Major cancer surgeries often involve significant intraoperative blood loss and require transfusion. Conventional markers, such as hemoglobin (Hb) and hematocrit (Hct), provide limited insight into tissue oxygenation and transfusion thresholds. Near-infrared spectroscopy (NIRS) is a non-invasive approach for monitoring regional tissue oxygen saturation and guiding transfusion decisions. This study aimed to evaluate the role of cerebral (cSO₂) and peripheral (pSO₂) NIRS measurements in identifying intraoperative blood loss and determining transfusion thresholds during major cancer surgeries.

This prospective observational study included 65 patients aged 18-75 years who underwent major cancer surgery. cSO₂ and pSO₂ were monitored at three time points: baseline (T1), pre-transfusion or significant blood loss (T2), and the end of surgery (T3).Hemodynamic parameters, acid-base status, hemoglobin levels, estimated blood loss, and transfusion volumes were recorded.Patients were divided into transfused (group 1) and non-transfused (group 2) cohorts. Statistical analyses included t-tests, Mann-Whitney U tests, and receiver operating characteristic (ROC) analysis.

Inclusion Criteria:

• American Society of Anesthesiologists (ASA) physical status I-III
• major cancer surgery in the General Surgery, Urology, and Obstetrics and Gynecology departments

Exclusion Criteria:

• carotid artery stenosis
• recent myocardial infarction
• history of cerebrovascular events
• prior neck surgery,
• cervical disc herniation
• spinal cord injury,
• sudden vision loss,
• deep vein thrombosis,
• refusal to participate.

Sixty-five adult patients (aged 18-75 years) with American Society of Anesthesiologists (ASA) physical status I-III who were scheduled for major cancer surgery in the General Surgery, Urology, and Obstetrics and Gynecology departments