Transcranial Direct Current Stimulation and EEG-Alpha power in elderly undergoing elective on-pump CABG: Design of a pilot exploratory proof-of-concept trial

Background : Cognitive decline is age-related, although some clinical situations and comorbidities may raise and worse the condition. Transcranial Direct Current Stimulation (tDCS), a neuromodulation technique which uses low electrical currents, has previously been used to enhance cognition in healthy elderly. Previous studies points that tDCS raises neuroplasticity markers such as EEG-alpha power. Postoperative cognitive decline (POCD) is a common complication of on-pump coronary artery bypass graft (CABG) surgery, leading to increased postoperative morbidity and mortality. There is no effective treatment to avoid POCD and the tDCS, through raising EEG-Alpha power, may offer better preoperative patient conditions to lower POCD incidence. Once tDCS has never been used in this population before, this is a proof-of-concept design to determine if 10 sessions of tDCS treatment increase EEG-alpha power as compared to sham tDCS in elderly at risk of POCD undergoing elective CABG surgery. Methods : The proposed study design describes a randomized, sham-controlled, double-blinded, single center trial. In total, 40 patients are to be equally divided in blocks of 4 patients and randomized with concealed allocation. Study arms: 1) anodal stimulation or 2) sham stimulation. The primary outcome is the mean EEG-alpha power (difference in tDCS group as compared to sham tDCS). The secondary outcomes include the measurements of cognitive performance before intervention, after intervention and postoperatively, as indexed by The Cambridge Neuropsychological Test Automated Battery (CANTAB) (higher score signalizes cognitive enhancement and lower score cognitive decline). Conclusion : This study is a considerable step before a larger randomized double-blind clinical trial, which provides the information needed for clinical use. This design sheds light on the mechanisms underlying POCD related to EEG-Alpha power and establish the role of tDCS as a tool to enhance cognitive reserve.