Abstract Body: Introduction: Patient recruitment is a critical factor in running successful and timely clinical studies. This is particularly crucial in cardiac arrest research where the timing of presentation of study participants is unpredictable and interventions are often time-sensitive. Previous studies have identified adequate staffing as one of the most important enablers of successful recruitment. However, studies have also shown that recruitment outside of business hours is less common even at major academic centers.

Hypothesis: We hypothesize that a substantial portion of potential study participants present outside of business hours and therefore providing coverage only during business hours results in missing a large number of potential study participants.

Aims: The objective of this study was to analyze the timing of all patient enrollments from our previous cardiac arrest trials to identify patterns and assess the impact of providing 24/7 coverage on participant recruitment.

Methods: We reviewed the patient enrollment time data for two cardiac arrest trials performed by our group (NCT02974257 and NCT03450707). We quantified the number of enrollments during business hours (9 AM - 5 PM) vs. outside of business hours and analyzed the frequency of enrollment by day of the week and time of day.

Results: There were 112 patients enrolled between 2016 and 2022 across the two trials. A total of 80 patients (71.4%) were enrolled outside of business hours (Fig. 1). 75% of patients were enrolled during weekdays and 25% during weekends. By day of the week, enrollments occurred most frequently on Friday (20, 17.9%) and least on Monday (12, 10.7%) and Sunday (12, 10.7%) (Fig. 2A). By time of day, enrollments occurred most frequently during 2 - 4 PM and 6 - 8 PM (15, 13.4%) and least frequently during 4 - 6 AM and 8 - 10 AM (2, 1.8%) (Fig. 2B). Recruiting only during business hours would have resulted in additional 18 and 11 years to complete each study (Fig. 3).

Conclusion: In our two most recent cardiac arrest trials, 75% of enrollment occurred outside of business hours. Limiting recruitment to only business hours would have resulted in a prohibitively longer time to complete the studies. This analysis provides a strong motivation and rationale for extending research staffing coverage beyond business hours.