Cameron Dezfulian

Nitrite Therapy After Cardiac Arrest Reduces Reactive Oxygen Species Generation, Improves Cardiac and Neurological Function, and Enhances Survival via Reversible Inhibition of Mitochondrial Complex I

Background— Three-fourths of cardiac arrest survivors die before hospital discharge or suffer significant neurological injury. Except for therapeutic hypothermia and revascularization, no novel therapies have been developed that improve survival or cardiac and neurological function after resuscitation. Nitrite (NO2−) increases cellular resilience to focal ischemia/reperfusion injury in multiple organs. We hypothesized that nitrite therapy may improve outcomes after the unique global ischemia/reperfusion insult of cardiopulmonary arrest. Methods and Results— We developed a mouse model of cardiac arrest characterized by 12 minutes of normothermic asystole and a high cardiopulmonary resuscitation rate. In this model, global ischemia and cardiopulmonary resuscitation were associated with blood and organ nitrite depletion, reversible myocardial dysfunction, impaired alveolar gas exchange, neurological injury, and an ≈50% mortality. A single low dose of intravenous nitrite (50 nmol=1.85 &mgr;mol/kg=0.13 mg/kg) compared with blinded saline placebo given at cardiopulmonary resuscitation initiation with epinephrine improved cardiac function, survival, and neurological outcomes. From a mechanistic standpoint, nitrite treatment restored intracardiac nitrite and increased S-nitrosothiol levels, decreased pathological cardiac mitochondrial oxygen consumption resulting from reactive oxygen species formation, and prevented oxidative enzymatic injury via reversible specific inhibition of respiratory chain complex I. Conclusion— Nitrite therapy after resuscitation from 12 minutes of asystole rapidly and reversibly modulated mitochondrial reactive oxygen species generation during early reperfusion, limiting acute cardiac dysfunction, death, and neurological impairment in survivors.

Clinical application of preconditioning and postconditioning to achieve neuroprotection.

Ischemic conditioning is a form of endogenous protection induced by transient, subcritical ischemia in a tissue. Organs with high sensitivity to ischemia, such as the heart, the brain, and spinal cord, represent the most critical and potentially promising targets for potential therapeutic applications of ischemic conditioning. Numerous preclinical investigations have systematically studied the molecular pathways and potential benefits of both pre- and postconditioning with promising results. The purpose of this review is to summarize the present knowledge on cerebral pre- and postconditioning, with an emphasis in the clinical application of these forms of neuroprotection. A systematic MEDLINE search for the terms preconditioning and postconditioning was performed. Publications related to the nervous system and to human applications were selected and analyzed. Pre- and postconditioning appear to provide similar levels of neuroprotection. The preconditioning window of benefit can be subdivided into early and late effects, depending on whether the effect appears immediately after the sublethal stress or with a delay of days. In general, early effects have been associated posttranslational modification of critical proteins (membrane receptors, mitochondrial respiratory chain) while late effects are the result of gene up- or downregulation. Transient ischemic attacks appear to represent a form of clinically relevant preconditioning by inducing ischemic tolerance in the brain and reducing the severity of subsequent strokes. Remote forms of ischemic pre- and postconditioning have been more commonly used in clinical studies, as the remote application reduces the risk of injuring the target tissue for which protection is pursued. Limb transient ischemia is the preferred method of induction of remote conditioning with evidence supporting its safety. Clinical studies in a variety of populations at risk of central nervous damage including carotid disease, cervical myelopathy, and subarachnoid hemorrhage have shown improvement in surrogate markers of injury. Promising preclinical and early clinical studies noting improvement in surrogate markers of central nervous injury after the use of remote pre- and postconditioning treatments demand follow-up systematic investigations to address effectiveness. Challenges in the application of these techniques to pressing clinical cerebrovascular disease ought to be overcome through careful, well-designed, translational investigations.

Validation of the Pittsburgh Cardiac Arrest Category illness severity score

BACKGROUND The purpose of this study was to validate the ability of an early post-cardiac arrest illness severity classification to predict patient outcomes. METHODS The Pittsburgh Cardiac Arrest Category (PCAC) is a 4-level illness severity score that was found to be strongly predictive of outcomes in the initial derivation study. We assigned PCAC scores to consecutive in and out-of-hospital cardiac arrest subjects treated at two tertiary care centers between January 2011 and September 2013. We made assignments prospectively at Site 1 and retrospectively at Site 2. Our primary outcome was survival to hospital discharge. Inter-rater reliability of retrospective PCAC assessments was assessed. Secondary outcomes were favorable discharge disposition (home or acute rehabilitation), Cerebral Performance Category (CPC) and modified Rankin Scale (mRS) at hospital discharge. We tested the association of PCAC with each outcome using unadjusted and multivariable logistic regression. RESULTS We included 607 cardiac arrest patients during the study (393 at Site 1 and 214 at Site 2). Site populations differed in age, arrest location, rhythm, use of hypothermia and distribution of PCAC. Inter-rater reliability of retrospective PCAC assignments was excellent (κ=0.81). PCAC was associated with survival (unadjusted odds ratio (OR) for Site 1: 0.33 (95% confidence interval (CI) 0.27-0.41)) Site 2: 0.32 (95% CI 0.24-0.43) even after adjustment for other clinical variables (adjusted OR Site 1: 0.32 (95% CI 0.25-0.41) Site 2: 0.31 (95% CI 0.22-0.44)). PCAC was predictive of secondary outcomes. CONCLUSIONS Our results confirm that PCAC is strongly predictive of survival and good functional outcome after cardiac arrest.

Nitrite therapy is neuroprotective and safe in cardiac arrest survivors

Cardiac arrest results in significant mortality after initial resuscitation due in most cases to ischemia-reperfusion induced brain injury and to a lesser degree myocardial dysfunction. Nitrite has previously been shown to protect against reperfusion injury in animal models of focal cerebral and heart ischemia. Nitrite therapy after murine cardiac arrest improved 22 h survival through improvements in myocardial contractility. These improvements accompanied transient mitochondrial inhibition which reduced oxidative injury to the heart. Based on preliminary evidence that nitrite may also protect against ischemic brain injury, we sought to test this hypothesis in a rat model of asphyxia cardiac arrest with prolonged survival (7d). Cardiac arrest resulted in hippocampal CA1 delayed neuronal death well characterized in this and other cardiac arrest models. Nitrite therapy did not alter post-arrest hemodynamics but did result in significant (75%) increases in CA1 neuron survival. This was associated with increases in hippocampal nitrite and S-nitrosothiol levels but not cGMP shortly after therapy. Mitochondrial function 1h after resuscitation trended towards improvement with nitrite therapy. Based on promising preclinical data, the first ever phase I trial of nitrite infusions in human cardiac arrest survivors has been undertaken. We present preliminary data showing low dose nitrite infusion did not result in hypotension or cause methemoglobinemia. Nitrite thus appears safe and effective for clinical translation as a promising therapy against cardiac arrest mediated heart and brain injury.

effectiveness of stepwise interventions targeted to decrease central catheter-associated bloodstream infections*

Objective: Determine the impact of three stepwise interventions on the rate of central catheter-associated bloodstream infections. Design: Quasi-experimental study. Setting: Three surgical intensive care units (general surgery, trauma, and neurosurgery) at a 1500-bed county teaching hospital in the Miami metro area. Patients: All consecutive central catheter-associated bloodstream infection cases as determined by the Infection Control Department. Interventions: Three interventions aimed at catheter maintenance were implemented at different times in the units: chlorhexidine “scrub-the-hub,” chlorhexidine daily baths, and daily nursing rounds aimed at assuring compliance with an intensive care unit goal-oriented checklist. Measurements and Main Results: The primary outcome was the monthly intensive care unit rate of central catheter-associated bloodstream infections (infections per 1000 central catheter days). Over 33 months of follow-up (July 2008 to March 2011), we found decreased rates in each of the three intensive care units evaluated during the interventions, especially after implementation of chlorhexidine daily baths. Rates in unit A decreased from a rate of 8.6 to 0.5, unit B from 6.9 to 1.6, and unit C from 7.8 to 0.6. Secondary bloodstream infection rates remained unchanged throughout the observation period in units A and B; however, unit C had a decrease in its rates over time. Conclusions: We report the progressive reduction of central catheter-associated bloodstream infection rates after the stepwise implementation of chlorhexidine “scrub-the-hub” and daily baths in surgical intensive care units, suggesting effectiveness of these interventions.

Myocardial Dysfunction and Shock after Cardiac Arrest

Postarrest myocardial dysfunction includes the development of low cardiac output or ventricular systolic or diastolic dysfunction after cardiac arrest. Impaired left ventricular systolic function is reported in nearly two-thirds of patients resuscitated after cardiac arrest. Hypotension and shock requiring vasopressor support are similarly common after cardiac arrest. Whereas shock requiring vasopressor support is consistently associated with an adverse outcome after cardiac arrest, the association between myocardial dysfunction and outcomes is less clear. Myocardial dysfunction and shock after cardiac arrest develop as the result of preexisting cardiac pathology with multiple superimposed insults from resuscitation. The pathophysiology involves cardiovascular ischemia/reperfusion injury and cardiovascular toxicity from excessive levels of inflammatory cytokine activation and catecholamines, among other contributing factors. Similar mechanisms occur in myocardial dysfunction after cardiopulmonary bypass, in sepsis, and in stress-induced cardiomyopathy. Hemodynamic stabilization after resuscitation from cardiac arrest involves restoration of preload, vasopressors to support arterial pressure, and inotropic support if needed to reverse the effects of myocardial dysfunction and improve systemic perfusion. Further research is needed to define the role of postarrest myocardial dysfunction on cardiac arrest outcomes and identify therapeutic strategies.

Activation of Protein Kinase C Delta following Cerebral Ischemia Leads to Release of Cytochrome C from the Mitochondria via Bad Pathway

Background The release of cytochrome c from the mitochondria following cerebral ischemia is a key event leading to cell death. The goal of the present study was to determine the mechanisms involved in post-ischemic activation of protein kinase c delta (δPKC) that lead to cytochrome c release. Methods/Findings We used a rat model of cardiac arrest as an in vivo model, and an in vitro analog, oxygen glucose deprivation (OGD) in rat hippocampal synaptosomes. Cardiac arrest triggered translocation of δPKC to the mitochondrial fraction at 1 h reperfusion. In synaptosomes, the peptide inhibitor of δPKC blocked OGD-induced translocation to the mitochondria. We tested two potential pathways by which δPKC activation could lead to cytochrome c release: phosphorylation of phospholipid scramblase-3 (PLSCR3) and/or protein phosphatase 2A (PP2A). Cardiac arrest increased levels of phosphorlyated PLSCR3; however, inhibition of δPKC translocation failed to affect the OGD-induced increase in PLSCR3 in synaptosomal mitochondria suggesting the post-ischemic phosphorylation of PLSCR3 is not mediated by δPKC. Inhibition of either δPKC or PP2A decreased cytochrome c release from synaptosomal mitochondria. Cardiac arrest results in the dephosphorylation of Bad and Bax, both downstream targets of PP2A promoting apoptosis. Inhibition of δPKC or PP2A prevented OGD-induced Bad, but not Bax, dephosphorylation. To complement these studies, we used proteomics to identify novel mitochondrial substrates of δPKC. Conclusions We conclude that δPKC initiates cytochrome c release via phosphorylation of PP2A and subsequent dephosphorylation of Bad and identified δPKC, PP2A and additional mitochondrial proteins as potential therapeutic targets for ischemic neuroprotection.

Repetitive Mild Traumatic Brain Injury in the Developing Brain: Effects on Long-Term Functional Outcome and Neuropathology

Although accumulating evidence suggests that repetitive mild TBI (rmTBI) may cause long-term cognitive dysfunction in adults, whether rmTBI causes similar deficits in the immature brain is unknown. Here we used an experimental model of rmTBI in the immature brain to answer this question. Post-natal day (PND) 18 rats were subjected to either one, two, or three mild TBIs (mTBI) or an equivalent number of sham insults 24 h apart. After one or two mTBIs or sham insults, histology was evaluated at 7 days. After three mTBIs or sham insults, motor (d1-5), cognitive (d11-92), and histological (d21-92) outcome was evaluated. At 7 days, silver degeneration staining revealed axonal argyrophilia in the external capsule and corpus callosum after a single mTBI, with a second impact increasing axonal injury. Iba-1 immunohistochemistry showed amoeboid shaped microglia within the amygdalae bilaterally after mTBI. After three mTBI, there were no differences in beam balance, Morris water maze, and elevated plus maze performance versus sham. The rmTBI rats, however, showed impairment in novel object recognition and fear conditioning. Axonal silver staining was observed only in the external capsule on d21. Iba-1 staining did not reveal activated microglia on d21 or d92. In conclusion, mTBI results in traumatic axonal injury and microglial activation in the immature brain with repeated impact exacerbating axonal injury. The rmTBI in the immature brain leads to long-term associative learning deficit in adulthood. Defining the mechanisms damage from rmTBI in the developing brain could be vital for identification of therapies for children.

Neurocognitive Outcomes Following Successful Resuscitation from Cardiac Arrest

INTRODUCTION Cardiac arrest commonly results in varying degrees of cognitive injury. Standard outcome measures used in the cardiac arrest cohort do not rigorously evaluate for these injury patterns. We examined the utility of the Computerized Assessment for Mild Cognitive Injury (CAMCI) in cardiac arrest (CA) survivors. We hypothesized that cognitive deficits would be more severe in patients who were comatose on hospital arrival. METHODS Prospective cohort of CA survivors at a single tertiary care facility where participants received neurocognitive testing using CAMCI. CAMCI results were subdivided into memory, attention, and executive functions. Scores between subjects who were initially comatose and were not comatose following resuscitation were compared using the Mann-Whitney test. RESULTS Of 72 subjects included, the majority (N=44) were initially comatose following resuscitation with mean age of 54 (±14) years. The majority experienced a good neurologic outcome based on Cerebral Performance Category (N=47; 66%) and Modified Rankin Scale (N=38; 53%). Time from resuscitation to CAMCI testing was not associated with total CAMCI score in this cohort (Pearsons r(2) value -0.1941, p=0.20). Initially comatose and not comatose subjects did not differ in their CAMCI overall scores (p=0.33), or in any subtest areas. The not comatose cohort had 1 subtest for which there was a Moderate Risk for mild cognitive impairment (Nonverbal Accuracy), and 2 for which there was a Moderately Low Risk (Verbal Accuracy and Executive Accuracy). The Comatose cohort had 4 subtests, which were deemed Moderately Low Risk for cognitive impairment (Verbal Accuracy, Attention Accuracy, Executive Accuracy and Nonverbal Accuracy). CONCLUSIONS In-hospital CAMCI testing suggests memory, attention and executive impairment are commonly in patients following resuscitation from cardiac arrest. Outcome evaluations should test for deficits in memory, attention, and executive function.

Use of UV Powder for Surveillance to Improve Environmental Cleaning

Commercially available UV powder was applied weekly to high-risk objects within patient rooms and inspected after 48 hours. We found a baseline cleaning rate of 41.8% that increased up to 80% (P < .001) after the institution of weekly electronic feedback (unit rates and rankings) to environmental services, hospital leadership, and unit administrators.