Objective. To identify anesthetic risk factors and prevention of loss of free transplanted flaps in breast reconstruction for cancer. Material and methods. Course of anesthesia, surgery and early postoperative period were analyzed in 75 patients who underwent reconstructive surgery for breast cancer. Ten patients with lost flap were subjected to comparative assessment. Anamnestic data, duration of anesthesia, surgery and flap anoxia, hemodynamic parameters, volume and rate of infusion therapy, blood loss, diuresis, intraoperative water balance, acid-based parameters, serum glucose and lactate in perioperative period were evaluated. Nature and timing of postoperative complications and flap loss were analyzed. Results. Intraoperative blood pressure, Hb and acid-based parameters in patients with postoperative flap loss did not significantly differ from patients with uncomplicated postoperative period (p>0.05). In early postoperative period, there were significant differences in acid-based parameters: pH 7.37±0.04, BE –2.6±1.1 mmol/l versus pH 7.43, BE –0.4±1.7 mmol/l, respectively (p<0.001). Serum lactate was higher in patients with flap loss (2.5±0.5 versus 1.6 mmol/l, p<0.001). There were significant differences in volume and rate of intraoperative infusion (4985±1206 versus 3934±1118 ml (p=0.008) and 7.70±2.58 ml/kg/h versus 6.02 ml/kg/h (p=0.023), respectively). Conclusion. Unbalanced infusion therapy could be a risk factor of free perforator flap loss. © 2025 Elsevier B.V., All rights reserved.