{
  "abstract": "BackgroundWhether predictors of intraoperative hypotension (IOH) add information beyond the mean arterial pressure (MAP) already displayed on the monitor is contested: selection bias in common evaluation designs inflates apparent performance, and the field has called for comparisons against simple MAP-based references under bias-resistant protocols. Existing predictors also depend on proprietary waveform analysis or pulse-contour monitors, restricting both deployment and external validation.\n\nMethodsUsing 807 non-cardiac surgery patients from the open VitalDB database, we derived an additive gradient boosting model (one split per tree: a learned shape function per variable, no interactions) from three variables computable from an arterial line alone: current MAP, its drift from the patients own 20-minute baseline, and the growth of its rolling variance (critical slowing down). Evaluation used patient-level 5-fold cross-validation under a strict protocol - exclusion of the 65-75 mmHg grey zone and of all samples already hypotensive at prediction time - with MAP alone (same learner class) as comparator. The frozen model was then validated, without any refitting, on an independent cohort from another continent (MOVER, University of California Irvine) following a pre-registered plan sealed before external data access.\n\nResultsIn development the pressure-only model reached AUROC 0.907 vs. 0.884 for MAP alone ({Delta}AUROC +0.023, 95% CI +0.017 to +0.029) at 5 min, with +0.031 and +0.032 at 10 and 15 min, and good calibration (Brier skill +0.418 vs. prevalence). In external validation on 3 069 patients (442 194 samples, 1-minute charting, event prevalence 5.8%), the advantage not only transferred but was larger than in development: AUROC 0.696 vs. 0.638, {Delta}AUROC +0.058 (95% CI +0.051 to +0.064), meeting both pre-registered gates. Discrimination transferred; calibration did not (external Brier skill -0.014), requiring local recalibration. In the unrestricted scenario, where samples already at threshold are retained, the advantage collapsed (+0.007), reproducing the selection effect this paper documents. A secondary model adding pulse-contour cardiac output and stroke volume variation improved development discrimination further ({Delta}AUROC +0.035) but could be externally validated in only 39 patients, because those signals are rarely recorded.\n\nConclusionsThe dynamics of arterial pressure itself -- drift from a patient-specific baseline and variance growth -- carry predictive information beyond its current value, in a fully interpretable additive model that requires only an arterial line, no waveform access and no proprietary hardware. The advantage is confirmed in a pre-registered frozen-model external validation of over three thousand patients, and is largest at coarse recording cadence, where instantaneous pressure is least informative.",
  "abstract_shown": true,
  "affiliations": [
    "Hospital Universitario Puerta del Mar, Cadiz, Spain"
  ],
  "article_type": "PUBLISHAHEADOFPRINT",
  "arxiv": null,
  "author_total": 2,
  "authors": [
    {
      "affs": [
        0
      ],
      "name": "R. Oyarzun"
    },
    {
      "name": "P. Hernandez"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/63yd0ggmfnsfj.bib",
  "cited_by": 0,
  "doi": "10.64898/2026.08.26.26361468",
  "fulltext_url": "https://www.medrxiv.org/content/10.64898/2026.08.26.26361468v1.full",
  "id": "63yd0ggmfnsfj",
  "issns": [],
  "landing_url": "https://www.medrxiv.org/content/10.64898/2026.08.26.26361468v1",
  "language": null,
  "licence": "CC-BY",
  "licence_label": "CC BY",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "medrxiv",
      "anesthesia"
    ],
    [
      "openalex",
      "2746|Hemodynamic Monitoring and Therapy"
    ]
  ],
  "openalex": "W7204825081",
  "pdf_url": "https://www.medrxiv.org/content/10.64898/2026.08.26.26361468v1.full.pdf",
  "pmcid": null,
  "pmid": null,
  "published": "2026-08-26",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/63yd0ggmfnsfj.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:17:26Z",
      "native_id": "10.64898/2026.08.26.26361468",
      "source": "medrxiv",
      "url": "https://www.medrxiv.org/content/10.64898/2026.08.26.26361468v1"
    }
  ],
  "subjects": [
    {
      "field": "medicine",
      "origin": "medrxiv:anesthesia",
      "subfield": "surgery"
    }
  ],
  "title": "The dynamics of arterial pressure itself predict intraoperative hypotension beyond its current value: an interpretable additive model validated in 3,069 external patients under a selection-bias-resistant protocol",
  "title_text": "The dynamics of arterial pressure itself predict intraoperative hypotension beyond its current value: an interpretable additive model validated in 3,069 external patients under a selection-bias-resistant protocol",
  "type": "preprint",
  "updated_at": "2026-10-30T12:17:42Z",
  "url": "https://research.draconitic.com/paper/63yd0ggmfnsfj",
  "venue": "medRxiv",
  "versions": []
}