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Emergency Medical Services (EMS) systems have developed protocols for prehospital activation of the cardiac catheterization laboratory for patients with suspected ST-elevation myocardial infarction (STEMI) to decrease first-medical-contact-to-balloon time (FMC2B). The rate of “false positive” prehospital activations is high. In order to decrease this rate and expedite care for patients with true STEMI, the American Heart Association (AHA; Dallas, Texas USA) developed the Mission Lifeline PreAct STEMI algorithm, which was implemented in Los Angeles County (LAC; California USA) in 2015. The hypothesis of this study was that implementation of the PreAct algorithm would increase the positive predictive value (PPV) of prehospital activation.
This is an observational pre-/post-study of the effect of the implementation of the PreAct algorithm for patients with suspected STEMI transported to one of five STEMI Receiving Centers (SRCs) within the LAC Regional System. The primary outcome was the PPV of cardiac catheterization laboratory activation for percutaneous coronary intervention (PCI) or coronary artery bypass graft (CABG). The secondary outcome was FMC2B.
A total of 1,877 patients were analyzed for the primary outcome in the pre-intervention period and 405 patients in the post-intervention period. There was an overall decrease in cardiac catheterization laboratory activations, from 67% in the pre-intervention period to 49% in the post-intervention period (95% CI for the difference, -14% to -22%). The overall rate of cardiac catheterization declined in post-intervention period as compared the pre-intervention period, from 34% to 30% (95% CI, for the difference -7.6% to 0.4%), but actually increased for subjects who had activation (48% versus 58%; 95% CI, 4.6%-15.0%). Implementation of the PreAct algorithm was associated with an increase in the PPV of activation for PCI or CABG from 37.9% to 48.6%. The overall odds ratio (OR) associated with the intervention was 1.4 (95% CI, 1.1-1.8). The effect of the intervention was to decrease variability between medical centers. There was no associated change in average FMC2B.
The implementation of the PreAct algorithm in the LAC EMS system was associated with an overall increase in the PPV of cardiac catheterization laboratory activation.
Previous evaluations of prehospital devices intended for spinal immobilization have focused on the device's ability to restrict motion only. This study defines six relevant criteria for evaluation of cervical immobilization device (CID) performance.
To suggest relevant criteria for evaluation and use available technology to improve measurements for performance testing of prehospital-care devices.
Six parameters (motion restriction, access, ease of application, environmental performance, radiolucency, and storage size) were used to evaluate three types of CIDs: Device A—a single-use corrugated board; Device B—a reusable foam-block CID; and Device C—hospital towels and adhesive tape. To test motion restriction, the most frequently compared parameters for immobilization devices, 20 volunteers were asked to move their heads and necks through a series of motions (flexion, extension, lateral bending and rotation). Their movements were videotaped, still images of each movement were generated, and the degrees of deflection recorded from these still images. To ensure a consistent level of force, electromyography (EMG) of the sternodydomastoid and extensor muscles was employed.
Data were produced for each parameter and presented for comparison. The use of video to determine deflection proved to be a useful and highly accurate (±1°) method for measurement. The use of EMG technology enabled force to be controlled indirectly when the subjects used moderate levels of exertion. Overall, Devices A and C restricted motion better than Device B. Although Device C required the shortest time for application, it took the longest to prepare for application. The total time required for preparation and application of A and B essentially were equivalent, with A requiring no preparation time but taking the longest for application, and B having an intermediate interval for application. Device A allowed for the best examination of the head and neck. No differences were detected in performance in extreme environmental conditions or in radiolucency for cervical spine X-ray examinations. Device A consumed the smallest storage volume, B the greatest storage volume, and C an intermediate volume substantially greater than that required for A.
Device evaluation should include examination of all relevant performance parameters using the most accurate and meaningful methods possible.