Evaluation of Oxidative Stress Biomarkers and Antioxidant Capacity as Prognostic Indicators in Canine Patients Undergoing Major Abdominal Surgery in South East Nigeria

Oxidative stress induced by surgical trauma activates reactive oxygen species pathways that can amplify systemic inflammatory responses and impair postoperative recovery in dogs undergoing major abdominal surgery. The utility of perioperative oxidative stress biomarkers as prognostic indicators for surgical outcomes has not been investigated in Nigerian canine patients. This doctoral study evaluates preoperative and perioperative oxidative stress biomarkers and total antioxidant capacity as prognostic indicators for postoperative complications and recovery in dogs undergoing major abdominal surgery at teaching hospitals in Enugu, Imo, and Anambra States, South East Nigeria, between 2022 and 2024. One hundred and eight dogs undergoing elective and emergency major abdominal surgery were prospectively enrolled. Serum malondialdehyde, superoxide dismutase activity, glutathione peroxidase, and total antioxidant capacity were measured at baseline, two hours intraoperatively, and at 24 and 72 hours postoperatively. Postoperative outcomes including wound healing quality, complication severity, and hospital stay duration were recorded. Preoperative malondialdehyde levels above the population 75th percentile were associated with a 2.9-fold higher risk of major postoperative complications. Dogs with low preoperative total antioxidant capacity had significantly prolonged hospital stays. Intraoperative malondialdehyde surge was the strongest predictor of 30-day postoperative morbidity. Preoperative antioxidant supplementation with vitamin E and selenium significantly moderated the intraoperative oxidative stress surge in a secondary intervention subgroup. This doctoral study provides original mechanistic and prognostic insights into the role of oxidative stress in canine surgical outcomes in South Eastern Nigeria, with direct implications for preoperative patient optimization protocols. Keywords: oxidative stress, malondialdehyde, canine abdominal surgery, prognostic biomarker, antioxidant capacity.