The design of the PRINCESS 2 trial: A randomized trial to study the impact of ultrafast hypothermia on complete neurologic recovery after out-of-hospital cardiac arrest with initial shockable rhythm.

BACKGROUND: Delayed hypothermia, initiated after hospital arrival, several hours after cardiac arrest with 8-10 hours to reach the target temperature, is likely to have limited impact on overall survival. However, the effect of ultrafast hypothermia, i.e., delivered intra-arrest or immediately after return of spontaneous circulation (ROSC), on functional neurologic outcome after out-of-hospital cardiac arrest (OHCA) is unclear. In two prior trials, prehospital trans-nasal evaporative intra-arrest cooling was safe, feasible and reduced time to target temperature compared to delayed cooling. Both studies showed trends towards improved neurologic recovery in patients with shockable rhythms. The aim of the PRINCESS2-study is to assess whether cooling, initiated either intra-arrest or immediately after ROSC, followed by in-hospital hypothermia, significantly increases survival with complete neurologic recovery as compared to standard normothermia care, in OHCA patients with shockable rhythms. METHODS/DESIGN: In this investigator-initiated, randomized, controlled trial, the emergency medical services (EMS) will randomize patients at the scene of cardiac arrest to either trans-nasal cooling within 20 minutes from EMS arrival with subsequent hypothermia at 33°C for 24 hours after hospital admission (intervention), or to standard of care with no prehospital or in-hospital cooling (control). Fever (>37,7°C) will be avoided for the first 72 hours in both groups. All patients will receive post resuscitation care and withdrawal of life support procedures according to current guidelines. Primary outcome is survival with complete neurologic recovery at 90 days, defined as modified Rankin scale (mRS) 0-1. Key secondary outcomes include survival to hospital discharge, survival at 90 days and mRS 0-3 at 90 days. In total, 1022 patients are required to detect an absolute difference of 9% (from 45 to 54%) in survival with neurologic recovery (80% power and one-sided α=0,025, ß=0,2) and assuming 2,5% lost to follow-up. Recruitment starts in Q1 2024 and we expect maximum enrolment to be achieved during Q4 2024 at 20-25 European and US sites. DISCUSSION: This trial will assess the impact of ultrafast hypothermia applied on the scene of cardiac arrest, as compared to normothermia, on 90-day survival with complete neurologic recovery in OHCA patients with initial shockable rhythm. TRIAL REGISTRATION: NCT06025123.

Neurodevelopmental problems, general health and academic achievements in a school-based cohort of 11-year-old Swedish children.

AIM: Assessing rates of neurodevelopmental problems (NDPs) in 11-year-old children and possible association with other health complaints and school performance. METHODS: In-school study of 11-year-old children as an add-on assessment to the 4th grade regular health check-up, comprising a structured physical neurodevelopmental examination, neuropsychological assessment, behavioural ratings, maternal interview, review of medical records and academic achievements. RESULTS: Out of 348 children recruited from eight schools, 223 (64%) participated. Any physical condition was found in 102/222 (46%), most commonly atopy (18%). One in five had a BMI z-score >2 standard deviations over the reference mean. One or more NDP was found in 86/221 (40%) children. The number of failed national tests correlated positively with NDP severity rated with the clinical global impression severity instrument (Spearman's r = 0.41, p < 0.001). The majority of participants with failed national tests, also had co-occurring health complaints (≥2 of: stomach or extremity ache, headache, difficulties sleeping, internalising symptoms or obesity) and NDPs. CONCLUSION: Health complaints, physical conditions and NDPs are very common in 11-year-old children and warrant adequately staffed, thoroughly equipped school healthcare services.

Automated external defibrillators delivered by drones to patients with suspected out-of-hospital cardiac arrest.

AIMS: Early defibrillation is critical for the chance of survival in out-of-hospital cardiac arrest (OHCA). Drones, used to deliver automated external defibrillators (AEDs), may shorten time to defibrillation, but this has never been evaluated in real-life emergencies. The aim of this study was to investigate the feasibility of AED delivery by drones in real-life cases of OHCA. METHODS AND RESULTS: In this prospective clinical trial, three AED-equipped drones were placed within controlled airspace in Sweden, covering approximately 80 000 inhabitants (125 km2). Drones were integrated in the emergency medical services for automated deployment in beyond-visual-line-of-sight flights: (i) test flights from 1 June to 30 September 2020 and (ii) consecutive real-life suspected OHCAs. Primary outcome was the proportion of successful AED deliveries when drones were dispatched in cases of suspected OHCA. Among secondary outcomes was the proportion of cases where AED drones arrived prior to ambulance and time benefit vs. ambulance. Totally, 14 cases were eligible for dispatch during the study period in which AED drones took off in 12 alerts to suspected OHCA, with a median distance to location of 3.1 km [interquartile range (IQR) 2.8-3.4). AED delivery was feasible within 9 m (IQR 7.5-10.5) from the location and successful in 11 alerts (92%). AED drones arrived prior to ambulances in 64%, with a median time benefit of 01:52 min (IQR 01:35-04:54) when drone arrived first. In an additional 61 test flights, the AED delivery success rate was 90% (55/61). CONCLUSION: In this pilot study, we have shown that AEDs can be carried by drones to real-life cases of OHCA with a successful AED delivery rate of 92%. There was a time benefit as compared to emergency medical services in cases where the drone arrived first. However, further improvements are needed to increase dispatch rate and time benefits. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov Identifier: NCT04415398.

Cardiac arrest in COVID-19: characteristics and outcomes of in- and out-of-hospital cardiac arrest. A report from the Swedish Registry for Cardiopulmonary Resuscitation.

AIM: To study the characteristics and outcome among cardiac arrest cases with COVID-19 and differences between the pre-pandemic and the pandemic period in out-of-hospital cardiac arrest (OHCA) and in-hospital cardiac arrest (IHCA). METHOD AND RESULTS: We included all patients reported to the Swedish Registry for Cardiopulmonary Resuscitation from 1 January to 20 July 2020. We defined 16 March 2020 as the start of the pandemic. We assessed overall and 30-day mortality using Cox regression and logistic regression, respectively. We studied 1946 cases of OHCA and 1080 cases of IHCA during the entire period. During the pandemic, 88 (10.0%) of OHCAs and 72 (16.1%) of IHCAs had ongoing COVID-19. With regards to OHCA during the pandemic, the odds ratio for 30-day mortality in COVID-19-positive cases, compared with COVID-19-negative cases, was 3.40 [95% confidence interval (CI) 1.31-11.64]; the corresponding hazard ratio was 1.45 (95% CI 1.13-1.85). Adjusted 30-day survival was 4.7% for patients with COVID-19, 9.8% for patients without COVID-19, and 7.6% in the pre-pandemic period. With regards to IHCA during the pandemic, the odds ratio for COVID-19-positive cases, compared with COVID-19-negative cases, was 2.27 (95% CI 1.27-4.24); the corresponding hazard ratio was 1.48 (95% CI 1.09-2.01). Adjusted 30-day survival was 23.1% in COVID-19-positive cases, 39.5% in patients without COVID-19, and 36.4% in the pre-pandemic period. CONCLUSION: During the pandemic phase, COVID-19 was involved in at least 10% of all OHCAs and 16% of IHCAs, and, among COVID-19 cases, 30-day mortality was increased 3.4-fold in OHCA and 2.3-fold in IHCA.

Effect of intra-arrest trans-nasal evaporative cooling in out-of-hospital cardiac arrest: a pooled individual participant data analysis.

BACKGROUND: Randomized trials have shown that trans-nasal evaporative cooling initiated during CPR (i.e. intra-arrest) effectively lower core body temperature in out-of-hospital cardiac arrest patients. However, these trials may have been underpowered to detect significant differences in neurologic outcome, especially in patients with initial shockable rhythm. METHODS: We conducted a post hoc pooled analysis of individual data from two randomized trials including 851 patients who eventually received the allocated intervention and with available outcome ("as-treated" analysis). Primary outcome was survival with favourable neurological outcome at hospital discharge (Cerebral Performance Category [CPC] of 1-2) according to the initial rhythm (shockable vs. non-shockable). Secondary outcomes included complete neurological recovery (CPC 1) at hospital discharge. RESULTS: Among the 325 patients with initial shockable rhythms, favourable neurological outcome was observed in 54/158 (34.2%) patients in the intervention and 40/167 (24.0%) in the control group (RR 1.43 [confidence intervals, CIs 1.01-2.02]). Complete neurological recovery was observed in 40/158 (25.3%) in the intervention and 27/167 (16.2%) in the control group (RR 1.57 [CIs 1.01-2.42]). Among the 526 patients with initial non-shockable rhythms, favourable neurological outcome was in 10/259 (3.8%) in the intervention and 13/267 (4.9%) in the control group (RR 0.88 [CIs 0.52-1.29]; p = 0.67); survival and complete neurological recovery were also similar between groups. No significant benefit was observed for the intervention in the entire population. CONCLUSIONS: In this pooled analysis of individual data, intra-arrest cooling was associated with a significant increase in favourable neurological outcome in out-of-hospital cardiac arrest patients with initial shockable rhythms. Future studies are needed to confirm the potential benefits of this intervention in this subgroup of patients.

Survival in Out-of-Hospital Cardiac Arrest After Standard Cardiopulmonary Resuscitation or Chest Compressions Only Before Arrival of Emergency Medical Services: Nationwide Study During Three Guideline Periods.

BACKGROUND: In out-of-hospital cardiac arrest, chest compression-only cardiopulmonary resuscitation (CO-CPR) has emerged as an alternative to standard CPR (S-CPR), using both chest compressions and rescue breaths. Since 2010, CPR guidelines recommend CO-CPR for both untrained bystanders and trained bystanders unwilling to perform rescue breaths. The aim of this study was to describe changes in the rate and type of CPR performed before the arrival of emergency medical services (EMS) during 3 consecutive guideline periods in correlation to 30-day survival. METHODS: All bystander-witnessed out-of-hospital cardiac arrests reported to the Swedish register for cardiopulmonary resuscitation in 2000 to 2017 were included. Nonwitnessed, EMS-witnessed, and rescue breath-only CPR cases were excluded. Patients were categorized as receivers of no CPR (NO-CPR), S-CPR, or CO-CPR before EMS arrival. Guideline periods 2000 to 2005, 2006 to 2010, and 2011 to 2017 were used for comparisons over time. The primary outcome was 30-day survival. RESULTS: A total of 30 445 patients were included. The proportions of patients receiving CPR before EMS arrival changed from 40.8% in the first time period to 58.8% in the second period, and to 68.2% in the last period. S-CPR changed from 35.4% to 44.8% to 38.1%, and CO-CPR changed from 5.4% to 14.0% to 30.1%, respectively. Thirty-day survival changed from 3.9% to 6.0% to 7.1% in the NO-CPR group, from 9.4% to 12.5% to 16.2% in the S-CPR group, and from 8.0% to 11.5% to 14.3% in the CO-CPR group. For all time periods combined, the adjusted odds ratio for 30-day survival was 2.6 (95% CI, 2.4-2.9) for S-CPR and 2.0 (95% CI, 1.8-2.3) for CO-CPR, in comparison with NO-CPR. S-CPR was superior to CO-CPR (adjusted odds ratio, 1.2; 95% CI, 1.1-1.4). CONCLUSIONS: In this nationwide study of out-of-hospital cardiac arrest during 3 periods of different CPR guidelines, there was an almost a 2-fold higher rate of CPR before EMS arrival and a concomitant 6-fold higher rate of CO-CPR over time. Any type of CPR was associated with doubled survival rates in comparison with NO-CPR. These findings support continuous endorsement of CO-CPR as an option in future CPR guidelines because it is associated with higher CPR rates and overall survival in out-of-hospital cardiac arrest.

Oxygen Therapy in Suspected Acute Myocardial Infarction.

BACKGROUND: The clinical effect of routine oxygen therapy in patients with suspected acute myocardial infarction who do not have hypoxemia at baseline is uncertain. METHODS: In this registry-based randomized clinical trial, we used nationwide Swedish registries for patient enrollment and data collection. Patients with suspected myocardial infarction and an oxygen saturation of 90% or higher were randomly assigned to receive either supplemental oxygen (6 liters per minute for 6 to 12 hours, delivered through an open face mask) or ambient air. RESULTS: A total of 6629 patients were enrolled. The median duration of oxygen therapy was 11.6 hours, and the median oxygen saturation at the end of the treatment period was 99% among patients assigned to oxygen and 97% among patients assigned to ambient air. Hypoxemia developed in 62 patients (1.9%) in the oxygen group, as compared with 254 patients (7.7%) in the ambient-air group. The median of the highest troponin level during hospitalization was 946.5 ng per liter in the oxygen group and 983.0 ng per liter in the ambient-air group. The primary end point of death from any cause within 1 year after randomization occurred in 5.0% of patients (166 of 3311) assigned to oxygen and in 5.1% of patients (168 of 3318) assigned to ambient air (hazard ratio, 0.97; 95% confidence interval [CI], 0.79 to 1.21; P=0.80). Rehospitalization with myocardial infarction within 1 year occurred in 126 patients (3.8%) assigned to oxygen and in 111 patients (3.3%) assigned to ambient air (hazard ratio, 1.13; 95% CI, 0.88 to 1.46; P=0.33). The results were consistent across all predefined subgroups. CONCLUSIONS: Routine use of supplemental oxygen in patients with suspected myocardial infarction who did not have hypoxemia was not found to reduce 1-year all-cause mortality. (Funded by the Swedish Heart-Lung Foundation and others; DETO2X-AMI ClinicalTrials.gov number, NCT01787110 .).

Leiter-3 generalizability in Scandinavia.

The Leiter-3 is a nonverbal assessment that evaluates cognitive abilities and has been adapted for use in Scandinavia. Generalizability of United States-based normative scoring for use with the Scandinavian population was evaluated. Leiter-3 scores from a sample of Scandinavian students were compared with scores obtained from the Leiter-3 standardization sample, controlling for confounding variables, across ages, using mixed-methods analysis. A Scandinavian-population-based sample was created from Leiter-3 standardization data and norms were constructed and were used to generate standardized scores from the sample data. Results suggest that overall the Scandinavian test-takers score higher than American test-takers, but that differences between groups were minimized when controlling for factors that may influence cognitive performance. Creating Scandinavian based scores was not effective at reducing gaps in performance, suggesting that differences in performance between the different populations may be attributable to factors other than those typically controlled for when constructing standardized tests. Implications of these results and recommendations for Leiter-3 adaptation are reviewed.

Oxygen therapy in ST-elevation myocardial infarction.

Aims: To determine whether supplemental oxygen in patients with ST-elevation myocardial infarction (STEMI) impacts on procedure-related and clinical outcomes. Methods and results: The DETermination of the role of Oxygen in suspected Acute Myocardial Infarction (DETO2X-AMI) trial randomized patients with suspected myocardial infarction (MI) to receive oxygen at 6 L/min for 6-12 h or ambient air. In this pre-specified analysis, we included only STEMI patients who underwent percutaneous coronary intervention (PCI). In total, 2807 patients were included, 1361 assigned to receive oxygen, and 1446 assigned to ambient air. The pre-specified primary composite endpoint of all-cause death, rehospitalization with MI, cardiogenic shock, or stent thrombosis at 1 year occurred in 6.3% (86 of 1361) of patients allocated to oxygen compared to 7.5% (108 of 1446) allocated to ambient air [hazard ratio (HR) 0.85, 95% confidence interval (95% CI) 0.64-1.13; P = 0.27]. There was no difference in the rate of death from any cause (HR 0.86, 95% CI 0.61-1.22; P = 0.41), rate of rehospitalization for MI (HR 0.92, 95% CI 0.57-1.48; P = 0.73), rehospitalization for cardiogenic shock (HR 1.05, 95% CI 0.21-5.22; P = 0.95), or stent thrombosis (HR 1.27, 95% CI 0.46-3.51; P = 0.64). The primary composite endpoint was consistent across all subgroups, as well as at different time points, such as during hospital stay, at 30 days and the total duration of follow-up up to 1356 days. Conclusions: Routine use of supplemental oxygen in normoxemic patients with STEMI undergoing primary PCI did not significantly affect 1-year all-cause death, rehospitalization with MI, cardiogenic shock, or stent thrombosis.

Effect of Trans-Nasal Evaporative Intra-arrest Cooling on Functional Neurologic Outcome in Out-of-Hospital Cardiac Arrest: The PRINCESS Randomized Clinical Trial.

Importance: Therapeutic hypothermia may increase survival with good neurologic outcome after cardiac arrest. Trans-nasal evaporative cooling is a method used to induce cooling, primarily of the brain, during cardiopulmonary resuscitation (ie, intra-arrest). Objective: To determine whether prehospital trans-nasal evaporative intra-arrest cooling improves survival with good neurologic outcome compared with cooling initiated after hospital arrival. Design, Setting, and Participants: The PRINCESS trial was an investigator-initiated, randomized, clinical, international multicenter study with blinded assessment of the outcome, performed by emergency medical services in 7 European countries from July 2010 to January 2018, with final follow-up on April 29, 2018. In total, 677 patients with bystander-witnessed out-of-hospital cardiac arrest were enrolled. Interventions: Patients were randomly assigned to receive trans-nasal evaporative intra-arrest cooling (n = 343) or standard care (n = 334). Patients admitted to the hospital in both groups received systemic therapeutic hypothermia at 32°C to 34°C for 24 hours. Main Outcomes and Measures: The primary outcome was survival with good neurologic outcome, defined as Cerebral Performance Category (CPC) 1-2, at 90 days. Secondary outcomes were survival at 90 days and time to reach core body temperature less than 34°C. Results: Among the 677 randomized patients (median age, 65 years; 172 [25%] women), 671 completed the trial. Median time to core temperature less than 34°C was 105 minutes in the intervention group vs 182 minutes in the control group (P < .001). The number of patients with CPC 1-2 at 90 days was 56 of 337 (16.6%) in the intervention cooling group vs 45 of 334 (13.5%) in the control group (difference, 3.1% [95% CI, -2.3% to 8.5%]; relative risk [RR], 1.23 [95% CI, 0.86-1.72]; P = .25). In the intervention group, 60 of 337 patients (17.8%) were alive at 90 days vs 52 of 334 (15.6%) in the control group (difference, 2.2% [95% CI, -3.4% to 7.9%]; RR, 1.14 [95% CI, 0.81-1.57]; P = .44). Minor nosebleed was the most common device-related adverse event, reported in 45 of 337 patients (13%) in the intervention group. The adverse event rate within 7 days was similar between groups. Conclusions and Relevance: Among patients with out-of-hospital cardiac arrest, trans-nasal evaporative intra-arrest cooling compared with usual care did not result in a statistically significant improvement in survival with good neurologic outcome at 90 days. Trial Registration: ClinicalTrials.gov Identifier: NCT01400373.

Early cardiopulmonary resuscitation in out-of-hospital cardiac arrest.

BACKGROUND: Three million people in Sweden are trained in cardiopulmonary resuscitation (CPR). Whether this training increases the frequency of bystander CPR or the survival rate among persons who have out-of-hospital cardiac arrests has been questioned. METHODS: We analyzed a total of 30,381 out-of-hospital cardiac arrests witnessed in Sweden from January 1, 1990, through December 31, 2011, to determine whether CPR was performed before the arrival of emergency medical services (EMS) and whether early CPR was correlated with survival. RESULTS: CPR was performed before the arrival of EMS in 15,512 cases (51.1%) and was not performed before the arrival of EMS in 14,869 cases (48.9%). The 30-day survival rate was 10.5% when CPR was performed before EMS arrival versus 4.0% when CPR was not performed before EMS arrival (P<0.001). When adjustment was made for a propensity score (which included the variables of age, sex, location of cardiac arrest, cause of cardiac arrest, initial cardiac rhythm, EMS response time, time from collapse to call for EMS, and year of event), CPR before the arrival of EMS was associated with an increased 30-day survival rate (odds ratio, 2.15; 95% confidence interval, 1.88 to 2.45). When the time to defibrillation in patients who were found to be in ventricular fibrillation was included in the propensity score, the results were similar. The positive correlation between early CPR and survival rate remained stable over the course of the study period. An association was also observed between the time from collapse to the start of CPR and the 30-day survival rate. CONCLUSIONS: CPR performed before EMS arrival was associated with a 30-day survival rate after an out-of-hospital cardiac arrest that was more than twice as high as that associated with no CPR before EMS arrival. (Funded by the Laerdal Foundation for Acute Medicine and others.).

Mobile-phone dispatch of laypersons for CPR in out-of-hospital cardiac arrest.

BACKGROUND: Cardiopulmonary resuscitation (CPR) performed by bystanders is associated with increased survival rates among persons with out-of-hospital cardiac arrest. We investigated whether rates of bystander-initiated CPR could be increased with the use of a mobile-phone positioning system that could instantly locate mobile-phone users and dispatch lay volunteers who were trained in CPR to a patient nearby with out-of-hospital cardiac arrest. METHODS: We conducted a blinded, randomized, controlled trial in Stockholm from April 2012 through December 2013. A mobile-phone positioning system that was activated when ambulance, fire, and police services were dispatched was used to locate trained volunteers who were within 500 m of patients with out-of-hospital cardiac arrest; volunteers were then dispatched to the patients (the intervention group) or not dispatched to them (the control group). The primary outcome was bystander-initiated CPR before the arrival of ambulance, fire, and police services. RESULTS: A total of 5989 lay volunteers who were trained in CPR were recruited initially, and overall 9828 were recruited during the study. The mobile-phone positioning system was activated in 667 out-of-hospital cardiac arrests: 46% (306 patients) in the intervention group and 54% (361 patients) in the control group. The rate of bystander-initiated CPR was 62% (188 of 305 patients) in the intervention group and 48% (172 of 360 patients) in the control group (absolute difference for intervention vs. control, 14 percentage points; 95% confidence interval, 6 to 21; P<0.001). CONCLUSIONS: A mobile-phone positioning system to dispatch lay volunteers who were trained in CPR was associated with significantly increased rates of bystander-initiated CPR among persons with out-of-hospital cardiac arrest. (Funded by the Swedish Heart-Lung Foundation and Stockholm County; ClinicalTrials.gov number, NCT01789554.).

Drones for Provision of Flotation Support in Simulated Drowning.

OBJECTIVE: The feasibility and potential of using drones for providing flotation devices in cases of drowning have not yet been assessed. We hypothesize that a drone carrying an inflatable life buoy is a faster way to provide flotation compared with traditional methods. The purpose of this study is to explore the feasibility and efficiency of using a drone for delivering and providing flotation support to conscious simulated drowning victims. METHODS: A simulation study was performed with a simulated drowning victim 100 m from the shore. A drone (DJI Phantom 4; dji, Shenzhen, China) equipped with an inflatable life buoy of 60 N was compared with traditional surf rescue swimming for providing flotation. The primary outcome was delay (minutes:seconds). RESULTS: A total number of 30 rescues were performed with a median time to delivery of the floating device of 30 seconds (interquartile range [IQR] = 24-32 seconds) for the drone compared with 65 seconds (IQR = 60-77 seconds) with traditional rescue swimming (P < .001). The drone had an accuracy of 100% in dropping the inflatable life buoy < 5 m from the victim, with a median of 1 m (IQR = 1-2 m). CONCLUSION: Using drones to deliver inflatable life buoys is safe and may be a faster method to provide early flotation devices to conscious drowning victims compared with rescue swimming.

Adaptive skills are useful for evaluating the effect of pharmacological treatment in children with attention-deficit/hyperactivity disorder.

AIM: There are few long-term studies of adaptive functions as an outcome measure of pharmacological treatment in attention-deficit/hyperactivity disorder (ADHD). This study assessed the adaptive abilities of children with ADHD before and after several years of pharmacological treatment. METHOD: We studied 12 children with a mean age of 15 years - seven boys and five girls - who had continued pharmacological treatment for ADHD for more than four years. The Adaptive Behaviour Assessment Scales - Second Edition ratings by their teachers were compared before and after they had received treatment for ADHD. RESULTS: On a group level, the conceptual, practical and general adaptive composite domains improved significantly between the baseline and follow-up study. There were clear individual variations: more than half of the group increased from an adaptive level far below average to average, a minority displayed no major changes, and one individual deteriorated. The girls tended to have better outcomes than the boys. CONCLUSION: This study was nonrandomised and only analysed within-group changes in a small number of participants. However, the findings suggest that four to five years of stimulant treatment had markedly positive effects on adaptive functioning in more than half of the school-age children with ADHD.

Improved outcome in Sweden after out-of-hospital cardiac arrest and possible association with improvements in every link in the chain of survival.

AIMS: To describe out-of-hospital cardiac arrest (OHCA) in Sweden from a long-term perspective in terms of changes in outcome and circumstances at resuscitation. METHODS AND RESULTS: All cases of OHCA (n = 59,926) reported to the Swedish Cardiac Arrest Register from 1992 to 2011 were included. The number of cases reported (n/100,000 person-years) increased from 27 (1992) to 52 (2011). Crew-witnessed cases, cardiopulmonary resuscitation prior to the arrival of the emergency medical service (EMS), and EMS response time increased (P < 0.0001). There was a decrease in the delay from collapse to calling for the EMS in all patients and from collapse to defibrillation among patients found in ventricular fibrillation (P < 0.0001). The proportion of patients found in ventricular fibrillation decreased from 35 to 25% (P < 0.0001). Thirty-day survival increased from 4.8 (1992) to 10.7% (2011) (P < 0.0001), particularly among patients found in a shockable rhythm and patients with return of spontaneous circulation (ROSC) at hospital admission. Among patients hospitalized with ROSC in 2008-2011, 41% underwent therapeutic hypothermia and 28% underwent percutaneous coronary intervention. Among 30-day survivors in 2008-2011, 94% had a cerebral performance category score of 1 or 2 at discharge from hospital and the results were even better if patients were found in a shockable rhythm. CONCLUSION: From a long-term perspective, 30-day survival after OHCA in Sweden more than doubled. The increase in survival was most marked among patients found in a shockable rhythm and those hospitalized with ROSC. There were improvements in all four links in the chain of survival, which might explain the improved outcome.

Improving Survival and Neurologic Function for Younger Age Groups After Out-of-Hospital Cardiac Arrest in Sweden: A 20-Year Comparison.

OBJECTIVE: To describe changes in the epidemiology of out-of-hospital cardiac arrest in Sweden with the emphasis on the younger age groups. DESIGN: Prospective observational study. SETTING: Sweden. PATIENTS: Patients were recruited from the Swedish Registry of Cardiopulmonary Resuscitation from 1990 to 2012. Only non-crew-witnessed cases were included. INTERVENTION: Cardiopulmonary resuscitation. MEASUREMENT AND MAIN RESULTS: The endpoint was 30-day survival. Cerebral function among survivors was estimated according to the cerebral performance category scores. In all, 50,879 patients in the survey had an out-of-hospital cardiac arrest, of which 1,321 (2.6%) were 21 years old or younger and 1,543 (3.0%) were 22-35 years old. On the basis of results from 2011 and 2012, we estimated that there are 4.9 cases per 100,000 person-years in the age group 0-21 years. The highest survival was found in the 13- to 21-year age group (12.6%). Among patients 21 years old or younger, the following were associated with an increased chance of survival: increasing age, male gender, witnessed out-of-hospital cardiac arrest, ventricular fibrillation, and a short emergency medical service response time. Among patients 21 years old or younger , there was an increase in survival from 6.2% in 1992-1998 to 14.0% in 2007-2012. Among 30-day survivors, 91% had a cerebral performance category score of 1 or 2 (good cerebral performance or moderate cerebral disability) at hospital discharge. CONCLUSIONS: In Sweden, among patients 21 years old or younger, five out-of-hospital cardiac arrests per 100,000 person-years occur and survival in this patient group has more than doubled during the past two decades. The majority of survivors have good or relatively good cerebral function.

Short-term effects of air pollution on out-of-hospital cardiac arrest in Stockholm.

BACKGROUND: Although ozone (O3) and other pollutants have been associated with cardiovascular morbidity and mortality, the effects of O3 on out-of-hospital cardiac arrest (OHCA) have rarely been addressed and existing studies have presented inconsistent findings. The objective of this study was to determine the effects of short-term exposure to air pollution including O3 on the occurrence of OHCA, and assess effect modification by season, age, and gender. METHODS AND RESULTS: A total of 5973 Emergency Medical Service-assessed OHCA cases in Stockholm County 2000-10 were obtained from the Swedish cardiac arrest register. A time-stratified case-crossover design was used to analyse exposure to air pollution and the risk of OHCA. Exposure to O3, PM2.5, PM10, NO2, and NOx was defined as the mean urban background level during 0-2, 0-24, and 0-72 h before the event and control time points. We adjusted for temperature and relative humidity. Ozone in urban background was associated with an increased risk of OHCA for all time windows. The respective odds ratio (confidence interval) for a 10 µg/m(3) increase was 1.02 (1.01-1.05) for a 2-h window, 1.04 (1.01-1.07) for 24-h, and 1.05 (1.01-1.09) for 3 day. The association with 2-h O3 was stronger for events that occurred outdoors: 1.13 (1.06-1.21). We observed no effects for other pollutants and no effect modification by age, gender, or season. CONCLUSION: Short-term exposure to moderate levels of O3 is associated with an increased risk of OHCA.

Chest compression alone cardiopulmonary resuscitation is associated with better long-term survival compared with standard cardiopulmonary resuscitation.

BACKGROUND: Little is known about the long-term survival effects of type-specific bystander cardiopulmonary resuscitation (CPR) in the community. We hypothesized that dispatcher instruction consisting of chest compression alone would be associated with better overall long-term prognosis in comparison with chest compression plus rescue breathing. METHODS AND RESULTS: The investigation was a retrospective cohort study that combined 2 randomized trials comparing the short-term survival effects of dispatcher CPR instruction consisting either of chest compression alone or chest compression plus rescue breathing. Long-term vital status was ascertained by using the respective National and State death records through July 31, 2011. We performed Kaplan-Meier method and Cox regression to evaluate survival according to the type of CPR instruction. Of the 2496 subjects included in the current investigation, 1243 (50%) were randomly assigned to chest compression alone and 1253 (50%) were randomly assigned to chest compression plus rescue breathing. Baseline characteristics were similar between the 2 CPR groups. During the 1153.2 person-years of follow-up, there were 2260 deaths and 236 long-term survivors. Randomization to chest compression alone in comparison with chest compression plus rescue breathing was associated with a lower risk of death after adjustment for potential confounders (adjusted hazard ratio, 0.91; 95% confidence interval, 0.83-0.99; P=0.02). CONCLUSIONS: The findings provide strong support for long-term mortality benefit of dispatcher CPR instruction strategy consisting of chest compression alone rather than chest compression plus rescue breathing among adult patients with cardiac arrest requiring dispatcher assistance.