Nociception monitoring during cardiac surgery with cardiopulmonary bypass: limitations and future directions.

Adequate suppression of nociception remains a fundamental objective of modern cardiac anaesthesia. Interpretation of nociception monitoring during cardiac surgery involving cardiopulmonary bypass (CPB), however, is complicated by profound physiological alterations including non-pulsatile circulation, cardioplegic arrest, temperature modulation, vasoactive and inotropic support, pacing, haemodilution, and systemic inflammatory responses. Current monitoring technologies rely on surrogate autonomic, vascular, pupillary, and electroencephalography-derived signals, many of which become difficult to interpret during CPB. Although several modalities demonstrate responsiveness to surgical stimulation under relatively stable perioperative conditions, cardiac-specific validation remains limited and extrapolation of available evidence into CPB conditions remains uncertain. This article discusses the principal physiological limitations affecting intraoperative nociception monitoring during adult cardiac surgery and highlights priorities for future cardiac-specific validation and context-aware analytical approaches.