Development and validation of the Hypotensive Exposure Duration Index for mortality risk prediction in critically ill patients.

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 (52-120 mmHg), exposure durations (5 min-5 h), 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 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 (0.47 [-0.20, 1.43] vs. -0.15 [-0.41, 0.27], p < 0.001). HEDI demonstrated increasing predictive capability, with AUC values rising from 0.624 at 24 h to 0.700 at 72 h post-admission. The Extra Trees classifier achieved exceptional performance (test AUC: 0.843), with HEDI ranking among the top predictive features. Both internal cross-validation and external validation confirmed the model's robustness, demonstrating HEDI's prognostic value across different patient populations, including both patients with and without vasopressor use. CONCLUSIONS: HEDI effectively quantifies cumulative hypotensive burden in critically ill patients, demonstrating significant predictive ability for ICU mortality validated across diverse populations.