Patients and Methods: This randomized, controlled, double-blind clinical trial was conducted at a single university hospital. Seventy patients undergoing non-emergency cardiac and aortic surgery requiring cardiopulmonary bypass were enrolled, and 68 patients were included in the final analysis. Patients were randomized to receive either dexmedetomidine (0.5 mcg/kg loading dose, followed by 0.5 mcg/kg/h) or saline. The infusion of dexmedetomidine or saline began at anesthesia induction and continued until the end of surgery. Key microcirculatory variables—total vessel density, proportion of perfused vessels, perfused vessel density, De Backer’s score, microvascular flow index, and heterogeneity index—were measured at five time points: baseline, 1 hour after cardiopulmonary bypass, 1 hour after arrival in the intensive care unit, 24 hours after surgery, and 48 hours after surgery. Data were analyzed using a mixed-effects model with Tukey’s Honestly Significant Difference correction. Intraoperative urine output, the incidence of postoperative acute kidney injury, and other postoperative complications were also compared.

Results: Patients in the dexmedetomidine group maintained higher postoperative proportion of perfused vessels and perfused vessel density compared to the saline group, with a significant interaction effect for perfused vessel density. Baseline perfused vessel density was comparable between the two study groups (17.5 [15.9– 18.6] vs 18.0 [16.1– 19.8] mm/mm², p = 0.540). At 48 hours postoperatively, patients in the dexmedetomidine group had significantly higher PVD values than those in the saline group (17.0 [15.0– 19.0] vs 15.6 [13.7– 16.9] mm/mm²; P = 0.041). The dexmedetomidine group also had significantly higher intraoperative urine output (950 vs 605 mL, p = 0.002). Additionally, the incidence of postoperative acute kidney injury was significantly lower in the dexmedetomidine group (11.8% vs 50%, p = 0.001).

Conclusion: Intraoperative dexmedetomidine infusion during cardiac surgery is associated with higher postoperative microcirculatory state and a reduced incidence of acute kidney injury.