Development and Validation of the Hypotensive Exposure Duration Index for Mortality Risk Prediction in Critically III Patients

Abstract Background Blood pressure management is crucial in critical care, but relationships between pressure patterns and outcomes remain incompletely understood. We analyzed minute-by-minute blood pressure data to develop and validate a novel index quantifying hypotensive exposure burden. Methods In this retrospective study using the Salzburg Intensive Care Database, 11,059 ICU admissions with continuous invasive arterial monitoring were analyzed. Heatmaps were constructed from high-resolution hemodynamic data to visualize relationships between blood pressure thresholds (50–120 mmHg), exposure durations (5 minutes to 6 hours), and mortality. The Hypotensive Exposure Duration Index (HEDI) was developed to quantify cumulative hypotensive burden by integrating exposure across multiple MAP thresholds. HEDI's prognostic value was evaluated through ROC analysis and nine machine learning algorithms. External validation using the eICU database assessed HEDI's consistency across different populations. Results Non-survivors showed significantly higher HEDI compared to survivors (0.75 [-0.25-2.37] vs -0.16 [-0.65-0.53], p < 0.001). HEDI demonstrated increasing predictive capability, with AUC values rising from 0.622 at 24h to 0.686 at 72h post-admission. The Extra Trees classifier achieved exceptional performance (test AUC: 0.996), with HEDI ranking among the top predictive features. Both internal cross-validation and external validation confirmed the model's robustness (accuracy 0.871), demonstrating HEDI's consistent prognostic value across different patient populations regardless of vasopressor use. Conclusions HEDI effectively quantifies cumulative hypotensive burden in critically ill patients, demonstrating significant predictive ability for ICU mortality validated across diverse populations.