Intra-arrest blood-based biomarkers for out-of-hospital cardiac arrest: A scoping review

Objective

Blood-based biomarkers play a central role in the diagnosis and treatment of critically ill patients, yet none are routinely measured during the intra-arrest phase of out-of-hospital cardiac arrest (OHCA). Our objective was to describe methodological aspects, sources of evidence, and gaps in research surrounding intra-arrest blood-based biomarkers for OHCA.

Methods

We used scoping review methodology to summarize existing literature. The protocol was designed a priori following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) Extension for Scoping Reviews. Inclusion criteria were peer-reviewed scientific studies on OHCA patients with at least one blood draw intra-arrest. We excluded in-hospital cardiac arrest and animal studies. There were no language, date, or study design exclusions. We conducted an electronic literature search using PubMed and Embase and hand-searched secondary literature. Data charting/synthesis were performed in duplicate using standardized data extraction templates.

Results

The search strategy identified 11,834 records, with 118 studies evaluating 105 blood-based biomarkers included. Only eight studies (7%) had complete reporting. The median number of studies per biomarker was 2 (interquartile range 1-4). Most studies were conducted in Asia (63 studies, 53%).  Only 22 studies (19%) had blood samples collected in the prehospital setting, and only six studies (5%) had samples collected by paramedics. Pediatric patients were included in only three studies (3%). Out of eight predefined biomarker categories of use, only two were routinely assessed: prognostic (97/105, 92%) and diagnostic (61/105, 58%).

Conclusions

Despite a large body of literature on intra-arrest blood-based biomarkers for OHCA, gaps in methodology and knowledge are widespread.

Prevalence and factors associated with initial and subsequent shockable cardiac arrest rhythms and their association with patient outcomes in dogs and cats undergoing cardiopulmonary resuscitation: A RECOVER registry study

OBJECTIVE

To report the prevalence of initial shockable cardiac arrest rhythms (I-SHKR), incidence of subsequent shockable cardiac arrest rhythms (S-SHKR), and factors associated with I-SHKRs and S-SHKRs and explore their association with return of spontaneous circulation (ROSC) rates in dogs and cats undergoing CPR.

DESIGN

Multi-institutional prospective case series from 2016 to 2021, retrospectively analyzed.

SETTING

Eight university and eight private practice veterinary hospitals.

ANIMALS

A total of 457 dogs and 170 cats with recorded cardiac arrest rhythm and event outcome reported in the Reassessment Campaign on Veterinary Resuscitation CPR registry.

MEASUREMENTS AND MAIN RESULTS

Logistic regression was used to evaluate association of animal, hospital, and arrest variables with I-SHKRs and S-SHKRs and with patient outcomes. Odds ratios (ORs) were generated, and significance was set at P < 0.05. Of 627 animals included, 28 (4%) had I-SHKRs. Odds for I-SHKRs were significantly higher in animals with a metabolic cause of arrest (OR 7.61) and that received lidocaine (OR 17.50) or amiodarone (OR 21.22) and significantly lower in animals experiencing arrest during daytime hours (OR 0.22), in the ICU (OR 0.27), in the emergency room (OR 0.13), and out of hospital (OR 0.18) and that received epinephrine (OR 0.19). Of 599 initial nonshockable rhythms, 74 (12%) developed S-SHKRs. Odds for S-SHKRs were significantly higher in animals with higher body weight (OR 1.03), hemorrhage (OR 2.85), or intracranial cause of arrest (OR 3.73) and that received epinephrine (OR 11.36) or lidocaine (OR 18.72) and significantly decreased in those arresting in ICU (OR 0.27), emergency room (OR 0.29), and out of hospital (OR 0.38). Overall, 171 (27%) animals achieved ROSC, 81 (13%) achieved sustained ROSC, and 15 (2%) survived. Neither I-SHKRs nor S-SHKRs were significantly associated with ROSC.

CONCLUSIONS

I-SHKRs and S-SHKRs occur infrequently in dogs and cats undergoing CPR and are not associated with increased ROSC rates.

Survivors of Sudden Cardiac Arrest Presenting With Pulseless Electrical Activity: Clinical Substrate, Triggers, Long-Term Prognosis

BACKGROUND

The proportion of sudden cardiac arrest (SCA) presenting as pulseless electrical activity (PEA) is rising, and survival remains low. The pathophysiology of PEA-SCA is poorly understood, and current clinical practice lacks specific options for the management of survivors.

OBJECTIVES

In this study, the authors sought to investigate clinical profile, triggers, and long-term prognosis in survivors of SCA presenting with PEA.

METHODS

The community-based Oregon SUDS (Sudden Unexpected Death Study) (since 2002) and Ventura PRESTO (Prediction of Sudden Death in Multi-ethnic Communities) (since 2015) studies prospectively ascertain all out-of-hospital SCAs of likely cardiac etiology. Lifetime clinical history and detailed evaluation of SCA events is available. We evaluated all SCA survivors with PEA as the presenting rhythm.

RESULTS

The study population included 201 PEA-SCA survivors. Of these, 97 could be contacted for access to their clinical records. Among the latter, the mean age was 67 ± 17 years and 58 (60%) were male. After in-hospital examinations, 29 events (30%) were associated with acute myocardial infarction, and 5 (5%) had bradyarrhythmias. Among the remaining 63 patients (65%), specific triggers remained undetermined, although 31 (49%) had a previous history of heart failure. Of the 201 overall survivors, 91 (45%) were deceased after a mean follow-up of 4.2 ± 4.0 years. Survivors under the age of 40 years had an excellent long-term prognosis.

CONCLUSIONS

Survivors of PEA-SCA are a heterogeneous group with high prevalence of multiple comorbidities, especially heart failure. Surprisingly good long-term survival was observed in young individuals. Acute myocardial infarction as the precipitating event was common, but triggers remained undetermined in the majority. Provision of individualized care to PEA survivors requires a renewed investigative focus on PEA-SCA.

Association of Initial Pulseless Electrical Activity Heart Rate and Clinical Outcomes Following Adult Non-Traumatic Out-of-Hospital Cardiac Arrest

OBJECTIVE

Studies evaluating the prognostic value of the pulseless electrical activity (PEA) heart rate in out-of-hospital cardiac arrest (OHCA) patients have reported conflicting results. The objective of this study was to evaluate the association between the initial PEA heart rate and favorable clinical outcomes for OHCA patients.

METHODS

The present post-hoc cohort study used the Resuscitation Outcomes Consortium Cardiac Epidemiologic Registry Version 3, which included OHCA patients in seven US and three Canadian sites from April 2011 to June 2015. The primary outcome was survival to hospital discharge and the secondary outcome was survival with a good functional outcome. For the primary analysis, the patients were separated into eight groups according to their first rhythms and PEA heart rates: (1) initial PEA heart rate of 1-20 beats per minute (bpm); (2) 21-40 bpm; (3) 41-60 bpm; (4) 61-80 bpm; (5) 81-100 bpm; (6) 101-120 bpm; (7) over 120 bpm; (8) initial shockable rhythm (reference category). Multivariable logistic regression models were used to assess the associations of interest.

RESULTS

We identified 17,675 patients (PEA: 7,089 [40.1%]; initial shockable rhythm: 10,797 [59.9%]). Patients with initial PEA electrical frequencies ≤100 bpm were less likely to survive to hospital discharge than patients with initial shockable rhythms (1-20 bpm: adjusted odds ratio [AOR] = 0.15 [95%CI 0.11-0.21]; 21-40 bpm: AOR =0.21 [0.18-0.25]; 41-60 bpm: AOR =0.30 [0.25-0.36]; 61-80 bpm: AOR =0.37 [0.28-0.49]; 81-100 bpm: AOR =0.55 [0.41-0.65]). However, there were no statistical outcome differences between PEA patients with initial electrical frequencies of >100 bpm and patients with initial shockable rhythms (101-120 bpm: AOR =0.65 [95%CI 0.42-1.01]; >120 bpm: AOR =0.72 [95%CI 0.37-1.39]). Similar results were observed for survival with good functional outcomes (101-120 bpm: AOR =0.60 [95%CI 0.31-1.15]; >120 bpm: AOR =1.08 [95%CI 0.50-2.28]).

CONCLUSIONS

We observed a good association between higher initial PEA electrical frequency and favorable clinical outcomes for OHCA patients. As there is no significant difference in outcomes between patients with initial PEA heart rates of more than 100 bpm and those with initial shockable rhythms, we can hypothesize that these patients could be considered in the same prognostic category.

Pulseless Electrical Activity: Echocardiographic Explanation of a Perplexing Phenomenon

Pulseless electrical activity (PEA) is considered an enigmatic phenomenon in resuscitation research and practice. Finding individuals with no consciousness or pulse but with continued electrocardiographic (EKG) complexes obviously raises the question of how they got there. The development of monitors that can display the underlying rhythm has allowed us to differentiate between VF, asystole, and PEA. Lack of clear understanding of the emergence of PEA has limited the research and development of interventions that might improve the low rates of survival typically associated with PEA. Over 30 years of studying and practicing resuscitation have allowed the authors to see a substantial rise in PEA with variable survival rates, based on the patients' illness spectrum and intensity of monitoring. This paper presents a small case series of individuals with brain death whose family members consented to the echocardiographic observation of the dying process after disconnection from life support. The observation from these cases confirms that PEA is a late phase in the clinical dying process. Echocardiographic images delineate the stages of pseudo-PEA with ineffective contractions, PEA, and then asystole. The process is contiuous with none of the sudden phase shifts seen in dysrhythmic events such as VF, VT or SVT. The implications of these findings are that PEA is a common manifestation of tissue hypoxia and metabolic substrate depletion. Our findings offer prospects for studies of the development of interventions to improve PEA survival.

Pulseless Electrical Activity as the Initial Cardiac Arrest Rhythm: Importance of Preexisting Left Ventricular Function

Background Pulseless electrical activity (PEA) is a common initial rhythm in cardiac arrest. A substantial number of PEA arrests are caused by coronary ischemia in the setting of acute coronary occlusion, but the underlying mechanism is not well understood. We hypothesized that the initial rhythm in patients with acute coronary occlusion is more likely to be PEA than ventricular fibrillation in those with prearrest severe left ventricular dysfunction. Methods and Results We studied the initial cardiac arrest rhythm induced by acute left anterior descending coronary occlusion in swine without and with preexisting severe left ventricular dysfunction induced by prior infarcts in non-left anterior descending coronary territories. Balloon occlusion resulted in ventricular fibrillation in 18 of 34 naïve animals, occurring 23.5±9.0 minutes following occlusion, and PEA in 1 animal. However, all 18 animals with severe prearrest left ventricular dysfunction (ejection fraction 15±5%) developed PEA 1.7±1.1 minutes after occlusion. Conclusions Acute coronary ischemia in the setting of severe left ventricular dysfunction produces PEA because of acute pump failure, which occurs almost immediately after coronary occlusion. After the onset of coronary ischemia, PEA occurred significantly earlier than ventricular fibrillation (<2 minutes versus 20 minutes). These findings support the notion that patients with baseline left ventricular dysfunction and suspected coronary disease who develop PEA should be evaluated for acute coronary occlusion.

Outcomes of in-hospital cardiac arrest in COVID-19 patients: A proportional prevalence meta-analysis

Background

Limited epidemiological data are available on the outcomes of in‐hospital cardiac arrest (CA) in COVID‐19 patients.

Methods

We performed literature search of PubMed, EMBASE, Cochrane, and Ovid to identify research articles that studied outcomes of in‐hospital cardiac arrest in COVID‐19 patients. The primary outcome was survival at discharge. Secondary outcomes included return of spontaneous circulation (ROSC) and types of cardiac arrest. Pooled percentages with a 95% confidence interval (CI) were calculated for the prevalence of outcomes.

Results

A total of 7,891 COVID patients were included in the study. There were 621 (pooled prevalence 8%, 95% CI 4–13%) cardiac arrest patients. There were 52 (pooled prevalence 3.0%; 95% CI 0.0–10.0%) patients that survived at the time of discharge. ROSC was achieved in 202 (pooled prevalence 39%;95% CI 21.0–59.0%) patients. Mean time to ROSC was 7.74 (95% CI 7.51–7.98) min. The commonest rhythm at the time of cardiac arrest was pulseless electrical activity (pooled prevalence 46%; 95% 13–80%), followed by asystole (pooled prevalence 40%; 95% CI 6–80%). Unstable ventricular arrhythmia occurred in a minority of patients (pooled prevalence 8%; 95% CI 4–13%).

Conclusion

This pooled analysis of studies showed that the survival post in‐hospital cardiac arrest in COVID patients is dismal despite adequate ROSC obtained at the time of resuscitation. Nonshockable rhythm cardiac arrest is commoner suggesting a non‐cardiac cause while cardiac related etiology is uncommon. Future studies are needed to improve the survival in these patients.

Effect of ICD implantation on cardiovascular outcomes in patients with cardiac amyloidosis: A systematic review and meta-anaylsis

INTRODUCTION

Cardiac amyloidosis is associated with a high rate of sudden cardiac death (SCD). Whether implantable cardioverter-defibrillator (ICD) use in such patients prevents SCD is uncertain. This study assesses outcomes of ICD use in patients with cardiac amyloidosis.

METHODS

A systematic review and meta-analysis of data were performed after searching multiple databases and scientific sites pertaining to ICD use and cardiac amyloidosis. Of 8260 citations identified, six studies comprising 194 patients met inclusion criteria.

RESULTS

Mean values and frequencies of patient characteristics were as follows: mean NT-proBNP: 6867.9 pg/mL, mean left ventricular ejection fraction: 48.1%, heart failure: 67%, nonsustained ventricular tachycardia: 51%, syncope: 21%, and secondary prevention: 33%. During the mean follow-up period of 18.21 months, 18% of patients received appropriate ICD treatment and 5% received inappropriate ICD treatment. The mortality rate was 31%. Two studies assessed the difference between patients with appropriate ICD treatment and patients with absence of appropriate ICD treatment. There was no difference between the two groups when stratified on multiple selected third variables except for two subgroups. Male gender was associated with a higher rate of appropriate ICD treatment, whereas New York Heart Association class III or IV heart failure patients was associated with a lower rate of appropriate ICD treatment.

CONCLUSION

The frequency of appropriate ICD treatment in cardiac amyloidosis is low and is not predicted by nonsustained ventricular tachycardia. Male gender is associated with appropriate ICD treatment. New York Heart Association class III or IV heart failure is associated with lower rate of appropriate ICD treatment.

UK ambulance service resuscitation management of pulseless electrical activity: a systematic review protocol of text and opinion

Background:

Out-of-hospital cardiac arrest patients with pulseless electrical activity are treated by paramedics using basic and advanced life support resuscitation. When resuscitation fails to achieve return of spontaneous circulation, there are limited evidence and national guidelines on when to continue or stop resuscitation. This has led to ambulance services in the United Kingdom developing local guidelines to support paramedics in the resuscitative management of pulseless electrical activity. The content of each guideline is unknown, as is any association between guideline implementation and patient survival. We aim to identify and synthesise local ambulance service guidelines to help improve the consistency of paramedic-led decision-making for the resuscitation of pulseless electrical activity in out-of-hospital cardiac arrest.

Methods:

A systematic review of text and opinion will be conducted on ambulance service guidelines for resuscitating adult cardiac arrest patients with pulseless electrical activity. Data will be gathered direct from the ambulance service website. The review will be guided by the methods of the Joanna Briggs Institute (JBI). The search strategy will be conducted in three stages: 1) a website search of the 14 ambulance services; 2) a search of the evidence listed in support of the guideline; and 3) an examination of the reference list of documents found in the first and second stages and reported using the Preferred Reporting Items for Systematic Reviews and Meta-analyses. Each document will be assessed against the inclusion criteria, and quality of evidence will be assessed using the JBI Critical Appraisal Checklist for Text and Opinion. Data will be extracted using the JBI methods of textual data extraction and a three-stage data synthesis process: 1) extraction of opinion statements; 2) categorisation of statements according to similarity of meaning; and 3) meta-synthesis of statements to create a new collection of findings. Confidence of findings will be assessed using the graded ConQual approach.

Fat Embolism Syndrome Revisited: A Case Report and Review of Literature, With New Recommendations for the Anesthetized Patient

Current criteria used to make the clinical diagnosis of fat embolism syndrome were never intended to be applied to an anesthetized, mechanically ventilated patient in the operating room and, as such, may not be applicable during intraoperative care. Because of this, confusion still exists among anesthesia providers in recognizing this potentially fatal clinical condition. Our goal was to develop and then present a more exacting and rigorous grading scale, tailored specifically for the anesthetized patient, with the hope that it will aid clinicians in recognizing and successfully managing the manifestations of the syndrome. A thorough review of the proposed mechanisms of fat embolism syndrome is provided, as well as a brief case report detailing a pediatric patient who experienced cardiovascular collapse during intramedullary nailing of a femur fracture. Also included is a proposal for new clinical guidelines for the intraoperative diagnosis of fat embolism.

Synchronized Chest Compressions for Pseudo-PEA: Proof of Concept and a Synching Algorithm

Objective: The two objectives of this report are: first, to describe a comparison of chest compressions unsynchronized or synchronized to native cardiac activity in a porcine model of hypotension, and second, to develop an algorithm to provide synchronized chest compressions throughout a range of native heart rates likely to be encountered when treating PEA cardiac arrest. Methods: We adapted our previously developed signal-guided CPR system to provide compressions synchronized to native electrical activity in a porcine model of hypotension as a surrogate of PEA arrest. We describe the first comparison of unsynchronized to synchronized compressions in a single animal as a proof-of-concept. We developed an algorithm to provide optimal synchronized chest compressions regardless of intrinsic PEA heart rate while simultaneously maintaining the chest compression rate within a desired range. We tested the algorithm with computer simulations measuring the proportion of intrinsic and compression beats that were synchronized, and the compression rate and its standard deviation, as a function of intrinsic heart rate and heart rate jitter. Results: We demonstrate and compare unsynchronized versus synchronized chest compressions in a single porcine model with an intrinsic rhythm and hypotension. Synchronized, but not unsynchronized, chest compressions were associated with increased blood pressure and coronary perfusion pressure. Our synchronized chest compression algorithm is able to provide synchronized chest compressions to over 90% of intrinsic beats for most heart rates while maintaining an average compression rate between 90 and 140 compressions per minute with relatively low variability. Conclusions: Synchronized chest compression therapy for pulseless electrical rhythms is feasible. A high degree of synchronization can be maintained over a broad range of intrinsic heart rates while maintaining the compression rate within a satisfactory range. Further investigation to assess benefit for treatment of PEA is warranted.

Cardiac arrest with pulseless electrical activity rhythm in newborn infants: a case series

The 2015 neonatal resuscitation guidelines added ECG to assess an infant's heart rate when determining the need for resuscitation at birth. However, a recent case report raised concerns about this technique in the delivery room. We report four cases of pulseless electrical activity during neonatal cardiopulmonary resuscitation in levels II-III neonatal intensive care units in Canada (Edmonton [n=3] and Winnipeg [n=1]).Healthcare providers should be aware that pulseless electrical activity can occur in newborn infants during cardiopulmonary resuscitation. We propose an adapted neonatal resuscitation algorithm to include pulseless electrical activity. Furthermore, in compromised newborns, heart rate should be assessed using a combination of methods/techniques to ensure accurate heart rate assessment. When ECG displays a heart rate but the infant is unresponsive, pulseless electrical activity should be suspected and chest compression should be started.

Deep Neural Networks for ECG-Based Pulse Detection during Out-of-Hospital Cardiac Arrest

The automatic detection of pulse during out-of-hospital cardiac arrest (OHCA) is necessary for the early recognition of the arrest and the detection of return of spontaneous circulation (end of the arrest). The only signal available in every single defibrillator and valid for the detection of pulse is the electrocardiogram (ECG). In this study we propose two deep neural network (DNN) architectures to detect pulse using short ECG segments (5 s), i.e., to classify the rhythm into pulseless electrical activity (PEA) or pulse-generating rhythm (PR). A total of 3914 5-s ECG segments, 2372 PR and 1542 PEA, were extracted from 279 OHCA episodes. Data were partitioned patient-wise into training (80%) and test (20%) sets. The first DNN architecture was a fully convolutional neural network, and the second architecture added a recurrent layer to learn temporal dependencies. Both DNN architectures were tuned using Bayesian optimization, and the results for the test set were compared to state-of-the art PR/PEA discrimination algorithms based on machine learning and hand crafted features. The PR/PEA classifiers were evaluated in terms of sensitivity (Se) for PR, specificity (Sp) for PEA, and the balanced accuracy (BAC), the average of Se and Sp. The Se/Sp/BAC of the DNN architectures were 94.1%/92.9%/93.5% for the first one, and 95.5%/91.6%/93.5% for the second one. Both architectures improved the performance of state of the art methods by more than 1.5 points in BAC.

Circulatory Failure During Noninhaled Forms of Cyanide Intoxication

Our objective was to determine how circulatory failure develops following systemic administration of potassium cyanide (KCN). We used a noninhaled modality of intoxication, wherein the change in breathing pattern would not influence the diffusion of CN into the blood, akin to the effects of ingesting toxic levels of CN. In a group of 300 to 400 g rats, CN-induced coma (CN i.p., 7 mg/kg) produced a central apnea within 2 to 3 min along with a potent and prolonged gasping pattern leading to autoresuscitation in 38% of the animals. Motor deficits and neuronal necrosis were nevertheless observed in the surviving animals. To clarify the mechanisms leading to potential autoresuscitation versus asystole, 12 urethane-anesthetized rats were then exposed to the lowest possible levels of CN exposure that would lead to breathing depression within 7 to 8 min; this dose averaged 0.375 mg/kg/min i.v. At this level of intoxication, a cardiac depression developed several minutes only after the onset of the apnea, leading to cardiac asystole as PaO2 reached value approximately 15 Torr, unless breathing was maintained by mechanical ventilation or through spontaneous gasping. Higher levels of KCN exposure in 10 animals provoked a primary cardiac depression, which led to a rapid cardiac arrest by pulseless electrical activity (PEA) despite the maintenance of PaO2 by mechanical ventilation. These effects were totally unrelated to the potassium contained in KCN. It is concluded that circulatory failure can develop as a direct consequence of CN-induced apnea but in a narrow range of exposure. In this "low" range, maintaining pulmonary gas exchange after exposure, through mechanical ventilation (or spontaneous gasping), can reverse cardiac depression and restore spontaneous breathing. At higher level of intoxication, cardiac depression is to be treated as a specific and spontaneously irreversible consequence of CN exposure, leading to a PEA.

Emergency Medicine Myths: Epinephrine in Cardiac Arrest

BACKGROUND

Sudden cardiac arrest accounts for approximately 15% of deaths in developed nations, with poor survival rate. The American Heart Association states that epinephrine is reasonable for patients with cardiac arrest, though the literature behind its use is not strong.

OBJECTIVE

To review the evidence behind epinephrine for cardiac arrest.

DISCUSSION

Sudden cardiac arrest causes over 450,000 deaths annually in the United States. The American Heart Association recommends epinephrine may be reasonable in patients with cardiac arrest, as part of Advanced Cardiac Life Support. This recommendation is partly based on studies conducted on dogs in the 1960s. High-dose epinephrine is harmful and is not recommended. Epinephrine may improve return of spontaneous circulation, but does not improve survival to discharge or neurologic outcome. Literature suggests that three phases of resuscitation are present: electrical, circulatory, and metabolic. Epinephrine may improve outcomes in the circulatory phase prior to 10 min post arrest, though further study is needed. Basic Life Support measures including adequate chest compressions and early defibrillation provide the greatest benefit.

CONCLUSIONS

Epinephrine may improve return of spontaneous circulation, but it does not improve survival to discharge or neurologic outcome. Timing of epinephrine may affect patient outcome, but Basic Life Support measures are the most important aspect of resuscitation and patient survival.

The Outcome and Predictors of Mortality in Patients Therapeutically Cooled Postcardiac Arrest

PURPOSE

To review the outcomes of patients postcardiac arrest admitted to a metropolitan intensive care unit (ICU) where therapeutic hypothermia is practiced.

MATERIALS AND METHODS

Patients admitted from 2004 to 2012 were reviewed. The management protocol included cooling to 33°C for 24 hours. The primary outcome assessed was hospital mortality. Secondary outcome measures included mortality in patients admitted to ICU after in-hospital cardiac arrest (IHCA) when compared to those with out-of-hospital cardiac arrest (OHCA) and to review initial cardiac rhythm as an indicator of mortality.

RESULTS

A total of 330 patients were included. The overall hospital mortality was 58.1%. Hospital mortality was significantly higher in patients who had OHCA when compared to IHCA (62.5% vs 51%; P = .04). Patients who had asystole and pulseless electrical activity (PEA) had a higher mortality when compared to ventricular tachycardia/ventricular fibrillation (VT/VF) arrest (81.7% vs 67.8% vs 41.9%, respectively; P < .01).

CONCLUSION

Patients admitted to ICU postcardiac arrest after therapeutic cooling have a high mortality. An initial rhythm of VT/VF confers a mortality benefit when compared to asystole and PEA.

Developing effective countermeasures against acute hydrogen sulfide intoxication: challenges and limitations

Hydrogen sulfide (H2 S) is a chemical hazard in the gas and farming industry. As it is easy to manufacture from common chemicals, it has also become a method of suicide. H2 S exerts its toxicity through its high affinity with metalloproteins, such as cytochrome c oxidase and possibly via its interactions with cysteine residues of various proteins. The latter was recently proposed to acutely alter ion channels with critical implications for cardiac and brain functions. Indeed, during severe H2 S intoxication, a coma, associated with a reduction in cardiac contractility, develops within minutes or even seconds leading to death by complete electromechanical dissociation of the heart. In addition, long-term neurological deficits can develop owing to the direct toxicity of H2 S on neurons combined with the consequences of a prolonged apnea and circulatory failure. Here, we review the challenges impeding efforts to offer an effective treatment against H2 S intoxication using agents that trap free H2 S, and present novel pharmacological approaches aimed at correcting some of the most harmful consequences of H2 S intoxication.

Cardiac arrest: the changing incidence of ventricular fibrillation

OPINION STATEMENT

There are more than 300,000 out-of-hospital cardiac arrests (OHCA) in the USA annually, which can be grouped into those presenting with tachyarrhythmic (shockable) rhythms and those presenting with non-tachyarrhythmic rhythms. The incidence of tachyarrhythmic rhythms, which include ventricular fibrillation (VF) and pulseless ventricular tachycardia (VT), has been noted to be progressively decreasing in multiple studies of OHCA. Improved medical and surgical therapies for ischemic heart disease, and the widespread use of implantable cardiac defibrillators (ICDs), have likely contributed to a declining incidence of VF arrest and may result in conversion of an otherwise VF event into a pulseless electrical activity (PEA) arrest. As the incidence of VF has declined, it is unclear if the absolute incidence of non-tachyarrhythmic rhythms has increased or remained largely unchanged. This article discusses the changing rates of presenting rhythms in sudden cardiac arrest, the underlying cellular mechanisms of PEA, the factors contributing to the relative increase in the rate of PEA arrests, and current treatment options.

Pyruvate stabilizes electrocardiographic and hemodynamic function in pigs recovering from cardiac arrest

Cardiac electromechanical dysfunction may compromise recovery of patients who are initially resuscitated from cardiac arrest, and effective treatments remain elusive. Pyruvate, a natural intermediary metabolite, energy substrate, and antioxidant, has been found to protect the heart from ischemia-reperfusion injury. This study tested the hypothesis that pyruvate-enriched resuscitation restores hemodynamic, metabolic, and electrolyte homeostasis following cardiac arrest. Forty-two Yorkshire swine underwent pacing-induced ventricular fibrillation and, after 6 min pre-intervention arrest, 4 min precordial compressions followed by transthoracic countershocks. After defibrillation and recovery of spontaneous circulation, the pigs were monitored for another 4 h. Sodium pyruvate or NaCl were infused i.v. (0.1 mmol·kg(-1)·min(-1)) throughout precordial compressions and the first 60 min recovery. In 8 of the 24 NaCl-infused swine, the first countershock converted ventricular fibrillation to pulseless electrical activity unresponsive to subsequent countershocks, but only 1 of 18 pyruvate-treated swine developed pulseless electrical activity (relative risk 0.17; 95% confidence interval 0.13-0.22). Pyruvate treatment also lowered the dosage of vasoconstrictor phenylephrine required to maintain systemic arterial pressure at 15-60 min recovery, hastened clearance of excess glucose, elevated arterial bicarbonate, and raised arterial pH; these statistically significant effects persisted up to 3 h after sodium pyruvate infusion, while infusion-induced hypernatremia subsided. These results demonstrate that pyruvate-enriched resuscitation achieves electrocardiographic and hemodynamic stability in swine during the initial recovery from cardiac arrest. Such metabolically based treatment may offer an effective strategy to support cardiac electromechanical recovery immediately after cardiac arrest.

A simplified and structured teaching tool for the evaluation and management of pulseless electrical activity

Cardiac arrest victims who present with pulseless electrical activity (PEA) usually have a grave prognosis. Several conditions, however, have cause-specific treatments which, if applied immediately, can lead to quick and sustained recovery. Current teaching focuses on recollection of numerous conditions that start with the letters H or T as potential causes of PEA. This teaching method is too complex, difficult to recall during resuscitation, and does not provide guidance to the most effective initial interventions. This review proposes a structured algorithm that is based on the differentiation of the PEA rhythm into narrow- or wide-complex subcategories, which simplifies the working differential and initial treatment approach. This, in conjunction with bedside ultrasound, can quickly point towards the most likely cause of PEA and thus guide resuscitation.

Hypoxic cardiopulmonary arrest with full recovery after induced hypothermic therapy

Case

The patient's chart was reviewed, summarized, and presented.

Outcome

A 41-year-old male collapsed after complaining of dyspnea just before the end of a hemodialysis session. He was just being introduced to hemodialysis. The patient's percutaneous oxygen saturation dropped to 50% even under inhalation of 10 L/minute of oxygen and he developed pulseless electrical activity. After tracheal intubation, a return of spontaneous circulation was noted. His truncal CT disclosed a bilateral diffuse ground glass appearance and pleural effusion were noted. Induced mild hypothermic therapy and mechanical ventilation resulted in the improvement of his respiratory function and consciousness. A coronary angiogram and left ventriculography showed no significant lesion, and his pulmonary edema was considered to have been induced by over-hydration due to renal failure, diastolic heart failure or dialysis disequilibrium syndrome. He was discharged without any neurological deficit.

Conclusion

Tracheal intubation with ventilation for hypoxic cardiopulmonary arrest and induced hypothermic therapy after obtaining spontaneous circulation may be factors of favorable outcome of this case.

Outcomes after cardiac arrest in an adult burn center

OBJECTIVE

Adult burn patients who experience in-hospital cardiac arrest (CA) and undergo cardiopulmonary resuscitation (CPR) represent a unique patient population. We believe that they tend to be younger and have the added burden of the burn injury compared to other populations. Our objective was to determine the incidence, causes and outcomes following cardiac arrest (CA) and cardio-pulmonary resuscitation (CPR) within this population.

METHODS

We conducted a retrospective review at the US Army Institute of Surgical Research (ISR) burn intensive care unit (BICU). Charts from 1st January 2000 through 31st August 2009 were reviewed for study. Data were collected all on adult burn patients who experienced in-hospital CA and CPR either in the BICU or associated burn operating room. Patients undergoing CPR elsewhere in our burn unit were excluded because we could not validate the time of CA since they are not routinely monitored with real-time rhythm strips. The study population included civilian burn patients from the local catchment area and burn casualties from the conflicts in Iraq and Afghanistan, but patients with do-not-resuscitate (DNR) orders were excluded.

RESULTS

We found 57 burn patients who had in-hospital CA and CPR yielding an incidence of one or more in-hospital CA of 34 per 1000 admissions (0.34%). Fourteen of these patients (25%) survived to discharge while 43 (75%) died. The most common initial cardiac rhythm was pulseless electrical activity (50.9%). The most common etiology of CA among burn patients was respiratory failure (49.1%). The most significant variable affecting survival to discharge was duration of CPR (P < 0.01) with no patient surviving more than 7 min of CPR.

CONCLUSIONS

CPR in burn patients is sometimes effective, and those patients who survive are likely to have good neurological outcomes. However, prolonged CPR times are unlikely to result in return of spontaneous circulation and may be considered futile. Further, those who experience multiple CA are unlikely to survive to discharge.

Pulseless electrical activity during electroconvulsive therapy: a case report

BACKGROUND

Arrhythmias resulting in cardiac arrest during electroconvulsive therapy have been reported. Most reported cases of cardiac arrest had asystole as the initial rhythm. Pulseless electrical activity as an initial rhythm of cardiac arrest during electroconvulsive therapy has never been reported. Also, thromboembolism after inflation of pneumatic tourniquet during lower limb surgery has been reported but never following tourniquet inflation during an electroconvulsive therapy.

CASE PRESENTATION

We report a case involving an 81- year- old female who presented to us for an electroconvulsive therapy for severe depression and developed pulseless electrical activity immediately after electroconvulsive therapy. She was successfully resuscitated and was later found to have bilateral pulmonary emboli with a complete occlusion of the right lower lobe pulmonary artery. The source of embolus was from her left lower extremity deep venous thrombus, which we believe, got dislodged intraoperatively after inflation of pneumatic tourniquet. Our patient not only survived the massive pulmonary embolus, but also showed significant improvement in her mental status compared to her pre-admission level at the time of discharge to a sub-acute rehabilitation centre.

CONCLUSION

We recommend that patients who are elderly and at high risk of thromboembolism should selectively undergo a preoperative doppler ultrasound for deep venous thrombosis. Also, selective application of tourniquet in the upper limb, to monitor for seizure activity, would reduce the incidence of pulmonary thrombo-embolism as embolic events are significantly less from deep venous thromboses of upper extremities when compared to lower extremities.