This prospective study aimed to identify clinical and laboratory predictors of return of spontaneous circulation (ROSC), 28-day survival, and favorable neurological outcomes in adult patients experiencing out-of-hospital cardiac arrest (OHCA) and brought to the emergency department (ED) by emergency medical services (EMS). Specifically, the prognostic value of hematologic, biochemical, and blood gas parameters on admission was assessed for ROSC, 28-day survival, and favorable neurological recovery. Additionally, the study investigated the influence of key patient-centered and prehospital variables, including demographic features, initial cardiac rhythm, and the timeliness and type of cardiopulmonary resuscitation (CPR), defibrillation, and airway interventions, on overall survival and neurological status.
This prospective, observational, and cross-sectional study was conducted in the ED of a tertiary urban hospital between May 2023 and May 2024. Adult patients (aged ≥18 years) who experienced OHCA and received attempted resuscitation by EMS personnel were screened for eligibility. All patients received advanced cardiac life support (ACLS) in accordance with the 2021 European Resuscitation Council (ERC) and 2020 American Heart Association (AHA) guidelines. Patients were initially categorized into survivors and non-survivors based on ROSC and 28-day survival status. Furthermore, 28-day survivors were stratified into two subgroups based on their neurological status using the Cerebral Performance Category (CPC) score. Favorable neurological outcome was defined as CPC 1-2 (good to moderate cerebral performance with independence), while CPC 3-5 (severe disability, coma, or death) constituted unfavorable outcome. Prior to the initiation of the study, a standardized and pre-piloted data collection form was developed based on current literature to ensure consistency and reproducibility. During the study period, patient data were initially recorded by board-certified emergency medicine specialists who were on duty in the ED at the time of each patient's arrival. These attending physicians were directly responsible for patient management and completed the data forms either during the resuscitation process or immediately thereafter. All physicians involved in data entry were blinded to the study hypothesis. Subsequently, all collected data were extracted, cross-checked, and verified for accuracy and completeness by an emergency medicine specialist with eight years of clinical experience, who was also blinded to the study hypothesis. Patient data were obtained from multiple sources, including hospital's automated systems and ED's archives, prehospital EMS reports, and the national digital healthcare database of Türkiye (e-Nabız), which was used to verify survival status and neurological outcomes at 28 days. Collected data includes, demographics (age, sex), comorbidities (hypertension, diabetes mellitus, coronary artery disease, chronic kidney disease, or malignancy), and prehospital variables such as whether the cardiac arrest was witnessed, whether bystander CPR was performed, the time from collapse to the initiation of CPR, the time from collapse to EMS arrival, the durations of no-flow (time without CPR) and low-flow (time with CPR but no ROSC), and the initial cardiac rhythm, categorized as ventricular fibrillation or pulseless ventricular tachycardia (VF/pVT), asystole, or pulseless electrical activity (PEA). The airway management method used by EMS was also recorded, including BVM, SGD, or ETI. Other recorded interventions included prehospital defibrillation, epinephrine administration (including total dose), and the use of mechanical chest compression devices. Whether ROSC was achieved in the field prior to ED arrival was also documented. On arrival to the ED, clinical examination findings included the patient's body temperature, the Glasgow Coma Score (if measurable), the presence or absence of pupillary light reflex, and the requirement for vasopressor support within the first hour. Laboratory data obtained upon admission included hematological parameters such as white blood cell count (WBC), hemoglobin level, platelet count, mean platelet volume (MPV), neutrophil count, monocyte count, and eosinophil count. Biochemical measurements included creatinine, urea, lactate dehydrogenase (LDH), aspartate aminotransferase (AST), alanine aminotransferase (ALT), sodium, potassium, chloride, calcium, and troponin-I levels. Arterial blood gas analysis results included pH, partial pressure of carbon dioxide (pCO₂), bicarbonate, lactate concentration, carboxyhemoglobin percentage, and methemoglobin percentage. Clinical outcomes, including ROSC, 28-day survival or mortality, and neurological status, were also recorded. Patients' demographics, initial rhythm, prehospital intubation status, and hematological, biochemical, and blood gas parameters on admission were compared to identify factors associated with 28-day survival and neurological status between the groups. Independent predictors of survival were determined via multivariate logistic regression analysis of variables that significantly differed between survivors and non-survivors.
Study Type
OBSERVATIONAL
Enrollment
327
The demographic profile of each patient was documented, including age and sex, to examine potential associations with survival and neurological outcomes.
Data on pre-existing chronic conditions were recorded, such as hypertension, diabetes mellitus, coronary artery disease, chronic kidney disease, and malignancy, in order to assess their potential impact on prognosis following OHCA.
Several prehospital factors were evaluated, including whether the cardiac arrest was witnessed, whether bystander CPR was performed, the time from collapse to the initiation of CPR, and the time from collapse to EMS arrival. Additionally, the durations of no-flow (i.e., time without any CPR) and low-flow (i.e., time with CPR but without ROSC) were noted. The initial cardiac rhythm was categorized as ventricular fibrillation or pulseless ventricular tachycardia (VF/pVT), asystole, or pulseless electrical activity (PEA). Airway management methods used in the field were documented and classified as bag-valve-mask (BVM), supraglottic airway devices (SGAs), or endotracheal intubation (ETI). Other recorded interventions included prehospital defibrillation, administration of epinephrine (including total dosage), and use of mechanical chest compression devices. Whether ROSC was achieved prior to arrival at the emergency department was also noted.
These included white blood cell count (WBC), hemoglobin level, platelet count, mean platelet volume (MPV), and differential counts such as neutrophils, monocytes, and eosinophils.
Measurements included creatinine, urea, lactate dehydrogenase (LDH), aspartate aminotransferase (AST), alanine aminotransferase (ALT), sodium, potassium, chloride, calcium, and troponin-I levels.
The primary clinical outcomes recorded for each patient included return of spontaneous circulation (ROSC), 28-day survival or mortality, and neurological status, which was later assessed using the Cerebral Performance Category (CPC) scale.
Haseki Training and Research Hospital
Istanbul, Sultangazi, Turkey (Türkiye)
Number of Participants with Return of Spontaneous Circulation (ROSC)
ROSC was defined as the return of sustained spontaneous perfusing rhythm lasting at least 20 minutes without the need for external chest compressions.
Time frame: Assessed within the first 20 minutes after emergency department admission.
Number of Participants Alive at Day 28
Survival was assessed as the patient being alive at 28 days following the cardiac arrest event.
Time frame: Assessed within the first 20 minutes after emergency department admission.
Number of Participants with Favorable Neurological Outcome (CPC 1-2) at Day 28
Neurological outcome was determined using the Cerebral Performance Category (CPC) scale, with a CPC score of 1 or 2 representing a favorable neurological outcome, and scores from 3 to 5 considered unfavorable, reflecting severe neurological disability, coma, or death.
Time frame: Assessed within the first 20 minutes after emergency department admission.
Comparison of 28-Day Survival Rates Between Participants Who Underwent Prehospital Endotracheal Intubation and Those Who Did Not
The investigators evaluate the impact of prehospital endotracheal intubation (ETI) on 28-day survival status. Survival was defined as being alive 28 days after the cardiac arrest event. Participants will be categorized into two groups based on whether or not they received ETI in the prehospital setting.
Time frame: Assessed within the first 20 minutes after emergency department admission.
Comparison of Favorable Neurological Outcome Rates at Day 28 Between Participants Who Underwent Prehospital Endotracheal Intubation and Those Who Did Not
The investigators evaluate the impact of prehospital endotracheal intubation (ETI) on neurological outcomes at Day 28 following cardiac arrest. Neurological status will be assessed using the Cerebral Performance Category (CPC) scale. A CPC score of 1 or 2 will be considered a favorable neurological outcome. Participants will be categorized into two groups based on whether or not they received ETI in the prehospital setting.
Time frame: Assessed within the first 20 minutes after emergency department admission.
Correlation Between Admission Serum Lactate Level and 28-Day Survival
The investigators evaluate the correlation between serum lactate level at emergency department admission and 28-day survival status following out-of-hospital cardiac arrest. Lactate will be measured in mmol/L using a standard arterial blood gas analyzer.
Time frame: Assessed within the first 20 minutes after emergency department admission.
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