C55-07 Code Blue Patterns: Diurnal Variation of Major Cardiovascular Events

Abstract Major Adverse Cardiovascular Events (MACE), are defined as a composite of stroke, acute myocardial infarction, cardiac death, angina and heart failure. These events frequently trigger Code Blue activations in the hospital setting. Prior studies have demonstrated a diurnal variation in MACE, attributed to fluctuations in cortisol, blood pressure, hematocrit, and platelet activity. A peak incidence of stroke between 8:00 am and 12:00 pm has been documented, highlighting the vulnerability of early morning hours. Sudden cardiac death also exhibits a bimodal distribution, with circadian rhythm hypothesized to underlie this pattern. Experimental models further support these findings, showing circadian-dependent changes in myocardial repolarization that predispose to sudden cardiac arrest. Obstructive sleep apnea (OSA), which is associated with surges in sympathetic activity and intermittent hypoxemia during sleep, may also play a role in amplifying the risk of cardiovascular collapse during these vulnerable hours. Objective To evaluate whether a similar diurnal pattern of cardiovascular-related Code Blue activations could be observed in an inpatient cohort across multiple Geisinger Northeast campuses. Methods We retrospectively reviewed Code Blue activations from November 1, 2024, to January 31, 2025, across three hospitals: Geisinger Community Medical Center (GCMC), Geisinger Wyoming Valley (GWV), and Geisinger South Wilkes-Barre (GSWB). Data were obtained via the Code Blue narrator. Exclusions included undocumented codes not logged in the dashboard and repeat codes in the same patient within 20 minutes of return of spontaneous circulation (ROSC). The time of each Code Blue activation was recorded. Results A total of 92 Code Blue events were analyzed (mean age 67.7 years). Distribution by hospital included 49 (53.3%) at GCMC, 30 (40.2%) at GWV, and 6 (6.5%) at GSWB. Temporal analysis revealed a sharp rise in activations at 8:00 am (9 codes), peaking at 11:00 am (10 codes). A smaller secondary rise was observed around 6:00 pm (5 codes). Overall, the majority of Code Blues occurred before 12:00 pm. Discussion The clustering of Code Blue events in the morning hours is consistent with circadian patterns of cardiovascular vulnerability described in prior literature. From a systems perspective, these findings have implications for ICU and inpatient staffing models. Many of the observed peaks coincide with morning rounding periods, when providers may be less readily available for emergent response. Ensuring adequate personnel and rapid response coverage during these high-risk times could improve outcomes. Additionally, preventive strategies such as optimizing OSA management may help reduce the burden of early morning cardiac events. This abstract is funded by: none