Bispectral-Index-measured sevoflurane requirement might be decreased in individuals with major depressive disorder

BACKGROUND: GABA (gamma- aminobutyric acid) is the primary inhibitory neurotransmitter in the CNS and well-known target for general anesthetics. In addition, the dysregulation of GABA could be involved in the etiology of major depressive disorder (MDD). In this study, we aimed to determine whether MDD has any effect on anesthetic requirement measured by Bispectral Index (BIS). METHODS: This study was designed as a prospective, observational study, registered ANZCTR (ACTRN 12616001295437), with institutional review board approval and written informed consent. Inpatients who were planned to undergo laparoscopic cholecystectomy as an elective surgery, were enrolled in this study. Patients were divided into two groups, based on the results of the Beck Depression Inventory (BDI) which was assessed the 21-item self-administered scale measuring various symptoms of depression. If the BDI score was under 10, it was accepted as control group. Patients were consulted to the psychiatrist if the BDI score was 17 or more. Patients who were diagnosed as MDD by the psychiatrist, were classified as MDD group. Anesthesia was standardized, and delivered sevoflurane concentration was adjusted according to BIS value in both groups. Parameters of the study were heart rate, non-invasive arterial blood pressure, arterial oxygen saturation, BIS, end-tidal carbon dioxide, and end-tidal concentration of sevoflurane at 5-minute intervals during the operation. RESULTS: End-tidal concentration of sevoflurane was found to be lower in MDD group during the maintenance phase of anesthesia. Mean end-tidal concentration of sevoflurane were significantly lower in MDD group (1.28 +/- 0.15) than control group (1.52 +/- 0.22) (P < 0.0001). BIS values were lower at 5- and 10-minute intervals in MDD group in comparison with control group. BIS values were similar at other time intervals in both groups during surgery. CONCLUSIONS: MDD might result in decreased end-tidal concentration of sevoflurane. Further study is required to identify the relationship between MDD and anesthetics.