Baseline cerebral oximetry values depend on non-modifiable patient characteristics.

Abstract Objective The aim of the present study was to evaluate baseline regional cerebral oxygen saturation (rSO 2 ) values and identify factors influencing preoperative rSO 2 in elective minor surgery. Study design Observational analysis post-hoc . Patients and methods Observational post-hoc analysis of data for the patient sample ( n  = 50) of a previously conducted clinical trial in patients undergoing tumourectomy for breast cancer or inguinal hernia repair. Exclusion criteria included pre-existing cerebrovascular diseases, anaemia, baseline pulse oximetry 2 sensor signals. Demographic data, comorbidities, and ASA physical status as well as height and weight were collected prospectively from all patients. Baseline rSO 2 values were recorded while the patient breathed room air, using the INVOS 5100C monitor™ (Covidien, Dublin, Ireland). Results Thirty-seven women (72%) and 13 men (28%) 48 ± 13 years of age were enrolled in this study. Baseline rSO 2 was 62.01 ± 10.38%. Baseline rSO 2 was significantly different between men (67.6 ± 11.2%) and women (60 ± 9.4%), ( P  = 0.023). There were also differences between baseline rSO 2 and ASA physical status (ASA I: 67.6 ± 10.7%, ASA II: 61.6 ± 8.4%, ASA III: 55.8 ± 13.9%, P  = 0.045). Baseline rSO 2 had a positive correlation with body weight ( r  = 0.347, P  = 0.014) and height ( r  = 0.345, P  = 0.014). We also found significant differences in baseline rSO 2 among patients with and without chronic renal failure ( P  = 0.005). No differences were found in any other studied variables. Conclusions Non-modifiable patient characteristics (ASA physical status, sex, chronic renal failure, body weight and height) influence baseline rSO 2 .