Hydrogel-Based Monitoring in Perioperative Anesthesia: A Conceptual Review and Translational Perspective.

Perioperative anesthesia monitoring increasingly extends beyond intermittent vital-sign measurements to continuous assessment of bioelectrical signals, tissue-device interfaces, local pressure, wound microenvironments, and selected biochemical markers. Hydrogels are attractive soft-interface materials because their water-rich networks can combine tissue-like mechanics, adhesion, ionic or electronic conductivity, microfluidic sampling, molecular recognition, and stimulus-responsive functions. This conceptual review evaluates hydrogel-based monitoring technologies from a perioperative perspective and maps evidence from wearable bioelectronics, microneedle and interstitial-fluid sensing, smart wound care, local drug delivery, and implantable interfaces onto preoperative, intraoperative, and postoperative use cases. Importantly, the current evidence base is predominantly preclinical or derived from adjacent clinical contexts; among the studies summarized, we identified no hydrogel monitoring device that has yet been prospectively evaluated in a dedicated perioperative patient cohort. Accordingly, this review distinguishes demonstrated material and device performance from proposed perioperative applications. We organize the field by dominant material-function systems rather than treating nanostructure as a standalone class, and examine soft-tissue matching, conductivity, wet adhesion, dehydration resistance, shelf life, biosensing accuracy, and device integration. We also discuss translational requirements for perioperative glycemic monitoring and AI-assisted systems, including reference-method validation, independent datasets, explainability, and Software as a Medical Device considerations. Hydrogels are therefore best viewed not as replacements for established anesthesia monitors, but as enabling interfaces that may add continuous local and molecular information. Future progress depends on standardized performance testing, storage and sterilization validation, prospective clinical studies, and regulatory-ready system integration.