Pressure-flow discordance in perioperative pulmonary hypertension: a mechanism-based review and provisional five-domain right-heart model for noncardiac surgery.

Pulmonary hypertension increases perioperative risk because anesthesia, positive-pressure ventilation, bleeding, and surgical stress can rapidly disturb coupling between the right ventricle and the pulmonary circulation. Pulmonary artery pressure alone cannot distinguish successful unloading from loss of right-ventricular output. This narrative review integrates contemporary guidance, noncardiac surgical cohorts, right-heart physiology, echocardiography, and critical-care evidence and then proposes a provisional five-domain model. The domains are pulmonary vascular load; right-ventricular reserve and ventricular-arterial coupling; systemic perfusion; effective preload and venous congestion; and forward flow and oxygen delivery. The underlying physiology and most component management principles are established; the novel contribution is their longitudinal organization into pressure-flow trajectories, provisional dominant phenotypes, and timestamped intervention-response pairs. Evidence provenance is labeled as guideline or consensus, direct perioperative clinical data, extrapolated physiologic or critical-care evidence, or an unvalidated framework hypothesis. A measurement hierarchy separates quantitative cardiac-output estimates from stroke-volume trends and from downstream perfusion surrogates. Provisional classification requires a core directional pattern plus corroboration from independent domains and permits mixed or indeterminate states. Disease group remains decisive because the same trajectory may imply different hazards in precapillary, postcapillary, lung-disease, or thromboembolic pulmonary hypertension. During controlled instability, one small matched intervention can test the working mechanism; during immediately life-threatening deterioration, parallel resuscitative actions take precedence. The proposed model must demonstrate reproducible classification and incremental value beyond contemporary clinical risk assessment, right-ventricular function, biomarkers, procedure characteristics, and conventional monitoring before it is used as a treatment algorithm.