On-scene Interval Research Articles

The association of the post-resuscitation on-scene interval and patient outcomes after out-of-hospital cardiac arrest

BackgroundAfter resuscitation from out-of-hospital cardiac arrest (OHCA) by Emergency Medical Services (EMS), the amount of time that should be dedicated to pre-transport stabilization is unclear. We examined whether the time spent on-scene after return of spontaneous circulation (ROSC) was associated with patient outcomes. MethodsWe examined consecutive adult EMS-treated OHCAs from the British Columbia Cardiac Arrest registry (January 1/2019-June 1/2021) that had on-scene ROSC (sustained to scene departure). The primary outcome was favourable neurological outcome (Cerebral Performance Category ≤ 2) at hospital discharge; secondary outcomes were re-arrest during transport and hospital-discharge survival. Using adjusted logistic regression models, we estimated the association between the post-resuscitation on-scene interval (divided into quartiles) and outcomes. ResultsOf 1653 cases, 611 (37%) survived to hospital discharge, and 523 (32%) had favourable neurological outcomes. The median post-resuscitation on-scene interval was 18.8 minutes (IQR:13.0–25.5). Compared to the first post-resuscitation on-scene interval quartile, neither the second (adjusted odds ratio [AOR] 1.19; 95% CI 0.72–1.98), third (AOR 1.10; 95% CI 0.67–1.81), nor fourth (AOR 1.54; 95% CI 0.93–2.56) quartiles were associated with favourable neurological outcomes; however, the fourth quartile was associated with a greater odds of hospital-discharge survival (AOR 1.73; 95% CI 1.05–2.85), and both the third (AOR 0.40; 95% CI 0.22–0.72) and fourth (AOR 0.44;95% CI 0.24–0.81) quartiles were associated with a lower odds of intra-transport re-arrest. ConclusionAmong resuscitated OHCAs, increased post-resuscitation on-scene time was not associated with improved neurological outcomes, but was associated with improved survival to hospital discharge and decreased intra-transport re-arrest.

Activation and on-scene intervals for severe trauma EMS interventions: An analysis of the NEMSIS database

Time to care is a determinant of trauma patient outcomes, and timely delivery of trauma care to severely injured patients is critical in reducing mortality. Numerous studies have analyzed access to care using prehospital intervals from a Carr et al. meta-analysis of studies from 1975-2005. Carr et al.’s research sought to determine national mean activation and on-scene intervals for trauma patients using contemporary emergency medical services (EMS) records. Since the Carr et al. meta-analysis was published, the National Highway Traffic Safety Administration (NHTSA) created and refined the National Emergency Medical Services Information System (NEMSIS) database. We sought to perform a modern analysis of prehospital intervals to establish current standards and temporal patterns. Methods: We utilized NEMSIS to analyze EMS data of trauma patients from 2016-2019. The dataset comprises more than 94 million EMS records, which we filtered to select for severe trauma and stratified by type of transport and rurality to calculate mean activation and on-scene intervals. Furthermore, we explored the impact of basic life support (BLS) and advanced life support (ALS) of ground units on activation and on-scene time intervals. Results: Mean activation and on-scene intervals for ground transport were statistically different when stratified by rurality. Urban, suburban, and rural ground activation intervals were 2.60 ± 3.94, 2.88 ± 3.89, and 3.33 ± 4.58 minutes, respectively. On-scene intervals were 15.50 ± 10.46, 17.56 ± 11.27, and 18.07 ± 16.13 minutes, respectively. Mean helicopter transport activation time was 13.75 ± 7.44 minutes and on-scene time was 19.42 ± 16.09 minutes. This analysis provides an empirically defined mean for activation and on-scene times for trauma patients based on transport type and rurality. Results from this analysis proved to be significantly longer than the previous analysis, except for helicopter transport on-scene time. Shorter mean intervals were seen in ALS compared to BLS for activation intervals, however ALS on-scene intervals were marginally longer than BLS. Conclusions: With the increasing sophistication of geospatial technologies employed to analyze access to care, these intervals are the most accurate and up-to-date and should be included in access to care models.

Factors influencing pre-hospital care time intervals in Iran: a qualitative study.

:Background:Pre-hospital time management provides better access to victims of road traffic crashes (RTCs) and can help minimize preventable deaths, injuries and disabilities. While most studies have been focused on measuring various time intervals in the pre-hospital phase, to our best knowledge there is no study exploring the barriers and facilitators that affects these various intervals qualitatively. The present study aimed to explore factors affecting various time intervals relating to road traffic incidents in the pre-hospital phase and provides suggestions for improvements in Iran.Methods:The study was conducted during 2013-2014 at both the national and local level in Iran. Overall, 18 face-to-face interviews with emergency medical services (EMS) personnel were used for data collection. Qualitative content analysis was employed to analyze the data.Results:The most important barriers in relation to pre-hospital intervals were related to the manner of cooperation by members of the public with the EMS and their involvement at the crash scene, as well as to pre-hospital system factors, including the number and location of EMS facilities, type and number of ambulances and manpower. These factors usually affect how rapidly the EMS can arrive at the scene of the crash and how quickly victims can be transferred to hospital. These two categories have six main themes: notification interval; activation interval; response interval; on-scene interval; transport interval; and delivery interval.Conclusions:Despite more focus on physical resources, cooperation from members of the public needs to be taken in account in order to achieve better pre-hospital management of the various intervals, possibly through the use of public education campaigns.

A validation of ground ambulance pre-hospital times modeled using geographic information systems

BackgroundEvaluating geographic access to health services often requires determining the patient travel time to a specified service. For urgent care, many research studies have modeled patient pre-hospital time by ground emergency medical services (EMS) using geographic information systems (GIS). The purpose of this study was to determine if the modeling assumptions proposed through prior United States (US) studies are valid in a non-US context, and to use the resulting information to provide revised recommendations for modeling travel time using GIS in the absence of actual EMS trip data.MethodsThe study sample contained all emergency adult patient trips within the Calgary area for 2006. Each record included four components of pre-hospital time (activation, response, on-scene and transport interval). The actual activation and on-scene intervals were compared with those used in published models. The transport interval was calculated within GIS using the Network Analyst extension of Esri ArcGIS 10.0 and the response interval was derived using previously established methods. These GIS derived transport and response intervals were compared with the actual times using descriptive methods. We used the information acquired through the analysis of the EMS trip data to create an updated model that could be used to estimate travel time in the absence of actual EMS trip records.ResultsThere were 29,765 complete EMS records for scene locations inside the city and 529 outside. The actual median on-scene intervals were longer than the average previously reported by 7–8 minutes. Actual EMS pre-hospital times across our study area were significantly higher than the estimated times modeled using GIS and the original travel time assumptions. Our updated model, although still underestimating the total pre-hospital time, more accurately represents the true pre-hospital time in our study area.ConclusionsThe widespread use of generalized EMS pre-hospital time assumptions based on US data may not be appropriate in a non-US context. The preference for researchers should be to use actual EMS trip records from the proposed research study area. In the absence of EMS trip data researchers should determine which modeling assumptions more accurately reflect the EMS protocols across their study area.

Epidemiology of Out-of Hospital Pediatric Cardiac Arrest due to Trauma

Objective. To determine the epidemiology and survival of pediatric out-of-hospital cardiac arrest (OHCA) secondary to trauma. Methods. The CanAm Pediatric Cardiac Arrest Study Group is a collaboration of researchers in the United States and Canada sharing a common goal to improve survival outcomes for pediatric cardiac arrest. This was a prospective, multicenter, observational study. Twelve months of consecutive data were collected from emergency medical services (EMS), fire, and inpatient records from 2000 to 2003 for all OHCAs secondary to trauma in patients aged ≤18 years in 36 urban and suburban communities supporting advanced life support (ALS) programs. Eligible patients were apneic and pulseless and received chest compressions in the field. The primary outcome was survival to discharge. Secondary measures included return of spontaneous circulation (ROSC), survival to hospital admission, and 24-hour survival. Results. The study included 123 patients. The median patient age was 7.3 years (interquartile range [IQR] 6.0–17.0). The patient population was 78.1% male and 59.0% African American, 20.5% Hispanic, and 15.7% white. Most cardiac arrests occurred in residential (47.1%) or street/highway (37.2%) locations. Initial recorded rhythms were asystole (59.3%), pulseless electrical activity (29.1%), and ventricular fibrillation/tachycardia (3.5%). The majority of cardiac arrests were unwitnessed (49.5%), and less than 20% of patients received chest compressions by bystanders. The median (IQR) call-to-arrival interval was 4.9 (3.1–6.5) minutes and the on-scene interval was 12.3 (8.4–18.3) minutes. Blunt and penetrating traumas were the most common mechanisms (34.2% and 25.2%, respectively) and were associated with poor survival to discharge (2.4% and 6.5%, respectively). For all OHCA patients, 19.5% experienced ROSC in the field, 9.8% survived the first 24 hours, and 5.7% survived to discharge. Survivors had triple the rate of bystander cardiopulmonary resuscitation (CPR) than nonsurvivors (42.9% vs. 15.2%). Unlike patients sustaining blunt trauma or strangulation/hanging, most post–cardiac arrest patients who survived the first 24 hours after penetrating trauma or drowning were discharged alive. Drowning (17.1% of cardiac arrests) had the highest survival-to-discharge rate (19.1%). Conclusions. The overall survival rate for OHCA in children after trauma was low, but some trauma mechanisms are associated with better survival rates than others. Most OHCA in children is preventable, and education and prevention strategies should focus on those overrepresented populations and high-risk mechanisms to improve mortality.

A Meta-Analysis of Prehospital Care Times for Trauma

Background. Time to definitive care is a major determinant of trauma patient outcomes yet little is empirically known about prehospital times at the national level. We sought to determine national averages for prehospital times based on a systematic review of published literature. Methods. We performed a systematic literature search for all articles reporting prehospital times for trauma patients transported by helicopter andground ambulance over a 30-year period. Forty-nine articles were included in a final meta-analysis. Activation time, response time, on-scene time, andtransport time were abstracted from these articles. Prehospital times were also divided into urban, suburban, rural, andair transports. Statistical tests were computed using weighted arithmetic means andstandard deviations. Results. The data were drawn from 20 states in all four U.S. Census Regions andrepresent the prehospital experience of 155,179 patients. Average duration in minutes for urban, suburban, andrural ground ambulances for the total prehospital interval were 30.96, 30.97, and43.17; for the response interval were 5.25, 5.21, and7.72; for the on-scene interval were 13.40, 13.39, and14.59; andfor the transport interval were 10.77, 10.86, and17.28. Average helicopter ambulance times were response 23.25, on-scene 20.43, andtransport 29.80 minutes. Conclusions. Despite the emphasis on time in the prehospital andtrauma literature there has been no national effort to empirically define average prehospital time intervals for trauma patients. We provide points of reference for prehospital intervals so that policymakers can compare individual emergency medical systems to national norms.

Effect of socioeconomic status on out-of-hospital transport delays of patients with chest pain

Study objective: The effect of socioeconomic status on out-of-hospital care has not been widely examined. We determine whether socioeconomic status was associated with out-of-hospital transport delays for patients with chest pain. Methods: A retrospective study of patients with chest pain transported by means of ambulance in Toronto, Ontario, Canada, in 1999 was conducted. The primary outcome measure was the 90th percentile system response interval, with secondary outcomes being the 90th percentile on-scene interval, transport interval, and total out-of-hospital interval. Socioeconomic status was the primary independent variable. Covariates were age, sex, case severity, dispatch and return priority, time and day of transport, paramedic training, and percentage of high-rise apartments in the region. Results: Four thousand three hundred fifty-six patients met the inclusion criteria. The 90th percentile system response interval and total out-of-hospital interval were 11 minutes and 49 minutes, respectively. In multivariate analyses, the highest socioeconomic status neighborhoods were significantly associated with decreased system response interval (34.0 seconds; 95% confidence interval [CI] 6.2 to 70.9 seconds) and transport interval (132.3 seconds; 95% CI 24.1 to 229.6 seconds). In addition, age (+45.3 seconds per 10 years; 95% CI 13.3 to 75.1 seconds), female sex (+205.0 seconds; 95% CI 78.1 to 287.7 seconds), and advanced care paramedic crews (+371.6 seconds; 95% CI 263.3 to 490.1 seconds) were associated with delays in total out-of-hospital interval. Lastly, calls originating from the highest socioeconomic status neighborhoods were dispatched the highest proportion of advanced care paramedic crews, despite similar dispatch priorities and case severities. Conclusion: High socioeconomic status neighborhoods were associated with shorter out-of-hospital transport intervals for patients with chest pain. In addition, out-of-hospital delays were associated with age, sex, and advanced care paramedic crew type, with calls from the highest socioeconomic status neighborhoods being most likely to receive advanced care paramedic crews. [Ann Emerg Med. 2003;41:481-490.]

D IVERSION OF ALS A MBULANCES : C HARACTERISTICS , C AUSES, AND E FFECTS IN A L ARGE U RBAN S YSTEM

Objective. To characterize the reasons for and effects of diversions of advanced life support (ALS) ambulances in a large urban area with a high concentration of receiving hospitals. Methods. A retrospective study was performed in a large urban region during a consecutive three-month period. Diversion was defined as the ALS transport of a patient to an emergency department (ED) other than the designated primary receiving facility. Case-matched concurrent cohorts of patients who were and were not diverted were studied to establish emergency medical services (EMS) time intervals, including total prehospital interval (TPI), on-scene interval (OSI), and patient transfer interval (PTI); age; gender; Glasgow Coma Score (GCS); ALS interventions; and insurance status. The reasons for diversion and the chief complaints of diverted patients were also studied. Results. During the study period, 2,534 ALS runs occurred, of which 147 (5.8%) were diverted. Twenty-four (16.3%) diversions had incomplete run times, leaving 123 (83.7%) for analysis. The most common chief complaints of diverted patients were shortness of breath (SOB), chest pain (CP), and altered mental status (AMS). The most common reason for diversion was special consideration (SC), defined as a diversion requested by a patient, family member, law enforcement officer, or private medical doctor. Diverted ambulances had significant increases in TPI, 36.4 [95% confidence interval (95% CI) 35.1–37.7] vs 33.4 [95% CI 32.13–34.7], and PTI, 10.3 [95% CI 9.4–11.2] vs 7.9 [95% CI 7.2–8.6], compared with nondiverted ambulances. Further analysis demonstrated that SC diversions accounted for all of the increases in TPI (p < 0.001) and PTI (p < 0.001) when compared with other types of diversions and nondiverted transports. Conclusion. “Special consideration” was the most common reason for diversion in this study. Special consideration diversions increased TPI and PTI, causing delays in arrival to the ED and decreased ALS ambulance availability.

Ability of laypersons to estimate short time intervals in cardiac arrest

Study objective: Estimates of time intervals by bystanders are considered critical in cardiac arrest, and are often used in other disorders such as stroke and myocardial infarction. Because they have never been previously studied, we sought to determine their accuracy. Methods: This study was performed by prospective collection of bystander estimates (made at the time of the arrest) of the time from calling 911 to the arrival of urban fire department first responders, and comparison with actual measured response interval from computerized records, in all out-of-hospital cardiac arrests from January 1996 through June 1998. Results: The fire department responded to 1,015 patients in cardiac arrest during the study period. First responders arrived before advanced life support providers to 831 patients, who thus met study entry criteria. Bystander estimates were obtained in 497 of these 831 patients, who did not differ in key characteristics from those lacking estimates. The bystander’s average estimated fire department response interval was 5.6 minutes (95% confidence interval [CI] 5.2 to 5.9 minutes) and the actual measured interval to the patient’s side from computer records was 6.1 minutes (95% CI 5.9 to 6.4 minutes). However, the median error of the bystander estimate (1.3 minutes) was 32% of the median of the actual measured on-scene interval, and there was no correlation between the bystander estimates and the measured interval in individual cases ( R ≤0.14), regardless of which intervals were examined. Seventy-five percent of the bystander estimates erred by 20% or more. When bystanders estimated a response interval as excessively long, they were almost invariably wrong, but they also usually failed to identify intervals that actually were long. Conclusion: Although many diagnostic and research conclusions are based on interval estimates from laypersons, we found no correlation between estimates and actual measured intervals in cardiac arrest. Current methodology may not be developed well enough to provide reliable data for research or quality assurance, and other clinical time estimates by patients and bystanders may be equally unreliable. [Isaacs E, Callaham ML. Ability of laypersons to estimate short time intervals in cardiac arrest. Ann Emerg Med. February 2000;35:147-154.]

Prehospital fluid therapy in pediatric trauma patients

In order to evaluate the impact of prehospital intravenous fluid therapy on the outcome of pediatric trauma patients and to evaluate the effect of such therapy on the on-scene interval, we performed a retrospective chart review of 50 pediatric trauma patients less than 18 years old transported directly from the field by Emergency Medical Services personnel with an intravenous catheter in place and admitted to the Trauma Service of a level I urban pediatric trauma center. As judged by an expert panel using a new grading system, prehospital intravenous fluid therapy was inconsequential to outcome in 47 of 50 patients, possibly beneficial in two of 50 patients, and possibly detrimental in one of 50 patients. Patients who received their catheters at the scene had significantly longer on-scene intervals than those who received them in the ambulance (15.4 vs 11.4 minutes, P < 0.05). The mean volume of fluid administered was 4.4 ml/kg body weight. Placement of the catheter (at the scene vs in the ambulance) and prehospital fluid volume administered were independent of the Injury Severity Score. The role of prehospital fluid therapy in pediatric trauma patients in an urban setting requires reevaluation.

Prehospital fluid therapy in pediatric trauma patients.

In order to evaluate the impact of prehospital intravenous fluid therapy on the outcome of pediatric trauma patients and to evaluate the effect of such therapy on the on-scene interval, we performed a retrospective chart review of 50 pediatric trauma patients less than 18 years old transported directly from the field by Emergency Medical Services personnel with an intravenous catheter in place and admitted to the Trauma Service of a level I urban pediatric trauma center. As judged by an expert panel using a new grading system, prehospital intravenous fluid therapy was inconsequential to outcome in 47 of 50 patients, possibly beneficial in two of 50 patients, and possibly detrimental in one of 50 patients. Patients who received their catheters at the scene had significantly longer on-scene intervals than those who received them in the ambulance (15.4 vs 11.4 minutes, P < 0.05). The mean volume of fluid administered was 4.4 ml/kg body weight. Placement of the catheter (at the scene vs in the ambulance) and prehospital fluid volume administered were independent of the Injury Severity Score. The role of prehospital fluid therapy in pediatric trauma patients in an urban setting requires reevaluation.

Prospective validation of a new model for evaluating emergency medical services systems by in-field observation of specific time intervals in prehospital care

To develop and validate a new time interval model for evaluating operational and patient care issues in emergency medical service (EMS) systems. DESIGN/SETTING/TYPE OF PARTICIPANT: Prospective analysis of 300 EMS responses among 20 advanced life support agencies throughout an entire state by direct, in-field observation. Mean times (minutes) were response, 6.8; patient access, 1.0; initial assessment, 3.3; scene treatment, 4.4; patient removal, 5.5; transport, 11.7; delivery, 3.5; and recovery, 22.9. The largest component of the on-scene interval was patient removal. Scene treatment accounted for only 31.0% of the on-scene interval, whereas accessing and removing patients took nearly half of the on-scene interval (45.8%). Operational problems (eg, communications, equipment, uncooperative patient) increased patient removal (6.4 versus 4.5; P = .004), recovery (25.4 versus 20.2; P = .03), and out-of-service (43.0 versus 30.1; P = .007) intervals. Rural agencies had longer response (9.9 versus 6.4; P = .014), transport (21.9 versus 10.3; P < .0005), and recovery (29.8 versus 22.1; P = .049) interval than nonrural. The total on-scene interval was longer if an IV line was attempted at the scene (17.2 versus 12.2; P < .0001). This reflected an increase in scene treatment (9.2 versus 2.8; P < .0001), while patient access and patient removal remained unchanged. However, the time spent attempting IV lines at the scene accounted for only a small part of scene treatment (1.3 minutes; 14.1%) and an even smaller portion of the overall on-scene interval (7.6%). Most of the increase in scene treatment was accounted for by other activities than the IV line attempts. A new model reported and studied prospectively is useful as an evaluative research tool for EMS systems and is broadly applicable to many settings in a demographically diverse state. This model can provide accurate information to system researchers, medical directors, and administrators for altering and improving EMS systems.