Topographic brain mapping of EEG before and after open-heart surgery

Cognitive Function Deterioration After Cardiopulmonary Bypass: Can Intraoperative Optimal Cerebral Regional Tissue Oxygen Saturation Predict Postoperative Cognitive Function?

OBJECTIVE

Cognitive impairment is a common neurologic complication after cardiac surgery with cardiopulmonary bypass (CPB). This study evaluated postoperative cognitive function to determine predictors of cognitive dysfunction, including intraoperative cerebral regional tissue oxygen saturation (rSO₂).

DESIGN

A prospective observational cohort study.

SETTING

At a single academic tertiary-care center.

PARTICIPANTS

A total of 60 adults undergoing cardiac surgery with CPB from January to August 2021.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

All patients underwent Mini-Mental State Examination (MMSE) and quantified electroencephalography (qEEG) 1 day before cardiac surgery, 7 days postoperatively (POD7), and POD60. Intraoperative cerebral rSO₂ was monitored continuously. For MMSE, no significant decrease in MMSE score was found on POD7 versus preoperatively (p = 0.09), but POD60 scores showed significant improvement compared with both preoperative (p = 0.02) and POD7 scores (p < 0.001). On qEEG, relative theta power on POD7 was increased versus preoperatively (p < 0.001), but it was decreased on POD60 (POD7 versus POD60, p < 0.001), and was close to preoperative data (p > 0.99). Baseline rSO₂ was an independent factor for postoperative MMSE. Both baseline and mean rSO₂ showed a significant influence in postoperative relative theta activity, whereas mean rSO₂ was the only predictor for the theta-gamma ratio (p = 0.04).

CONCLUSIONS

The MMSE in patients undergoing CPB declined at POD7 and recovered by POD60. Lower baseline rSO₂ indicated a higher potential for MMSE decline at POD60. Inferior intraoperative mean rSO₂ was related to higher postoperative relative theta activity and theta-gamma ratio, implying subclinical or further cognitive impairment.

Electroencephalography as a tool for assessment of brain ischemic alterations after open heart operations

Cardiac surgery is commonly associated with brain ischemia. Few studies addressed brain electric activity changes after on-pump operations. Eyes closed EEG was performed in 22 patients (mean age: 45.2 ± 11.2) before and two weeks after valve replacement. Spouses of patients were invited to participate as controls. Generalized increase of beta power most prominent in beta-1 band was an unambiguous pathological sign of postoperative cortex dysfunction, probably, manifesting due to gamma-activity slowing (“beta buzz” symptom). Generalized postoperative increase of delta-1 mean frequency along with increase of slow-wave activity in right posterior region may be hypothesized to be a consequence of intraoperative ischemia as well. At the same time, significant changes of alpha activity were observed in both patient and control groups, and, therefore, may be considered as physiological. Unexpectedly, controls showed prominent increase of electric activity in left temporal region whereas patients were deficient in left hemisphere activity in comparison with controls at postoperative followup. Further research is needed in order to determine the true neurological meaning of the EEG findings after on-pump operations.

Cerebral functional changes following cardiac surgery: Neuropsychological and EEG assessment

OBJECTIVE

Some form of organic and functional cerebral deficit may occur in up to one third of patients following cardiopulmonary bypass surgery. This study was designed to assess cerebral functional deficit in cardiac surgical patients.

METHODS

Neuropsychological and quantitative electroencephalographic (EEG) changes were assessed in 62 first time coronary artery bypass graft surgery patients before surgery and within 1 week and 2 months after surgery. Patients underwent surgery with a standard Hammersmith Hospital anaesthesia and hypothermic cardiopulmonary bypass (28 degrees C), using either bubble (Harvey 1700, n = 28) or membrane (Cobe CML, n = 34) oxygenators with arterial line filters (Pall 40 microm). Neuropsychological performance was assessed using a well established battery of ten tests. Four EEG relative power frequency bands; delta (1-3.5 Hz), theta (4-7.5 Hz), alpha (8-11.5 Hz), and beta (12-23 Hz), were determined using Fast Fourier Transformation (FFT).

RESULTS

Neuropsychological and EEG deficits were found in 48% of patients 1 week after surgery and in 34% 2 months after surgery. Post-operative deficits were not associated with duration of perfusion, type of oxygenator used in surgery or patient age. Neuropsychological and EEG deficits were associated 2 months after surgery, but not 1 week after surgery. Post-operative EEG deficit was associated with pre-operative deficit.

CONCLUSIONS

Cerebral functional deficit was found following CABG surgery using quantitative EEG and neuropsychological assessments. Patients who had neuropsychological deficit were also more likely to show EEG deficit. EEG deficit before and after surgery suggests vulnerability of patients with already compromised cerebral function to the effects of CPB procedure.

Quantitative EEG before and after open heart surgery in children. A significant decrease in the beta and alpha 2 bands postoperatively

Quantitative EEGs of 30 patients undergoing open heart surgery were investigated before, 6 days, 11 days and 44 days after operation. The study was conducted in order to investigate whether quantitative EEGs can show postoperative changes in children after open heart surgery. In 28 children, no new neurological signs of cerebral involvement were seen postoperatively. The most striking feature in these children was a significant decrease in the beta and the alpha 2 bands 6 and 11 days postoperatively. The pattern in the delta band was dominated by an increase 6 days postoperatively. Except for a slight decrease in alpha 2 waves, all variables were restored to preoperative values at 44 days after the operation. We found a significant decrease in plasma sodium and chloride after surgery but children with no or slight declines (1-3 mmol/l) also showed increased slow activity postoperatively. Therefore we conclude that an organic brain syndrome, although usually mild and transient, is a general phenomenon after open heart surgery.