Safety and Adverse Events During Primary Care Paramedic Interfacility Transfer of Stable STEMI Patients

OBJECTIVE

Current guidelines recommend that patients presenting with ST-elevation myocardial infarction (STEMI) to hospitals not capable of performing primary percutaneous coronary intervention (PCI) be transferred to a PCI-capable hospital if reperfusion can be accomplished within 120 min. Most STEMI patients are accompanied by an advanced care paramedic (ACP, equivalent to EMT-P), nurse, or physician who can manage complications should they arise. In our region, stable STEMI patients are transported by primary care paramedics (PCPs, similar scope of practice to advanced EMT) in cases where a nurse, physician, or ACP paramedic is not available. Our goal was to describe adverse events and need for advanced interventions among initially stable STEMI patients during interfacility transfer by PCPs.

METHODS

We reviewed ambulance and hospital records of initially stable STEMI patients (as determined by first set of vital signs documented by paramedics) transferred to a PCI-capable hospital by PCPs between March 1, 2014, and December 31, 2019. We identified whether pre-determined adverse clinical events occurred during the transport as well as the potential need for advanced care interventions not within the PCP scope of practice. Adverse events upon arrival in the PCI lab were also identified.

RESULTS

Of 346 STEMI patients transferred, 179 met inclusion criteria. The mean age of included patients was 61 years (SD 12.1) and 74.9% (134/179) were male. Median transport interval was 36 min (IQR 3.0). During transport, 47/179 (26.0%) patients experienced pre-defined adverse events; for 16/47 (34%), one or more adverse events was major. Three patients met criteria for ACP interventions. One patient suffered a cardiac arrest and was promptly resuscitated with defibrillation by the PCPs.

CONCLUSIONS

We found PCP-interfacility transport of initially stable STEMI patients was safe and associated with a moderate proportion of adverse events, the majority of which did not require an advanced care intervention. These findings may help decision-making to avoid delays transferring stable patients to PCI-capable centers.

Defibrillation Strategies for Refractory Ventricular Fibrillation

BACKGROUND

Despite advances in defibrillation technology, shock-refractory ventricular fibrillation remains common during out-of-hospital cardiac arrest. Double sequential external defibrillation (DSED; rapid sequential shocks from two defibrillators) and vector-change (VC) defibrillation (switching defibrillation pads to an anterior-posterior position) have been proposed as defibrillation strategies to improve outcomes in patients with refractory ventricular fibrillation.

METHODS

We conducted a cluster-randomized trial with crossover among six Canadian paramedic services to evaluate DSED and VC defibrillation as compared with standard defibrillation in adult patients with refractory ventricular fibrillation during out-of-hospital cardiac arrest. Patients were treated with one of these three techniques according to the strategy that was randomly assigned to the paramedic service. The primary outcome was survival to hospital discharge. Secondary outcomes included termination of ventricular fibrillation, return of spontaneous circulation, and a good neurologic outcome, defined as a modified Rankin scale score of 2 or lower (indicating no symptoms to slight disability) at hospital discharge.

RESULTS

A total of 405 patients were enrolled before the data and safety monitoring board stopped the trial because of the coronavirus disease 2019 pandemic. A total of 136 patients (33.6%) were assigned to receive standard defibrillation, 144 (35.6%) to receive VC defibrillation, and 125 (30.9%) to receive DSED. Survival to hospital discharge was more common in the DSED group than in the standard group (30.4% vs. 13.3%; relative risk, 2.21; 95% confidence interval [CI], 1.33 to 3.67) and more common in the VC group than in the standard group (21.7% vs. 13.3%; relative risk, 1.71; 95% CI, 1.01 to 2.88). DSED but not VC defibrillation was associated with a higher percentage of patients having a good neurologic outcome than standard defibrillation (relative risk, 2.21 [95% CI, 1.26 to 3.88] and 1.48 [95% CI, 0.81 to 2.71], respectively).

CONCLUSIONS

Among patients with refractory ventricular fibrillation, survival to hospital discharge occurred more frequently among those who received DSED or VC defibrillation than among those who received standard defibrillation. (Funded by the Heart and Stroke Foundation of Canada; DOSE VF ClinicalTrials.gov number, NCT04080986.).

Clinical considerations for out-of-hospital cardiac arrest management during COVID-19

Managing out-of-hospital cardiac arrest requires paramedics to perform multiple aerosol generating medical procedures in an uncontrolled setting. This increases the risk of cross infection during the COVID-19 pandemic. Modifications to conventional protocols are required to balance paramedic safety with optimal patient care and potential stresses on the capacity of critical care resources. Despite this, little specific advice has been published to guide paramedic practice. In this commentary, we highlight challenges and controversies regarding critical decision making around initiation of resuscitation, airway management, mechanical chest compression, and termination of resuscitation. We also discuss suggested triggers for implementation and revocation of recommended protocol changes and present an accompanying paramedic-specific algorithm.

Improving Temporal Trends in Survival and Neurological Outcomes After Out-of-Hospital Cardiac Arrest

BACKGROUND

Considerable effort has gone into improving outcomes from out-of-hospital cardiac arrest (OHCA). Studies suggest that survival is improving; however, prior studies had insufficient data to pursue the relationship between markers of guideline compliance and temporal trends. The objective of the study was to evaluate trends in OHCA survival over an 8-year period that included the implementation of the 2005 and 2010 international cardiopulmonary resuscitation (CPR) guidelines.

METHODS AND RESULTS

This was a population-based cohort study of all consecutive treated OHCA patients of presumed cardiac cause between 2006 and 2013 in the City of Toronto, Canada, and surrounding regions. Temporal changes were measured by χ² trend test. The association between year of the OHCA and survival was evaluated using logistic regression and joinpoint analysis. A total of 23 619 patients with OHCA met study inclusion criteria. During the study period, survival to hospital discharge doubled (4.8% in 2006 to 9.4% in 2013; P<0.0001), and survival with good neurological outcome increased (6.2% in 2010 to 8.5% in 2013; P=0.005). Improvements occurred in the rates of bystander CPR and automated external defibrillator application, high-quality CPR metrics, and in-hospital targeted temperature management. After adjusting for the Utstein variables, survival to hospital discharge (odds ratio, 1.12; 95% confidence interval, 1.09-1.15) and survival with good neurological outcome (odds ratio, 1.13; 95% confidence interval, 1.05-1.22) increased with each year of study.

CONCLUSIONS

Survival after OHCA has improved over time. This trend was associated with improved rates of bystander CPR, automated external defibrillator use, high-quality CPR metrics, and in-hospital targeted temperature management. The results suggest that multiple factors, each improving over time, may have contributed to the observed increase in survival.

Catecholaminergic Polymorphic Ventricular Tachycardia: An Unusual Case of Fright-Induced Prehospital Cardiac Arrest in a Healthy 6-Year-Old Child

Catecholaminergic Polymorphic Ventricular Tachycardia is a rare but often lethal genetic disorder that affects approximately 1 in 10,000 people. It often first manifests as stress or exercise-related syncope or sudden unexplained cardiac death, primarily in the pediatric and young adult population. We present a case of a 6-year-old male who had a sudden unexplained prehospital cardiac arrest after being scared by a domestic animal and who presented in ventricular fibrillation. The patient was subsequently defibrillated with a return of spontaneous circulation. During the course of care, medications with beta-1 and -2 agonist properties were administered, followed by multiple further episodes of polymorphic ventricular tachycardia (PVT)/ventricular fibrillation (VF). Once these medications were discontinued and beta blockers were administered, the patient had no further episodes of PVT/VF and was subsequently discharged from hospital 7 days later, completely neurologically intact. This case suggests the need for caution when considering administering beta agonists in a pediatric cardiac arrest patient with no known history of heart disease who presents in VF or PVT after an incident of extreme stress or strenuous physical activity.

Extracorporeal cardiopulmonary resuscitation in out-of-hospital cardiac arrest: Ethical considerations

Out-of-hospital cardiac arrest (OHCA) continues to be a leading cause of mortality worldwide. In Canada over 40,000 cardiac arrests that occur each year, a majority occur unexpectedly outside of the hospital setting. However, the reality is that without rapid and appropriate treatment within minutes, most victims will die before reaching the hospital. In the late 1980s case reports identifying favorable outcomes with the use of extracorporeal cardiopulmonary resuscitation (eCPR) in out-of-hospital cardiac arrest (OHCA) began to be reported. Since then case reports, observational studies, propensity analysis, and a systematic review of international practices continues to suggest eCPR as a feasible intervention for refractory ventricular fibrillation (VF) and pulseless ventricular tachycardia (VT) in select adult patients. However, in spite of this mounting base of evidence, clinicians continue to report concerns over a paucity of robust data showing definitive eCPR effectiveness compared with conventional resuscitation. This review will explore the ethical issues related to the impact eCPR might have on the orthodoxy pertaining to current resuscitation strategies, the impact of shifting decision-making on families particularly in dealing with a "bridge to nowhere" scenario, a call to accounting for greater data integrity and improved outcome reporting to assess eCPR effectiveness, and addressing the "Should we just do it" question. A recommendation is proposed for the creation of an ethics consultation service to assist families and staff in dealing with the invariable value conflicts and stresses likely to arise.

Prehospital cooling to improve successful targeted temperature management after cardiac arrest: A randomized controlled trial

RATIONALE

Targeted temperature management (TTM) improves survival with good neurological outcome after out-of-hospital cardiac arrest (OHCA), but is delivered inconsistently and often with delay.

OBJECTIVE

To determine if prehospital cooling by paramedics leads to higher rates of 'successful TTM', defined as achieving a target temperature of 32-34°C within 6h of hospital arrival.

METHODS

Pragmatic RCT comparing prehospital cooling (surface ice packs, cold saline infusion, wristband reminders) initiated 5min after return of spontaneous circulation (ROSC) versus usual resuscitation and transport. The primary outcome was rate of 'successful TTM'; secondary outcomes were rates of applying TTM in hospital, survival with good neurological outcome, pulmonary edema in emergency department, and re-arrest during transport.

RESULTS

585 patients were randomized to receive prehospital cooling (n=279) or control (n=306). Prehospital cooling did not increase rates of 'successful TTM' (30% vs 25%; RR, 1.17; 95% confidence interval [CI] 0.91-1.52; p=0.22), but increased rates of applying TTM in hospital (68% vs 56%; RR, 1.21; 95%CI 1.07-1.37; p=0.003). Survival with good neurological outcome (29% vs 26%; RR, 1.13, 95%CI 0.87-1.47; p=0.37) was similar. Prehospital cooling was not associated with re-arrest during transport (7.5% vs 8.2%; RR, 0.94; 95%CI 0.54-1.63; p=0.83) but was associated with decreased incidence of pulmonary edema in emergency department (12% vs 18%; RR, 0.66; 95%CI 0.44-0.99; p=0.04).

CONCLUSIONS

Prehospital cooling initiated 5min after ROSC did not increase rates of achieving a target temperature of 32-34°C within 6h of hospital arrival but was safe and increased application of TTM in hospital.

Long-term clinical outcomes and predictors for survivors of out-of-hospital cardiac arrest

AIMS

Improvement in resuscitation efforts has translated to an increasing number of survivors after out-of-hospital cardiac arrest (OHCA). Our objectives were to assess the long-term outcomes and predictors of mortality for patients who survived OHCA.

METHODS

We conducted a population-based cohort study linking the Toronto RescuNET cardiac arrest database with administrative databases in Ontario, Canada. We included patients with non-traumatic OHCA from December 1, 2005 to December 31, 2014. The primary outcomes were mortality at 1 year and 3 years. Cox proportional hazard models were constructed to evaluate the predictors of mortality.

RESULTS

Among the 28,611 OHCA patients who received treatment at the scene of arrest, 1591 patients survived to hospital discharge. During hospitalization, 36% received coronary revascularizations and 27% received an implantable cardioverter defibrillator. At one year after discharge, 12.6% of patients had died and 37.3% were readmitted. At 3 years, mortality rate was 20% and all-cause readmission rate was 54.1%. Older age and a history of cancer were associated with higher risk of 3-year mortality. Shockable rhythm at presentation (hazard ratio [HR] 0.62, 95% CI 0.45-0.85), use of coronary revascularization (HR 0.37, 95% CI 0.28-0.51) or implantable cardioverter defibrillator (HR 0.28, 95% CI 0.20-0.41) was associated with substantially lower 3-year mortality. Prior cardiac conditions and other arrest characteristics were not associated with long-term mortality.

CONCLUSIONS

Survivors of OHCA face significant morbidity and mortality after hospital discharge. Clinical trials are needed to evaluate the potential benefits of invasive cardiac procedures in OHCA survivors.

A comparison of the universal TOR Guideline to the absence of prehospital ROSC and duration of resuscitation in predicting futility from out-of-hospital cardiac arrest

INTRODUCTION

The Universal Termination of Resuscitation (TOR) Guideline accurately identifies potential out-of-hospital cardiac arrest (OHCA) survivors. However, implementation is inconsistent with some Emergency Medical Service (EMS) agencies using absence of return of spontaneous circulation (ROSC) as sole criterion for termination.

OBJECTIVE

To compare the performance of the Universal TOR Guideline with the single criterion of no prehospital ROSC. Second, to determine factors associated with survival for patients transported without a ROSC. Lastly, to compare the impact of time to ROSC as a marker of futility to the Universal TOR Guideline.

DESIGN

Retrospective, observational cohort study.

PARTICIPANTS

Non-traumatic, adult (≥18 years) OHCA patients of presumed cardiac etiology treated by EMS providers.

SETTING

ROC-PRIMED and ROC-Epistry post ROC-PRIMED databases between 2007 and 2011.

OUTCOMES

Primary outcome was survival to hospital discharge and the secondary outcome was functional survival. We used multivariable regression to evaluate factors associated with survival in patients transported without a ROSC.

RESULTS

36,543 treated OHCAs occurred of which 9467 (26%) were transported to hospital without a ROSC. Patients transported without a ROSC who met the Universal TOR Guideline for transport had a survival of 3.0% (95% CI 2.5-3.4%) compared to 0.7% (95% CI 0.4-0.9%) in patients who met the Universal TOR Guideline for termination. The Universal TOR Guideline identified 99% of survivors requiring continued resuscitation and transportation to hospital including early identification of survivors who sustained a ROSC after extended durations of CPR.

CONCLUSION

Using absence of ROSC as a sole predictor of futility misses potential survivors. The Universal TOR Guideline remains a strong predictor of survival.

A Novel Approach to Improve Time to First Shock in Prehospital STEMI Complicated by Ventricular Fibrillation

Lethal cardiac arrhythmias such as ventricular fibrillation and pulseless ventricular tachycardia (VF/pVT) complicate up to 6% of all out-of-hospital STEMIs. Typically, paramedics respond to this by applying defibrillation pads and delivering a shock as soon as possible. A recently introduced "pads-on" protocol directed paramedics to apply defibrillation pads to all STEMI patients (regardless of clinical stability) with the aim of decreasing time to first shock. In this article we present two cases of prehospital STEMI complicated by VF to illustrate times to first shock for the two different protocols. One case each of a STEMI complicated by VF before implementation of the pads-on protocol and after the implementation of the protocol is presented. An important difference in the time to first shock is noted between the two patients with STEMI complicated by VF. While it took 2 min 43 s for the pads-off patient to be defibrillated, only 27 s elapsed before the pads-on patient was defibrillated. These two cases demonstrate that the application of defibrillation pads immediately following the diagnosis of prehospital STEMI has the potential to decrease the time to shock in patients suffering VF/pVT.

Prehospital vs. emergency department pronouncement of death: a cost analysis

Objective:

National survival rates for out-of-hospital cardiac arrests are less than 5%, and substantial resources are associated with transporting cardiac arrest victims to hospital for emergency department (ED) resuscitation. The low overall survival rate and the identification of predictors of unsuccessful resuscitation have opened debate on the “futility” of transporting such patients to the ED. This study compares the costs of prehospital pronouncement of death to the costs of transporting patients to a hospital ED for physician pronouncement.

Methods:

The study was a retrospective chart review on a matched cohort of out-of-hospital cardiac arrest patients. Patients were included if documentation was adequate and ambulance response time was less than 8 minutes. A cohort of 20 patients pronounced dead in the field were matched to 20 patients pronounced dead in an ED. Cases were matched on 6 evidence-based predictors of unsuccessful resuscitation. Direct medical costs and mean physician and prehospital provider times were compared.

Results:

The total cost of pronouncement of death in the ED was $45.35 higher than the cost of field pronouncement (p &lt; 0.001). Paramedics spent more time delivering care when death was pronounced in the field (83.3 vs. 55.9 min; p &lt; 0.001). Base hospital physicians spent more time when patients were transported to hospital for ED pronouncement (16.3 vs. 4.3 min; p &lt; 0.001). Total provider time for field pronouncement was 15.5 min longer (p = 0.004), but field pronouncement consumed 12.0 min less physician time.

Conclusions:

Paramedic pronouncement of death in the field is less costly than transporting patients to hospital for physician pronouncement. Pronouncement in the field requires more paramedic time but less physician time.

The association between manual mode defibrillation, pre-shock pause duration and appropriate shock delivery when employed by basic life support paramedics during out-of-hospital cardiac arrest

BACKGROUND

Pre-shock pause duration of <20s is associated with improved survival after cardiac arrest. Manual mode defibrillation has been associated with the shortest duration of pre-shock pause but is largely practiced by advanced life support paramedics (ALS) whereas defibrillator only paramedics (basic life support or BLS) routinely use the defibrillator in automatic mode.

OBJECTIVE

We sought to explore the relationship between manual mode defibrillation, pre-shock pause duration and rate of inappropriate shocks when defibrillation is provided by ALS vs. BLS trained in manual mode defibrillation.

METHODS

We performed a retrospective review of all treated non-traumatic adult out-of-hospital cardiac arrest (OHCA) presenting in a shockable rhythm over a one year period beginning January 1, 2012. Our primary outcome measure was the proportion of manual mode shocks delivered by BLS with pre-shock pause duration of <20s when compared to ALS. Our secondary outcome measures were the duration of pre-, post- and peri-shock pause and the proportion of appropriate shocks (defined as correct identification and shock delivery to patients in a shockable rhythm) delivered by either level of paramedic. This study had a power of 90% to detect an absolute difference of 15% between paramedic levels in proportion of shocks delivered with pre-shock pause duration <20s.

RESULTS

Among 2019 treated OHCA, 335 (20%) presented in a shockable rhythm. Manual defibrillation was performed in 155 (46%) of these cases (196 shocks by ALS, 143 shocks by BLS). There were no differences in the proportion of shocks delivered with pre-shock pause duration <20s (ALS 82.8% vs. BLS 84.8%, p=.65) nor pre-shock pause duration (s) (median, Q1, Q3); ALS: 12.0 (7.0,17.0) vs. BLS: 11.0 (5.0,17.0), p=.13 while BLS had a significantly shorter peri-shock pause duration (s) (median, Q1, Q3); ALS: 17.0 (12.0, 23.0) vs. BLS: 15.0 (9.0, 22.0), p=.05. There were no differences in the rate of inappropriate shocks (ALS 1.0% vs. BLS 0.7%), p=1.0 between levels of paramedics.

CONCLUSIONS

Manual mode defibrillation by BLS paramedics produced similar measures of pre-shock pause duration when compared to ALS paramedics without increasing the incidence of inappropriate shocks. Further study is required to determine the potential impact of BLS manual mode defibrillation on clinical outcomes.

The impact of peri-shock pause on survival from out-of-hospital shockable cardiac arrest during the Resuscitation Outcomes Consortium PRIMED trial

BACKGROUND

Previous research has demonstrated significant relationships between peri-shock pause and survival to discharge from out-of-hospital shockable cardiac arrest (OHCA).

OBJECTIVE

To determine the impact of peri-shock pause on survival from OHCA during the ROC PRIMED randomized controlled trial.

METHODS

We included patients in the ROC PRIMED trial who suffered OHCA between June 2007 and November 2009, presented with a shockable rhythm and had CPR process data for at least one shock. We used multivariable logistic regression to determine the association between peri-shock pause duration and survival to hospital discharge.

RESULTS

Among 2006 patients studied, the median (IQR) shock pause duration was: pre-shock pause 15s (8, 22); post-shock pause 6s (4, 9); and peri-shock pause 22.0 s (14, 31). After adjusting for Utstein predictors of survival as well as CPR quality measures, the odds of survival to hospital discharge were significantly higher for patients with pre-shock pause <10s (OR: 1.52, 95% CI: 1.09, 2.11) and peri-shock pause <20s (OR: 1.82, 95% CI: 1.17, 2.85) when compared to patients with pre-shock pause ≥ 20s and peri-shock pause ≥ 40s. Post-shock pause was not significantly associated with survival to hospital discharge. Results for neurologically intact survival (Modified Rankin Score ≤ 3) were similar to our primary outcome.

CONCLUSIONS

In patients with cardiac arrest presenting in a shockable rhythm during the ROC PRIMED trial, shorter pre- and peri-shock pauses were significantly associated with higher odds of survival. Future cardiopulmonary education and technology should focus on minimizing all peri-shock pauses.

Clinical events and treatment in prehospital patients with ST-segment elevation myocardial infarction

BACKGROUND

Little is known about clinically important events and advanced care treatment that patients with ST-segment elevation myocardial infarction (STEMI) encounter in the prehospital setting.

OBJECTIVES

We sought to determine the proportion of community patients with STEMI who experienced a clinically important event or received advanced care treatment prior to arrival at a designated percutaneous coronary intervention (PCI) laboratory or emergency department (ED).

METHODS

We reviewed 487 consecutive community patients with STEMI between May 2008 and June 2009. All patients were geographically within a single large "third-service" urban emergency medical services (EMS) system and were transported by paramedics with an advanced care scope of practice. We recorded predefined clinically important events and advanced care treatment that occurred in patients being transported directly to a PCI laboratory or ED (group 1) or interfacility transfer to a PCI laboratory (group 2).

RESULTS

One or more clinically important events occurred in 92 of 342 (26.9%) group 1 patients and nine of 145 (6.2%) group 2 patients. The most common were sinus bradycardia, hypotension, and cardiac arrest. Additionally, 33 of 342 (9.6%) group 1 and nine of 145 (6.2%) group 2 patients received one or more advanced care treatments. The most common were administration of morphine and administration of atropine. Eight group 1 patients and three group 2 patients received cardiopulmonary resuscitation (CPR) or defibrillation.

CONCLUSIONS

Clinically important events and advanced care treatment are common in community STEMI patients undergoing prehospital transport or interfacility transfer to a PCI center. Several patients required CPR or defibrillation. Further research is needed to define the clinical experience of STEMI patients during the out-of-hospital phase and the scope of practice required of EMS providers to safely manage these patients.

Bias in a prehospital esophageal detector device trial: lessons learned

OBJECTIVES

Our goals were to determine whether selection bias occurred in a prehospital study comparing an esophageal detector device (EDD) to a disposable capnometer for detecting esophageal intubation, and to determine whether such a bias would have changed the study's conclusions about EDD effectiveness.

METHODS

In a study of patients requiring prehospital intubation, we determined the sensitivity, specificity and predictive values of the EDD for detecting esophageal intubation. We then compared intubation success rate in patients who were enrolled in the study (n = 129) to that in eligible patients who were excluded from it (n = 107). After finding that the incidence of failed intubation was higher in the "excluded" group, we used sensitivity and specificity parameters derived from the study population to assess whether EDD test characteristics would differ in studied vs. excluded patients.

RESULTS

The first intubation attempt was successful in 125 of 129 study patients and 76 of 107 excluded patients (97% vs. 71%, p = 0.03), confirming the presence of selection bias. The negative predictive value of the EDD for esophageal intubation was 98% in the study cohort and would have been 77% in patients like those excluded (i.e., difficult intubation cases).

CONCLUSIONS

The high "first attempt" intubation success rate seen in this study was due to selective exclusion of failed intubations. This selection bias led to a clinically important overestimation of the EDD's negative predictive value. Bias may substantially alter the estimations of test accuracy reported in scientific studies. To reduce the chance of unrecognized selection bias in studies of diagnostic tests, investigators must determine whether recruited subjects resemble patients in whom the test will ultimately be used.

Serial prehospital 12-lead electrocardiograms increase identification of ST-segment elevation myocardial infarction

BACKGROUND

Many prehospital protocols require acquisition of a single 12-lead electrocardiogram (ECG) when assessing a patient for ST-segment elevation myocardial infarction (STEMI). However, it is known that ECG evidence of STEMI can evolve over time.

OBJECTIVES

To determine how often the first and, if necessary, second or third prehospital ECGs identified STEMI, and the time intervals associated with acquiring these ECGs and arrival at the emergency department (ED).

METHODS

We retrospectively analyzed 325 consecutive prehospital STEMIs identified between June 2008 and May 2009 in a large third-service emergency medical services (EMS) system. If the first ECG did not identify STEMI, protocol required a second ECG just before transport and, if necessary, a third ECG before entering the receiving ED. Paramedics who identified STEMI at any time bypassed participating local EDs, taking patients directly to the percutaneous coronary intervention (PCI) center. Paramedics used computerized ECG interpretation with STEMI diagnosis defined as an "acute MI" report by GE/Marquette 12-SL software in ZOLL E-series defibrillator/cardiac monitors (ZOLL Medical, Chelmsford, MA). We recorded the time of each ECG, and the ordinal number of the diagnostic ECG. We then determined the number of cases and frequency of STEMI diagnosis on the first, second, or third ECG. We also measured the interval between ECGs and the interval from the initial positive ECG to arrival at the ED. Results. STEMI was identified on the first prehospital ECG in 275 cases, on the second ECG in 30 cases, and on the third ECG in 20 cases (cumulative percentages of 84.6%, 93.8%, and 100%, respectively). For STEMIs identified on the second or third ECG, 90% were identified within 25 minutes after the first ECG. The median times from identification of STEMI to arrival at the ED were 17.5 minutes, 11.0 minutes, and 0.7 minutes for STEMIs identified on the first, second, and third ECGs, respectively.

CONCLUSIONS

A single prehospital ECG would have identified only 84.6% of STEMI patients. This suggests caution using a single prehospital ECG to rule out STEMI. Three serial ECGs acquired over 25 minutes is feasible and may be valuable in maximizing prehospital diagnostic yield, particularly where emergent access to PCI exists.

Evidence-based optimization of urban firefighter first response to emergency medical services 9-1-1 incidents

INTRODUCTION

Many emergency medical services (EMS) systems dispatch nonparamedic firefighter first responders (FFRs) to selected EMS 9-1-1 calls, intending to deliver time-sensitive interventions such as defibrillation, cardiopulmonary resuscitation (CPR), and bag-mask ventilation prior to arrival of paramedics. Deciding when to send FFRs is complicated because critical cases are rare, paramedics often arrive before FFRs, and lights-and-siren responses by emergency vehicles are associated with the risk of en-route traffic collisions.

OBJECTIVE

To describe a methodology allowing EMS systems to optimize their own FFR programs using local data, and reflecting local medical oversight policy and local risk-benefit opinion.

METHODS

We constructed a generalized input-output model that retrospectively reviews EMS dispatch and electronic prehospital clinical records to identify a subset of Medical Priority Dispatch System (MPDS) call categories ("determinants") that maximize the opportunities for FFR interventions while minimizing unwarranted responses. Input parameters include local FFR interventions, the local FFR "first-on-scene" rate, and the locally acceptable ratio of risk to benefit. The model uses a receiver-operating characteristic (ROC) curve to identify the optimal mix of response specificity and sensitivity achieved by sending FFRs to progressively more categories of EMS calls while remaining within a defined risk-benefit ratio. The model was applied to a 16-month retrospective sample of 220,358 incidents from a large urban EMS system to compare the model's recommendations with the system's current practices.

RESULTS

The model predicts that FFR lights-and-siren responses in the sample could be reduced by 83%, from 93,058 to 16,091 incidents, by confining FFR responses to 27 of 509 MPDS dispatch determinants, representing 7.3% of incidents but 58.9% of all predicted FFR interventions. Of the 93,058 incidents, another 58,275 incidents could be downgraded to safer nonemergency FFR responses and 18,692 responses could be eliminated entirely, improving the specificity of FFR response from 57.8% to 93.0%.

CONCLUSIONS

This model provides a robust generalized methodology allowing EMS systems to optimize FFR lights-and-siren responses to emergency medical calls. Further validation is warranted to assess the model's generality.

Use of Treat-and-Release Medical Directives for Paramedics at a Mass Gathering

INTRODUCTION

Paramedics provide a substantial proportion of care at mass gatherings but do not typically release patients without physician assessment.

OBJECTIVE

To evaluate treat-and-release medical directives implemented at a large single-day summer rock concert.

METHODS

Medical directives allowed paramedics to administer acetaminophen, dimenhydrinate, diphenhydramine, or polymyxin B ointment for common complaints without evidence of serious illness on history or examination. After treatment, patients were released or transferred to a medical facility according to predefined criteria. Patient demographics, chief complaint, treatment, and disposition were obtained from paramedic records. To determine whether any patients released by paramedic subsequently required ambulance transport, all ambulance records were searched for a period of eight hours before to 24 hours after the event.

RESULTS

More than 450,000 people attended the concert, with 1,870 presenting for medical attention. Four hundred seven patients received medications under the directives. No disposition was recorded in 13 cases. Two hundred ninety-nine patients were treated with acetaminophen, of whom 269 (90.0%) were released and 23 (7.7%) required additional care. Sixty-two patients received dimenhydrinate, 44 (71%) were released, and 14 (23%) required transport. Thirty-six patients received diphenhydramine, and 34 (94%) were released. Ten patients received polymyxin B and were released. No patient released by paramedics was found to have later required ambulance transport.

CONCLUSIONS

Treat-and-release medical directives for paramedics at mass gatherings may help divert patients from requiring care at a medical facility. Future research is needed to determine the safety (morbidity and mortality) of these directives.

Derivation and evaluation of a termination of resuscitation clinical prediction rule for advanced life support providers

OBJECTIVES

The primary aim was to derive a new termination of resuscitation (TOR) clinical prediction rule for advanced life support paramedics (ALS) and to measure both its pronouncement rate and diagnostic test characteristics. Secondary aims included measuring the test characteristics of a previously derived and published basic life support termination of resuscitation (BLS TOR) clinical prediction rule [Morrison LJ, Visentin LM, Kiss A, et al. Validation of a rule for termination of resuscitation in out-of-hospital cardiac arrest. N Engl J Med 2006;355(5):478-87] on the same cohort of patients for comparison purposes.

METHODS

Secondary data analysis of adult cardiac arrests treated by ALS in rural and urban EMS systems participating in the OPALS study (data extracted from Phase III). A previous study for a basic life support termination of resuscitation (BLS TOR) clinical prediction rule proposed Termination of Resuscitation if the patient had no return of spontaneous circulation (ROSC) before transport; no shock administered; EMS personnel did not witness the arrest [Morrison LJ, Visentin LM, Kiss A, et al. Validation of a rule for termination of resuscitation in out-of-hospital cardiac arrest. N Engl J Med 2006;355(5):478-87]. Multivariable logistic regression was used to examine the relationship between these variables, additional Utstein variables, and the primary outcome of survival to hospital discharge. Diagnostic test characteristics were measured for both the ALS TOR and BLS TOR models on this derivation cohort.

RESULTS

Four thousand six hundred and seventy-three cardiac arrest patients were included; 3098 (66%) were male, mean (S.D.) age 69 (15); 239 (5.1%; 95% CI 4.5-5.8) survived to hospital discharge; 3841 patients had no ROSC (82%) and of these only three survived (0.08%; 95% CI 0.02, 0.23). The final ALS TOR model associated with survival, included: ROSC (OR 260.9; 95% CI 96.3, 706.7), bystander witnessed (OR 2.0; 95% CI 1.3, 3.1), bystander CPR (OR 2.8; 95% CI 1.9, 4.1), EMS witnessed (OR 12.3; 95% CI 7.1, 21.3) and shock prior to transport (OR 6.4; 95% CI 4.1, 10.1). A new ALS TOR clinical prediction rule based on these variables was 100% sensitive (95% CI 99.9-100) for survival and had 100% negative predictive value (95% CI 99.9-100) for death. Under the ALS TOR clinical prediction rule, 30% of patients would be pronounced in the field. The BLS TOR clinical prediction rule, was 100% sensitive (95% CI 99.9, 100), had 100% negative predictive value (95% CI 99.9-100) and the field pronouncement rate was 48%.

CONCLUSION

Cardiac arrest patients may be considered for prehospital ALS TOR when there is no ROSC prior to transport, no shock delivered, no bystander CPR and the arrest was not witnessed by bystanders or EMS. A single EMS termination clinical prediction rule for all levels of providers would be optimal for EMS systems to implement. Prospective evaluation of the ALS TOR clinical prediction rule in the hands of ALS providers will be required before implementation.

Comparison of the medical priority dispatch system to an out-of-hospital patient acuity score

BACKGROUND

Although the Medical Priority Dispatch System (MPDS) is widely used by emergency medical services (EMS) dispatchers to determine dispatch priority, there is little evidence that it reflects patient acuity. The Canadian Triage and Acuity Scale (CTAS) is a standard patient acuity scale widely used by Canadian emergency departments and EMS systems to prioritize patient care requirements.

OBJECTIVES

To determine the relationship between MPDS dispatch priority and out-of-hospital CTAS.

METHODS

All emergency calls on a large urban EMS communications database for a one-year period were obtained. Duplicate calls, nonemergency transfers, and canceled calls were excluded. Sensitivity and specificity to detect high-acuity illness, as well as positive predictive value (PPV) and negative predictive value (NPV), were calculated for all protocols.

RESULTS

Of 197,882 calls, 102,582 met inclusion criteria. The overall sensitivity of MPDS was 68.2% (95% confidence interval [CI] = 67.8% to 68.5%), with a specificity of 66.2% (95% CI = 65.7% to 66.7%). The most sensitive protocol for detecting high acuity of illness was the breathing-problem protocol, with a sensitivity of 100.0% (95% CI = 99.9% to 100.0%), whereas the most specific protocol was the one for psychiatric problems, with a specificity of 98.1% (95% CI = 97.5% to 98.7%). The cardiac-arrest protocol had the highest PPV (92.6%, 95% CI = 90.3% to 94.3%), whereas the convulsions protocol had the highest NPV (85.9%, 95% CI = 84.5% to 87.2%). The best-performing protocol overall was the cardiac-arrest protocol, and the protocol with the overall poorest performance was the one for unknown problems. Sixteen of the 32 protocols performed no better than chance alone at identifying high-acuity patients.

CONCLUSIONS

The Medical Priority Dispatch System exhibits at least moderate sensitivity and specificity for detecting high acuity of illness or injury. This performance analysis may be used to identify target protocols for future improvements.

Validation of a rule for termination of resuscitation in out-of-hospital cardiac arrest

BACKGROUND

We prospectively evaluated a clinical prediction rule to be used by emergency medical technicians (EMTs) trained in the use of an automated external defibrillator for the termination of basic life support resuscitative efforts during out-of-hospital cardiac arrest. The rule recommends termination when there is no return of spontaneous circulation, no shocks are administered, and the arrest is not witnessed by emergency medical-services personnel. Otherwise, the rule recommends transportation to the hospital, in accordance with routine practice.

METHODS

The study included 24 emergency medical systems in Ontario, Canada. All patients 18 years of age or older who had an arrest of presumed cardiac cause and who were treated by EMTs trained in the use of an automated external defibrillator were included. The patients were treated according to standard guidelines. Characteristics of diagnostic tests for the prediction rule were calculated. These characteristics include sensitivity, specificity, and positive and negative predictive values.

RESULTS

Follow-up data were obtained for all 1240 patients. Of 776 patients with cardiac arrest for whom the rule recommended termination, 4 survived (0.5 percent). The rule had a specificity of 90.2 percent for recommending transport of survivors to the emergency department and had a positive predictive value for death of 99.5 percent when termination was recommended. Implementation of this rule would result in a decrease in the rate of transportation from 100 percent of patients to 37.4 percent. The addition of other criteria (a response interval greater than eight minutes or a cardiac arrest not witnessed by a bystander) would further improve both the specificity and positive predictive value of the rule but would result in the transportation of a larger proportion of patients.

CONCLUSIONS

The use of a clinical prediction rule for the termination of resuscitation may help clinicians decide whether to terminate basic life support resuscitative efforts in patients having an out-of-hospital cardiac arrest.

Prehospital transcutaneous cardiac pacing for symptomatic bradycardia or bradyasystolic cardiac arrest: A systematic review

BACKGROUND

Advanced cardiac life support (ACLS) guidelines suggest transcutaneous cardiac pacing (TCP) for the treatment of symptomatic bradycardia (SB) and bradyasystolic cardiac arrest (BACA). Many EMS systems are extrapolating these guidelines and employing TCP in the prehospital setting. Our objective was to conduct a systematic review to determine the efficacy of prehospital TCP in the management of these two conditions.

METHODS

MEDLINE (1966-2004), EMBase and Science Citation Index (1980-2004) were searched using: prehospital/emergency medical services; external/transcutaneous; pacing. Two reviewer teams blinded to the source and author conducted a hierarchical selection (title, abstract, article) and quality assessment using a validated scale. Kappa agreement at each level of review was measured. Data abstraction was done by consensus.

RESULTS

Thirty-four articles were identified and seven selected (Kappa agreement; title: 0.85, abstract: 0.78, full article: 0.82). Article quality was poor in all trials. There were three case series (BACA, n=215), three unblinded randomised controlled trials (one BACA, two BACA+SB), and one subgroup (SB) analysis. In the case series of paced BACA patients, 0/215 survived to hospital discharge. In the BACA trials 16/509 (paced) versus14/497 (control) survived to discharge. In a subgroup of one SB trial 5/6 (paced) versus 1/7 (control) survived to discharge (p=0.01). When a SB trial subgroup was combined with a case series 4/27 (paced) versus 0/24 (control) survived to discharge (p=0.07).

CONCLUSIONS

In the prehospital setting, there is no evidence to support the use of TCP in bradyasystolic cardiac arrest. There is inadequate evidence to determine the efficacy of prehospital TCP in the treatment of symptomatic bradycardia.

Prehospital 12-lead electrocardiography impact on acute myocardial infarction treatment times and mortality: a systematic review

OBJECTIVES

Prehospital 12-lead electrocardiogram (PHECG) interpretation and advance emergency department (ED) notification may improve time-to-treatment intervals for a variety of treatment strategies to improve outcome in acute myocardial infarction. Despite consensus guidelines recommending this intervention, few emergency medical services (EMS) employ this. The authors systematically reviewed the literature to report whether mortality or treatment time intervals improved when compared with standard care.

METHODS

The authors used the Cochrane strategy to search MEDLINE, EMBASE, Current Contents, Dissertation Abstracts, Cochrane Library, and Index of Scientific and Technical Proceedings. Bibliographies and grant-agency Websites were reviewed, and primary investigators and industry were contacted for published and unpublished studies. Inclusion criteria included PHECG and advance ED notification versus standard EMS care; controlled trials; English only; and evaluation of treatment time intervals, all-cause mortality, or both. Study selection was hierarchical, blinded, and independent. Agreement at each level of review was evaluated by using a kappa statistic. Study quality was measured with a validated scale and was interpreted by two independent reviewers.

RESULTS

A total of 1,283 citations were identified, and five studies met the inclusion criteria. The weighted kappa for selection was 0.61 (standard error [SE], 0.045) for titles, 0.63 (SE, 0.051) for abstracts, and 0.79 (SE, 0.146) for full articles. Mean study quality measures by two independent reviewers were 6.0/15 and 5.5/15 (correlation coefficient, 0.85; p = 0.06). PHECG and advance ED notification increased the weighted mean on-scene time by 1.2 minutes (95% confidence interval [95% CI] = -0.84 to 3.2). The weighted mean door-to-needle interval was shortened by 36.1 minutes (95% CI = 9.3 to 63.0: range of means, 22-48 minutes vs. 50-97 minutes). One study reported all-cause mortality, with a statistically nonsignificant reduction from 15.6% to 8.4%.

CONCLUSIONS

For patients with AMI, the literature would suggest that PHECG and advanced ED notification reduces in hospital time to fibrinolysis. One controlled trial found no difference in mortality with this out-of-hospital intervention.

A Canadian fellowship training program in emergency medical services

Emergency medical services (EMS) is increasingly recognized to be an integral part of the health care system. Given the expanding role and scope of EMS, there is need for structured education of emergency physicians interested in pursuing subspecialization in EMS. In 2001, a group of academic emergency specialists at the University of Toronto developed the first Canadian EMS Fellowship Program. This paper describes the development, current status, and future directions of this Program. The University of Toronto EMS Fellowship Program may serve as a template for the development of similar programs elsewhere in Canada and internationally.

A paramedic-staffed medical rehydration unit at a mass gathering

INTRODUCTION

Heat-related illness is reported to be a significant cause of morbidity at outdoor mass gatherings during warm weather. Paramedics are traditionally present at mass gatherings to provide prehospital care for people in need.

OBJECTIVES

To describe a paramedic-staffed medical rehydration unit and a new role for paramedics at a mass gathering attended by more than 450,000 people.

METHODS

A 48-bed medical rehydration unit was deployed adjacent to the main field hospital. Paramedics admitted patients to the unit if they met predetermined criteria for mild to moderate heat-related illness. Each paramedic was responsible for four beds. Paramedics initiated oral and intravenous rehydration therapy by following medical directives. Emergency medical services (EMS) physicians reviewed patients before discharge.

RESULTS

The medical rehydration unit managed 143 patients (3/10,000 attendees). The mean number of patients admitted per hour was nine. The average age was 24 years; 103 (72%) were female. The main presenting complaint was syncope, presyncope, or dizziness in 43 (30%). Forty-four (31%) patients received parenteral and oral fluids; the remainder received oral fluids alone. The average length of stay was 94 minutes (95% CI 82-106). One hundred seven (75%) patients were discharged, 17 (12%) were transferred to the main field hospital, four (3%) left against medical advice, and two (1%) required transfer to a hospital off site. In 13 (9%) cases, records of patient disposition were incomplete.

CONCLUSIONS

This article defines a new role for paramedics and describes the operation of a medical rehydration unit at a large, single-day mass gathering in summer.

Loss of paramedic availability in an urban emergency medical services system during a severe acute respiratory syndrome outbreak

OBJECTIVES

To describe the loss of paramedic availability to Toronto Emergency Medical Services during a biphasic (SARS-1 and SARS-2) outbreak of severe acute respiratory syndrome (SARS).

METHODS

During the SARS outbreak, a dedicated paramedic surveillance and quarantine program was developed. The authors determined the number of paramedics on quarantine each day, the type of quarantine (either home quarantine [HQ] or work quarantine [WQ]), and the development of SARS-like symptoms.

RESULTS

During the SARS outbreak, there were five cases of probable SARS and three cases of suspect SARS. SARS-1 lasted 30 days, during which 234 paramedics were placed on HQ. The total number of HQ days was 1,615. During the five peak days of SARS-1, the total number of HQ days was 664. SARS-2 lasted 18 days, during which 292 paramedics were placed on either HQ or WQ, for a combined number of quarantine days of 1,637. During the five peak days of SARS-2, the combined number of quarantine days was 910. Of these, paramedics were available for duty on 708 days (78%) due to the WQ program. The primary reason for quarantine was unprotected exposure to a health care institution experiencing a SARS outbreak. Under quarantine, SARS-like symptoms developed in 68 paramedics, including cough (53 [78%]), myalgia (33 [48%]), fatigue (30 [44%]), headache (29 [43%]), fever (11 [16%]), and shortness of breath (7 [10%]).

CONCLUSIONS

Paramedics were among the health care workers who developed SARS. During SARS-2, WQ optimized the number of days on which paramedics were available for duty. Many paramedics developed SARS-like symptoms without being diagnosed as having SARS. A dedicated paramedic surveillance and quarantine program provided a useful means to manage the paramedic resource during the SARS outbreak.

Derivation of a termination-of-resuscitation guideline for emergency medical technicians using automated external defibrillators

OBJECTIVES

To determine the association between characteristics of cardiac arrest and survival to hospital discharge following failed resuscitation by defibrillation-trained emergency medical technicians (EMT-Ds), and to propose an out-of-hospital termination-of-resuscitation (TOR) guideline for EMT-Ds.

METHODS

A 22-month retrospective review of 700 out-of-hospital primary cardiac arrest patients in a large emergency medical services (EMS) system who received exclusively EMT-D care.

RESULTS

Seven hundred primary cardiac arrest patients were identified. Follow-up was obtained in 662 cases (94.6%). Of these, 36 (5.4%) achieved a return of spontaneous circulation (ROSC) prior to transport. Among the 626 patients who failed to achieve ROSC at any time, two (0.3%) survived to discharge. Multivariate analysis showed that ROSC at any time had the strongest association with survival [odds ratio (OR) 45.5; 95% confidence interval (95% CI) = 8.5 to 243.7]. A shock prior to transport (OR 6.9; 95% CI = 1.2 to 40.3) and cardiac arrest witnessed by EMS personnel (OR 4.4; 95% CI = 1.0 to 18.5) were also independently associated with survival. These variables were incorporated into a TOR guideline. The guideline was 100% sensitive (95% CI = 99.1 to 100) in identifying survivors and had 100% negative predictive value (95% CI = 75.3 to 100) for identifying nonsurvivors of out-of-hospital cardiac arrest in the study population.

CONCLUSIONS

In this EMS system, cardiac arrest patients may be considered for out-of-hospital TOR following EMT-D resuscitation attempts when there has been no ROSC, no shock has been given, and the arrest was not witnessed by EMS personnel. These guidelines require prospective validation.

Prehospital emergency medical services

OBJECTIVES

Our primary objectives were to estimate how frequently emergency medical technicians with defibrillation skills (EMT-Ds) are forced to deal with prehospital do-not-resuscitate (DNR) orders, to assess their comfort in doing so, and to describe the prehospital care provided to patients with DNR orders in a system without a prehospital DNR policy (i.e., where resuscitation is mandatory).

METHODS

Using Dillman methodology, the authors developed a 13-item survey and mailed it to 382 of 764 EMT-Ds in the metropolitan Toronto area. Responses were evaluated using 5-point Likert scales, limited-option and open-ended questions. Narrative responses were categorized. Two authors independently categorized narrative responses from 20 surveys, and kappa values for agreement beyond chance were determined.

RESULTS

Among 382 EMT-Ds surveyed, 236 (62%) responded, of whom 221 (94%) answered the questionnaire. Overall, 126 of 219 (58%) indicated that they were called to resuscitate patients with DNR orders "sometimes," "frequently," or "all the time." In such situations, 22 of 207 (11%) stated they would honour the DNR order and 55 of 207 (27%) would honour the order but appear to provide basic resuscitation, in order to adhere to mandatory resuscitation regulations. Willingness to honour a DNR order did not vary by years of emergency medical service. EMT-Ds cited concern for the family and the patient, fear of repercussions and conflict with personal ethics as key factors contributing to this ethical dilemma. If legally allowed to honour DNR orders, 212 of 221 (96%) respondents would be comfortable with a written order and 137 of 220 (62%) with a verbal order.

CONCLUSIONS

Prehospital DNR orders are common, and a significant number of EMT-Ds disregard current regulations by honouring them. EMT-Ds would be more comfortable with written than verbal DNR orders. An ethical prehospital DNR policy should be developed and applied.