Abstract
BackgroundThe 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.MethodsIn 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.ResultsTwenty-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.ConclusionCompared 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 registrationThe 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.
Highlights
The obstructive sleep apnea syndrome (OSAS) is characterized by intermittent cerebral hypoxia which can cause cognitive alterations
Using volatile anesthetic agents such as sevoflurane, clinical studies described its effects on postoperative cognitive dysfunction (POCD) in elderly patients inconsistently and varying conclusions were found
The patients allocated to the moderate to high risk group had a higher score in the STOP-BANG test and a higher risk for OSAS as compared with the patients in the low risk group
Summary
The obstructive sleep apnea syndrome (OSAS) is characterized by intermittent cerebral hypoxia which can cause cognitive alterations. Cognitive reserve, level of education, type of surgery, the anesthetic procedure and reduced or impaired oxygen saturation affects POCD occurrence [6, 7]. Due to respiratory alterations, serious oxygen desaturation and reduced cerebral oxygen supply occur in undetected and undiagnosed obstructive sleep apnea syndrome (OSAS) patients while asleep frequently. Attention, episodic memory, working memory and executive function have been identified as the cognitive abilities mostly affected in OSAS patients [12]. In contrast to these findings, during the last few years preconditioning aspects have gained increasing importance. In surgery settings sevoflurane exhibits neuroprotective effects in acute and repeated preconditioning models in particular [15]
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