Temporal overlap of intraoperative hypotension and hypocapnia and postoperative outcomes after major open intracranial surgery: a time-weighted dual-hit cohort study.

Background: Intraoperative hypotension reduces cerebral perfusion pressure, whereas hypocapnia may reflect either ventilation-related cerebral vasoconstriction or reduced pulmonary perfusion during a low-flow state. We evaluated whether the time-weighted overlap of hypotension and hypocapnia was associated with adverse postoperative outcomes after major open intracranial surgery. Methods: We conducted a retrospective cohort study using INSPIRE version 1.4.2. Adults undergoing major open intracranial surgery were included if mean arterial pressure (MAP) and end-tidal carbon dioxide (EtCO Results: The final cohort included 2,286 operations in 2,092 patients. Concurrent hypotension and hypocapnia occurred in 708 operations (31.0%), and the composite outcome occurred after 676 operations (29.6%). Each 5-percentage-point increase in DHCB was associated with higher odds of the composite outcome (adjusted odds ratio, 1.19; 95% CI, 1.10-1.28; Conclusions: Greater temporal overlap between intraoperative hypotension and hypocapnia was associated with adverse short-term postoperative outcomes beyond the corresponding non-overlapping exposure burdens. DHCB should be interpreted as a hypothesis-generating marker of concurrent physiological exposure rather than evidence of two independent causal insults, and requires external validation with neurologically specific outcomes before clinical application.