[Significance of patient-specific risk factors for regional cerebral oxygen saturation in beach chair position].

Abstract

Background: Despite numerous studies on the regional cerebral oxygen saturation (rSO₂) measured by near infrared spectroscopy (NIRS) in orthopedic patients in the beach chair position, it is still unclear whether patient-specific factors, such as concomitant cardiovascular diseases, are more frequently associated with the occurrence of cerebral desaturation events (CDE).

Objective: The aim of the present study was therefore to identify possible patient-specific risk factors that enable prediction of CDE.

Methods: Data were collected on 397 orthopedic patients undergoing shoulder surgery in the beach chair position. Routine anesthesia management and standard monitoring was used in all patients. Target value for the inspiratory oxygen concentration (F_IO₂) was set to 50% and for the end-tidal carbon dioxide partial pressure to 35-45 mm Hg. RSO₂ was quantified using NIRS. The responsible anesthesiologist was blinded to the rSO₂ data. A decrease in rSO₂ > 20% or a value < 50% in the beach chair position was defined as CDE. Patients with and without CDE were analyzed with respect to different classifications, American Society of Anesthesiologists (ASA) and Revised Cardiac Risk Index (RCRI) as well as existing arterial hypertension and age. A value of p <0.05 was considered statistically significant.

Results: Patients with CDE (n = 238) were significantly more often classified as ASA > 2 (p = 0.01) and RCRI > 1 (p = 0.01), suffered more often from arterial hypertension (p = 0.01) and were older (median: 60 years compared to 55 years; p = 0.01) than patients without CDE (n = 159) in the beach chair position (Wilcoxon rank sum test). Arterial hypertension remained significant after removing the effect of age (p = 0.03) and RCRI classification (p = 0.04; two-way ANOVA multivariate analysis).

Conclusion: On the basis of our study, patient-specific prognosis and risk factors for the occurrence of CDE, such as higher age, ASA > 2 and RCRI > 1 classification as well as pre-existing arterial hypertension could be determined. Arterial hypertension represents the main risk factor for the occurrence of CDE in the beach chair position. RCRI > 1 classification or age, however, only has an effect on the occurrence of pathological rSO₂ values due to the greater probability of simultaneous arterial hypertension.