Intraoperative Dexmedetomidine Enhances Postoperative Microcirculation and Reduces Acute Kidney Injury in Cardiac Surgery: A Double-Blind Randomized Trial

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Purpose: Dexmedetomidine, an alpha-2 adrenergic agonist, has shown potential benefits in various surgical settings, but its impact on microcirculation and renal function in cardiac surgery patients remains unclear. 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. Plain Language Summary: This study examined whether a drug called dexmedetomidine can help improve small blood flow (microcirculation) and protect kidney function during heart surgery. Heart surgeries that use a heart-lung machine can disturb blood flow to tiny vessels and may lead to complications like acute kidney injury (AKI). Dexmedetomidine is a commonly used sedative with anti-inflammatory and organ-protective effects. In this single center study, 68 patients undergoing cardiac or aortic surgery were randomly assigned to receive either dexmedetomidine or a saline during surgery. The researchers measured blood flow in the small vessels under the tongue at several time points and tracked urine output and kidney function after surgery. Patients who received dexmedetomidine showed better blood flow in their small vessels and had more urine output during surgery. Most importantly, they had a significantly lower chance of developing AKI compared to those who received saline (11.8% vs 50%). These results suggest that using dexmedetomidine during heart surgery may improve microcirculation and help protect the kidneys. This could lead to better recovery and fewer complications after surgery. The findings provide valuable insight for doctors seeking safer anesthesia options and ways to reduce organ damage in heart surgery patients. Keywords: dexmedetomidine, microcirculation, acute kidney injury, cardiac surgery

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