Effect of prehospital induction of mild hypothermia on survival and neurological status among adults with cardiac arrest: a randomized clinical trial.

IMPORTANCE: Hospital cooling improves outcome after cardiac arrest, but prehospital cooling immediately after return of spontaneous circulation may result in better outcomes. OBJECTIVE: To determine whether prehospital cooling improves outcomes after resuscitation from cardiac arrest in patients with ventricular fibrillation (VF) and without VF. DESIGN, SETTING, AND PARTICIPANTS: A randomized clinical trial that assigned adults with prehospital cardiac arrest to standard care with or without prehospital cooling, accomplished by infusing up to 2 L of 4°C normal saline as soon as possible following return of spontaneous circulation. Adults in King County, Washington, with prehospital cardiac arrest and resuscitated by paramedics were eligible and 1359 patients (583 with VF and 776 without VF) were randomized between December 15, 2007, and December 7, 2012. Patient follow-up was completed by May 1, 2013. Nearly all of the patients resuscitated from VF and admitted to the hospital received hospital cooling regardless of their randomization. MAIN OUTCOMES AND MEASURES: The primary outcomes were survival to hospital discharge and neurological status at discharge. RESULTS: The intervention decreased mean core temperature by 1.20°C (95% CI, -1.33°C to -1.07°C) in patients with VF and by 1.30°C (95% CI, -1.40°C to -1.20°C) in patients without VF by hospital arrival and reduced the time to achieve a temperature of less than 34°C by about 1 hour compared with the control group. However, survival to hospital discharge was similar among the intervention and control groups among patients with VF (62.7% [95% CI, 57.0%-68.0%] vs 64.3% [95% CI, 58.6%-69.5%], respectively; P = .69) and among patients without VF (19.2% [95% CI, 15.6%-23.4%] vs 16.3% [95% CI, 12.9%-20.4%], respectively; P = .30). The intervention was also not associated with improved neurological status of full recovery or mild impairment at discharge for either patients with VF (57.5% [95% CI, 51.8%-63.1%] of cases had full recovery or mild impairment vs 61.9% [95% CI, 56.2%-67.2%] of controls; P = .69) or those without VF (14.4% [95% CI, 11.3%-18.2%] of cases vs 13.4% [95% CI,10.4%-17.2%] of controls; P = .30). Overall, the intervention group experienced rearrest in the field more than the control group (26% [95% CI, 22%-29%] vs 21% [95% CI, 18%-24%], respectively; P = .008), as well as increased diuretic use and pulmonary edema on first chest x-ray, which resolved within 24 hours after admission. CONCLUSION AND RELEVANCE: Although use of prehospital cooling reduced core temperature by hospital arrival and reduced the time to reach a temperature of 34°C, it did not improve survival or neurological status among patients resuscitated from prehospital VF or those without VF. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT00391469.

Understanding of sepsis among emergency medical services: a survey study.

BACKGROUND: Emergency medical services (EMS) personnel commonly encounter sepsis, yet little is known about their understanding of sepsis. STUDY OBJECTIVES: To determine the awareness, knowledge, current practice, and attitudes about sepsis among EMS personnel. METHODS: We performed an anonymous, multi-agency, online survey of emergency medical technicians (EMTs), firefighter-emergency medical technicians (FF-EMTs), and paramedics in a metropolitan, 2-tier EMS system. We compared responses according to the level of EMS training and used multivariable logistic regression to determine the odds of correctly identifying the definition of sepsis, independent of demographic and professional factors. RESULTS: Overall response rate of study participants was 57% (786/1390), and was greatest among EMTs (79%; 276/350). A total of 761 respondents (97%) had heard of the term "sepsis." EMTs and FF-EMTs were at significantly reduced odds of correctly defining sepsis compared to paramedics, independent of age, sex, and years of experience (EMTs: odds ratio 0.44, 95% confidence interval 0.3-0.8; FF-EMTs: odds ratio 0.32, 95% confidence interval 0.2-0.6. Overall, knowledge of the clinical signs and symptoms and recommended treatments for sepsis was typically>75%, though better among paramedics than EMTs or FF-EMTs (p<0.01). The majority of respondents believed sepsis is not recognized by EMS "some" or "a lot" of the time (76%, 596/786). CONCLUSIONS: EMS personnel demonstrated an overall sound awareness of sepsis. Knowledge of sepsis was less among FF-EMTs and EMTs compared to paramedics. These results suggest that paramedics could be integrated into strategies of early identification and treatment of sepsis, and EMTs may benefit from focused education and training.

The association between obesity and difficult prehospital tracheal intubation.

BACKGROUND: Nonphysician advanced life support (ALS) providers often perform tracheal intubation (TI) for cardiac arrest or other life-threatening indications in the prehospital setting, where airway assessment and airway management tools are limited. However, the frequency of difficult TI in obese patients in this setting is unclear. In this study we determined factors associated with TI success, and determined TI difficulty as a function of body mass index (BMI) in a system of ALS providers experienced in TI, to guide future prehospital education efforts. METHODS: A retrospective review was performed of all patients ≥15 years of age who underwent prehospital TI by paramedics in the Seattle Medic One system over a 4-year period, and were transported to the regional level 1 trauma center (Harborview Medical Center). Data were abstracted from a prospectively collected prehospital airway management database and from the hospital medical records, including demographic information, number of TI attempts, TI success or failure, and body weight/height (BMI). Descriptive statistics and multivariable logistic regression were calculated, with the primary end point being difficult TI (defined as ≥4 TI attempts or the need to use an alternative airway management technique). RESULTS: Of 80,501 patient contacts in whom 4114 TIs were attempted during the 4-year study period, 823 met study entry criteria (including a calculable BMI). The overall TI success rate in the study population was 98.5% (811 out of 823), with 6.8% (56 out of 823) meeting the predetermined definition for difficult TI. There was no significant association between difficult TI and patient age, gender, use of succinylcholine, or medical diagnosis (trauma vs. nontrauma). In comparison with the lean patient subgroup (BMI <30 kg/m(2)), patients with class III obesity (BMI >40 kg/m(2)) had a significant association with difficult TI (odds ratio 3.68; confidence interval [CI] 1.27-10.59), whereas those with class I/II obesity (BMI ≥30 kg/m(2) and <40 kg/m(2)) did not (odds ratio 0.98; CI 0.46 -2.07). CONCLUSIONS: Among prehospital ALS providers with previously documented and published successful TI performance, increased difficulty with TI was observed in patients with extreme obesity, but not in patients with lesser degrees of obesity. Because extreme obesity is an easily identifiable patient characteristic, didactic and clinical (e.g., operating room) airway management education for such providers should emphasize airway management challenges and strategies associated with obesity, including specific equipment, patient positioning, and practice recommendations that may facilitate both TI and alternative airway management techniques in this population.

Paramedic training for proficient prehospital endotracheal intubation.

BACKGROUND: Emergency airway management is an important component of resuscitation of critically ill patients. Multiple studies demonstrate variable endotracheal intubation (ETI) success by prehospital providers. Data describing how many ETI training experiences are required to achieve high success rates are sparse. OBJECTIVES: To describe the relationship between the number of prehospital ETI experiences and the likelihood of success on subsequent ETI and to specifically look at uncomplicated first-pass ETI in a university-based training program with substantial resources. METHODS: We conducted a secondary analysis of a prospectively collected cohort of paramedic student prehospital intubation attempts. Data collected on prehospital ETIs included indication, induction agents, number of direct laryngoscopy attempts, and advanced airway procedures performed. We used multivariable generalized estimating equations (GEE) analysis to determine the effect of cumulative ETI experience on first-pass and overall ETI success rates. RESULTS: Over a period of three years, 56 paramedic students attempted 576 prehospital ETIs. The odds of overall ETI success were associated with cumulative ETI experience (odds ratio [OR] 1.097 per encounter, 95% confidence interval [CI] = 1.026-1.173, p = 0.006). The odds of first-pass ETI success were associated with cumulative ETI experience (OR 1.061 per encounter, 95% CI = 1.014-1.109, p = 0.009). CONCLUSION: In a training program with substantial clinical opportunities and resources, increased ETI success rates were associated with increasing clinical exposure. However, first-pass placement of the ETT with a high success rate requires high numbers of ETI training experiences that may exceed the number available in many training programs.

Sodium azide-associated laryngospasm after air bag deployment.

The advent and incorporation of the air bag into motor vehicles has resulted in the mitigation of many head and truncal injuries in motor vehicle collisions. However, air bag deployment is not risk free. We present a case of sodium azide-induced laryngospasm after air bag deployment. An unrestrained male driver was in a moderate-speed motor vehicle collision with air bag deployment. Medics found him awake, gasping for air with stridorous respirations and guarding his neck. The patient had no external signs of trauma and was presumed to have tracheal injury. The patient was greeted by the Anesthesiology service, which intubated him using glidescope-assisted laryngoscopy. The patient was admitted for overnight observation and treatment of alkaline ocular injury and laryngospasm. Although air bags represent an important advance in automobile safety, their use is not without risk. Bruising and tracheal rupture secondary to air bag deployment have been reported in out-of-position occupants. Additionally, alkaline by-products from the combustion of sodium azide in air bags have been implicated in ocular injury and facial burns. Laryngospasm after sodium azide exposure presents another diagnostic challenge for providers. Therefore, it is incumbent to maintain vigilance in the physical examination and diagnosis of occult injuries after air bag deployment.

Clinical trials in the out-of-hospital setting: rationale and strategies for successful implementation.

Cardiopulmonary arrest and trauma are two of the major epidemics of our time. In most cases, the final outcome is altered, for better or for worse, by how interventions are provided in the prehospital setting, making that venue critical for lifesaving community research efforts. In certain venues, out-of-hospital emergency medical services personnel are highly skilled at managing resuscitations and routinely operate under strict, highly scrutinized protocols, resulting in extraordinary study compliance. Larger patient enrollment derived from population-based investigations can lead to faster study completion, less selection bias, higher-powered data, and enhanced subgroup analysis. Most importantly, the concomitant training, expert protocol development, and rigid scrutiny all lead to improved patient outcomes, regardless of study intervention. For successful implementation, emergency medical services personnel should be involved in study design, and utilize routine, automated data collection. Technologies should be provided that simplify tasks and diminish confounding variables. Considering that exception to informed consent is a critical component, prospective education and involvement of the medical community, community leaders, employee groups and the media, long before protocol implementation, is essential. Such efforts should be led by respected, academically authoritative, grassroots emergency medical services medical directors and trauma chiefs, preferably those based at the main trauma centers or public receiving facilities.

Active surface cooling protocol to induce mild therapeutic hypothermia after out-of-hospital cardiac arrest: a retrospective before-and-after comparison in a single hospital.

OBJECTIVE: To evaluate whether implementation of a therapeutic hypothermia protocol on arrival in a community hospital improved survival and neurologic outcomes in patients initially found to have ventricular fibrillation, pulseless electrical activity, or asystole, and then successfully resuscitated from out-of-hospital cardiac arrest. DESIGN: A retrospective study of patients who presented after implementation of a therapeutic hypothermia protocol compared with those who presented before the protocol was implemented. SETTING: Harborview Medical Center, Seattle, WA. PATIENTS: A total of 491 consecutive adults with out-of-hospital, nontraumatic cardiac arrest who presented between January 1, 2000 and December 31, 2004. INTERVENTIONS: An active cooling therapeutic hypothermia protocol, using ice packs, cooling blankets, or cooling pads to achieve a temperature of 32 degrees C to 34 degrees C was initiated on November 18, 2002 for unconscious patients resuscitated from cardiac arrest. MEASUREMENTS AND MAIN RESULTS: Demographics and outcomes were obtained from medical records and an emergency medical database. The primary outcomes were survival and favorable neurologic outcome at discharge associated with the therapeutic hypothermia protocol. An adjusted analysis was performed, using a multivariate regression. During the therapeutic hypothermia period, 204 patients were brought to the emergency department; of these 204 patients, 132 (65%) ultimately achieved temperatures of <34 degrees C. Of the 72 patients who did not achieve goal temperatures: 40 (20%) died in the emergency department or shortly after being admitted to the hospital, 15 (7%) regained consciousness, four (2%) had contraindications, 13 (6%) had temperature increase or did not have documented use of the therapeutic hypothermia protocol. In the prior period, none of the 287 patients received active cooling. Patients admitted in the therapeutic hypothermia period had a mean esophageal temperature of 34.1 degrees C during the first 12 hrs compared with 35.2 degrees C in the pretherapeutic hypothermia period (p < .01). Survival to hospital discharge improved in the therapeutic hypothermia period in patients with an initial rhythm of ventricular fibrillation (odds ratio, 1.88, 95% confidence interval, 1.03-3.45), however not in patients with nonventricular fibrillation (odds ratio, 1.17, 95% confidence interval, 0.66-2.05). In adjusted analysis, ventricular fibrillation patients during the therapeutic hypothermia period trended toward improved survival (odds ratio, 1.71, 95% confidence interval, 0.85-3.46) and had favorable neurologic outcome (odds ratio, 2.62, 95% confidence interval, 1.1-6.27) compared with the earlier period. This benefit was not observed in patients whose initial rhythm was pulseless electrical activity or asystole. CONCLUSIONS: The therapeutic hypothermia period was associated with a significant improvement in neurologic outcomes in patients whose initial rhythm was ventricular fibrillation, but not in patients with other rhythms.

The utility of early end-tidal capnography in monitoring ventilation status after severe injury.

BACKGROUND: An arterial CO2 (Paco2) of 30 mm Hg to 39 mm Hg has been shown to be the ideal target range for early ventilation in trauma patients; however, this requires serial arterial blood gases. The use of end-tidal capnography (EtCO2) has been recommended as a surrogate measure of ventilation in the prehospital arena. This is based on the observation of close EtCO2 Pa(CO2) correlation in healthy patients, yet trauma patients frequently suffer from impaired pulmonary ventilation/perfusion. Thus, we hypothesize that EtCO2 will demonstrate a poor reflection of actual ventilation status after severe injury. METHODS: Prospective observational study on consecutive intubated trauma patients treated in our emergency department (ED) during 9 months. Arterial blood gas values and concomitant EtCO2 levels were recorded. Regression was used to determine the strength of correlation among all trauma patients and subgroups based on injury severity (Abbreviated Injury Score and Injury Severity Score) and physiologic markers of perfusion status (lactate, shock index, and arterial base deficit). RESULTS: During 9 months, 180 patients were evaluated. The EtCO2 Paco2 correlation was poor at R2 = 0.277. Patients ventilated in the recommended EtCO2 (range, 35 to 40) were likely to be under ventilated (Pa(CO2) > 40 mm Hg) 80% of the time, and severely under ventilated (Pa(CO2) > 50 mm Hg) 30% of the time. Correlation was best for patients with isolated traumatic brain injury and worst for those with evidence of poor tissue perfusion. CONCLUSION: EtCO2 has low correlation with Pa(CO2), and therefore should not be used to guide ventilation in intubated trauma patients in the ED. Better strategies for guiding prehospital and ED ventilation are needed.

Prehospital management of the difficult airway: a prospective cohort study.

The role of prehospital endotracheal intubation (ETI) remains controversial, with significant national variability in practice. The purpose of this project was to evaluate ETI management in a system of advanced life support (ALS) providers experienced in ETI and other advanced airway techniques, and describe management and outcomes of patients with a "difficult airway." Data were collected prospectively for all ETIs performed by the fire department over a 4-year period (2001-2005), and included demographics, number of laryngoscopy attempts, airway procedures, complications, and outcomes. Of 80,501 ALS patient contacts, 4091 (5.1%) underwent attempted oral ETI, with a 96.8% success rate in four or fewer attempts. The difficult airway cohort included 130 patients (3.2%), whose airway management consisted of oral ETI after more than four attempts (46%), bag-valve-mask ventilation (33%), cricothyroidotomy (8%), retrograde ETI (5%), and digital ETI (1%). Procedural success rates ranged from 14% (digital ETI) to 91% (cricothyroidotomy). Nine patients (7%) had failed airway management, of whom 5 were found in cardiac arrest. The two most common reasons subjectively reported by ALS providers for airway difficulty were anterior trachea (39%) and small mouth (30%). Overall mortality for the difficult airway cohort was 44%. Prehospital ETI can be performed with a high success rate by experienced ALS providers, but may still require advanced airway techniques in a small subset of patients. Patient anatomy is a primary factor in failed ETI. Among the advanced procedures, cricothyroidotomy had the highest success rate and should not be delayed by other interventions.

Pilot randomized clinical trial of prehospital induction of mild hypothermia in out-of-hospital cardiac arrest patients with a rapid infusion of 4 degrees C normal saline.

BACKGROUND: Although delayed hospital cooling has been demonstrated to improve outcome after cardiac arrest, in-field cooling started immediately after the return of spontaneous circulation may be more beneficial. The aims of the present pilot study were to assess the feasibility, safety, and effectiveness of in-field cooling. METHODS AND RESULTS: We determined the effect on esophageal temperature, before hospital arrival, of infusing up to 2 L of 4 degrees C normal saline as soon as possible after resuscitation from out-of-hospital cardiac arrest. A total of 125 such patients were randomized to receive standard care with or without intravenous cooling. Of the 63 patients randomized to cooling, 49 (78%) received an infusion of 500 to 2000 mL of 4 degrees C normal saline before hospital arrival. These 63 patients experienced a mean temperature decrease of 1.24+/-1 degrees C with a hospital arrival temperature of 34.7 degrees C, whereas the 62 patients not randomized to cooling experienced a mean temperature increase of 0.10+/-0.94 degrees C (P<0.0001) with a hospital arrival temperature of 35.7 degrees C. In-field cooling was not associated with adverse consequences in terms of blood pressure, heart rate, arterial oxygenation, evidence for pulmonary edema on initial chest x-ray, or rearrest. Secondary end points of awakening and discharged alive from hospital trended toward improvement in ventricular fibrillation patients randomized to in-field cooling. CONCLUSIONS: These pilot data suggest that infusion of up to 2 L of 4 degrees C normal saline in the field is feasible, safe, and effective in lowering temperature. We propose that the effect of this cooling method on neurological outcome after cardiac arrest be studied in larger numbers of patients, especially those whose initial rhythm is ventricular fibrillation.

Emergency department ventilation effects outcome in severe traumatic brain injury.

BACKGROUND: Recently, we have demonstrated that patients with traumatic brain injury (TBI) with an arrival PaCo2 30 to 35 mm Hg have improved outcome compared with those outside this target range. We sought to determine whether achieving ventilation into a target range would translate into better outcomes in patients with TBI. METHODS: Data were retrospectively reviewed for all trauma prehospital intubations during a period of 24 months (n = 851). Targeted ventilation was defined as a PaCo2 between 30 and 39 mm Hg. Arterial blood gases collected within 15 minutes of patient arrival were assessed and compared with subsequent arterial blood gases to determine patient's ventilation status over time. RESULTS: There was no difference in patient demographics between various ventilation groups. Patients with TBI who achieved the target range had a mortality of 21.2% compared with 33.7% for those who persistently remained outside this range (p = 0.03). Logistic regression demonstrated a trend toward lower mortality for those TBI patients who achieved the target range while in the emergency department (odds ratio 0.33, 95% confidence interval 0.15-0.75). CONCLUSION: Optimal outcome is achieved when the patient is in the target ventilation range on arrival and remains within it. Ventilation status in trauma patients should be closely monitored after intubation to develop an optimal ventilation strategy for patients with severe TBI.

Transthoracic incremental monophasic versus biphasic defibrillation by emergency responders (TIMBER): a randomized comparison of monophasic with biphasic waveform ascending energy defibrillation for the resuscitation of out-of-hospital cardiac arrest due to ventricular fibrillation.

BACKGROUND: Although biphasic, as compared with monophasic, waveform defibrillation for cardiac arrest is increasing in use and popularity, whether it is truly a more lifesaving waveform is unproven. METHODS AND RESULTS: Consecutive adults with nontraumatic out-of-hospital ventricular fibrillation cardiac arrest were randomly allocated to defibrillation according to the waveform from automated external defibrillators administered by prehospital medical providers. The primary event of interest was admission alive to the hospital. Secondary events included return of rhythm and circulation, survival, and neurological outcome. Providers were blinded to automated defibrillator waveform. Of 168 randomized patients, 80 (48%) and 68 (40%) consistently received only monophasic or biphasic waveform shocks, respectively, throughout resuscitation. The prevalence of ventricular fibrillation, asystole, or organized rhythms at 5, 10, or 20 seconds after each shock did not differ significantly between treatment groups. The proportion of patients admitted alive to the hospital was relatively high: 73% in monophasic and 76% in biphasic treatment groups (P=0.58). Several favorable trends were consistently associated with receipt of biphasic waveform shock, none of which reached statistical significance. Notably, 27 of 80 monophasic shock recipients (34%), compared with 28 of 68 biphasic shock recipients (41%), survived (P=0.35). Neurological outcome was similar in both treatment groups (P=0.4). Earlier administration of shock did not significantly alter the performance of one waveform relative to the other, nor did shock waveform predict any clinical outcome after multivariate adjustment. CONCLUSIONS: No statistically significant differences in outcome could be ascribed to use of one waveform over another when out-of-hospital ventricular fibrillation was treated.

The impact of prehospital ventilation on outcome after severe traumatic brain injury.

BACKGROUND: Prehospital intubation has been challenged on the grounds that it predisposes to hyperventilation, which is detrimental after traumatic brain injury (TBI), and impairs venous return in patients with hypovolemia. We sought to determine the incidence of hyperventilation among a cohort of trauma patients undergoing prehospital intubation and the impact of ventilation on outcome after severe TBI. METHODS: Data were prospectively collected for all intubated trauma patients transported directly from the field for a period of 14 months (n = 574). An arrival Pco2 <30 mm Hg was termed severe hypocapnea and considered a marker of hyperventilation. Patients with a Pco2 >45 mm Hg were considered severely hypercapneic. Targeted ventilation was defined as a Pco2 between 30 and 35 mm Hg based on the Brain Trauma Foundation guidelines. RESULTS: The rate of severe hypocapnea was 18% and women were more likely to be hyperventilated (p < 0.05). Patients with severe hypercapnia had higher Injury Severity Scores and were more likely hypotensive, hypoxic, and acidodic (p < 0.05). Patients in the targeted ventilation range were less likely to die than were those outside the range even after excluding the severe hypercapnea group (odds ratio, 0.57; 95% confidence interval, 0.33-0.99). This effect was even greater among patients with isolated TBI (odds ratio, 0.31; 95% confidence interval, 0.10-0.96). CONCLUSION: Targeted prehospital ventilation is associated with lower mortality after severe TBI.

Pilot study of rapid infusion of 2 L of 4 degrees C normal saline for induction of mild hypothermia in hospitalized, comatose survivors of out-of-hospital cardiac arrest.

BACKGROUND: Recent clinical studies have demonstrated that mild hypothermia (32 degrees C to 34 degrees C) induced by surface cooling improves neurological outcome after resuscitation from out-of-hospital cardiac arrest. Results from animal models suggest that the effectiveness of mild hypothermia could be improved if initiated as soon as possible after return of spontaneous circulation. Infusion of cold, intravenous fluid has been proposed as a safe, effective, and inexpensive technique to induce mild hypothermia after cardiac arrest. METHODS AND RESULTS: In 17 hospitalized survivors of out-of-hospital cardiac arrest, we determined the effect on temperature and hemodynamics of infusing 2 L of 4 degrees C cold, normal saline during 20 to 30 minutes into a peripheral vein with a high-pressure bag. Data on vital signs, electrolytes, arterial blood gases, and coagulation were collected before and after fluid infusion. Cardiac function was assessed by transthoracic echocardiography before fluid administration and 1 hour after infusion. Passive (fans, leaving patient uncovered) or active (cooling blankets, neuromuscular blockade) cooling measures were used to maintain mild hypothermia for 24 hours. Infusion of 2 L of 4 degrees C cold, normal saline resulted in a mean temperature drop of 1.4 degrees C 30 minutes after the initiation of infusion. Rapid infusion of fluid was not associated with clinically important changes in vital signs, electrolytes, arterial blood gases, or coagulation parameters. The initial mean ejection fraction was 34%, and fluid infusion did not affect ejection fraction or increase central venous pressure, pulmonary pressures, or left atrial filling pressures as assessed by echocardiography. Passive measures were ineffective in maintaining hypothermia compared with active measures. CONCLUSIONS: Infusion of 2 L of 4 degrees C cold, normal saline is safe and effective in rapidly lowering body temperature in survivors of out-of-hospital cardiac arrest.

Public access defibrillation in out-of-hospital cardiac arrest: a community-based study.

BACKGROUND: The dissemination and use of automated external defibrillators (AEDs) beyond traditional emergency medical services (EMS) into the community has not been fully evaluated. We evaluated the frequency and outcome of non-EMS AED use in a community experience. METHODS AND RESULTS: The investigation was a cohort study of out-of-hospital cardiac arrest cases due to underlying heart disease treated by public access defibrillation (PAD) between January 1, 1999, and December 31, 2002, in Seattle and surrounding King County, Washington. Public access defibrillation was defined as out-of-hospital cardiac arrest treated with AED application by persons outside traditional emergency medical services. The EMS of Seattle and King County developed a voluntary Community Responder AED Program and registry of PAD AEDs. During the 4 years, 475 AEDs were placed in a variety of settings, and more than 4000 persons were trained in cardiopulmonary resuscitation and AED operation. A total of 50 cases of out-of-hospital cardiac arrest were treated by PAD before EMS arrival, which represented 1.33% (50/3754) of all EMS-treated cardiac arrests. The proportion treated by PAD AED increased each year, from 0.82% in 1999 to 1.12% in 2000, 1.41% in 2001, and 2.05% in 2002 (P=0.019, test for trend). Half of the 50 persons treated with PAD survived to hospital discharge, with similar survival for nonmedical settings (45% [14/31]) and out-of-hospital medical settings (58% [11/19]). CONCLUSIONS: PAD was involved in only a small but increasing proportion of out-of-hospital cardiac arrests.

Cell membrane trans-fatty acids and the risk of primary cardiac arrest.

BACKGROUND: The relation of trans-fatty acid intake to life-threatening arrhythmias and primary cardiac arrest is unknown. METHODS AND RESULTS: We investigated the association of trans-fatty acid intake, assessed through a biomarker, with the risk of primary cardiac arrest in a population-based case-control study. Cases, aged 25 to 74 years, were out-of-hospital cardiac arrest patients attended by paramedics in Seattle, Washington from 1988 to 1999 (n=179). Controls, matched to cases by age and sex, were randomly identified from the community (n=285). Participants were free of previous clinically diagnosed heart disease. Blood was obtained at the time of cardiac arrest (cases) or at the time of an interview (controls) to assess trans-fatty acid intake. Higher total trans-fatty acids in red blood cell membranes was associated with a modest increase in the risk of primary cardiac arrest after adjustment for medical and lifestyle risk factors (odds ratio for interquintile range, 1.5; 95% CI, 1.0 to 2.1). However, trans isomers of oleic acid were not associated with risk (odds ratio for interquintile range, 0.8; 95% CI, 0.5 to 1.2), whereas higher levels of trans isomers of linoleic acid were associated with 3-fold increase in risk (odds ratio for interquintile range, 3.1; 95% CI, 1.7 to 5.4). CONCLUSIONS: These findings suggest that dietary intake of total trans-fatty acids is associated with modest increase and trans isomers of linoleic acid with a larger increase in the risk of primary cardiac arrest. These associations need to be confirmed in future studies that distinguish between trans isomers of linoleic acid and trans isomers of oleic acid.

Automated external defibrillators: to what extent does the algorithm delay CPR?

STUDY OBJECTIVE: Maximizing cardiopulmonary resuscitation (CPR) during resuscitation may improve survival. Resuscitation protocols stack up to 3 shocks to achieve defibrillation, followed by an immediate postdefibrillation pulse check. The purpose of this study is to evaluate outcomes of rhythm reanalyses immediately after shock, stacked shocks, and initial postshock pulse checks in relation to achieving a pulse and initiating CPR. METHODS: We conducted an observational study of patients with ventricular fibrillation treated by first-tier emergency medical services (EMS). We collected data from EMS, dispatch, and hospital records. Additionally, we analyzed automatic external defibrillator recordings to determine the proportion of cardiac arrest victims who were defibrillated and achieved a pulse according to shock number (single versus stacked shock), proportion of victims with a pulse during the initial postdefibrillation pulse check, and interval from initial shock to CPR. RESULTS: The study included 481 cardiac arrest subjects. Automatic external defibrillators terminated ventricular fibrillation with the initial shock in 83.6% (n=402) of cases. A second shock terminated ventricular fibrillation in an additional 7.5% (n=36) of cases, and a third shock terminated ventricular fibrillation in 4.8% (n=23) of cases. The initial sequence of 3 shocks failed to terminate ventricular fibrillation in 4.1% (n=20) of cases. In total, automatic external defibrillators performed 560 rhythm reanalyses during the initial shock sequence and delivered 122 "stacked" shocks. Termination of ventricular fibrillation was not synonymous with return of a pulse. The initial shock produced a pulse that was eventually detected in 21.8% (105/481) of cases. Stacked shocks produced a pulse in 10.7% (13/122) of cases. For the 24.5 % (n=118) of cases in which a pulse returned, the pulse was detected during the initial postshock pulse check only 12 times, or 2.5% of all cases. The median interval from initial shock until CPR was 29 (23,41) seconds. CONCLUSION: Rhythm reanalyses, stacked shocks, and postshock pulse checks had low yield for achieving or detecting return of a pulse. CPR was not initiated until 29 seconds after the initial shock.

Effect of prehospital induction of mild hypothermia on 3-month neurological status and 1-year survival among adults with cardiac arrest: long-term follow-up of a randomized, clinical trial.

BACKGROUND: Randomized trials of prehospital cooling after cardiac arrest have shown that neither prehospital cooling nor targeted temperature management differentially affected short-term survival or neurological function. In this follow-up study, we assess the association of prehospital hypothermia with neurological function at least 3 months after cardiac arrest and survival 1 year after cardiac arrest. METHODS AND RESULTS: There were 508 individuals who were discharged alive from hospitals in King County, Washington; 373 (73%) were interviewed by telephone 123±43 days after the initial event. Overall, 59% of the treatment group and 58% of the control group had Cerebral Performance Category (CPC) 1 or 2 (P=0.70), and 50% of the treatment group and 49% of the control group had slight disability or better by the Modified Rankin Scale (MRS; (P=0.35). One-year survival was 87% in the treatment group and 84% in the control group (P=0.42). Of those with CPC 1 at hospital discharge, 68% had CPC 1 or 2 at follow-up, and 59% had MRS of slight disability or better. Of 41 patients with CPC 3 or 4 at discharge, only 12% had CPC 2 at follow-up, and just 5% had MRS of slight disability or better. One-year survival was 92% for CPC 1 at discharge, but only 40% for CPC 4. CONCLUSION: In addition to excellent survival, patients who had good neurological function at discharge continued to have good function at least 3 months after the event. CLINICAL TRIAL REGISTRATION: URL: Clinicaltrials.gov. Unique identifier: NCT00391469.