Rapid Response System Escalation During Recovery of Hospital Bed Occupancy: An Observational Longitudinal Study

BACKGROUND: Early warning scores (EWS) identify patient deterioration, but their impact depends on how they are integrated into workflows and escalation culture, particularly as hospitals recover from pandemic-related bed pressures. AIMS: To evaluate changes in rapid response system (RRS) escalation processes and rare safety outcomes after embedding an EWS within proactive Critical Care Outreach Team (CCOT) rounds as hospital bed occupancy recovered. STUDY DESIGN: Observational longitudinal study at a single tertiary hospital in Japan comparing one pre-intervention year (2021) with three post-intervention years (2022-2024). In January 2022, a standardised EWS was embedded into proactive CCOT rounds and used as a prompt for shared clinical reasoning rather than a strict numeric trigger. Monthly aggregated ward-level data were analysed using Poisson regression, adjusting for seasonality, patient characteristics and bed occupancy. RESULTS: Across 71 985 admissions and 692 942 general-ward patient-days, rates of nurse-initiated escalations, RRS activations and resuscitation-status updates per 1000 patient-days increased in post-intervention analyses, but these differences were attenuated after full adjustment. In fully adjusted models, post-intervention incidence rate ratios (IRRs) were close to 1.0 for all process outcomes. For nurse-initiated escalations, IRRs ranged from 0.94 to 1.14, and all 95% confidence intervals included 1.0. Rates of unexpected in-hospital cardiac arrest and unplanned ICU admission remained low and stable. Bed occupancy increased over the study period, but within-year associations with outcomes were weak. CONCLUSIONS: After adjustment for patient characteristics and hospital bed occupancy, embedding an EWS within proactive CCOT rounds was associated with broadly stable escalation process indicators and no clear evidence of deterioration in rare safety outcomes. RELEVANCE TO CLINICAL PRACTICE: These findings suggest that approaches to the RRS afferent limb that embed EWS use within structured dialogue between ward nurses and outreach teams may provide one plausible mechanism for sustaining escalation behaviours under operational pressure.