Timing of Redox Imbalances in Cardiac Surgery

Cardiac surgery perturbs oxidative metabolism, increasing reactive oxygen species (ROS) and reduces various endogenous antioxidants. Yet, most clinical studies rely on indirect oxidative stress markers. We assessed whether direct perioperative ROS measurement is feasible and whether vitamin C supplementation is associated with altered ROS dynamics.

We quantified highly reactive oxidants in venous blood of cardiac surgery patients (n=37) and healthy controls (N=38) using electron paramagnetic resonance (EPR) spectroscopy with X-band EMX-nano spectrometer. Patients were sampled preoperatively (T1), at the end of surgery (T2), on postoperative day (POD) 1 (T3), and POD 7 (T4). Serum zinc, selenium, vitamins A/C/E, and coenzyme Q10 were measured by standardized laboratory methods. Patients were grouped by perioperative intravenous vitamin C supplementation (C+, n = 22; C-, n = 15). Clinical variables were extracted from medical records.

Patients had higher preoperative ROS than controls (5.40 ± 2.94 vs 1.49 ± 0.89 µM; p < 0.001) and reduced antioxidant reserves, with 23-47% showing subnormal zinc, selenium, or vitamin C. Zinc, selenium, vitamin A, and coenzyme Q10 declined further during and after surgery. ROS were consistently lower in C+ than C- with greatest difference at T2 (p = 0.054) and significance at T3 (p = 0.027). Serum vitamin C inversely correlated with ROS (r = -0.47; p < 0.00001).

Perioperative ROS measurement by EPR can be performed in routine clinical practice. Cardiac surgery patients have elevated preoperative oxidative burden that worsens perioperatively. Vitamin C supplementation is associated with lower perioperative ROS, supporting targeted perioperative redox interventions.