Current Affairs of the Heart: Hydration Status in Cardiac Patients Assessed by Bioelectrical Impedance Analysis.

Fluid management in patients with cardiovascular disease and after cardiac surgery remains clinically challenging because of the interplay of surgical trauma, effects of anesthesia, and cardiopulmonary bypass. Both restrictive and liberal fluid management strategies are associated with adverse outcomes. At the same time, current methods for assessing hydration status are limited by invasiveness, operator dependence, or poor reliability. Bioelectrical impedance analysis (BIA) offers a rapid, noninvasive, and cost-effective alternative for evaluating hydration and body composition. Through the measurement of resistance and reactance, BIA provides estimations of total, intracellular, and extracellular water, as well as the degree of overhydration, using BIA-derived indices. Bioelectrical impedance vector analysis and phase angle provide further insights into hydration status, cellular integrity, and prognosis. Evidence supports the value of BIA for detecting overhydration, monitoring decongestion, and predicting outcomes such as mortality, rehospitalization, and cardiac cachexia in congenital and chronic heart failure. In acute heart failure, BIA-derived indices are associated with biomarkers, imaging, and clinical improvements while adding diagnostic and prognostic value. In cardiac surgery, perioperative BIA detects shifts in fluid compartments, helps predict postoperative complications, and is associated with intensive care unit and overall hospital length of stay, as well as mechanical ventilation duration. Despite concerns regarding interference with implantable cardiac devices, multiple studies demonstrate its safety in this population. Overall, BIA represents a promising adjunct to conventional monitoring, offering objective and dynamic fluid assessment that may improve individualized management and risk assessment in cardiovascular care.