Huashan Wang

Induced hypothermia by central venous infusion: Saline ice slurry versus chilled saline

Objective:Surface cooling improves outcome in selected comatose survivors of cardiac arrest. Internal cooling with considerable volumes of intravenous cold saline may accelerate hypothermia induction. This study compares core temperatures in swine after central catheter infusions of saline ice slurry (saline with smoothed 100-&mgr;m-size ice particles) vs. an equal volume of chilled saline. We hypothesized that slurry would achieve core hypothermia (32–34°C) more consistently and at a faster rate. Design:A total of 11 swine were randomized to receive microparticulate ice slurry, chilled saline infusion, or anesthesia alone in a monitored laboratory setting. Interventions:Intravenous bolus (50 mL/kg) of slurry or chilled 1.5% NaCl saline. Slurry was composed of a 1:1 mixture of ice and distilled H2O plus NaCl. Measurements:Cerebral cortex, tympanic membrane, inferior vena cava, rectal temperatures, electrocardiogram, arterial blood pressure, and arterial oxygen saturation were recorded for 1 hr after bolus. Main Results:Compared with anesthetized controls, core brain temperatures of the saline and slurry groups dropped by 3.4 ± 0.4°C and 5.3 ± 0.7°C (p = .009), respectively. With an infusion rate of 120 mL/min, cooling rates for the saline and slurry groups were −11.6 ± 1.8°C/hr and −18.2 ± 2.9°C/hr, respectively, during the first 20 mins. Four of four animals in the slurry group vs. zero of four animals in the saline group achieved target cortical temperatures of <34°C. Conclusions:Cold intravenous fluids rapidly induce hypothermia in swine with intact circulation. A two-phase (liquid plus ice) saline slurry cools more rapidly than an equal volume of cold saline at 0°C. Ice-slurry could be a significant improvement over other cooling methods when rate of cooling and limited infusion volumes are important to the clinician.

Inhibition of sphingosine-1-phosphate lyase rescues sphingosine kinase-1-knockout phenotype following murine cardiac arrest.

AIMS To test the role of sphingosine-1-phosphate (S1P) signaling system in the in vivo setting of resuscitation and survival after cardiac arrest. MAIN METHODS A mouse model of potassium-induced cardiac arrest and resuscitation was used to test the importance of S1P homeostasis in resuscitation and survival. C57BL/6 and sphingosine kinase-1 knockout (SphK1-KO) female mice were arrested for 8 min then subjected to 5 minute CPR with epinephrine bolus given at 90s after the beginning of CPR. Animal survival was monitored for 4h post-resuscitation. Upregulation of tissue and circulatory S1P levels were achieved via inhibition of S1P lyase by 2-acetyl-5-tetrahydroxybutyl imidazole (THI). Plasma and heart tissue S1P and ceramide levels were quantified by targeted ESI-LC/MS/MS. KEY FINDINGS Lack of SphK1 and low tissue/circulatory S1P levels in SphK1-KO mice led to poor animal resuscitation after cardiac arrest and to impaired survival post-resuscitation. Inhibition of S1P lyase in SphK1-KO mice drastically improved animal resuscitation and survival. Improved resuscitation and survival of THI-treated SphK1-KO mice were better correlated with cardiac dihydro-S1P (DHS1P) than S1P levels. The lack of SphK1 and the inhibition of S1P lyase by THI were accompanied by modulation in cardiac S1PR1 and S1PR2 expression and by selective changes in plasma N-palmitoyl- and N-behenoyl-ceramide levels. SIGNIFICANCE Our data provide evidence for the crucial role for SphK1 and S1P signaling system in resuscitation and survival after cardiac arrest, which may form the basis for development of novel therapeutic strategy to support resuscitation and long-term survival of cardiac arrest patients.

A novel pharmacological strategy by PTEN inhibition for improving metabolic resuscitation and survival after mouse cardiac arrest.

Sudden cardiac arrest (SCA) is a leading cause of death in the United States. Despite return of spontaneous circulation, patients die due to post-SCA syndrome that includes myocardial dysfunction, brain injury, impaired metabolism, and inflammation. No medications improve SCA survival. Our prior work suggests that optimal Akt activation is critical for cooling protection and SCA recovery. Here, we investigate a small inhibitor of PTEN, an Akt-related phosphatase present in heart and brain, as a potential therapy in improving cardiac and neurological recovery after SCA. Anesthetized adult female wild-type C57BL/6 mice were randomized to pretreatment of VO-OHpic (VO) 30 min before SCA or vehicle control. Mice underwent 8 min of KCl-induced asystolic arrest followed by CPR. Resuscitated animals were hemodynamically monitored for 2 h and observed for 72 h. Outcomes included heart pressure-volume loops, energetics (phosphocreatine and ATP from (31)P NMR), protein phosphorylation of Akt, GSK3β, pyruvate dehydrogenase (PDH) and phospholamban, circulating inflammatory cytokines, plasma lactate, and glucose as measures of systemic metabolic recovery. VO reduced deterioration of left ventricular maximum pressure, maximum rate of change in the left ventricular pressure, and Petco2 and improved 72 h neurological intact survival (50% vs. 10%; P < 0.05). It reduced plasma lactate, glucose, IL-1β, and Pre-B cell colony enhancing factor, while increasing IL-10. VO increased phosphorylation of Akt and GSK3β in both heart and brain, and cardiac phospholamban phosphorylation while reducing p-PDH. Moreover, VO improved cardiac bioenergetic recovery. We concluded that pharmacologic PTEN inhibition enhances Akt activation, improving metabolic, cardiovascular, and neurologic recovery with increased survival after SCA. PTEN inhibitors may be a novel pharmacologic strategy for treating SCA.

Plasma and myocardial visfatin expression changes are associated with therapeutic hypothermia protection during murine hemorrhagic shock/resuscitation

AIM Cytokine production during hemorrhagic shock (HS) could affect cardiac function during the hours after resuscitation. Visfatin is a recently described protein that functions both as a proinflammatory plasma cytokine and an intracellular enzyme within the nicotinamide adenine dinucleotide (NAD(+)) salvage pathway. We developed a mouse model of HS to study the effect of therapeutic hypothermia (TH) on hemodynamic outcomes and associated plasma and tissue visfatin content. METHODS Mice were bled and maintained at a mean arterial pressure (MAP) of 35 mmHg. After 30 min, animals (n=52) were randomized to normothermia (NT, 37+/-0.5 degrees C) or TH (33+/-0.5 degrees C) followed by rewarming at 60 min following resuscitation. After 90 min of HS (S90), mice were resuscitated and monitored for 180 min (R180). Visfatin, interleukin 6 (IL-6), keratinocyte-derived chemokine (KC), tumor necrosis factor-alpha (TNF-alpha), and myoglobin were measured by ELISA. RESULTS Compared to NT, TH animals exhibited improved R180 survival (23/26 [88.5%] vs. 13/26 [50%]; p=0.001). Plasma visfatin, IL-6, KC, and TNF-alpha increased by S90 in both groups (p<0.05). TH attenuated S90 plasma visfatin and, after rewarming, decreased R180 plasma IL-6, KC, and myoglobin (p<0.05) relative to NT. Heart and gut KC increased at S90 while IL-6 increases were delayed until R180 (p<0.05). NT produced sustained elevations of myocardial KC but decreased visfatin by R180, effects abrogated by TH (p<0.05). CONCLUSIONS In a mouse model of HS, TH improves hemodynamics and alters plasma and tissue proinflammatory cytokines including the novel cytokine visfatin. TH modulation of cytokines may attenuate cardiac dysfunction following HS.

Therapeutic hypothermia cardioprotection in murine hemorrhagic shock/resuscitation differentially affects p38α/p38γ, Akt, and HspB1.

BACKGROUND Therapeutic hypothermia (TH) has demonstrated great potential for forestalling cardiovascular collapse and improving outcomes in the setting of severe hemorrhagic shock (HS). We used an established mouse model of severe HS to study the response of interrelated cardiac-signaling proteins p38, HspB1, and Akt to shock, resuscitation, and cardioprotective TH. METHODS Adult female C57BL6/J mice were bled and maintained at a mean arterial pressure of 35 mm Hg. After 30 minutes, mice were randomized to 120 minutes of TH (33°C ± 0.5°C) or continued normothermia at 37°C. After 90 minutes, animals were resuscitated and monitored for 180 minutes. Cardiac p38, Akt, and HspB1 phosphorylation (p-p38, p-Akt, and p-HspB1), expression, and Akt/HspB1 interactions were measured at serial time points during HS and resuscitation. Markers of mitochondrial damage (plasma cytochrome c), inflammation (myeloperoxidase), and apoptosis (terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling) were analyzed. RESULTS By 15 minutes HS, p-p38 and p-HspB1 significantly increased while p-Akt(T308) decreased (p < 0.05). TH attenuated phosphorylation of the p38α isoform during HS and increased phosphorylation of the p38γ isoform during both HS and early resuscitation (p < 0.05). TH increased Akt/HspB1 coimmunoprecipitation during early resuscitation and increased p-Akt and HspB1 expression during late resuscitation (p < 0.05). Finally, TH attenuated the myocardial myeloperoxidase and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling staining and plasma cytochrome c during late resuscitation. CONCLUSIONS TH increases phosphorylation of p38γ during both HS and early resuscitation, but attenuates phosphorylation of p38α, increases Akt/HspB1 interaction, and modulates Akt phosphorylation during HS and resuscitation. Such TH-related signaling events are associated with reduced cardiac inflammation, apoptosis, and mitochondrial injury.