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

Electroencephalography findings in patients with acute post coronary artery bypass graft encephalopathy

OBJECTIVE

To determine the EEG findings associated with acute post coronary artery bypass graft encephalopathy (aPCE), and to study the demographics and neuroimaging findings.

METHODS

We reviewed the EEG in all patients with the diagnosis of PCE between February 2006 and December 2011.

RESULTS

We identified 21 (20 males, and one female) patients with aPCE. The mean age (+/-SD) was 64 (+/-11.2) years. Thirteen patients had altered level of consciousness, and 8 presented with confusion out of which 3 had acute seizures. The EEG patterns observed were: a) generalized theta plus intermixed diffuse delta in 7 (33%); b) generalized theta with focal epileptiform discharges in 5 (24%); c) generalized triphasic pattern in 3 (14%); d) generalized theta with lateralized delta in 3 (14%); e) generalized theta with periodic lateralized epileptiform discharges (PLEDs), and bilateral synchronous periodic epileptiform discharges (BIPLEDs) in 2 (10%); and f) one patient (5%) with electrographic seizures. On EEG/neuroimaging correlation, the EEGs that showed generalized slowing and generalized triphasic patterns had no acute changes on imaging, while the EEGs that showed lateralized slowing, focal epileptiform discharges, electrographic seizures and PLEDs had fresh infarcts. Patients with BIPLEDs had unremarkable imaging.

CONCLUSION

The EEG features such as lateralized slowing, PLEDs, and electrographic seizure were associated with acute cerebral insults. An altered level of consciousness was the most common symptomatology in our cohort, and could possibly be related to hypoxic/toxic-metabolic etiology. Electrographic seizure detected by EEG may clinically present as aPCE.

Effects of acute bleeding followed by hydroxyethyl starch 130/0.4 or a crystalloid on propofol concentrations, cerebral oxygenation, and electroencephalographic and haemodynamic variables in pigs

Bleeding changes the haemodynamics, compromising organ perfusion. In this study, the effects of bleeding followed by replacement with hydroxyethyl starch 130/0.4 (HES) or lactated Ringer's (LR) on cerebral oxygenation and electroencephalogram-derived parameters were investigated. Twelve young pigs under propofol-remifentanil anaesthesia were bled 30 mL/kg and, after a 20-minute waiting period, volume replacement was performed with HES (GHES; N = 6) or LR (GRL; N = 6). Bleeding caused a decrease of more than 50% in mean arterial pressure (P < 0.01) and a decrease in cerebral oximetry (P = 0.039), bispectral index, and electroencephalogram total power (P = 0.04 and P < 0.01, resp.), while propofol plasma concentrations increased (P < 0.01). Both solutions restored the haemodynamics and cerebral oxygenation similarly and were accompanied by an increase in electroencephalogram total power. No differences between groups were found. However, one hour after the end of the volume replacement, the cardiac output (P = 0.03) and the cerebral oxygenation (P = 0.008) decreased in the GLR and were significantly lower than in GHES (P = 0.02). Volume replacement with HES 130/0.4 was capable of maintaining the cardiac output and cerebral oxygenation during a longer period than LR and caused a decrease in the propofol plasma concentrations.

Cognitive dysfunction after on-pump operations: neuropsychological characteristics and optimal core battery of tests

Postoperative cognitive dysfunction (POCD) is a mild form of perioperative ischemic brain injury, which emerges as memory decline, decreased attention, and decreased concentration during several months, or even years, after surgery. Here we present results of our three neuropsychological studies, which overall included 145 patients after on-pump operations. We found that the auditory memory span test (digit span) was more effective as a tool for registration of POCD, in comparison with the word-list learning and story-learning tests. Nonverbal memory or visuoconstruction tests were sensitive to POCD in patients after intraoperative opening of cardiac chambers with increased cerebral air embolism. Psychomotor speed tests (digit symbol, or TMT A) registered POCD, which was characteristic for elderly atherosclerotic patients. Finally, we observed that there were significant effects of the order of position of a test on the performance on this test. For example, the postoperative performance on the core tests (digit span and digit symbol) showed minimal impairment when either of these tests was administered at the beginning of testing. Overall, our data shows that the selection of tests, and the order of which these tests are administered, may considerably influence the results of studies of POCD.

SYNTAX score effect on electroencephalography power dynamics in patients undergoing on-pump coronary artery bypass grafting

Background

The severity of angiographically assessed coronary artery disease may be the factor that influences the degree of brain damage during on-pump surgery. Modern technology such as computed electroencephalography (EEG) that is used to detect signs of brain damage could also be used to determine the advantages and disadvantages of various surgical myocardial revascularization methods in certain categories of patients. The present study investigated EEG power dynamics for 1 postoperative month in patients undergoing on-pump coronary artery bypass grafting (CABG) who were divided into two groups: those with moderate coronary lesions (SYNTAX score ≤ 22, n = 12) and those with severe coronary lesions (SYNTAX score ≥ 23, n = 18).

Results

At 7–10 days after CABG, all patients showed theta type 1 rhythm power higher than that seen preoperatively, possibly indicating that brain damage occurred during bypass. At 1 month after CABG, the theta type 1 rhythm power had decreased to the baseline level in patients with SYNTAX scores of ≤22, whereas it had increased in patients with SYNTAX scores ≥23.

Conclusions

SYNTAX scores ≥ 23 are associated with EEG markers of perioperative brain damage during CABG. Careful preoperative assessment, preparation, and more effective intraoperative brain protection are essential for this category of coronary heart disease (CHD) patients.