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

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.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.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%.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.