Cumulative multi-threshold intraoperative blood pressure exposure patterns and postoperative mortality
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Cristina Barboi1, LaKeisha Boyd2, Michael P Schnetz3
1Department of Anesthesiology, Indiana University School of Medicine, Indianapolis, IN, USA; Center for Biomedical Informatics, Regenstrief Institute, 101 W 10(th) Street, Indianapolis, IN, USA.
Background:
Intraoperative hypotension is commonly defined as MAP <65 mmHg. We evaluated whether cumulative exposure across multiple MAP thresholds provides additional mortality-associated information beyond this single threshold.
Methods:
We conducted a retrospective cohort study of adults having non-cardiac, non-obstetric surgery using perioperative electronic health record data. Pressure-time burden and proportion of operative time were calculated across MAP thresholds from 50 to 150 mmHg. Decision-tree analysis using recursive partitioning sequentially grouped patients according to MAP exposure patterns associated with 30-day mortality. Discrimination of the multi-threshold blood-pressure-only model was compared with that of a model restricted to exposure below MAP 65 mmHg. Medication associations were exploratory.
Results:
Among 388,407 patients, 30-day mortality was 1.49%. The multi-threshold model had greater validation discrimination than the MAP 65 mmHg model (AUROC, 0.619 vs. 0.591; ΔAUROC, 0.028; 95% CI, 0.025-0.037; p < 0.001), although the improvement was modest. Terminal exposure groups defined by complete combinations of MAP level and cumulative exposure had different observed mortality rates. Medication associations varied across groups. Observed 30-day mortality was generally higher with deeper hypotension and a greater proportion of operative time spent below MAP thresholds, although the relationship was not uniformly monotonic.
Conclusions:
Multi-threshold MAP exposure captured mortality-associated information not represented by exposure below MAP 65 mmHg alone, complementing this clinical threshold. The multi-threshold analysis identified groups with distinct pressure-time exposure patterns, providing a basis for hemodynamic profiling and investigation of hypotension-related outcomes. External validation is needed to assess the reproducibility and discrimination of these groups in other populations, followed by prospective studies to determine whether management informed by these patterns improves outcomes.
