The effect of perioperative hyperoxia on microcirculation after cardiac surgery remains inconclusive. We evaluated the relationship between intraoperative fractional inspired oxygen and microcirculation after off-pump coronary artery bypass grafting (OPCAB).

Exploratory secondary analysis of a multicenter cluster-randomized trial.

Three teaching hospitals.

Adult patients who underwent OPCAB.

Seven postoperative microcirculatory parameters, including De Backer scores and the proportion of perfused vessels via sublingual microscopy (from all and small vessels), and thenar muscle tissue oxygenation, occlusion slope, and recovery slope via the vascular occlusion test, were compared between patients receiving 30% and 80% oxygen intraoperatively. Generalized estimating equations were used to account for intracluster correlation.

The analysis included 52 and 51 patients from the 30% and 80% oxygen groups, respectively, for sublingual microscopy and 59 and 53 patients for the vascular occlusion test. Although all microcirculatory parameters were similar between groups, the 80% oxygen group had higher De Backer scores for all vessels (mean, 9.8 ± 2.9 mm⁻¹ vs. 8.7 ± 2.0 mm⁻¹; p = 0.011) and small vessels (4.0 ± 1.8 mm⁻¹ vs. 3.4 ± 1.1 mm⁻¹; p = 0.024) than the 30% oxygen group at the end of surgery. The 80% oxygen group also exhibited greater thenar muscle tissue oxygenation immediately before vascular occlusion (78.4% ± 10.5 vs. 74.0% ± 9.3; p = 0.031) and a higher recovery score (4.1%·s⁻¹ ± 1.7 vs. 3.2%·s⁻¹ ± 1.4; p = 0.001).

Patients receiving 80% oxygen during OPCAB had significantly better postoperative microcirculatory profiles than those receiving 30% oxygen. These findings highlight the potential for optimizing perioperative oxygenation to improve or mitigate microcirculatory impairment, thereby reducing postoperative complications.