Perioperative Fluid Management in Cardiac Surgery: Contemporary Evidence and Clinical Controversies

Perioperative fluid therapy is a cornerstone of anesthetic management in cardiac surgery, where both hypovolemia and hypervolemia are associated with increased morbidity, forming a ``U-shaped'' relationship with outcomes. This narrative review synthesizes evidence from peer-reviewed literature (2000–2024) identified via PubMed, Scopus, and the Cochrane Database, focusing on randomized trials, meta-analyses, and guidelines for adult cardiac surgery. A central debate persists regarding fluid choice. Current evidence supports the preferential use of balanced crystalloids over normal saline, as large-volume saline is linked to hyperchloremic acidosis and reduced renal perfusion. Colloids like albumin and hydroxyethyl starch (HES) offer efficient volume expansion but require caution: contemporary data favor albumin over synthetic colloids in high-risk patients due to coagulation and renal concerns with HES. The review also addresses the impact of cardiopulmonary bypass on hemodilution, inflammation, and electrolyte balance. Key findings indicate that goal-directed or restrictive fluid strategies, guided by advanced monitoring, reduce postoperative complications compared to liberal regimens. However, significant uncertainty remains regarding optimal volumes in specific subgroups (e.g., ventricular dysfunction, complex procedures) and the comparative effectiveness of different balanced crystalloids. Ultimately, fluid management in cardiac surgery must be tailored, evidence-informed, and guided by real-time physiological data.