine formation and extravascular albumin accumulation.In conclusion, hyperoxia proved to be safe during resuscitation from hemorrhagic shock. The lacking organ-protective effects of hyperoxia compared to resuscitation from near-lethal hemorrhage suggest a dependence of the effectiveness of hyperoxia from shock severity. In line with our previous report, therapeutic hypothermia (and rewarming) was confirmed to be detrimental most likely due to vascular barrier dysfunction.

Metabolic, Cardiac, and Renal Effects of the Slow Hydrogen Sulfide-Releasing Molecule GYY4137 During Resuscitated Septic Shock in Swine with Pre-Existing Coronary Artery Disease.

Decreased levels of endogenous hydrogen sulfide (H2S) contribute to atherosclerosis, whereas equivocal data are available on H2S effects during sepsis. Moreover, H2S improved glucose utilization in anaesthetized, ventilated, hypothermic mice, but normothermia and/or sepsis blunted this effect. The metabolic effects of H2S in large animals are controversial. Therefore, we investigated the effects of the H2S donor GYY4137 during resuscitated, fecal peritonitis-induced septic shock in swine with genetically and diet-induced coronary artery disease (CAD). Twelve and 18 h after peritonitis induction, pigs received either GYY4137 (10 mg kg, n = 9) or vehicle (n = 8). Before, at 12 and 24 h of sepsis, we assessed left ventricular (pressure-conductance catheters) and renal (creatinine clearance, blood NGAL levels) function. Endogenous glucose production and glucose oxidation were derived from the plasma glucose isotope and the expiratory CO2/CO2 enrichment during continuous i.v. 1,2,3,4,5,6-C6-glucose infusion. GYY4137 significantly increased aerobic glucose oxidation, which coincided with higher requirements of exogenous glucose to maintain normoglycemia, as well as significantly lower arterial pH and decreased base excess. Apart from significantly lower cardiac eNOS expression and higher troponin levels, GYY4137 did not significantly influence cardiac and kidney function or the systemic inflammatory response. During resuscitated septic shock in swine with CAD, GYY4137 shifted metabolism to preferential carbohydrate utilization. Increased troponin levels are possibly due to reduced local NO availability. Cautious dosing, the timing of GYY4137 administration, and interspecies differences most likely account for the absence of any previously described anti-inflammatory or organ-protective effects of GYY4137 in this model.

Left ventricular function during porcine-resuscitated septic shock with pre-existing atherosclerosis.

BACKGROUND: Reversible, depressed cardiac function is frequently encountered during septic shock and commonly called septic cardiomyopathy. Previous studies demonstrated reduced ejection fraction and left ventricular dilatation in both humans and animal models. However, the majority of the studies in humans excluded pre-existing cardiac disease and animal studies were performed on healthy specimen and/or without vasopressor support during sepsis. In order to more closely mimic the actual patients' conditions on intensive care units and to assess the influence of both cardiac comorbidity and vasopressor support on septic cardiomyopathy, we evaluated the left ventricular function in a porcine model of resuscitated septic shock with pre-existing atherosclerosis. METHODS: Hypercholesterolaemic, atherosclerotic pigs due to homozygous low-density lipoprotein receptor mutation and high-fat diet were anaesthetised and surgically instrumented. Faecal peritonitis was induced by inoculation of autologous faeces into the peritoneal cavity in n = 8 animals; n = 5 pigs underwent sham procedure. Sepsis resuscitation included administration of fluids and noradrenaline. Left ventricular function was analysed via pressure-conductance catheters before, 12 and 24 h after the induction of sepsis. RESULTS: The main findings were impaired ventricular dilatation (no significant change in the left ventricular end-diastolic volume) and unchanged ejection fraction in septic pigs with pre-existing atherosclerosis. The relaxation time constant τ decreased while dp/dtmax increased. Cardiac nitrotyrosine formation increased while expression of the endogenous hydrogen sulphide (H2S)-producing enzyme cystathionine γ-lyase (CSE) decreased. CONCLUSIONS: The data of the present study are in conflict with previously published data from healthy animal models, most likely as a result of ongoing resuscitation including noradrenaline treatment or intrinsic pathophysiologic processes of the pre-existing atherosclerosis. Moreover, increased nitrotyrosine formation and decreased expression of CSE suggest the implication of augmented oxidative/nitrosative stress and/or reduced bioavailability of nitric oxide as well as diminished endogenous H2S release in the pathophysiology of septic cardiomyopathy.

Effects of Hyperoxia and Mild Therapeutic Hypothermia During Resuscitation From Porcine Hemorrhagic Shock.

OBJECTIVE: Hemorrhagic shock-induced tissue hypoxia induces hyperinflammation, ultimately causing multiple organ failure. Hyperoxia and hypothermia can attenuate tissue hypoxia due to increased oxygen supply and decreased demand, respectively. Therefore, we tested the hypothesis whether mild therapeutic hypothermia and hyperoxia would attenuate postshock hyperinflammation and thereby organ dysfunction. DESIGN: Prospective, controlled, randomized study. SETTING: University animal research laboratory. SUBJECTS: Thirty-six Bretoncelles-Meishan-Willebrand pigs of either gender. INTERVENTIONS: After 4 hours of hemorrhagic shock (removal of 30% of the blood volume, subsequent titration of mean arterial pressure at 35 mm Hg), anesthetized and instrumented pigs were randomly assigned to "control" (standard resuscitation: retransfusion of shed blood, fluid resuscitation, norepinephrine titrated to maintain mean arterial pressure at preshock values, mechanical ventilation titrated to maintain arterial oxygen saturation > 90%), "hyperoxia" (standard resuscitation, but FIO2, 1.0), "hypothermia" (standard resuscitation, but core temperature 34°C), or "combi" (hyperoxia plus hypothermia) (n = 9 each). MEASUREMENTS AND MAIN RESULTS: Before, immediately at the end of and 12 and 22 hours after hemorrhagic shock, we measured hemodynamics, blood gases, acid-base status, metabolism, organ function, cytokine production, and coagulation. Postmortem kidney specimen were taken for histological evaluation, immunohistochemistry (nitrotyrosine, cystathionine γ-lyase, activated caspase-3, and extravascular albumin), and immunoblotting (nuclear factor-κB, hypoxia-inducible factor-1α, heme oxygenase-1, inducible nitric oxide synthase, B-cell lymphoma-extra large, and protein expression of the endogenous nuclear factor-κB inhibitor). Although hyperoxia alone attenuated the postshock hyperinflammation and thereby tended to improve visceral organ function, hypothermia and combi treatment had no beneficial effect. CONCLUSIONS: During resuscitation from near-lethal hemorrhagic shock, hyperoxia attenuated hyperinflammation, and thereby showed a favorable trend toward improved organ function. The lacking efficacy of hypothermia was most likely due to more pronounced barrier dysfunction with vascular leakage-induced circulatory failure.

Physiological and immune-biological characterization of a long-term murine model of blunt chest trauma.

Blunt chest trauma causes pulmonary and systemic inflammation. It is still a matter of debate whether the long-term course of this inflammatory response is associated with persistent impairment of lung function. We hypothesized that an increase of inflammatory biomarkers may still be present at later time points after blunt chest trauma, eventually, despite normalized lung mechanics and gas exchange. Anesthetized spontaneously breathing male C57BL/6J mice underwent a blast wave-induced blunt chest trauma or sham procedure. Twelve and 24 h later, blood gases and lung mechanics were measured, together with blood, bronchoalveolar lavage (BAL), and tissue cytokine concentrations (multiplex cytokine kit); heme oxygenase 1 (HO-1), activated caspase-3, Bcl-xL, and Bax expression (Western blotting); nuclear factor-κB activation (electrophoretic mobility shift assay); nitrotyrosine formation; and purinergic (P2XR4 and P2XR7) receptor expression (immunohistochemistry). Histological damage was assessed by hematoxylin and eosin and periodic acid-Schiff staining. High-resolution respirometry allowed assessing mitochondrial respiration in diaphragm biopsies. Chest trauma significantly increased tissue and BAL cytokine levels, associated with a significant increase in HO-1, purinergic receptor expression, and tissue nitrotyrosine formation. In contrast, lung mechanics, gas exchange, and histological damage did not show any significant difference between sham and trauma groups. Activation of the immune response remains present at later time points after murine blunt chest trauma. Discordance of the increased local inflammatory response and preserved pulmonary function may be explained by a dissociation of the immune response and lung function, such as previously suggested after experimental sepsis.

Effects of pretreatment hypothermia during resuscitated porcine hemorrhagic shock.

OBJECTIVES: Accidental hypothermia increases mortality and morbidity after hemorrhage, but controversial data are available on the effects of therapeutic hypothermia. Therefore, we tested the hypothesis whether moderate pretreatment hypothermia would beneficially influence organ dysfunction during long-term, porcine hemorrhage and resuscitation. DESIGN: Prospective, controlled, randomized study. SETTING: University animal research laboratory. SUBJECTS: Twenty domestic pigs of either gender. INTERVENTIONS: Using an extracorporeal heat exchanger, anesthetized and instrumented animals were maintained at 38°C, 35°C, or 32°C core temperature and underwent 4 hours of hemorrhage (removal of 40% of the blood volume and subsequent blood removal/retransfusion to maintain mean arterial pressure at 30 mm Hg). Resuscitation comprised of hydroxyethyl starch and norepinephrine infusion titrated to maintain mean arterial pressure at preshock values. MEASUREMENTS AND MAIN RESULTS: Before, immediately at the end of, and 12 and 22 hours after hemorrhage, we measured systemic and regional hemodynamics (portal vein, hepatic and right kidney artery ultrasound flow probes) and oxygen transport, and nitric oxide and cytokine production. Hemostasis was assessed by rotation thromboelastometry. Postmortem biopsies were analyzed for histomorphology (hematoxylin and eosin staining) and markers of apoptosis (kidney Bcl-xL and caspase-3 expression). Hypothermia at 32°C attenuated the shock-related lactic acidosis but caused metabolic acidosis, most likely resulting from reduced carbohydrate oxidation. Although hypothermia did not further aggravate shock-related coagulopathy, it caused a transitory attenuation of kidney and liver dysfunction, which was ultimately associated with reduced histological damage and more pronounced apoptosis. CONCLUSIONS: During long-term porcine hemorrhage and resuscitation, moderate pretreatment hypothermia was associated with a transitory attenuation of organ dysfunction and less severe histological tissue damage despite more pronounced metabolic acidosis. This effect is possibly due to a switch from necrotic to apoptotic cell death, ultimately resulting from reduced tissue energy deprivation during the shock phase.

Carbamylated erythropoietin-FC fusion protein and recombinant human erythropoietin during porcine kidney ischemia/reperfusion injury.

PURPOSE: To test the hypothesis that a carbamylated EPO-FC fusion protein (cEPO-FC) or recombinant human erythropoietin (rhEPO) would protect against kidney ischemia/reperfusion (I/R) injury in pigs with atherosclerosis. METHODS: Anesthetized and mechanically ventilated animals received cEPO-FC (50 µg kg(-1)), rhEPO (5,000 IU kg(-1)), or vehicle (n = 9 per group) prior to 120 min of aortic occlusion and over 4 h of reperfusion. During aortic occlusion, mean arterial pressure (MAP) was maintained at 80-120 % of baseline values by esmolol, nitroglycerin, and ATP. During reperfusion, noradrenaline was titrated to keep MAP at pre-ischemic levels. Blood creatinine and neutrophil gelatinase-associated lipocalin (NGAL) levels, creatinine clearance, fractional Na(+) excretion, and HE and PAS staining were used to assess kidney function and histological damage. Plasma interleukin-6, tumor necrosis factor-α, nitrate + nitrite and 8-isoprostane levels were measured to assess systemic inflammation, and nitrosative and oxidative stress. RESULTS: I/R caused acute kidney injury with reduced creatinine clearance, increased fractional Na(+) excretion and NGAL levels, moderate to severe glomerular and tubular damage and apoptosis, systemic inflammation and oxidative and nitrosative stress, but there were no differences between the treatment groups. Pre-ischemia nitrate + nitrite and 8-isoprostanes levels were lower and higher, respectively, than in healthy animals of a previous study, and immune histochemistry showed higher endothelial nitric oxide synthase and lower EPO receptor expression in pre-ischemia kidney biopsies than in biopsies from healthy animals. CONCLUSIONS: In swine with atherosclerosis, rhEPO and cEPO-FC failed to attenuate prolonged ischemia-induced kidney injury within an 8-h reperfusion period, possibly due to reduced EPO receptor expression resulting from pre-existing oxidative stress and/or reduced NO release.

Effects of the PPAR-ß/δ agonist GW0742 during resuscitated porcine septic shock.

BACKGROUND: In un-resuscitated rodent models of septic shock, the peroxisome proliferator-activated receptor-ß/δ (PPAR-ß/δ) agonist GW0742 improved visceral organ function. Therefore, we tested the hypothesis whether GW0742 would attenuate kidney injury during long-term, resuscitated, porcine polymicrobial septic shock. METHODS: Six, 12, and 18 h after the induction of fecal peritonitis by inoculation of autologous feces, anesthetized, mechanically ventilated, and instrumented male pigs with pre-existing atherosclerosis resulting from familial hypercholesteremia and atherogenic diet randomly received either vehicle (dimethyl sulfoxide, n = 12) or GW0742 (n = 10). Resuscitation comprised hydroxyethyl starch and norepinephrine infusion titrated to maintain mean arterial pressure at baseline values. RESULTS: Despite aggressive fluid resuscitation, fecal peritonitis was associated with arterial hypotension requiring norepinephrine infusion, ultimately resulting in progressive lactic acidosis and acute kidney injury. GW0742 did not beneficially affect any parameter of systemic and regional hemodynamics, gas exchange, metabolism, or organ function. The parameters of inflammation, oxidative and nitrosative stress, and organ injury (post-mortem analysis for histomorphology and markers of apoptosis) were not influenced either. Immunohistochemistry of pre-shock kidney biopsies from a previous study in this swine strain showed markedly lower PPAR-ß/δ receptor expression than in healthy animals. CONCLUSIONS: In swine with pre-existing atherosclerosis, the PPAR-ß/δ agonist GW0742 failed to attenuate septic shock-induced circulatory failure and kidney dysfunction, most likely due to reduced receptor expression coinciding with cardiovascular and metabolic co-morbidity.

Bladder tissue oxygen tension monitoring in pigs subjected to a range of cardiorespiratory and pharmacological challenges.

PURPOSE: A fall in tissue oxygen tension (tPO(2)) is an early indicator of organ hypoxia in both patients and animal models. We previously demonstrated the utility of bladder tPO(2) in various rodent shock models. As a prelude to clinical testing, we aimed to provide further validation of bladder tPO(2) monitoring in a large animal model undergoing a range of cardiorespiratory insults and vasoactive drug interventions. METHODS: Anaesthetized, mechanically ventilated, instrumented female pigs (n = 8) were subjected to a range of short-term cardiorespiratory (changes in inspired oxygen concentration (FiO(2)), haemorrhage, positive end-expiratory pressure) and pharmacologic (inotrope, pressor) challenges. Global haemodynamics, arterial and pulmonary blood gases and bladder tPO(2) were measured before and after each challenge. RESULTS: Bladder tPO(2) values fell in line with increasing degrees of hypoxaemia and haemorrhage, and were restored during resuscitation. These changes often preceded those seen in global haemodynamics, arterial base excess and lactate. The rise in bladder tPO(2) with hyperoxia, performed as an oxygen challenge test, was incrementally blunted by progressive haemorrhage. Dobutamine and norepinephrine both increased cardiac output and global O(2) delivery, but had no effect on bladder tPO(2) or lactataemia in these healthy pigs. CONCLUSIONS: In this pig model bladder tPO(2) provides a sensitive indicator of organ hypoxia compared to traditional biochemical markers during various cardiorespiratory challenges. This technique offers a potentially useful tool for clinical monitoring.

Temperature and cell-type dependency of sulfide effects on mitochondrial respiration.

Previous studies suggest that sulfide-induced inhibition of cytochrome c oxidase (cCox) and, consequently, the metabolic and toxic effects of sulfide are less pronounced at low body temperature. Because the temperature-dependent effects of sulfide on the inflammatory response are still a matter of debate, we investigated the impact of varying temperature on the cCox excess capacity and the mitochondrial sulfide oxidation by the sulfide-ubiquinone oxidoreductase in macrophage-derived cell lines (AMJ2-C11 and RAW 264.7). Using an oxygraph chamber, the inhibition of mitochondrial respiration was measured by stepwise titrations with sulfide and the nonmetabolizable cCox inhibitor sodium azide at 25°C and 37°C. Using the latter of the two inhibitors, the excess capacity of the cCox was obtained. Furthermore, we quantified the capacity of these cells to withstand sulfide inhibition by measuring the amount required to inhibit respiration by 50% and 90% and the viability of the cells after 24-h exposure to 100 ppm of hydrogen sulfide. At low titration rates, the AMJ2-C11 cells, but not the RAW 264.7 cells, increased their capacity to withstand exogenously added sulfide. This effect was even greater at 25°C than at 37°C. Furthermore, only the AMJ2-C11 cells remained viable after sulfide exposure for 24 h. In contrast, only in the RAW 264.7 cells that an increase in cCox excess capacity was found at low temperatures. In macrophage-derived cell lines, both the excess capacity of cCox and the efficiency of sulfide elimination may increase at low temperatures. These properties may modify the effects of sulfide in immune cells and, potentially, the inflammatory response during sulfide exposure at different body temperatures.

Effects of intravenous sulfide during resuscitated porcine hemorrhagic shock*.

OBJECTIVE: Controversial data are available on the effects of hydrogen sulfide during hemorrhage. Because the clinical significance of hydrogen sulfide administration in rodents may not be applicable to larger species, we tested the hypothesis whether intravenous Na2S (sulfide) would beneficially influence organ dysfunction during long-term, porcine hemorrhage and resuscitation. DESIGN: Prospective, controlled, randomized study. SETTING: University animal research laboratory. SUBJECTS: Forty-five domestic pigs of either gender. INTERVENTIONS: Anesthetized and instrumented animals underwent 4 hrs of hemorrhage (removal of 40% of the blood volume and subsequent blood removal/retransfusion to maintain mean arterial pressure at 30 mm Hg). Sulfide infusion was started 2 hrs before hemorrhage, simultaneously with blood removal or at the beginning of retransfusion of shed blood, and continued for 12 hrs. Resuscitation comprised hydroxyethyl starch and norepinenephrine infusion titrated to maintain mean arterial pressure at preshock values. MEASUREMENTS AND MAIN RESULTS: Before, immediately at the end of and 12 and 22 hrs after hemorrhage, we measured systemic and regional hemodynamics (portal vein, hepatic and right kidney artery ultrasound flow probes) and oxygen transport, nitric oxide and cytokine production (nitrate+nitrite, interleukin-6, tumor necrosis factor-α levels). Postmortem biopsies were analyzed for histomorphology (hematoxylin and eosin staining) and DNA damage (terminal deoxynucleotidyltransferase-mediated dUTP nick-end labeling staining). The progressive kidney (creatinine levels, creatinine clearance), liver (transaminase activities, bilirubin levels), and cardiocirculatory (norepipnehrine requirements, troponin I levels) dysfunction was attenuated in the simultaneous treatment group only, which coincided with reduced lung, liver, and kidney histological damage. Sulfide reduced mortality, however, irrespective of the timing of its administration. CONCLUSIONS: While the sulfide-induced protection against organ injury was only present when initiated simultaneously with blood removal, it was largely unrelated to hypothermia. The absence of sulfide-mediated protection in the pretreatment protocol may be due to the accumulation of sulfide during low flow states. In conclusion, sulfide treatment can be effective in hemorrhagic shock, but its effectiveness is restricted to a narrow timing and dosing window.