Postoperative Cognitive Dysfunction and the Change of Regional Cerebral Oxygen Saturation in Elderly Patients Undergoing Spinal Surgery

Background: In this study, we examined the relationship between postoperative cognitive dysfunction (POCD) and intraoperative regional cerebral oxygen saturation (rSO₂) in elderly patients undergoing spinal surgery. Methods: We enrolled 87 patients older than 65 years. All patients were tested using a battery of cognitive function tests (Korean Mini-Mental State Examination and visuomotor test of Dynamic Lowenstein Occupational Therapy Cognitive Assessment-Geriatric Version) the day before their surgical operation and on the seventh postoperative day. Our threshold for defining POCD for a given patient was a Reliable Change Index score of <-1.96 occurring on 2 tests. RESULTS: POCD was detected in 20 patients (23%) at the seventh postoperative day. Between-patient baseline characteristics, surgical data, and baseline cognitive function were similar for both those who developed POCD and those who did not. A univariate analysis that included age, female sex, education level, presence of diabetes, and duration of intraoperative decline in rSO₂ to a level of <60% of baseline revealed that only diabetes and duration of rSO₂ <60% (odds ratio, 1.01; 95% confidence interval [CI], 1.005-1.010) were found to be risk factors for POCD. After multivariate logistic regression analysis of these 2 variables, only the duration of rSO₂ <60% (odds ratio, 1.006; 95% CI, 1.00-1.01, P = 0.014) remained as an independent risk factor for POCD. The area under the receiver operation characteristic of the duration of rSO₂ <60% was 0.70 (95% CI, 0.57-0.82; P = 0.008). The optimal cutoff value was 157 minutes with a sensitivity of 75% and specificity of 72%. CONCLUSIONS: This study showed that the duration of decline in rSO₂ <60% during lumbar spinal surgery was correlated with the development of POCD at the seventh postoperative day in elderly patients.