Brain Monitoring with Electroencephalography and the Electroencephalogram-Derived Bispectral Index During Cardiac Surgery

Abstract

Cardiac surgery presents particular challenges for the anesthesiologist. In addition to standard and advanced monitors typically used during cardiac surgery, anesthesiologists may consider monitoring the brain with raw or processed electroencephalography (EEG). There is strong evidence that a protocol incorporating the processed EEG Bispectral Index (BIS) decreases the incidence intraoperative awareness compared with standard practice. However there is conflicting evidence that incorporating the BIS into cardiac anesthesia practice improves “fast-tracking,” decreases anesthetic drug use, or detects cerebral ischemia. Recent research, including many cardiac surgical patients, shows that a protocol based on BIS monitoring is not superior to a protocol based on end tidal anesthetic concentration monitoring in preventing awareness. There has been a resurgence of interest in the anesthesia literature in limited montage EEG monitoring, including nonproprietary processed indices. This has been accompanied by research showing that with structured training, anesthesiologists can glean useful information from the raw EEG trace. In this review, we discuss both the hypothesized benefits and limitations of BIS and frontal channel EEG monitoring in the cardiac surgical population.

Independent Predictors of Delay in Emergence From General Anesthesia

“…18,19 Propofol rate was negatively correlated with emergence time, and was significantly decreased in patients using clobazam or clonazepam in this study. Because the depth of the general anesthesia was adjusted according to bispectral index, which is a reliable monitor of conscious level during general anesthesia, 20,21 it is considered that the effect of propofol was enhanced by clobazam and clonazepam, and that a lower propofol rate was enough to maintain the depth of general anesthesia in patients using these drugs. Despite a lower propofol rate, both clobazam and clonazepam were still independent predictors of delay of emergence, suggesting strongly that both drugs enhance the anesthetic effect of propofol.…”

The Feasibility of a Completely Automated Total IV Anesthesia Drug Delivery System for Cardiac Surgery

“…The latter impacts the electroencephalogram decreasing BIS values. 23 Conversely, we found a median PE of −9.9%, including CPB time. It indicates that the median BIS was below the target with a median BIS value of 36 demonstrating that the controller performance tends to overshoot.…”

Neuromonitoring in der Kardioanästhesie

“…Andererseits werden Zeichen einer zu flachen Narkose, wie zum Beispiel Tachykardie oder arterielle Hypertension, durch eine vorbestehende β-Blockade maskiert oder eine Katecholamintherapie überla-gert. Tatsächlich ist die Inzidenz einer intraoperativen Wachheit (Awareness) mit 0,2-2% bei kardiochirurgischen Patienten höher als beim Gesamtpatientenkollektiv (0,1-0,2%, [40,41]). In der prospektiven B-Aware-Studie, die zur Hälfte aus herzchirurgischen Patienten bestand und in der sowohl TIVAs als auch balancierte Anästhesien durchgeführt wurden, konnten Myles et al [41] zeigen, dass das BISMonitoring (Ziel-BIS: 40-60) die Awareness-Rate bei Risikopatienten von 0,91 auf 0,17% senken konnte.…”

“…Ein plötzlicher Abfall des entsprechenden EEG-Index (BIS, Entropie etc.) ist -bei unveränderter Narkosetiefe -verdächtig für das Auftreten einer zerebralen Ischämie [40].…”