Search

Abstract: Background: The compensatory reserve index (CRI) is a noninvasive, continuous measure designed to detect intravascular volume loss. CRI is derived from the pulse oximetry waveform and reflects the proportion of physiologic reserve remaining before clinical hemodynamic decompensation. Methods: In this prospective, observational, prehospital cohort study, we measured CRI in injured patients transported by emergency medical services (EMS) to a single Level I trauma center. We determined whether the rolling average of CRI values over 60 s (CRI trend [CRI-T]) predicts in-hospital diagnosis of hemorrhagic shock, defined as blood product administration in the prehospital setting or within 4 h of hospital arrival. We hypothesized that lower CRI-T values would be associated with an increased likelihood of hemorrhagic shock and better predict hemorrhagic shock than prehospital vital signs. Results: Prehospital CRI was collected on 696 adult trauma patients, 21% of whom met our definition of hemorrhagic shock. The minimum CRI-T was 0.14 (interquartile range [IQR], 0.08-0.31) in those with hemorrhagic shock and 0.31 (IQR 0.15-0.50) in those without ( P = <0.0001). The positive likelihood ratio of a CRI-T value <0.2 predicting hemorrhagic shock was 1.85 (95% confidence interval [CI], 1.55-2.22). The area under the ROC curve (AUC) for the minimum CRI-T predicting hemorrhagic shock was 0.65 (95% CI, 0.60-0.70), which outperformed initial prehospital HR (0.56; 95% CI, 0.50-0.62) but underperformed EMS systolic blood pressure and shock index (0.74; 95% CI, 0.70-0.79 and 0.72; 95% CI, 0.67-0.77, respectively). Conclusions: Low prehospital CRI-T predicts blood product transfusion by EMS or within 4 hours of hospital arrival but is less prognostic than EMS blood pressure or shock index. The evaluated version of CRI may be useful in an austere setting at identifying injured patients that require the most significant medical resources. CRI may be improved with noise filtering to attenuate the effects of vibration and patient movement., (Copyright © 2023 by the Shock Society.)

Background: Studies of outcome differences by sex in out-of-hospital cardiac arrest (OHCA) have produced mixed results that may depend on age, a potential surrogate for menopausal status., Objective: We used quantitative measures of ventricular fibrillation (VF) waveforms - indicators of the myocardium's physiology - to assess whether survival differences according to sex and age group may be mediated via a biologic mechanism., Methods: We conducted a cohort study of VF-OHCA in a metropolitan EMS system. We used multivariable logistic regression to assess the association of survival to hospital discharge with sex and age group (<55, ≥55 years). We determined the proportion of outcome difference mediated by VF waveform measures: VitalityScore and amplitude spectrum area (AMSA)., Results: Among 1526 VF-OHCA patients, the 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), while survival among older women and older men did not differ (40% vs 44%, p = 0.3). Adjusting for Utstein characteristics, women <55 compared to men <55 had greater odds of survival to hospital discharge (OR = 1.93, 95% CI 1.23-3.09), an association not observed between the ≥55 groups. Waveform measures were more favorable among women and mediated some of the beneficial association between female sex and survival among those <55 years: 47% for VitalityScore and 25% for AMSA., Conclusions: Women <55 years were more likely to survive than men <55 years following VF-OHCA. The biologic mechanism represented by VF waveform mediated some, though not all, of the outcome difference., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: ‘TR and HK received modest support provided to the University of Washington by Philips, a major defibrillator manufacturer.’., (Copyright © 2023. Published by Elsevier B.V.)

Background: Geospatial smartphone application alert systems are used in some communities to crowdsource community response for out-of-hospital cardiac arrest (OHCA). Although the clinical focus of this strategy is OHCA, dispatch identification of OHCA is imperfect so that activation may occur for the non-arrest patient. The frequency and clinical profile of such non-arrest patients has not been well-investigated., Methods: We undertook a prospective 3-year cohort investigation of patients for whom a smartphone geospatial application was activated for suspected OHCA in four United States communities (total population ~1 million). The current investigation evaluates those patients with an activation for suspected OHCA who did not experience cardiac arrest. The volunteer response cohort included off-duty, volunteer public safety personnel (verified responders) notified regardless of location (public or private) and laypersons notified to public locations. The study linked the smartphone application information with the EMS records to report the frequency, condition type, and EMS treatment for these non-arrest patients., Results: Of 1779 calls where volunteers were activated, 756 had suffered OHCA, resulting in 1023 non-arrest patients for study evaluation. The most common EMS assessments were syncope (15.9%, n=163), altered mental status (15.5%, n=159), seizure (14.3%, n=146), overdose (13.0%, n=133), and choking (10.5%, n=107). The assessment distribution was similar for private and public locations. Overall, the most common EMS interventions included placement of an intravenous line (43.1%, n=441), 12-Lead ECG(27.9%, n=285), naloxone treatment (9.8%, n=100), airway or ventilation assistance (8.7%, n=89), and oxygen administration (6.6%, n=68)., Conclusions: More than half of patients activated for suspected OHCA had conditions other than cardiac arrest. A subset of these conditions may benefit from earlier care that could be provided by both layperson and public safety volunteers if they were appropriately trained and equipped., (© 2023. The Author(s).)

Background: Anoxic brain injury is a common mode of death following out-of-hospital cardiac arrest (OHCA). We assessed the course of regional cerebral oxygen saturation (rSO 2 ) at the outset and during first responder resuscitation to understand its relationship with return of spontaneous circulation (ROSC) and functional survival. Methods: We undertook a prospective observational investigation of adult OHCA patients treated by a first-responder EMS agency in King County, WA. Cerebral oximetry was performed using the SenSmart® Model X-100 Universal Oximetry System (Nonin Medical, Inc). We determined cerebral oximetry rSO 2 overall and stratified according to ROSC and favorable survival status defined by Cerebral Performance Category (CPC) of 1-2. Results: Among the 59 OHCA cases enrolled, 47% ( n  = 28) achieved ROSC and 14% ( n  = 8) survived with CPC 1-2. On average, initial rSO 2 cerebral oximetry was 41% and was not different at the outset according to return of spontaneous circulation (ROSC) or survival status. Within 5 minutes of first responder resuscitation, those who would subsequently achieve ROSC had a higher rSO 2 than those who would not achieve ROSC (51% vs. 43%, p  = 0.03). Among patients who achieved ROSC, those who would survive with CPC 1-2 had a higher rSO 2 cerebral oximetry following ROSC than nonsurvivors (74% vs. 60%, p  = 0.04 at 5 minutes post ROSC), a difference that was not evident in the minutes prior to ROSC (55% vs. 51% at 3 minutes prior to ROSC, p  = 0.5). Conclusion: In this observational study, where first responders applied cerebral oximetry, higher rSO 2 during the course of care predicted ROSC among all patients and predicted favorable survival among those who achieved ROSC. Future investigation should evaluate whether and how treatments might modify rSO 2 and in turn may influence prognosis.

Background The 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 Results We 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. Conclusions Bystander 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.

Background: There is substantial investment in layperson and first responder training involving tourniquet use for hemorrhage control. Little is known however about prehospital tourniquet application, field conversion, or outcomes in the civilian setting. We describe the experience of a metropolitan region with prehospital tourniquet application., Methods: We conducted a retrospective cohort study characterizing prehospital tourniquet use treated by emergency medical services (EMS) in King County, Washington, from January 2018 to June 2019. Emergency medical services and hospital records were abstracted for demographics, injury mechanism, tourniquet details, clinical care, and outcomes. We evaluated the incidence of tourniquet application, who applied the device (EMS, law enforcement, or layperson), and subsequent course., Results: A total of 168 patients received tourniquet application, an incidence of 5.1 per 100,000 person-years and 3.48 per 1,000 EMS responses for trauma. Tourniquets were applied for penetrating trauma (64%), blunt trauma (30%), and bleeding ateriovenous fistulas (7%). A subset was critically ill: 13% had systolic blood pressures of <90 mm Hg, 8% had Glasgow Coma Scale score of <13, and 3% had cardiac arrest. Among initial applications, 48% were placed by law enforcement, 33% by laypersons, and 18% by EMS. Among tourniquets applied by layperson or law enforcement (n = 137), EMS relied solely on the original tourniquet in 45% (n = 61), placed a second tourniquet in 20% (n = 28), and removed the tourniquet without replacement in 35% (n = 48). Overall, 24% required massive transfusion, 59% underwent urgent surgery, and 21% required vascular surgery. Mortality was 3% (n = 4). At hospital discharge, the tourniquet limb was fully functional in 81%, partially functional in 10%, and nonfunctional in 9%; decreased function was not attributed to tourniquet application., Conclusion: The high rate of application, need for urgent hospital intervention in a subset, and low incidence of apparent complication suggest that efforts to increase access and early tourniquet use can provide public health benefit., Level of Evidence: Therapeutic, level IV., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Background: Emergency Medical Services (EMS) are often involved in end-of-life circumstances, yet little is known about how EMS interfaces with advance directives to forego unwanted resuscitation (Do Not Attempt Resuscitation (DNAR)). We evaluated the frequency of these directives involved in out-of-hospital cardiac arrest (OHCA) and how they impact care., Methods: We conducted a cohort investigation of adult, EMS-attended OHCA from January 1 to December 31, 2018 in King County, WA. DNAR status was ascertained from dispatch, EMS, and hospital records. Resuscitation was classified according to DNAR status: not initiated, initiated but ceased due to the DNAR, or full efforts., Results: Of 3152 EMS-attended OHCA, 314 (9.9%) had a DNAR directive. DNAR was present more often among those for whom EMS did not attempt resuscitation compared to when EMS provided some resuscitation (13.2% [212/1611] vs 6.6% [101/1541], (p < 0.05). Of those receiving resuscitation with a DNAR directive (n = 101), the DNAR was presented on average 6 min following EMS arrival. A total of 82% (n = 83) had EMS efforts ceased as a consequence of the DNAR while 18% (n = 18) received full efforts. Full-efforts compared to ceased-efforts were more likely to have a witnessed arrest (67% vs 36%), present with shockable rhythm (22% vs 6%), achieve spontaneous circulation by time of DNAR presentation (50% vs 4%), and have family contradict the DNAR (33% vs 0%) (p < 0.05 for each comparison)., Conclusions: Approximately 10% of EMS-attended OHCA involved DNAR. EMS typically fulfilled this end-of-life preference, though wishes were challenged by delayed directive presentation or contradictory family wishes., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Background: Survival following out-of-hospital cardiac arrest (OHCA) decreases as the interval from collapse to CPR and defibrillation increases. Innovative approaches are needed to reduce response intervals, especially for private locations., Methods: We undertook the Verified Responder Program in 5 United States communities during 2018, whereby off-duty EMS professionals volunteered and were equipped with automated external defibrillators (AEDs). Volunteers were alerted using a geospatial smartphone application (PulsePoint) and could respond to nearby private and public suspected OHCA. The study evaluated the frequency of Verified Responder notification, response, scene arrival, and initial care prior to EMS arrival. OHCA surveillance used the CARES registry., Results: Of the 651 OHCA events (475 private, 176 public), Verified Responders were notified in 7.4% (n = 49). Among the 475 in a private location, volunteers were alerted in 8% (n = 38), responded in 2.7% (n = 13), arrived on scene in 2.3% (n = 11), and provided initial care in 1.7% (n = 8). Among the 176 in a public location, volunteers were alerted in 6.3% (n = 11), responded in 2.3% (n = 4), arrived on-scene in 2.3% (n = 4), and provided initial care in 2.3% (n = 4). Over 96% surveyed had positive impression of the program and intended to continue participation. No responder reported any adverse event., Conclusions: In this initial US-based experience of a smartphone program for suspected OHCA in private and public locations, Verified Responders reported a positive experience, though were only involved in a small fraction of OHCA. Studies should determine how this type of program could be enhanced to involve more OHCA events., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Introduction: Field information available to emergency medical services (EMS) about a patient's chronic health conditions or medication therapies could help direct patient care or be used to investigate outcome disparities. However, little is known about the field availability or accuracy of information of chronic health conditions or chronic medication treatments in emergent circumstances, especially when the patient cannot serve as an information resource. We evaluated the prehospital availability and accuracy of specific chronic health conditions and medication treatments among out-of-hospital cardiac arrest (OHCA) patients., Methods: The investigation was a retrospective cohort study of adult persons suffering ventricular fibrillation OHCA treated by EMS in a large metropolitan county from January 1, 2007, to December 31, 2013. The study was designed to determine the availability and accuracy of EMS ascertainment of selected chronic health conditions and medication treatments. We evaluated chronic health conditions of "any heart disease," congestive heart failure (CHF), and diabetes and medication treatments of beta blockers and loop diuretics using two distinct sources: 1) EMS report, and 2) hospital record specific to the OHCA event. Because hospital information was considered the gold standard, we restricted the primary analysis to those who were admitted to hospital., Results: Of the 1,496 initially eligible patients, 387 could not be resuscitated and were pronounced dead in the field, one patient was left alive at scene due to Physician's Orders for Life-sustaining Treatment (POLST) orders, 125 expired in the emergency department (n=125), and 983 were admitted to hospital. A total of 832 of 1,496 (55.6%) had both sources of data for comparison and comprised the primary analytic group. Using the hospital record as the gold standard, EMS ascertainment had a sensitivity of 0.79 (304/384) and a specificity of 0.88 (218/248) for any prior heart disease; sensitivity 0.45 (47/105) and specificity 0.87 (477/516) for CHF; sensitivity 0.71 (143/201) and specificity 0.98 (416/424) for diabetes; sensitivity 0.70 (118/169) and specificity 0.94 (273/290) for beta blockers; sensitivity 0.70 (62/89) and specificity 0.97 (358/370) for loop diuretics., Conclusion: In this cohort of OHCA, information about selected chronic health conditions and medication treatments based on EMS ascertainment was available for many patients, generally revealing moderate sensitivity and greater specificity., Competing Interests: Conflicts of Interest: By the WestJEM article submission agreement, all authors are required to disclose all affiliations, funding sources and financial or management relationships that could be perceived as potential sources of bias. The study was supported in part by a grant from the Laerdal Foundation and the Life Sciences Discovery Fund, neither of which had any involvement in data gathering or writing of the paper.

Background: Public access defibrillation can improve survival but is involved in only a small fraction of out-of-hospital cardiac arrest. One approach to increase involvement is to couple emergency dispatch with mapping technology to identify public access automated external defibrillators (AEDs) that are on-site or nearby., Methods: We conducted a retrospective observational cohort investigation of out-of-hospital cardiac arrest who received dispatch by a community dispatch center between January 1, 2007 and December 31, 2009. The dispatch system is linked to the public access AED registry. The technology enables dispatcher alert of an on-site AED and the potential to alert for an AED within 0.1 mile. We report the observed and potential frequency of AED involvement., Results: Of the 763 cardiac arrest events, 4.2% (32/763) had an AED applied by non-EMS persons, 1.3% (10/763) by police and 2.9% (22/763) in layperson settings. Among the remaining 731 where an AED was not applied, 8.1% (59/731) had an AED identified through dispatch; 18 with an AED on-site and an additional 41 with an AED within 0.1 mile. When restricting to ventricular fibrillation arrests, 8.9% (16/179) had an AED applied by non-EMS persons, 2.8% (5/179) by police and 6.1% (11/179) in layperson settings. Among the remaining 163 where an AED was not applied, 11.7% (19/163) had an AED identified through dispatch; 9 with an AED on-site and an additional 10 with an AED within 0.1 mile., Conclusion: A working link between emergency dispatch and an AED registry may provide an opportunity to improve resuscitation., (Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.)