Carbon monoxide as a cellular protective agent in a swine model of cardiac arrest protocol

Out-of-hospital cardiac arrest (OHCA) affects over 360,000 adults in the United States each year with a 50-80% mortality prior to reaching medical care. Despite aggressive supportive care and targeted temperature management (TTM), half of adults do not live to hospital discharge and nearly one-third of survivors have significant neurologic injury. The current treatment approach following cardiac arrest resuscitation consists primarily of supportive care and possible TTM. While these current treatments are commonly used, mortality remains high, and survivors often develop lasting neurologic and cardiac sequela well after resuscitation. Hence, there is a critical need for further therapeutic development of adjunctive therapies. While select therapeutics have been experimentally investigated, one promising agent that has shown benefit is CO. While CO has traditionally been thought of as a cellular poison, there is both experimental and clinical evidence that demonstrate benefit and safety in ischemia with lower doses related to improved cardiac/neurologic outcomes. While CO is well known for its poisonous effects, CO is a generated physiologically in cells through the breakdown of heme oxygenase (HO) enzymes and has potent antioxidant and anti-inflammatory activities. While CO has been studied in myocardial infarction itself, the role of CO in cardiac arrest and post-arrest care as a therapeutic is less defined. Currently, the standard of care for post-arrest patients consists primarily of supportive care and TTM. Despite current standard of care, the neurological prognosis following cardiac arrest and return of spontaneous circulation (ROSC) remains poor with patients often left with severe disability due to brain injury primarily affecting the cortex and hippocampus. Thus, investigations of novel therapies to mitigate post-arrest injury are clearly warranted. The primary objective of this proposed study is to combine our expertise in swine models of CO and cardiac arrest for future investigations on the cellular protective effects of low dose CO. We will combine our innovative multi-modal diagnostic platform to assess cerebral metabolism and changes in mitochondrial function in swine that undergo cardiac arrest with therapeutic application of CO.

Anaerobic Lactate Production Is Associated With Decreased Microcirculatory Blood Flow and Decreased Mitochondrial Respiration Following Cardiovascular Surgery With Cardiopulmonary Bypass

OBJECTIVES

Quantify the relationship between perioperative anaerobic lactate production, microcirculatory blood flow, and mitochondrial respiration in patients after cardiovascular surgery with cardiopulmonary bypass.

DESIGN

Serial measurements of lactate-pyruvate ratio (LPR), microcirculatory blood flow, plasma tricarboxylic acid cycle cycle intermediates, and mitochondrial respiration were compared between patients with a normal peak lactate (≤ 2 mmol/L) and a high peak lactate (≥ 4 mmol/L) in the first 6 hours after surgery. Regression analysis was performed to quantify the relationship between clinically relevant hemodynamic variables, lactate, LPR, and microcirculatory blood flow.

SETTING

This was a single-center, prospective observational study conducted in an academic cardiovascular ICU.

PATIENTS

One hundred thirty-two patients undergoing elective cardiovascular surgery with cardiopulmonary bypass.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Patients with a high postoperative lactate were found to have a higher LPR compared with patients with a normal postoperative lactate (14.4 ± 2.5 vs. 11.7 ± 3.4; p = 0.005). Linear regression analysis found a significant, negative relationship between LPR and microcirculatory flow index (r = -0.225; β = -0.037; p = 0.001 and proportion of perfused vessels: r = -0.17; β = -0.468; p = 0.009). There was not a significant relationship between absolute plasma lactate and microcirculation variables. Last, mitochondrial complex I and complex II oxidative phosphorylation were reduced in patients with high postoperative lactate levels compared with patients with normal lactate (22.6 ± 6.2 vs. 14.5 ± 7.4 pmol O2/s/106 cells; p = 0.002).

CONCLUSIONS

Increased anaerobic lactate production, estimated by LPR, has a negative relationship with microcirculatory blood flow after cardiovascular surgery. This relationship does not persist when measuring lactate alone. In addition, decreased mitochondrial respiration is associated with increased lactate after cardiovascular surgery. These findings suggest that high lactate levels after cardiovascular surgery, even in the setting of normal hemodynamics, are not simply a type B phenomenon as previously suggested.

Investigation of Cerebral Mitochondrial Injury in a Porcine Survivor Model of Carbon Monoxide Poisoning

INTRODUCTION

Carbon monoxide (CO) is a colorless and odorless gas that is a leading cause of environmental poisoning in the USA with substantial mortality and morbidity. The mechanism of CO poisoning is complex and includes hypoxia, inflammation, and leukocyte sequestration in brain microvessel segments leading to increased reactive oxygen species. Another important pathway is the effects of CO on the mitochondria, specifically at cytochrome c oxidase, also known as Complex IV (CIV). One of the glaring gaps is the lack of rigorous experimental models that may recapitulate survivors of acute CO poisoning in the early phase. The primary objective of this preliminary study is to use our advanced swine platform of acute CO poisoning to develop a clinically relevant survivor model to perform behavioral assessment and MRI imaging that will allow future development of biomarkers and therapeutics.

METHODS

Four swine (10 kg) were divided into two groups: control (n = 2) and CO (n = 2). The CO group received CO at 2000 ppm for over 120 min followed by 30 min of re-oxygenation at room air for one swine and 150 min followed by 30 min of re-oxygenation for another swine. The two swine in the sham group received room air for 150 min. Cerebral microdialysis was performed to obtain semi real-time measurements of cerebral metabolic status. Following exposures, all surviving animals were observed for a 24-h period with neurobehavioral assessment and imaging. At the end of the 24-h period, fresh brain tissue (cortical and hippocampal) was immediately harvested to measure mitochondrial respiration.

RESULTS

While a preliminary ongoing study, animals in the CO group showed alterations in cerebral metabolism and cellular function in the acute exposure phase with possible sustained mitochondrial changes 24 h after the CO exposure ended.

CONCLUSIONS

This preliminary research further establishes a large animal swine model investigating survivors of CO poisoning to measure translational metrics relevant to clinical medicine that includes a basic neurobehavioral assessment and post exposure cellular measures.

Low postoperative perfused vessel density is associated with increased soluble endothelial cell adhesion molecules during circulatory shock after cardiac surgery

INTRODUCTION

Microcirculatory dysfunction after cardiovascular surgery is associated with significant morbidity and worse clinical outcomes. Abnormal capillary blood flow can occur from multiple causes, including cytokine-mediated vascular endothelial injury, microthrombosis, and an inadequate balance between vasoconstriction and vasodilation. In response to proinflammatory cytokines, endothelial cells produce cellular adhesion molecules (CAMs) which regulate leukocyte adhesion, vascular permeability, and thus can mediate tissue injury. The relationship between changes in microcirculatory flow during circulatory shock and circulating adhesion molecules is unclear. The objective of this study was to compare changes in plasma soluble endothelial cell adhesion molecules (VCAM-1, ICAM-1, and E-Selectin) in patients with functional derangements in microcirculatory blood flow after cardiovascular surgery.

METHODS

Adult patients undergoing elective cardiac surgery requiring cardiopulmonary bypass who exhibited postoperative shock were enrolled in the study. Sublingual microcirculation imaging was performed prior to surgery and within 2 h of ICU admission. Blood samples were taken at the time of microcirculation imaging for biomarker analysis. Plasma soluble VCAM-1, ICAM-1, and E-selectin in addition to plasma cytokines (IL-6, IL-8, and IL-10) were measured by commercially available enzyme-linked immunoassay.

RESULTS

Of 83 patients with postoperative shock who were evaluated, 40 patients with clinical shock had a postoperative perfused vessel density (PVD) >1 SD above (High PVD group = 28.5 ± 2.3 mm/mm2, n = 20) or below (Low PVD = 15.5 ± 2.0 mm/mm2, n = 20) the mean postoperative PVD and were included in the final analysis. Patient groups were well matched for comorbidities, surgical, and postoperative details. Overall, there was an increase in postoperative plasma VCAM-1 and E-Selectin compared to preoperative levels, but there was no difference between circulating ICAM-1. When grouped by postoperative microcirculation, patients with poor microcirculation were found to have increased circulating VCAM-1 (2413 ± 1144 vs. 844 ± 786 ng/mL; p < 0.0001) and E-Selectin (242 ± 119 vs. 87 ± 86 ng/mL; p < 0.0001) compared to patients with increased microcirculatory blood flow. Microcirculatory flow was not associated with a difference in plasma soluble ICAM-1 (394 ± 190 vs. 441 ± 256; p = 0.52).

CONCLUSIONS

Poor postoperative microcirculatory blood flow in patients with circulatory shock after cardiac surgery is associated with increased plasma soluble VCAM-1 and E-Selectin, indicating increased endothelial injury and activation compared to patients with a high postoperative microcirculatory blood flow. Circulating endothelial cell adhesion molecules may be a useful plasma biomarker to identify abnormal microcirculatory blood flow in patients with shock.

Cell-Free DNA as a Biomarker in a Rodent Model of Chlorpyrifos Poisoning Causing Mitochondrial Dysfunction

INTRODUCTION

Organophosphates (OPs) are a major public health problem worldwide due to ease of access and high toxicity lacking effective biomarkers and treatment. Cholinergic agents such as OPs and carbamates are responsible for many pesticide-related deaths. While the inhibition of AChE is thought to be the main mechanism of injury, there are other important pathways that contribute to the overall toxicity of OPs such as mitochondrial dysfunction. An existing gap in OP poisoning are biomarkers to gauge severity and prognosis. Cell-free DNA (cfDNA) are novel biomarkers that have gained increased attention as a sensitive biomarker of disease with novel use in acute poisoning. This study investigates alterations in cerebral mitochondrial function in a rodent model of chlorpyrifos poisoning with the use of cfDNA as a potential biomarker.

METHODS

Twenty rodents were divided into two groups: Control (n = 10) and Chlorpyrifos (n = 10). Chlorpyrifos was administered through the venous femoral line with a Harvard Apparatus 11 Elite Syringe pump (Holliston, MA, USA) at 2 mg/kg. Animals were randomized to receive chlorpyrifos versus the vehicle (10% DMSO) for 60 min which would realistically present an acute exposure with continued absorption. At the end of the exposure (60 min), isolated mitochondria were measured for mitochondrial respiration along with measures of acetylcholinesterase activity, cfDNA, cytokines and western blot.

RESULTS

The Chlorpyrifos group showed a significant decrease in heart rate but no change in the blood pressure. There was a significant increase in bulk cfDNA concentrations and overall decrease in mitochondrial respiration from brain tissue obtained from animals in the Chlorpyrifos group when compared to the Control group with no difference in acetylcholinesterase activity. In addition, there was a significant increase in both IL-2 and IL-12 in the Chlorpyrifos group.

CONCLUSIONS

In our study, we found that the total cfDNA concentration may serve as a more accurate biomarker of OP exposure compared to acetylcholinesterase activity. In addition, there was an overall decrease in cerebral mitochondrial function in the Chlorpyrifos group when compared to the Control group.

Alteration in Cerebral Metabolism in a Rodent Model of Acute Sub-lethal Cyanide Poisoning

INTRODUCTION

Cyanide exposure can occur in various settings such as industry and metallurgy. The primary mechanism of injury is cellular hypoxia from Complex IV (CIV) inhibition. This leads to decreased ATP production and increased reactive oxygen species production. The brain and the heart are the organs most affected due to their high metabolic demand. While the cardiac effects of cyanide are well known, the cerebral effects on cellular function are less well described. We investigated cerebral metabolism with a combination of brain respirometry, microdialysis, and western blotting using a rodent model of sub-lethal cyanide poisoning.

METHODS

Twenty rodents were divided into two groups: control (n = 10) and sub-lethal cyanide (n = 10). Cerebral microdialysis was performed during a 2 mg/kg/h cyanide exposure to obtain real-time measurements of cerebral metabolic status. At the end of the exposure (90 min), brain-isolated mitochondria were measured for mitochondrial respiration. Brain tissue ATP concentrations, acyl-Coenzyme A thioesters, and mitochondrial content were also measured.

RESULTS

The cyanide group showed significantly increased lactate and decreased hypotension with decreased cerebral CIV-linked mitochondrial respiration. There was also a significant decrease in cerebral ATP concentration in the cyanide group and a significantly higher cerebral lactate-to-pyruvate ratio (LPR). In addition, we also found decreased expression of Complex III and IV protein expression in brain tissue from the cyanide group. Finally, there was no change in acyl-coenzyme A thioesters between the two groups.

CONCLUSIONS

The key finding demonstrates mitochondrial dysfunction in brain tissue that corresponds with a decrease in mitochondrial function, ATP concentrations, and an elevated LPR indicating brain dysfunction at a sub-lethal dose of cyanide.

Topical nitroglycerin to detect reversible microcirculatory dysfunction in patients with circulatory shock after cardiovascular surgery: an observational study

Persistent abnormalities in microcirculatory function are associated with poor clinical outcomes in patients with circulatory shock. We sought to identify patients with acutely reversible microcirculatory dysfunction using a low-dose topical nitroglycerin solution and handheld videomicroscopy during circulatory shock after cardiac surgery. Forty subjects were enrolled for the study, including 20 preoperative control and 20 post-operative patients with shock. To test whether microcirculatory dysfunction is acutely reversible during shock, the sublingual microcirculation was imaged with incident dark field microscopy before and after the application of 0.1 mL of a 1% nitroglycerin solution (1 mg/mL). Compared to the control group, patients with shock had a higher microcirculation heterogeneity index (MHI 0.33 vs. 0.12, p < 0.001) and a lower microvascular flow index (MFI 2.57 vs. 2.91, p < 0.001), total vessel density (TVD 22.47 vs. 25.90 mm/mm2, p = 0.005), proportion of perfused vessels (PPV 90.76 vs. 95.89%, p < 0.001) and perfused vessel density (PVD 20.44 vs. 24.81 mm/mm2, p < 0.001). After the nitroglycerin challenge, patients with shock had an increase in MFI (2.57 vs. 2.97, p < 0.001), TVD (22.47 vs. 27.51 mm/mm2, p < 0.009), PPV (90.76 vs. 95.91%, p < 0.001), PVD (20.44 vs. 26.41 mm/mm2, p < 0.001), venular RBC velocity (402.2 vs. 693.9 µm/s, p < 0.0004), and a decrease in MHI (0.33 vs. 0.04, p < 0.001. Thirteen of 20 patients showed a pharmacodynamic response, defined as an increase in PVD > 1.8 SD from shock baseline. Hemodynamics and vasoactive doses did not change during the 30-min study period. Our findings suggest a topical nitroglycerin challenge with handheld videomicroscopy can safely assess for localized recruitment of the microcirculatory blood flow in patients with circulatory shock and may be a useful test to identify nitroglycerin responsiveness.

Protocol for the MicroRESUS study: The impact of circulatory shock and resuscitation on microcirculatory function and mitochondrial respiration after cardiovascular surgery

Background

Despite current resuscitation strategies, circulatory shock and organ injury after cardiac surgery occur in 25–40% of patients. Goal-directed resuscitation after cardiac surgery has generated significant interest, but clinical practice to normalize hemodynamic variables including mean arterial pressure, cardiac filling pressures, and cardiac output may not reverse microcirculation abnormalities and do not address cellular dysoxia. Recent advances in technology have made it possible to measure critical components of oxygen delivery and oxygen utilization systems in live human tissues and blood cells. The MicroRESUS study will be the first study to measure microcirculatory and mitochondrial function in patients with circulatory shock and link these findings with clinical outcomes.

Methods and analysis

This will be a prospective, observational study that includes patients undergoing elective cardiovascular surgery with cardiopulmonary bypass (CPB). Microcirculation will be quantified with sublingual incident dark field videomicroscopy. Mitochondrial respiration will be measured by performing a substrate–uncoupler–inhibitor titration protocol with high resolution respirometry on peripheral blood mononuclear cells at baseline and serial timepoints during resuscitation and at recovery as a possible liquid biomarker. Plasma samples will be preserved for future analysis to examine endothelial injury and other mechanisms of microcirculatory dysfunction. Thirty-day ventilator and vasopressor-free days (VVFDs) will be measured as a primary outcome, along with sequential organ failure assessment scores, and other clinical parameters to determine if changes in microcirculation and mitochondrial respiration are more strongly associated with clinical outcomes compared to traditional resuscitation targets.

Discussion

This will be the first prospective study to examine both microcirculatory and mitochondrial function in human patients with circulatory shock undergoing cardiac bypass and address a key mechanistic knowledge gap in the cardiovascular literature. The results of this study will direct future research efforts and therapeutic development for patients with shock.

Low Microcirculatory Perfused Vessel Density and High Heterogeneity are Associated With Increased Intensity and Duration of Lactic Acidosis After Cardiac Surgery with Cardiopulmonary Bypass

INTRODUCTION

Lactic acidosis after cardiac surgery with cardiopulmonary bypass is common and associated with an increase in postoperative morbidity and mortality. A number of potential causes for an elevated lactate after cardiopulmonary bypass include cellular hypoxia, impaired tissue perfusion, ischemic-reperfusion injury, aerobic glycolysis, catecholamine infusions, and systemic inflammatory response after exposure to the artificial cardiopulmonary bypass circuit. Our goal was to examine the relationship between early abnormalities in microcirculatory convective blood flow and diffusive capacity and lactate kinetics during early resuscitation in the intensive care unit. We hypothesized that patients with impaired microcirculation after cardiac surgery would have a more severe postoperative hyperlactatemia, represented by the lactate time-integral of an arterial blood lactate concentration greater than 2.0 mmol/L.

METHODS

We measured sublingual microcirculation using incident darkfield video microscopy in 50 subjects on intensive care unit admission after cardiac surgery. Serial measurements of systemic hemodynamics, blood gas, lactate, and catecholamine infusions were recorded each hour for the first 6 h after surgery. Lactate area under the curve (AUC) was calculated over the first 6 h. The lactate AUC was compared between subjects with normal and low perfused vessel density (PVD < 18 mm/mm2), high microcirculatory heterogeneity index (MHI > 0.4), and low vessel-by-vessel microvascular flow index (MFIv < 2.6).

RESULTS

Thirteen (26%) patients had a low postoperative PVD, 20 patients (40%) had a high MHI, and 26 (52%) patients had a low MFIv. Patients with low perfused vessel density had higher lactate AUC compared with subjects with a normal PVD (22.3 [9.4-31.0] vs. 2.6 [0-8.8]; P < 0.0001). Patients with high microcirculatory heterogeneity had a higher lactate AUC compared with those with a normal MHI (2.5 [0.1-8.2] vs. 13.1 [3.7-31.1]; P < 0.001). We did not find a difference in lactate AUC when comparing high and low MFIv.

CONCLUSION

Low perfused vessel density and high microcirculatory heterogeneity are associated with an increased intensity and duration of lactic acidosis after cardiac surgery with cardiopulmonary bypass.

Emerging cellular-based therapies in carbon monoxide poisoning

Carbon monoxide (CO) is an odorless and colorless gas with multiple sources that include engine exhaust, faulty furnaces, and other sources of incomplete combustion of carbon compounds such as house fires. The most serious complications for survivors of consequential CO exposure are persistent neurological sequelae occurring in up to 50% of patients. CO inhibits mitochondrial respiration by specifically binding to the heme a₃ in the active site of CIV-like hydrogen sulfide, cyanide, and phosphides. Although hyperbaric oxygen remains the cornerstone for treatment, it has variable efficacy requiring new approaches to treatment. There is a paucity of cellular-based therapies in the area of CO poisoning, and there have been recent advancements that include antioxidants and a mitochondrial substrate prodrug. The succinate prodrugs derived from chemical modification of succinate are endeavored to enhance delivery of succinate to cells, increasing uptake of succinate into the mitochondria, and providing metabolic support for cells. The therapeutic intervention of succinate prodrugs is thus potentially applicable to patients with CO poisoning via metabolic support for fuel oxidation and possibly improving efficacy of HBO therapy.

Management of Adult Patients Supported with Venovenous Extracorporeal Membrane Oxygenation (VV ECMO): Guideline from the Extracorporeal Life Support Organization (ELSO)

Disclaimer: The use of venovenous extracorporeal membrane oxygenation (VV ECMO) in adults has rapidly increased worldwide. This ELSO guideline is intended to be a practical guide to patient selection, initiation, cannulation, management, and weaning of VV ECMO for adult respiratory failure. This is a consensus document which has been updated from the previous version to provide guidance to the clinician.

Characteristics, Outcomes, and Trends of Patients With COVID-19-Related Critical Illness at a Learning Health System in the United States

BACKGROUND

The coronavirus disease 2019 (COVID-19) pandemic continues to surge in the United States and globally.

OBJECTIVE

To describe the epidemiology of COVID-19-related critical illness, including trends in outcomes and care delivery.

DESIGN

Single-health system, multihospital retrospective cohort study.

SETTING

5 hospitals within the University of Pennsylvania Health System.

PATIENTS

Adults with COVID-19-related critical illness who were admitted to an intensive care unit (ICU) with acute respiratory failure or shock during the initial surge of the pandemic.

MEASUREMENTS

The primary exposure for outcomes and care delivery trend analyses was longitudinal time during the pandemic. The primary outcome was all-cause 28-day in-hospital mortality. Secondary outcomes were all-cause death at any time, receipt of mechanical ventilation (MV), and readmissions.

RESULTS

Among 468 patients with COVID-19-related critical illness, 319 (68.2%) were treated with MV and 121 (25.9%) with vasopressors. Outcomes were notable for an all-cause 28-day in-hospital mortality rate of 29.9%, a median ICU stay of 8 days (interquartile range [IQR], 3 to 17 days), a median hospital stay of 13 days (IQR, 7 to 25 days), and an all-cause 30-day readmission rate (among nonhospice survivors) of 10.8%. Mortality decreased over time, from 43.5% (95% CI, 31.3% to 53.8%) to 19.2% (CI, 11.6% to 26.7%) between the first and last 15-day periods in the core adjusted model, whereas patient acuity and other factors did not change.

LIMITATIONS

Single-health system study; use of, or highly dynamic trends in, other clinical interventions were not evaluated, nor were complications.

CONCLUSION

Among patients with COVID-19-related critical illness admitted to ICUs of a learning health system in the United States, mortality seemed to decrease over time despite stable patient characteristics. Further studies are necessary to confirm this result and to investigate causal mechanisms.

PRIMARY FUNDING SOURCE

Agency for Healthcare Research and Quality.

Alterations in cerebral and cardiac mitochondrial function in a porcine model of acute carbon monoxide poisoning

OBJECTIVES

The purpose of this study is the development of a porcine model of carbon monoxide (CO) poisoning to investigate alterations in brain and heart mitochondrial function.

DESIGN

Two group large animal model of CO poisoning.

SETTING

Laboratory.

SUBJECTS

Ten swine were divided into two groups: Control (n = 4) and CO (n = 6).

INTERVENTIONS

Administration of a low dose of CO at 200 ppm to the CO group over 90 min followed by 30 min of re-oxygenation at room air. The Control group received room air for 120 min.

MEASUREMENTS

Non-invasive optical monitoring was used to measure cerebral blood flow and oxygenation. Cerebral microdialysis was performed to obtain semi real time measurements of cerebral metabolic status. At the end of the exposure, both fresh brain (cortical and hippocampal tissue) and heart (apical tissue) were immediately harvested to measure mitochondrial respiration and reactive oxygen species (ROS) generation and blood was collected to assess plasma cytokine concentrations.

MAIN RESULTS

Animals in the CO group showed significantly decreased Complex IV-linked mitochondrial respiration in hippocampal and apical heart tissue but not cortical tissue. There also was a significant increase in mitochondrial ROS generation across all measured tissue types. The CO group showed a significantly higher cerebral lactate-to-pyruvate ratio. Both IL-8 and TNFα were significantly increased in the CO group compared with the Control group obtained from plasma. While not significant there was a trend to an increase in optically measured cerebral blood flow and hemoglobin concentration in the CO group.

CONCLUSIONS

Low-dose CO poisoning is associated with early mitochondrial disruption prior to an observable phenotype highlighting the important role of mitochondrial function in the pathology of CO poisoning. This may represent an important intervenable pathway for therapy and intervention.

Severe Impairment of Microcirculatory Perfused Vessel Density Is Associated With Postoperative Lactate and Acute Organ Injury After Cardiac Surgery

OBJECTIVE

Resuscitation after cardiac surgery needs to address multiple pathophysiological processes that are associated with significant morbidity and mortality. Functional microcirculatory derangements despite normal systemic hemodynamics have been previously described but must be tied to clinical outcomes. The authors hypothesized that microcirculatory dysfunction after cardiac surgery would include impaired capillary blood flow and impaired diffusive capacity and that subjects with the lowest quartile of perfused vessel density would have an increased postoperative lactate level and acute organ injury scores.

DESIGN

Prospective, observational study.

SETTING

A single, tertiary university cardiovascular surgical intensive care unit.

PARTICIPANTS

25 adults undergoing elective cardiac surgery requiring cardiopulmonary bypass.

INTERVENTION

Sublingual microcirculation was imaged using incident dark field microscopy before and 2 to 4 hours after surgery in the intensive care unit.

MEASUREMENTS AND MAIN RESULTS

Compared with baseline measurements, postoperative vessel-by-vessel microvascular flow index (2.9 [2.8-2.9] v 2.5 [2.4-2.7], p < 0.0001) and perfused vessel density were significantly impaired (20.7 [19.3-22.9] v 16.3 [12.8-17.9], p < 0.0001). The lowest quartile of perfused vessel density (<12.8 mm/mm2) was associated with a significantly increased postoperative lactate level (6.0 ± 2.9 v 1.8 ± 1.2, p < 0.05), peak lactate level (7.6 ± 2.8 v 2.8 ± 1.5, p = 0.03), and sequential organ failure assessment (SOFA) score at 24 and 48 hours.

CONCLUSION

In patients undergoing cardiac surgery, there was a significant decrease in postoperative microcirculatory convective blood flow and diffusive capacity during early postoperative resuscitation. Severely impaired perfused vessel density, represented by the lowest quartile of distribution, is significantly related to hyperlactatemia and early organ injury.

Association of an Emergency Department-embedded Critical Care Unit with Hospital Outcomes and Intensive Care Unit Use

Rationale: A small but growing number of hospitals are experimenting with emergency department-embedded critical care units (CCUs) in an effort to improve the quality of care for critically ill patients with sepsis and acute respiratory failure (ARF).Objectives: To evaluate the potential impact of an emergency department-embedded CCU at the Hospital of the University of Pennsylvania among patients with sepsis and ARF admitted from the emergency department to a medical ward or intensive care unit (ICU) from January 2016 to December 2017.Methods: The exposure was eligibility for admission to the emergency department-embedded CCU, which was defined as meeting a clinical definition for sepsis or ARF and admission to the emergency department during the intervention period on a weekday. The primary outcome was hospital length of stay (LOS); secondary outcomes included total emergency department plus ICU LOS, hospital survival, direct admission to the ICU, and unplanned ICU admission. Primary interrupted time series analyses were performed using ordinary least squares regression comparing monthly means. Secondary retrospective cohort and before-after analyses used multivariable Cox proportional hazard and logistic regression.Results: In the baseline and intervention periods, 3,897 patients met the inclusion criteria for sepsis and 1,865 patients met the criteria for ARF. Among patients admitted with sepsis, opening of the emergency department-embedded CCU was not associated with hospital LOS (β = -1.82 d; 95% confidence interval [CI], -4.50 to 0.87; P = 0.17 for the first month after emergency department-embedded CCU opening compared with baseline; β = -0.26 d; 95% CI, -0.58 to 0.06; P = 0.10 for subsequent months). Among patients admitted with ARF, the emergency department-embedded CCU was not associated with a significant change in hospital LOS for the first month after emergency department-embedded CCU opening (β = -3.25 d; 95% CI, -7.86 to 1.36; P = 0.15) but was associated with a 0.64 d/mo shorter hospital LOS for subsequent months (β = -0.64 d; 95% CI, -1.12 to -0.17; P = 0.01). This result persisted among higher acuity patients requiring ventilatory support but was not supported by alternative analytic approaches. Among patients admitted with sepsis who did not require mechanical ventilation or vasopressors in the emergency department, the emergency department-embedded CCU was associated with an initial 9.9% reduction in direct ICU admissions in the first month (β = -0.099; 95% CI, -0.153 to -0.044; P = 0.002), followed by a 1.1% per month increase back toward baseline in subsequent months (β = 0.011; 95% CI, 0.003-0.019; P = 0.009). This relationship was supported by alternative analytic approaches and was not seen in ARF. No associations with emergency department plus ICU LOS, hospital survival, or unplanned ICU admission were observed among patients with sepsis or ARF.Conclusions: The emergency department-embedded CCU was not associated with clinical outcomes among patients admitted with sepsis or ARF. Among less sick patients with sepsis, the emergency department-embedded CCU was initially associated with reduced rates of direct ICU admission from the emergency department. Additional research is necessary to further evaluate the impact and utility of the emergency department-embedded CCU model.

In vitro comparison of hydroxocobalamin (B12a) and the mitochondrial directed therapy by a succinate prodrug in a cellular model of cyanide poisoning

The objective of this study was to compare the use of hydroxocobalamin (B12a) and a succinate prodrug to evaluate for improvement in mitochondrial function in an in vitro model of cyanide poisoning. Peripheral blood mononuclear cells (PBMC) and human aortic smooth muscle cells (HASMC) incubated with 50 mM of sodium cyanide (CN) for five minutes serving as the CN group compared to controls. We investigated the following: (1) Mitochondrial respiration; (2) Superoxide and mitochondrial membrane potential with microscopy; (3) Citrate synthase protein expression. All experiments were performed with a cell concentration of 2-3 × 106 cells/ml for both PBMC and HASMC. There were four conditions: (1) Control (no exposure); (2) Cyanide (exposure only); (3) B12a (cyanide exposure followed by B12a treatment); (4) NV118 (cyanide followed by NV118 treatment). In this study the key findings include: (1) Improvement in key mitochondrial respiratory states with the succinate prodrug (NV118) but not B12a; (2) Attenuation of superoxide production with treatment of NV118 but not with B12a treatment; (3) The changes in respiration were not secondary to increased mitochondrial content as measured by citrate synthase; (4) The use of easily accessible human blood cells showed similar mitochondrial response to both cyanide and treatment to HASMC. The use of a succinate prodrug to circumvent partial CIV inhibition by cyanide with clear reversal of cellular respiration and superoxide production that was not attributed to changes in mitochondrial content not seen by the use of B12a.

The management of the poisoned patient using a novel emergency department-based resuscitation and critical care unit (ResCCU)

OBJECTIVES

The Resuscitation & Critical Care Unit (ResCCU) is a novel ED-based ICU designed to provide early critical care services. This study sought to identify characteristics of poisoned patients treated in the ResCCU.

METHODS

We conducted a retrospective, single-center case study of poisoned patients over the age of 18 years old over a 16-month period. Patient demographics, drug concentrations, and severity of illness scores were extracted from electronic medical records. Patients were divided into two groups, those who required short term ICU level care (< 24 h) and prolonged ICU care (> 24 h).

RESULTS

A total of 58 ED visits with a tox-related illness were analyzed. There were 24 women (41%) and 34 men (59%). There were 42 patients (72%) who required short term ICU level care and 16 patients (28%) who required prolonged ICU care. In the short-term ICU group, 13 patients (31%) were discharged home directly from the ResCCU, 29 patients (69%) were sent to the inpatient floor, and 1 of the admitted floor patients expired. There were no patients admitted to the floor that required a step-up to the inpatient ICU. 56 patients (97%) were alive at post-admit day 7 and 28, and only 8 (14%) were re-admitted within 30 days.

CONCLUSIONS

Patients who were treated in the ED-based ICU for toxicology-related illnesses were frequently able to be either discharged home or admitted to a regular floor after their initial stabilization and treatment, and none that were sent to the floor required an ICU step-up.

Combining qSOFA criteria with initial lactate levels: Improved screening of septic patients for critical illness

OBJECTIVE

To determine if the addition of lactate to Quick Sequential Organ Failure Assessment (qSOFA) scoring improves emergency department (ED) screening of septic patients for critical illness.

METHODS

This was a multicenter retrospective cohort study of consecutive adult patients admitted to the hospital from the ED with infectious disease-related illnesses. We recorded qSOFA criteria and initial lactate levels in the first 6 h of ED stay. Our primary outcome was a composite of hospital death, vasopressor use, and intensive care unit stay ≤72 h of presentation. Diagnostic test characteristics were determined for: 1) lactate levels ≥2 and ≥4; 2) qSOFA scores ≥1, ≥2, and =3; and 3) combinations of these.

RESULTS

Of 3743 patients, 2584 had a lactate drawn ≤6 h of ED stay and 18% met the primary outcome. The qSOFA scores were ≥1, ≥2, and =3 in 59.2%, 22.0%, and 5.3% of patients, respectively, and 34.4% had a lactate level ≥2 and 7.9% had a lactate level ≥4. The combination of qSOFA ≥1 OR Lactate ≥2 had the highest sensitivity, 94.0% (95% CI: 91.3-95.9).

CONCLUSIONS

The combination of qSOFA ≥1 OR Lactate ≥2 provides substantially improved sensitivity for the screening of critical illness compared to isolated lactate and qSOFA thresholds.

Anatomy of resuscitative care unit: expanding the borders of traditional intensive care units

Resuscitation lacks a place in the hospital to call its own. Specialised intensive care units, though excellent at providing longitudinal critical care, often lack the flexibility to adapt to fluctuating critical care needs. We offer the resuscitative care unit as a potential solution to ensure that patients receive appropriate care during the most critical hours of their illnesses. These units offer an infrastructure for resuscitation and can meet the changing needs of their institutions.

Beyond Mean Arterial Pressure and Lactate: Perfusion End Points for Managing the Shocked Patient

Patients in shock present frequently to the emergency department. The emergency physician must be skilled in the resuscitation of both differentiated and undifferentiated shock. Early, aggressive resuscitation of patients in shock is essential, using macrocirculatory, microcirculatory, and clinical end points to guide interventions. Therapy should focus on the restoration of oxygen delivery to match tissue demand. This article reviews the evidence supporting common end points of resuscitation for common etiologies of shock and limitations to their use.

Predictors of Short Intensive Care Unit Stay for Patients with Diabetic Ketoacidosis Using a Novel Emergency Department-Based Resuscitation and Critical Care Unit

BACKGROUND

The resuscitation and critical care unit is a novel emergency department-intensive care unit designed to provide early critical care to emergency department patients for ≤24 h.

OBJECTIVES

This study sought to identify clinical variables associated with short intensive care unit (ICU) stays in patients with diabetic ketoacidosis (DKA), who commonly require ICU-level care.

METHODS

We conducted a retrospective, single-center, cross-sectional study of DKA patients ≥18 years of age who presented to an academic, urban hospital emergency department over 16 months. Patient demographics and clinical variables extracted from medical records were compared between prolonged ICU stay patients of ≥24 h versus short ICU stay patients (SSPs) of <24 h. ICU care was defined as treatment in the resuscitation and critical care unit or inpatient ICU.

RESULTS

One hundred sixty-eight emergency department visits with a primary diagnosis of DKA were analyzed. There were 53 prolonged ICU stay patients, 58 SSPs, and 57 patients required no ICU time. SSPs had significantly higher initial serum bicarbonate (13.0 vs. 9.0 mEq/L, p = 0.01) and shorter anion gap closure time (9.8 vs. 14.4 hours, p = 0.003). Medication nonadherence was a significantly more frequent precipitant in SSPs (67.2% vs. 47.2%, p = 0.03). Initial anion gap, glucose, beta-hydroxybutyrate, and severity of illness scores were not significantly different between groups. After multivariate logistic regression adjusting for variables significant from univariate analysis, higher initial bicarbonate (p = 0.04) and medication nonadherence (p = 0.03) remained significantly associated with SSPs.

CONCLUSIONS

Patients with DKA with short ICU stays have higher initial bicarbonate levels and are more likely to have medication nonadherence than patients requiring prolonged critical care. These variables may identify patients with DKA who are best treated in an emergency department-intensive care unit to potentially reduce inpatient ICU use.

Comparison of qSOFA with current emergency department tools for screening of patients with sepsis for critical illness

OBJECTIVE

We sought to compare the quick sequential organ failure assessment (qSOFA) to systemic inflammatory response syndrome (SIRS), severe sepsis criteria and lactate levels for their ability to identify ED patients with sepsis with critical illness.

METHODS

We conducted this multicenter retrospective cohort study at five US hospitals, enrolling all adult patients admitted to these hospitals from their EDs with infectious disease-related illnesses from 1 January 2016 to 30 April 2016. We abstracted clinical variables for SIRS, severe sepsis and qSOFA scores, using values in the first 6 hours of ED stay. Our primary outcome was critical illness, defined as one or more of the composite outcomes of death, vasopressor use or intensive care unit (ICU) admission within 72 hours of presentation. We determined diagnostic test characteristics for qSOFA scores, SIRS, severe sepsis criteria and lactate level thresholds.

MAIN RESULTS

Of 3743 enrolled patients, 512 (13.7%) had the primary composite outcome. The qSOFA scores were ≥1, >2 and 3 in 1839 (49.1%), 626 (16.7%) and 146 (3.9%) patients, respectively; 2202 (58.8%) met SIRS criteria and 1085 (29.0%) met severe sepsis criteria. qSOFA ≥1 and SIRS had similarly high sensitivity [86.1% (95% CI 82.8% to 89.0%) vs 86.7% (95% CI 83.5% to 89.5%)], but qSOFA ≥1 had higher specificity [56.7% (95% CI 55.0% to 58.5%) vs 45.6% (43.9% to 47.3%); mean difference 11.1% (95% CI 8.7% to 13.6%)]. qSOFA ≥2 had higher specificity than severe sepsis criteria [89.1% (88.0% to 90.2%) vs 77.5% (76.0% to 78.9%); mean difference 11.6% (9.8% to 13.4%)]. qSOFA ≥1 had greater sensitivity than a lactate level ≥2 (mean difference 24.6% (19.2% to 29.9%)).

CONCLUSION

For patients admitted from the ED with infectious disease diagnoses, qSOFA criteria performed as well or better than SIRS criteria, severe sepsis criteria and lactate levels in predicting critical illness.

Mitochondrial networking in human blood cells with application in acute care illnesses

Mitochondria are dynamic organelles that adapt in response to environmental stresses or mutations. Dynamic processes involving mitochondria include their locomotion within cells and fusion and fission events in which mitochondrial join together or split apart. Various imaging strategies have been utilized to track mitochondrial dynamics. One common limitation of most of the methods available is that the time required to perform the technique and analyze the results prohibits application to clinical diagnosis and therapy. We recently demonstrated "whole-cell" mitochondrial analysis in a two-dimensional fashion with fluorescence microscopy. Our developed technique allows evaluation of whole-cell mitochondrial networking, including assessment of mitochondrial motility and rates of fission and fusion events using human blood cells (peripheral blood mononuclear cells (PBMCs)) on a clinically relevant timescale. We demonstrate this methodology in a cohort of healthy subjects as well as a cohort of hospitalized subjects having sepsis, an acute care illness. As there is increasing use of human blood cells as a proxy of organ mitochondrial function with respiration in various disease states, the addition of mitochondrial dynamics will now allow for more thorough clinical evaluation of mitochondrial networking in human disease with potential exploration of therapeutics.

End Points of Sepsis Resuscitation

Resuscitation goals for the patient with sepsis and septic shock are to return the patient to a physiologic state that promotes adequate end-organ perfusion along with matching metabolic supply and demand. Ideal resuscitation end points should assess the adequacy of tissue oxygen delivery and oxygen consumption, and be quantifiable and reproducible. Despite years of research, a single resuscitation end point to assess adequacy of resuscitation has yet to be found. Thus, the clinician must rely on multiple end points to assess the patient's overall response to therapy. This review will discuss the role and limitations of central venous pressure (CVP), mean arterial pressure (MAP), and cardiac output/index as macrocirculatory resuscitation targets along with lactate, central venous oxygen saturation (ScvO₂), central venous-arterial CO₂ gradient, urine output, and capillary refill time as microcirculatory resuscitation endpoints in patients with sepsis.

Measurement of Mitochondrial Respiration and Motility in Acute Care: Sepsis, Trauma, and Poisoning

Metabolic biomarkers have potentially wider use in disease diagnosis and prognosis as well as in monitoring disease response to treatment. While biomarkers such as interleukins, microRNA, and lactate have been proposed for disease surveillance, there are still conflicting results regarding their clinical utility. Treatment of commonly encountered disease of acute care such as sepsis, trauma, and poisoning often relies on clinical diagnosis and therapy guided by use of surrogate markers of illness severity. The measurement of mitochondrial function, including respiration and motility, may offer superior alternatives to such markers. Assessing mitochondrial function in a clinical context has the potential to impact the area of acute care in terms of diagnosis, prognosis, and treatment. The study of mitochondrial bioenergetics has become critical in understanding the pathophysiology and treatment of complex diseases such as diabetes and cardiovascular disorders.

Management of Crashing Patients with Pulmonary Hypertension

Critically ill patients with pulmonary hypertension (PH) often seem well, but they can decompensate dramatically in a short time. PH has several causes, classes, and complications; but the natural progression eventually leads to right ventricular failure, which can be extraordinarily difficult to manage. The purpose of this review is to discuss the causes, signs, and symptoms of PH as well as its management strategies and emergent complications. Treatment options are often limited, so it is imperative that the emergency department physician can recognize and manage these patients in a timely fashion.

Implementation of a team-based physician staffing model at an academic emergency department

Introduction

There is scant literature regarding the optimal resident physician staffing model of academic emergency departments (ED) that maximizes learning opportunities. A department of emergency medicine at a large inner-city academic hospital initiated a team-based staffing model. Its pre-interventional staffing model consisted of residents and attending physicians being separately assigned patients, resulting in residents working with two different faculty providers in the same shift. This study aimed to determine if the post-interventional team-based system, in which residents were paired with a single attending on each shift, would result in improved residents’ learning and clinical experiences as manifested by resident evaluations and the number of patients seen.

Methods

This retrospective before-and-after study at an academic ED with an annual volume of 52,000 patients examined the mean differences in five-point Likert-scale evaluations completed by residents assessing their ED rotation experiences in both the original and team-based staffing models. The residents were queried on their perceptions of feeling part of the team, decision-making autonomy, clinical experience, amount of supervision, quality of teaching, and overall rotational experience. We also analyzed the number of patients seen per hour by residents. Paired sample t-tests were performed. Residents who were in the program in the year preceding and proceeding the intervention were eligible for inclusion.

Results

34 of 38 eligible residents were included (4 excluded for lack of evaluations in either the pre- or post-intervention period). There was a statistically significant improvement in resident perception of the quality and amount of teaching, 4.03 to 4.27 (mean difference=0.24, p=0.03). There were non-statistically significant trends toward improved mean scores for all other queries. Residents also saw more patients following the initiation of the team-based model, 1.24 to 1.56 patients per hour (mean difference=0.32, p=0.0005).

Conclusion

Adopting a team-based physician staffing model is associated with improved resident perceptions of quality and amount of teaching. Residents also experience a greater number of patient evaluations in a team-based model.

Mechanical circulatory support

The role for temporary and durable mechanical circulatory support is rapidly expanding. As the use of these technologies continues to grow, the emergency physician has an increasing opportunity to participate in the advancement of these potentially life-saving technologies. This review discusses the current role of the intra-aortic balloon pump in cardiogenic shock, describes the complications and management strategies for the critically ill patient with a left ventricular assist device, and explores the emerging role of ECMO in the emergency department for patients presenting in refractory cardiogenic shock and cardiac arrest.

Alpha conditioning as an adjunct treatment for drug dependence: part I

The effects of alpha conditioning on the habits of four methadone maintained patients were assessed. All four learned some control over alpha activity in the 5-week, 10-session training period. The most striking results, however, related to the subjects' substitution of self-initiated mental states associated with alpha for previously used drug-seeking or self-medicating methods of coping with everday problem situations. All four subject reported a decrease in illicit drug usage and an increased feeling of self-control. Verification of improvement in adjustment and drug abuse was shown by counseling reports and narcotic screens from the maintenance program.