Short term cognitive function after sevoflurane anesthesia in patients suspect to obstructive sleep apnea syndrome: an observational study

BACKGROUND: The obstructive sleep apnea syndrome (OSAS) is characterized by intermittent cerebral hypoxia which can cause cognitive alterations. Likewise, hypoxia induced neurocognitive deficits are detectable after general anesthesia using volatile anesthetics. The objective of this study was to evaluate the association between a moderate to high risk patients of OSAS and postoperative cognitive dysfunction after volatile anesthesia. METHODS: In this single center prospective, observational study between May 2013 and September 2013, 46 patients aged 55 to 80 years with an estimated hospital stay of at least 3 days undergoing surgery were enrolled. Patients were screened using the STOP-BANG test with score of 3 or higher indicating moderate to high risk of OSAS. The cognitive function was assessed using a neuropsychological assessment battery, including the DemTect test for cognitive impairment among other tests e.g. SKT memory, the day before surgery and within 2 days after extubation. RESULTS: Twenty-three of the 46 analyzed patients were identified with a moderate to high risk of OSAS. When comparing post- to preoperative phase a significant better performance for the SKT was found for both groups (p < 0.001). While the moderate to high risk group scores increased postoperative in the DemTect test, they decreased in the low risk group (p < 0.003). When comparing the changes between groups, the moderate to high risk patients showed significant better test result for DemTect testing after anaesthesia. This effect remained robust when adjusting for potential confounding variables using a two-factor ANOVA. CONCLUSION: Compared to low risk, a moderate to high risk of OSAS based on the STOP-BANG score was associated with improved postoperative cognitive function measured by the DemTect test. TRIAL REGISTRATION: The study was approved by the local Ethics committee (Ethikkommission der Medizinischen Fakultät der Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany) (reference number: 87_12 B) on 19.04.2012.