Study objectives: Emergency medical services (EMS) directors are often forced to rapidly make protocol changes in response to events in an EMS system. These changes are expected to have an immediate impact on patient care. Success depends on the speed at which the protocol is adopted, its continued use rate, and the rate at which providers stop using the protocol as a defined end date approaches. No study has attempted to characterize compliance with rapid protocol changes. We characterize compliance by EMS providers when a 1-month protocol is introduced and then terminated.

Methods: This is a descriptive study. To reduce individual emergency department crowding, a protocol instructing EMS providers to contact an EMS medical control staffed by attending EMS physicians was introduced into a regional EMS system. Providers were instructed to call for all patients inbound to a 2-hospital system to receive destination instructions. A high compliance would allow medical control to triage patients to the most appropriate hospital after consideration of patient needs, resource availability, and waiting times. Medical control physicians logged all calls prospectively. Registration records were reviewed to determine the total number of patients arriving by EMS. Compliance was defined as the daily percentage of EMS patients being called in to medical control. The protocol functioned for 31 days and was terminated on short notice.

Results: Compliance rose from 56% on day 1 to 88% by day 4. Day 5 through day 30 compliance ranged from 59% to 93% (mean 72%). On the final day of the protocol's operation, after an announcement the previous day of its termination, compliance decreased from 68% to 39%.

Conclusion: EMS providers will rapidly adopt and continue to comply with a protocol. Announcement of protocol termination causes an immediate drop in compliance even before a defined termination date. Medical directors should consider these factors when considering the results of the introduction of a protocol into an EMS system.