Evaluating the Resilience of ICU Nurse Staffing Standard Operating Procedures Under Demand Variability: A Discrete Event Simulation Study Using MIMIC-IV.

Background/Objectives: ICU nurse staffing Standard Operating Procedures (SOPs) govern nurse-to-patient assignment and escalation rules, yet their robustness under demand variability and workforce disruption has not been quantitatively evaluated. Methods: A Discrete Event Simulation model of a 20-bed ICU was parameterized from 20,419 MICU stays extracted from MIMIC-IV v3.1. Three SOPs-Fixed Ratio, Acuity-Adjusted, and Dynamic Escalation-were evaluated across four scenarios (baseline, census surge, nurse shortage, combined disruption), each with 100 replications, using Kruskal-Wallis and Dunn's post hoc tests. Results: Dynamic Escalation achieved the lowest adverse event rate at baseline (4.25 per 100 patient days), a 16.8% reduction relative to Fixed Ratio (5.11). However, a resource-constrained comparison equalizing total nurse hours across protocols reversed this ranking: Dynamic Escalation performed significantly worse than both static protocols (p < 0.0001), which were themselves statistically indistinguishable, indicating that its primary advantage stems from greater staffing capacity rather than superior decision logic. Conclusions: Apparent differences between ICU staffing SOPs are largely driven by total available nurse hours rather than allocation logic. Investment in staffing capacity, rather than a specific allocation rule, may be the primary lever for improving ICU patient safety outcomes.