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Pulmonary embolism (PE) is a life-threatening condition resulting from the obstruction of pulmonary arteries by blood clots, usually originating from deep veins. Symptoms of PE might vary from nothing to sudden death. Clinically, individuals may present very differently. When a diagnosis of PE is suspected, any possible life-saving intervention must be implemented because survival from cardiac arrest following PE is often quite low. Although there are not many randomized controlled trials that provide guidelines for treating suspected PE in cardiac arrest victims, the few published case reports and other minor studies suggest that thrombolysis and other therapies are associated with good outcomes. We report a patient with PE who presented in cardiac arrest with its clinical, electrographic, and radiologic findings, along with the appropriate therapy chosen based on hemodynamic stability. It is important to intervene early to prevent severe complications and improve the patient's outcomes.
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STUDY OBJECTIVE: Evaluate the association between early naloxone use and outcomes after out-of-hospital cardiac arrest (OHCA) with initial non-shockable rhythms. METHODS: This study was a secondary analysis of data collected in the Portland Cardiac Arrest Epidemiologic Registry, a database containing details of emergency medical services (EMS)-treated OHCA cases in the Portland, Oregon metropolitan region. Eligible patients had non-traumatic OHCA with an initial non-shockable rhythm and received naloxone by EMS or law enforcement prior to IV/IO access (exposure group). The primary outcome was ROSC at emergency department (ED) arrival. Secondary outcomes included survival to admission, survival to hospital discharge, and cerebral performance category score ≤2 at discharge (good neurologic outcome). We performed multivariable logistic regressions adjusting for age, sex, arrest location, witness status, bystander interventions, dispatch to EMS arrival time, initial rhythm, and county of arrest. RESULTS: There were 1807 OHCA cases from 2018 to 2021 meeting eligibility criteria, with 57 receiving naloxone before vascular access. Patients receiving naloxone prior to vascular access attempts had higher adjusted odds (aOR [95% CI]) of ROSC at any time (2.14 [1.20-3.81]), ROSC at ED arrival (2.14 [1.18-3.88]), survival to admission (2.86 [1.60-5.09]), survival to discharge (4.41 [1.78-10.97]), and good neurologic outcome (4.61 [1.74-12.19]). CONCLUSIONS: Patients with initial non-shockable OHCA who received law enforcement or EMS naloxone prior to IV/IO access attempts had higher adjusted odds of ROSC at any time, ROSC at ED arrival, survival to admission, survival to discharge, and good neurologic outcome.
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Servicios Médicos de Urgencia , Naloxona , Antagonistas de Narcóticos , Paro Cardíaco Extrahospitalario , Sistema de Registros , Humanos , Paro Cardíaco Extrahospitalario/mortalidad , Paro Cardíaco Extrahospitalario/terapia , Naloxona/uso terapéutico , Masculino , Femenino , Persona de Mediana Edad , Anciano , Antagonistas de Narcóticos/uso terapéutico , Servicios Médicos de Urgencia/estadística & datos numéricos , Servicios Médicos de Urgencia/métodos , Reanimación Cardiopulmonar/métodos , Reanimación Cardiopulmonar/estadística & datos numéricos , Oregon/epidemiología , Tiempo de Tratamiento/estadística & datos numéricosRESUMEN
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.
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Background: During pulseless electrical activity (PEA) the cardiac mechanical and electrical functions are dissociated, a phenomenon occurring in 25-42% of in-hospital cardiac arrest (IHCA) cases. Accurate evaluation of the likelihood of a PEA patient transitioning to return of spontaneous circulation (ROSC) may be vital for the successful resuscitation. The aim: We sought to develop a model to automatically discriminate between PEA rhythms with favorable and unfavorable evolution to ROSC. Methods: A dataset of 190 patients, 120 with ROSC, were acquired with defibrillators from different vendors in three hospitals. The ECG and the transthoracic impedance (TTI) signal were processed to compute 16 waveform features. Logistic regression models where designed integrating both automated features and characteristics annotated in the QRS to identify PEAs with better prognosis leading to ROSC. Cross validation techniques were applied, both patient-specific and stratified, to evaluate the performance of the algorithm. Results: The best model consisted in a three feature algorithm that exhibited median (interquartile range) Area Under the Curve/Balanced accuracy/Sensitivity/Specificity of 80.3(9.9)/75.6(8.0)/ 77.4(15.2)/72.3(16.4) %, respectively. Conclusions: Information hidden in the waveforms of the ECG and TTI signals, along with QRS complex features, can predict the progression of PEA. Automated methods as the one proposed in this study, could contribute to assist in the targeted treatment of PEA in IHCA.
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Point-of-care ultrasound (POCUS) holds immense potential to manage critically deteriorating infants within the neonatal intensive care unit (NICU) and is increasingly used in neonatal clinical practice worldwide. Recent ultrasound-based protocols such as the Sonographic Assessment of liFe-threatening Emergencies-Revised (SAFE-R) and Crashing Neonate Protocol (CNP) offer step-by-step guidance for diagnosing and addressing reversible causes of cardiorespiratory collapse. Traditionally, pulseless electrical activity (PEA) has been diagnosed solely based on absent pulses on clinical examination, disregarding myocardial activity. However, integrating POCUS into resuscitation unveils the concept of pseudo-PEA, where cardiac motion activity is observed visually on the ultrasound but fails to generate a detectable pulse due to inadequate cardiac output. Paradoxically, existing neonatal resuscitation protocols lack directives for identifying and effectively leveraging pseudo-PEA insights in infants, limiting their potential to enhance outcomes. Pseudo-PEA is extensively described in adult literature owing to routine POCUS use in resuscitation. This review article comprehensively evaluates the adult pseudo-PEA literature to glean insights adaptable to neonatal care. Additionally, we propose a simple strategy to integrate POCUS during neonatal resuscitation, especially in infants who do not respond to routine measures. CONCLUSION: Pseudo-PDA is a newly recognized diagnosis in infants with the use of POCUS during resuscitation. This article highlights the importance of cross-disciplinary learning in tackling emerging challenges within neonatal medicine. WHAT IS KNOWN: ⢠Point-of-Care ultrasound (POCUS) benefits adult cardiac arrest management, particularly in distinguishing true Pulseless Electrical Activity (PEA) from pseudo-PEA. ⢠Pseudo-PEA is when myocardial motion can be seen on ultrasound but fails to generate palpable pulses or sustain circulation despite evident cardiac electrical activity. WHAT IS NEW: ⢠Discuss recognition and management of pseudo-PEA in infants. ⢠A proposed algorithm to integrate POCUS into active neonatal cardiopulmonary resuscitation (CPR) procedures.
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Reanimación Cardiopulmonar , Paro Cardíaco , Lactante , Adulto , Recién Nacido , Humanos , Pisum sativum , Paro Cardíaco/diagnóstico por imagen , Paro Cardíaco/terapia , Ultrasonografía , Reanimación Cardiopulmonar/métodos , Pruebas en el Punto de AtenciónRESUMEN
Background: Alcohol septal ablation (ASA) can be recommended for patients with drug-refractory hypertrophic obstructive cardiomyopathy (HOCM). Recently, percutaneous intramyocardial septal radiofrequency ablation (PIMSRA) was reported as a safe and effective treatment for HOCM. Case summary: We present a case report of pulseless electrical activity (PEA), cardiac arrest, and pericardial tamponade occurring post-PIMSRA. We performed PIMSRA for the patient with HOCM after failed ASA. Two hours post-PIMSRA, transthoracic echocardiography (TTE) revealed that the hypokinetic basal intraventricular septal (IVS) thickness increased with aggravation of systolic anterior motion of the mitral valve. After the occurrence of subsequent PEA cardiac arrest, veno-arterial extracorporeal membrane oxygenation (VA-ECMO) support was provided. With sinus rhythm restoration and blood pressure stabilization after ECMO removal, the patient had pericardial tamponade on Day 3 post-PIMSRA. After excluding apparent myocardial perforation and draining haemorrhagic effusion under TTE guidance, her symptoms and haemodynamic status improved. She was asymptomatic at her one-year follow-up. The left ventricular outflow tract gradient (LVOTG) at rest and the thickness of the basal IVS reduced to 5â mmHg and 12â mm, respectively. Discussion: We assumed that the main causes of PEA cardiac arrest and pericardial tamponade in our case were ablation-related tissue oedema at the basal IVS and blood leakage possibly related to puncture haemorrhage, respectively. While waiting for myocardial oedema to resolve, ECMO was applied as a bridge-to-recovery therapeutic approach. Pericardiocentesis is a strategy for the emergency drainage of pericardial effusion. It is essential to distinguish life-threatening complications with TTE for management planning post-PIMSRA.
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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.
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Reanimación Cardiopulmonar , Enfermedades de los Gatos , Enfermedades de los Perros , Servicios Médicos de Urgencia , Paro Cardíaco , Humanos , Gatos , Perros , Animales , Reanimación Cardiopulmonar/veterinaria , Estudios Retrospectivos , Prevalencia , Enfermedades de los Gatos/epidemiología , Enfermedades de los Gatos/terapia , Enfermedades de los Perros/epidemiología , Enfermedades de los Perros/terapia , Epinefrina , Lidocaína , Paro Cardíaco/epidemiología , Paro Cardíaco/terapia , Paro Cardíaco/veterinaria , Sistema de RegistrosRESUMEN
A patient with trauma presents a unique and/or complex challenge to the ethical foundation that guides nursing care. Patients with trauma, by the very nature of the suddenness of their injury, are unable to predetermine or express their wishes in the event of a catastrophic injury. The providers who care for patients with trauma do not have an established patient relationship to aid them in decision-making based on what they think the patient would wish or based on past conversations. Yet, they provide expert care and use ethical principles to direct their professional responsibility to these patients.
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Comunicación , Ética Médica , Heridas y Lesiones , Humanos , Heridas y Lesiones/terapia , Toma de Decisiones ClínicasRESUMEN
OBJECTIVE: The proportion of sudden cardiac arrests (SCA) manifesting with pulseless electrical activity (PEA) has increased significantly, and the survival rate remains lower than ventricular fibrillation (VF). However, a subgroup of PEA-SCA cases does survive and may yield key predictors of improved outcomes when compared to non-survivors. We aimed to identify key predictors of survival from PEA-SCA. METHODS: Our study sample is drawn from two ongoing community-based, prospective studies of out-of-hospital SCA: Oregon SUDS from the Portland, OR metro area (Pop. approx. 1 million; 2002-2017) and Ventura PRESTO from Ventura County, CA (Pop. approx. 850,000, 2015-2021). For the present sub-study, we included SCA cases with PEA as the presenting rhythm where emergency medical services (EMS) personnel attempted resuscitation. RESULTS: We identified 1,704 PEA-SCA cases, of which 173 (10.2%) were survivors and 1,531 (89.8%) non-survivors. Patients whose PEA-SCA occurred in a healthcare unit (16.9%) or public location (18.1%) had higher survival than those whose PEA-SCA occurred at home (9.3%) or in a care facility (5.7%). Young age, witness status, PEA-SCA location and pre-existing COPD/asthma were independent predictors of survival. Among witnessed cases the survival rate was 10% even if EMS response time was >10 minutes. CONCLUSIONS: Key determinants for survival from PEA-SCA were young age, witnessed status, public location and pre-existing COPD/asthma. Survival outcomes in witnessed PEA cases were better than expected, even with delayed EMS response.
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Asma , Reanimación Cardiopulmonar , Servicios Médicos de Urgencia , Paro Cardíaco Extrahospitalario , Enfermedad Pulmonar Obstructiva Crónica , Humanos , Estudios Prospectivos , Muerte Súbita Cardíaca/epidemiología , Muerte Súbita Cardíaca/etiología , Muerte Súbita Cardíaca/prevención & control , Paro Cardíaco Extrahospitalario/etiología , Paro Cardíaco Extrahospitalario/terapia , Tasa de SupervivenciaRESUMEN
A 38-year-old with Turner syndrome presented with acute myocardial infarction due to multivessel spontaneous coronary artery dissection (SCAD) complicated by left ventricular free wall rupture. Conservative management for SCAD was pursued. She underwent sutureless repair for an oozing-type left ventricular free wall rupture. SCAD has not been previously reported in Turner syndrome. (Level of Difficulty: Advanced.).
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Asfixia Neonatal , Reanimación Cardiopulmonar , Paro Cardíaco , Lactante , Humanos , Recién Nacido , Paro Cardíaco/terapia , ResucitaciónRESUMEN
INTRODUCTION: Pulseless electrical activity (PEA) is commonly observed in in-hospital cardiac arrest (IHCA). Universally available ECG characteristics such as QRS duration (QRSd) and heart rate (HR) may develop differently in patients who obtain ROSC or not. The aim of this study was to assess prospectively how QRSd and HR as biomarkers predict the immediate outcome of patients with PEA. METHOD: We investigated 327 episodes of IHCA in 298 patients at two US and one Norwegian hospital. We assessed the ECG in 559 segments of PEA nested within episodes, measuring QRSd and HR during pauses of compressions, and noted the clinical state that immediately followed PEA. We investigated the development of HR, QRSd, and transitions to ROSC or no-ROSC (VF/VT, asystole or death) in a joint longitudinal and competing risks statistical model. RESULTS: Higher HR, and a rising HR, reflect a higher transition intensity ("hazard") to ROSC (p < 0.001), but HR was not associated with the transition intensity to no-ROSC. A lower QRSd and a shrinking QRSd reflect an increased transition intensity to ROSC (p = 0.023) and a reduced transition intensity to no-ROSC (p = 0.002). CONCLUSION: HR and QRSd convey information of the immediateoutcome during resuscitation from PEA. These universally available and promising biomarkers may guide the emergency team in tailoring individual treatment.
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Reanimación Cardiopulmonar , Paro Cardíaco , Humanos , Frecuencia Cardíaca , Paro Cardíaco/terapia , Hospitales , BiomarcadoresRESUMEN
A diaphragmatic hernia is a protrusion of the abdominal contents into the negative pressure thoracic cavity through a congenital or acquired diaphragmatic defect. Generally, acquired diaphragmatic hernia is a rare, life-threatening condition that usually follows blunt/penetrating trauma or an iatrogenic cause, resulting in the diaphragmatic rupture, accompanied by the herniation of abdominal visceral organs. We report a 47-year-old male construction worker who sustained a fall from a height of about 30 feet height. He presented with hypoxia initially and, after a primary survey, was found to have a traumatic rupture of the diaphragm with herniation of the stomach and abdominal contents, causing signs of obstructive shock. After adequate resuscitation in the Emergency Department, he was rushed to operating room. There, he suffered two very short pulseless electrical activity cardiac arrests. Therefore, an emergency anterolateral thoracotomy was done, and it was extended into laparotomy to reduce the abdominal contents through the diaphragmatic tear of 12 cm, which restored the spontaneous circulation. He recovered eventually, despite chest infections and pulmonary atelectasis, and was discharged on the 28th day and remained in good condition during the outpatient visit. Tension gastrothorax or viscerothorax is rare, but an under-recognized cause of cardiac arrest in the trauma setting necessitates a vigilant evaluation and early suspicion to prevent a catastrophic outcome. This case report emphasizes the inclusion of tension viscero or abdominal thorax as one of the recognizable causes of a pulseless electrical activity cardiac arrest.
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We describe a case of severe biventricular failure and cardiovascular collapse following exposure to the manure gas hydrogen sulfide. Initial tests indicated uncoupling of cellular bioenergetics in addition to myocardial damage. Cardiopulmonary support with venoarterial extracorporeal membrane oxygenation was initiated, and the patient could be successfully weaned from support after 28 days. (Level of Difficulty: Advanced.).
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Aims: The Prehospital Optimal Shock Energy for Defibrillation (POSED) study will assess the feasibility of conducting a cluster randomised controlled study of clinical effectiveness in UK ambulance services to identify the optimal shock energy for defibrillation. Methods: POSED is a pragmatic, allocation concealed, open label, cluster randomised, controlled feasibility study. Defibrillators within a single UK ambulance service will be randomised in an equal ratio to deliver one of three shock strategies 120-150-200 J, 150-200-200 J, 200-200-200 J. Consecutive adults (≥18 years) presenting with out of hospital cardiac arrest requiring defibrillation will be eligible. The study plans to enrol 90 patients (30 in each group). Patients (or their relatives for non-survivors) will be informed about trial participation after the initial emergency has resolved. Survivors will be invited to consent to participate in follow-up (i.e., at 30 days or discharge).The primary feasibility outcome is the proportion of eligible patients who receive the randomised study intervention. Secondary feasibility outcomes will include recruitment rate, adherence to allocated treatment and data completeness. Clinical outcomes will include Return of an Organised Rhythm (ROOR) at 2 minutes post-shock, refibrillation rate, Return of Spontaneous Circulation (ROSC) at hospital handover, survival and neurological outcome at 30 days. Conclusion: The POSED study will assess the feasibility of a large-scale trial and explore opportunities to optimise the trial protocol.Trial registration: ISRCTN16327029.
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Carotid sinus syncope is a temporary, exaggerated circulatory response to carotid massage, characterized by marked drop in arterial pressure, and varying degree of bradycardia, or even asystole lasting for several seconds, resulting in short lasting loss of consciousness. A related reflex mediated disorder is a fainting precipitated by a parapharyngeal space-occupying lesion, manifests in prolonged episodes of hemodynamic instability. We report a case, where the hemodynamic features of the syncope are well documented. The case illustrates the potential overlap between pulseless electrical activity and syncope, and a simple noninvasive solution for the frightening symptoms is also suggested.
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Seno Carotídeo , Paro Cardíaco , Humanos , Síncope/etiología , Síncope/diagnóstico , MasajeRESUMEN
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.
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Paro Cardíaco , Insuficiencia Cardíaca , Infarto del Miocardio , Humanos , Masculino , Persona de Mediana Edad , Anciano , Anciano de 80 o más Años , Adulto , Femenino , Muerte Súbita Cardíaca/epidemiología , Muerte Súbita Cardíaca/etiología , Paro Cardíaco/etiología , Paro Cardíaco/complicaciones , Pronóstico , Sobrevivientes , Infarto del Miocardio/complicaciones , Insuficiencia Cardíaca/complicacionesRESUMEN
INTRODUCTION: Respiratory failure is a common cause of pulseless electrical activity (PEA) and asystolic cardiac arrest, but the changes in heart rate (HR) pre-arrest are not well described. We describe HR dynamics prior to in-hospital cardiac arrest (IHCA) among PEA/asystole arrest patients with respiratory etiology. METHODS: In this retrospective study, we evaluated 139 patients with 3-24 hours of continuous electrocardiogram data recorded preceding PEA/asystole IHCA from 2010-2017. We identified respiratory failure cases by chart review and evaluated electrocardiogram data to identify patterns of HR changes, sinus bradycardia or sinus arrest, escape rhythms, and development right ventricular strain prior to IHCA. RESULTS: A higher proportion of respiratory cases (58/73, 79 %) fit a model of HR response characterized by tachycardia followed by rapid HR decrease prior to arrest, compared to non-respiratory cases (30/66, 45 %, p < 0.001). Among the 58 respiratory cases fitting this model, 36 (62 %) had abrupt increase in HR occurring 64 (IQR 23-191) minutes prior to arrest, while 22 (38 %) had stable tachycardia until time of HR decrease. Mean peak HR was 123 ± 21 bpm. HR decrease occurred 3.0 (IQR 2.0-7.0) minutes prior to arrest. Sinus arrest occurred during the bradycardic phase in 42/58 of cases; escape rhythms were present in all but 2/42 (5 %) cases. Right ventricular strain ECG pattern, when present, occurred at a median of 2.2 (IQR -0.05-17) minutes prior to onset of HR decrease. CONCLUSION: IHCAs of respiratory etiology follow a model of HR increase from physiologic compensation to hypoxia, followed by rapid HR decrease prior to arrest.