Metropolitan Emergency Medical Services System Research Articles

Abstract 258: Age, Sex And Survival Of Ventricular Fibrillation Out-of-Hospital Cardiac Arrest: The Influence Of Electrocardiogram Waveform Measures

Background: Studies of sex-based outcome in out-of-hospital cardiac arrest (OHCA) have produced mixed results that may depend on age. Menopause produces a range of effects that may influence resuscitation. We used quantitative measures of the presenting OHCA ventricular fibrillation (VF) waveform - a surrogate of the myocardium’s acute physiology - to assess whether outcome differences according to sex and age group may be mediated via a biologic mechanism. Methods: We conducted a retrospective cohort study of adults with non-traumatic VF-OHCA in a metropolitan Emergency Medical Services system between 2008-2020. We used multivariable logistic regression to assess the association of outcome (survival to hospital discharge, favorable neurological outcome (Cerebral Performance Category (CPC) 1 or 2), with sex and age group (<55, > 55 yrs). We then determined the proportion of the outcome difference mediated by the waveform measure by incorporating previously described quantitative VF waveform measures - an estimated probability of survival (P Survival ) and amplitude spectrum area (AMSA - into the model individually. Results: Of 1526 VF-OHCA patients, average age was 62 years, and 29% were female. Overall, younger women were more likely to survive than younger men (survival 67% vs 54%, p=0.02 with CPC 1-2 61% vs 51%, p=0.07), while older women and older men had similar worse outcomes. After adjusting for Utstein characteristics, women <55 compared to men <55 was associated with greater odds of survival to hospital discharge (OR 1.93, 95% CI 1.23-3.09, p=0.005) and CPC 1-2 survival (OR 1.72, 95% CI 1.10-2.71, p=0.02), whereas no associated sex-based differences in these outcomes were observed between the older groups. Each waveform measure mediated some of the beneficial association between sex and age group with survival: 47% for P Survival and 25% AMSA. Conclusions: Women <55 years were more likely to survive to hospital discharge and with favorable neurological status compared to men <55 years, a sex-associated outcome difference not observed in the older age group. The biologic mechanism represented by VF waveform measures mediated some (47% at most), though not all, of the outcome differences.

Linkage of Emergency Medical Services and Hospital Data: A Necessary Precursor to Improve Understanding of Outcomes of Prehospital Care

Objective: Linking emergency medical services (EMS) data to hospital outcomes is important for quality assurance and research initiatives. However, non-linkage due to missing or incomplete patient information may increase the risk of bias and distort findings. The purpose of this study was to explore if an optimization strategy, in addition to an existing linkage process, improved the linkage rate and reduced selection and information bias. Methods: 4,150 transported patients in a metropolitan EMS system in Alberta, Canada from 2016/17 were linked to two Emergency Department (ED) databases by a standard strategy using a unique health care number, date/time of ED arrival, and hospital name. An optimized strategy added additional linkage steps incorporating last name, year of birth, and a manual search. The strategies were compared to assess the rate of linkage, and to describe event and patient-level characteristics of unlinked records. Results: The standard strategy resulted in 3,650 out of 4,150 (88.0%) linked records (95% CI 86.9%-88.9%). Of the 500 non-linked records, an additional 381 were linked by the optimized strategy (n = 4,031/4,150 [97.1%; 95% CI: 96.6%-97.6%]). There were no false positive linkages. The highest linkage failure was in 25 to 34 year-old patients (n = 93/478, 19.5%), males (n = 236/1975, 12.0%), Echo level events (n = 15/77, 19.5%), and emergency transport (45/231, 19.5%). The optimized strategy improved linkage in these groups by 68.8% (64/93), 79.2% (187/236), 40.0% (6/15), and 51.1% (23/45) respectively. For dispatch card, the highest linkage failure occurred in Card 24-Pregnancy/Childbirth/Miscarriage (n = 30/44, 68.2%), Card 27-Stab/Gunshot/Penetrating Trauma (n = 6/17, 35.3%), and Card 9-Cardiac/Respiratory Arrest/Death (n = 12/46, 26.1%). The optimized strategy improved linkage by 10.0% (3/30), 83.3% (5/6), and 41.7% (5/12) respectively. For the 119 unlinked records, 71 (59.7%) had sufficient information for linkage, but no appropriately matching records could be found. Conclusion: An optimized sequential deterministic strategy linking EMS data to ED outcomes improved the linkage rate without increasing the number of false positive links, and reduced the potential for bias. Even with adequate information, some records were not linked to their ED visit. This study underscores the importance of understanding how data are linked to hospital outcomes in EMS research and the potential for bias.

Insights From the Ventricular Fibrillation Waveform Into the Mechanism of Survival Benefit From Bystander Cardiopulmonary Resuscitation.

BackgroundThe mechanism by which bystander cardiopulmonary resuscitation (CPR) improves survival following out‐of‐hospital cardiac arrest is unclear. We hypothesized that ventricular fibrillation (VF) waveform measures, as surrogates of myocardial physiology, mediate the relationship between bystander CPR and survival.Methods and ResultsWe performed a retrospective cohort study of adult, bystander‐witnessed patients with out‐of‐hospital cardiac arrest with an initial rhythm of VF who were treated by a metropolitan emergency medical services system from 2005 to 2018. Patient, resuscitation, and outcome variables were extracted from emergency medical services and hospital records. A total of 3 VF waveform measures (amplitude spectrum area, peak frequency, and median peak amplitude) were computed from a 3‐second ECG segment before the initial shock. Multivariable logistic regression estimated the association between bystander CPR and survival to hospital discharge adjusted for Utstein elements. Causal mediation analysis quantified the proportion of survival benefit that was mediated by each VF waveform measure. Of 1069 patients, survival to hospital discharge was significantly higher among the 814 patients who received bystander CPR than those who did not (0.52 versus 0.43, respectively; P<0.01). The multivariable‐adjusted odds ratio for bystander CPR and survival was 1.6 (95% CI, 1.2, 2.1), and each VF waveform measure attenuated this association. Depending on the specific waveform measure, the proportion of mediation varied: 53% for amplitude spectrum area, 31% for peak frequency, and 29% for median peak amplitude.ConclusionsBystander CPR correlated with more robust initial VF waveform measures, which in turn mediated up to one‐half of the survival benefit associated with bystander CPR. These results provide insight into the biological mechanism of bystander CPR in VF out‐of‐hospital cardiac arrest.

Diurnal, weekly and seasonal variations of chest pain in patients transported by emergency medical services

ObjectivesChest pain is among the leading causes for emergency medical services (EMS) activation. Acute myocardial infarction (MI) is not only one of the most critical aetiologies of chest pain, but...

Receiving Hospital Characteristics Associated With Survival in Patients Transported by Emergency Medical Services After Out-of-hospital Cardiac Arrest.

To test whether primary emergency medical services (EMS) transport to hospitals with certain characteristics (24/7 percutaneous coronary intervention [PCI] availability, trauma center status, large [>24 bed] intensive care unit [ICU]) versus hospitals without those characteristics is associated with improved hospital survival after out-of-hospital cardiac arrest (OHCA). This is an analysis of a prospectively collected EMS database, which archives patients with OHCA treated by a single large metropolitan EMS system. The database contains Utstein data, EMS transport data, and survival to hospital discharge. EMS providers uniformly apply advanced cardiac life support protocols to OHCA patients in the field. Patients with return of spontaneous circulation (ROSC) are transported to one of 10 hospitals in the area. If ROSC is not achieved within 30 minutes, efforts are terminated and the patient is not transported. We used multivariate logistic regression to test if receiving hospital characteristics were independently associated with survival among those transported after ROSC. We excluded patients not transported to a hospital and patients with incomplete outcome data. Between January 2011 and December 2014, a total of 1,188 OHCA patients were resuscitated in the field and transported to an area hospital. After patients with missing data were excluded, 1,024 patients were included in the analysis. The mean (±SD) age was 61.1 (±17.0) years, and 57.7% were male. Of transported patients, 76% were taken to 24/7 PCI centers, 46% were taken to trauma centers, and 37% were taken to hospitals with large ICUs. There was considerable overlap in these hospital characteristics. A multivariate logistic regression model including age, sex, shockable rhythm, EMS time to scene, and dispatch complaint of cardiac arrest found that none of the hospital characteristics were independently associated with increased survival to discharge. The odds ratios (95% confidence intervals) for survival were as follows: PCI center, 1.28 (0.80 to 2.04); trauma center, 1.44 (0.73 to 2.85); and large ICU, 1.39 (0.69 to 2.80). After adjusting for patient demographic data, we found no significant independent association between receiving hospital characteristics and survival to discharge among OHCA patients transported after ROSC by a single EMS agency.

Pediatric Intubation by Paramedics in a Large Emergency Medical Services System: Process, Challenges, and Outcomes

Pediatric intubation is a core paramedic skill in some emergency medical services (EMS) systems. The literature lacks a detailed examination of the challenges and subsequent adjustments made by paramedics when intubating children in the out-of-hospital setting. We undertake a descriptive evaluation of the process of out-of-hospital pediatric intubation, focusing on challenges, adjustments, and outcomes. We performed a retrospective analysis of EMS responses between 2006 and 2012 that involved attempted intubation of children younger than 13 years by paramedics in a large, metropolitan EMS system. We calculated the incidence rate of attempted pediatric intubation with EMS and county census data. To summarize the intubation process, we linked a detailed out-of-hospital airway registry with clinical records from EMS, hospital, or autopsy encounters for each child. The main outcome measures were procedural challenges, procedural success, complications, and patient disposition. Paramedics attempted intubation in 299 cases during 6.3 years, with an incidence of 1 pediatric intubation per 2,198 EMS responses. Less than half of intubations (44%) were for patients in cardiac arrest. Two thirds of patients were intubated on the first attempt (66%), and overall success was 97%. The most prevalent challenge was body fluids obscuring the laryngeal view (33%). After a failed first intubation attempt, corrective actions taken by paramedics included changing equipment (33%), suctioning (32%), and repositioning the patient (27%). Six patients (2%) experienced peri-intubation cardiac arrest and 1 patient had an iatrogenic tracheal injury. No esophageal intubations were observed. Of patients transported to the hospital, 86% were admitted to intensive care and hospital mortality was 27%. Pediatric intubation by paramedics was performed infrequently in this EMS system. Although overall intubation success was high, a detailed evaluation of the process of intubation revealed specific challenges and adjustments that can be anticipated by paramedics to improve first-pass success, potentially reduce complications, and ultimately improve clinical outcomes.

Prehospital Pediatric Care: Opportunities for Training, Treatment, and Research

Objective. Pediatric transports comprise approximately 10% of emergency medical services (EMS) requests for aid, but little is known about the clinical characteristics of pediatric EMS patients and the interventions they receive. Our objective was to describe the pediatric prehospital patient cohort in a large metropolitan EMS system. Methods. This retrospective analysis of all pediatric (age <19 years) EMS patients transported from October 2011 to September 2013 was conducted by reviewing a system-wide National EMS Information System (NEMSIS)-compliant database of all EMS patient encounters. We identified the most common primary working assessments, the frequency of abnormal initial vital signs, and the interventions provided. Vital signs included systolic blood pressure (SBP), respiratory (RR) and pulse rate, Glasgow Coma Scale (GCS), pulse oximetry (Pox), and respiratory effort. We defined abnormal vital signs using previously reported age-specific standards. We identified the working assessments most frequently associated with abnormal vital signs and the working assessments associated with the most commonly performed interventions. Data were analyzed using descriptive statistics. Results. There were 9,956 pediatric transports, 8.7% of the total call volume. The most common working assessments were “other” (16.1%), respiratory distress (13.7%), seizure (12.4%), and blunt trauma (12.0%). Vital signs were documented at variable rates: RR (91.1%), GCS (82.9%), SBP (71.3%), pulse (69.4%), respiratory effort (49.7%), and Pox (33.5%). Of all transported patients, 61.5% had a documented abnormal initial vital sign. Patients with an abnormal vital sign had the same most common working assessments as those with normal vital signs. Glucometry (16.9%), medication delivery (13.6%), and IV placement (11.5%) were the most common interventions and were most often provided to patients with working assessments of seizure, asthma, trauma, altered consciousness, or “other.” Cardiopulmonary resuscitation (0.4%), bag mask ventilation (0.4%), and advanced airway (0.4%) occurred rarely and were most often performed for cardiac arrest and trauma. Conclusions. Children made up a small part of EMS providers’ clinical practice; those encountered most frequently had respiratory distress, seizures, trauma, or an undefined assessment (i.e., “other”). EMS providers frequently encounter children with physiologic evidence of acute illness, although vital sign documentation was incomplete. Prehospital providers infrequently perform pediatric interventions. Describing EMS providers’ interaction with children provides the opportunity to target improvements in pediatric prehospital treatment, training, and research.

Use of rapid sequence intubation predicts improved survival among patients intubated after out-of-hospital cardiac arrest

ObjectiveSome observational studies indicate that endotracheal intubation is associated with a worse outcome compared to bag-mask ventilation after out-of-hospital cardiac arrest in emergency medical services (EMS) systems without rapid sequence intubation (RSI). We evaluated the role of RSI in airway management following cardiac arrest. MethodsWe conducted a cohort study of all non-traumatic arrest patients treated by a metropolitan EMS system from 2007 to 2011. Advanced airway management information was obtained from a prospective airway registry and linked to a cardiac arrest registry. We used multivariate logistic regression to estimate the association between attempted intubation status and survival to hospital discharge. ResultsOf 3133 patients, 82% underwent attempted intubation without RSI, 15% underwent attempted RSI, and 3% experienced no intubation attempt. Survival to hospital discharge differed by attempted intubation status: 11% (n=291/2576) for intubation without RSI, 48% (n=226/471) for RSI, and 71% (n=61/86) for “no intubation.” Compared to the intubation without RSI group, the adjusted odds ratios of survival were 5.6 (95% CI 4.3, 7.2) for the RSI group and 15 (95% CI 9, 27) for the “no intubation” group. ConclusionIn this population-based cohort of out-of-hospital cardiac arrest, RSI was used in 15% of patients and associated with a better prognosis than intubation attempted without paralytics. Because this subset with a favorable prognosis may not be readily intubated in systems without paralytics, these findings could help to explain the adverse relationship between intubation and survival observed in prior studies.

Does Ambulance Response Time Influence Patient Condition among Patients with Specific Medical and Trauma Emergencies?

The relation between patient outcome and ambulance response times is unknown. We sought to measure the influence of shorter response times on patient outcomes. The objective of the study was to determine whether ambulance response time makes a difference in the outcomes of emergency medical services (EMS) patients with specific traumatic and medical emergencies. This study was conducted in a metropolitan EMS system serving a population of 800,000, including urban and rural areas. Cases were included if the private EMS service was the first medical provider on scene, the case was priority 1, and the patients were 13 years old and older. A 14-month time period was used for the data evaluation. Four diagnoses were examined: motor vehicle crash injuries, penetrating trauma, difficulty breathing, and chest pain complaints. Data collected included ambulance response times, initial vital signs, and the number of vital signs out of range. Cases seen at the single major trauma center were selected for evaluation of hospital outcome. Correlation coefficients were used to evaluate interactions between independent and outcome variables. Of the 2164 cases we reviewed, the EMS service responded significantly faster to trauma complaints at 4.5 minutes (n = 254) than medical complaints at 5.9 minutes (n = 1910). In the trauma center sample of 559 cases, response time was not related to hospital days (P = 0.5), admissions (P = 0.7), intensive care unit admissions (P = 0.4), or deaths (P = 0.3). This study showed that in cases seen at a major trauma center, longer response times were not associated with worse outcomes for the diagnostic groups tested.

Outcomes from out-of-hospital cardiac arrest in Metropolitan Taipei: Does an advanced life support service make a difference?

Out-of-hospital cardiac arrest (OHCA) is of major medical and public health significance. It also serves as a good indicator in assessing the performance of local emergency medical services system (EMS). There have been arguments for and against the benefits of advanced life support (ALS) over basic life support with defibrillator (BLS-D) for treating OHCA. The study was conducted to characterise the outcomes of cardiac arrest victims in an Asian metropolitan city; to evaluate the impacts of ALS versus BLS-D services; and to explore the possible patient and arrest factors that may be associated with the observed differences in the outcomes between the two pre-hospital care models. Taipei is an Asian metropolitan city with an area of 272 km(2) and a population of 2.65 million. The fire-based BLS-D EMS system was in the process of phasing in ALS capability. While there were 40 BLS-D teams in the 12 city districts, two ALS teams were set up in the central part of the city. In this prospective study, all adult non-traumatic OHCA from September 2003 to August 2004 were included. Patient, arrest, care, and outcome variables for OHCA victims were collected from prehospital run sheets, automatic defibrillators, and emergency department and hospital records. Among 1423 OHCA included in the analysis, 1037 (73%) received BLS-D service, and 386 (27%) received ALS services. The initial shockable rhythms and early bystander CPR were strongly associated with better survival for victims of cardiac arrests. Compared to BLS-D, ALS patients had similar age, sex, witness status, the rate of bystander CPR, and response timeliness but more patients in asystole (84% versus 72%, p=0.005). Patients treated by ALS were more likely to result in significantly higher rates of return of spontaneous circulation (29% versus 21%; OR=1.51 (95% CI 1.15-2.00); p=0.002) and survival to emergency department/intensive care unit admission (23% versus 15%; OR=1.66 (95% CI 1.22-2.24); p=0.001), but there was no difference in the rate of survival to hospital discharge (7% versus 5%; OR=1.39 (95% CI 0.84-2.23); p=0.17). The outcome difference from ALS services was more pronounced among patients in asystole and without bystander CPR. In this metropolitan EMS in Asia, the implementation of ALS services improved the intermediate, but not the final outcomes. Communities with larger populations and lower incidence of initial shockable rhythms than the OPALS study should also prioritise their resources in setting up and optimising systems of basic life support and early defibrillations. Further studies are warranted to configure the optimal care model for combating cardiac arrest.

Spirituality of EMTs: a study of the spiritual nature of EMS workers and its effects on perceived happiness and prayers for patients.

There is reason to believe that traumatic events experienced on the job make emergency medical services (EMS) workers more skeptical about their spiritual beliefs. Little is known about the spiritual lives and experiences of emergency medical technicians (EMTs). No studies have measured the responses of EMTs to the spiritual needs of their patients. This study investigates whether EMS workers are less spiritual than the average U.S. citizen, and what effect this has on prayer for patients and perceived happiness. Data were collected in a major metropolitan EMS system from 125 EMTs and paramedics through a questionnaire about their beliefs and behaviors regarding their spirituality. Pearson product-moment correlation coefficients (r) were used to analyze variables. The religious attitudes of EMTs were compared with those of the general population as defined in the Gallup studies. Ninety-one percent of the EMS workers interviewed and 94% of Gallup's sample of the general population said they believe in God. The findings on other measures in the EMT sample also were very similar to those defined in the general population. Of the EMTs, 60% said they never have doubted the existence of God. Eighty-four percent believe God still works miracles, and 80% of the EMTs believe in life after death. Eighty-seven percent of EMS workers pray; 62% pray for their patients, and 54% pray for their coworkers. Frequency of church or synagogue attendance is positively and significantly correlated with the degree of perceived life happiness (r = 0.226, p < 0.025 > 0.005). Frequency of prayer also is correlated positively to perceived life happiness (r = 0.182, p < 0.025 > 0.005). Emergency medical services workers are interested and willing to talk about their spiritual lives. They do have more doubts about the existence of God than does the average civilian, but are just as spiritual. Those EMTs with more active spiritual lives perceive themselves as happier. The majority of EMS workers pray for their patients.

Dispatcher-assisted telephone CPR: Common delays and time standards for delivery

To determine the rate of bystander CPR before and after implementation of a telephone CPR program in King County; to determine the reasons for dispatcher delays in identifying patients in cardiac arrest in delivering CPR instructions over the telephone; and to suggest time standards for delivery of the telephone CPR message. An ongoing cardiac arrest surveillance system to calculate the annual bystander CPR rates from 1976 through 1988. Two hundred sixty-seven taped recordings of calls reporting cardiac arrests to nine emergency dispatch centers during 1988 were reviewed and timed. King County, Washington, excluding the city of Seattle. Two hundred sixty-seven persons with out-of-hospital cardiac arrests receiving emergency medical services. Arrests in doctors' offices, clinics, or nursing homes were excluded. Dispatcher-assisted telephone CPR. The rate of bystander CPR increased from 32% (1976 through 1981) to 54% (1982 through 1988) after implementation of the dispatcher-assisted telephone CPR program, although an increase in survival could not be demonstrated. The median time for dispatchers to identify the problem was 75 seconds; to deliver the early protocols, 19 seconds; to deliver the ventilation instructions, 25 seconds; and to deliver compression instructions, 30 seconds. The total time to deliver the entire CPR message was 2.3 minutes. The most frequent cause for delay was unnecessary questions (57%) with questions about patient age asked most frequently (32%). Other causes included the caller not being near the patient (29%) and deviations from protocol (22%). In a metropolitan emergency medical services system, a dispatcher-assisted telephone CPR program was associated with an increase in bystander CPR. Delays in proper delivery of telephone CPR can be minimized through training.

Prehospital cardiac arrest: The impact of witnessed collapse and bystander CPR in a metropolitan EMS system with short response times

Numerous studies have shown initiation of bystander CPR to significantly improve survival from prehospital cardiac arrest. However, in emergency medical services (EMS) systems with very short response times, bystander CPR has not been shown to impact outcome. The purpose of this study was to determine the effect of bystander CPR on survival from out-of-hospital cardiac arrest in such a system. Prehospital, hospital, and death certificate data from a medium-sized metropolitan area were retrospectively analyzed for adult, nontraumatic cardiac arrest during a 16-month period. A total of 298 patients met study criteria. One hundred ninety-five arrests (65.4%) were witnessed, and 103 (34.6%) were unwitnessed. Twenty-five witnessed victims (12.8%) were discharged alive, whereas no unwitnessed victims survived (P less than .001). Patients suffering a witnessed episode of ventricular fibrillation/tachycardia (VF/VT) were more likely to survive (21.9%) than were other patients (2.0%, P less than .0001). Among witnessed patients, initiation of bystander CPR was associated with a significant improvement in survival (20.0%) compared with the no-bystander CPR group (9.2%, P less than .05). Bystander CPR was also associated with improved outcome when witnessed patients with successful prehospital resuscitation were evaluated as a group; 18 had bystander CPR, of whom 13 (72.2%) survived compared with only 12 of 38 patients with no bystander CPR (31.6%, P less than .01). Our data revealed improved survival rates when bystander CPR was initiated on victims of witnessed cardiac arrest in an EMS system with short response times.

A review of prehospital care litigation in a large metropolitan EMS system

A retrospective review of all claims brought against a large, metropolitan emergency medical services (EMS) system related to paramedic-patient encounters during the 12-year period from 1976 through 1987 was undertaken to review and describe the incidence and types of malpractice claims. During this period, EMS units responded to approximately 2 million calls and transported more than 1 million patients. Sixty claims occurred during the incidence study period (1976 through 1985). The overall litigation rate was one lawsuit per 27,371 paramedic-patient encounters and one lawsuit per 17,995 patient transports. While the total number of runs and transports did not change significantly during the study period, the data indicate a trend of increasing claims filed against the prehospital care provider. To date, 26 cases (38%) have been settled with the majority involving either no monetary awards or nominal out-of-court settlements.

Ground versus air transport of trauma victims: Medical and logistical considerations

Emergency aeromedical transport for trauma victims varies widely, from 10% or less in some programs to more than 90% in others. There is the potential in all such programs for dramatic, lifesaving efforts as well as for costly and dangerous overuse. We propose the following preliminary guidelines for emergency aeromedical transport of trauma victims. Trauma scene flights should be dispatched only for seriously injured patients who are potentially salvageable. Trauma scene flights are not justified if the flight does not significantly reduce the interval between injury and patient arrival at an appropriate hospital (eg, from motor vehicle accident with entrapment) unless the flight delivers needed medical expertise or equipment to the scene. Critically injured patients should be returned to the closest hospital of appropriate capabilities and demonstrated expertise. Flight services should be a public service fully integrated into the metropolitan emergency medical services system. Scene flights should be dispatched within medical guidelines established by the regional emergency medical services system. Emergency aeromedical evacuation of trauma victims should assist the regionalization of trauma care to centers with special capabilities for the management of seriously injured patients. Promulgation of more detailed guidelines will depend on the accumulation of clinical experience and will be possible only if consistent efforts are made to obtain measures of injury severity, categories of injury, and long-term outcomes of management.