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Zerebrales Monitoring
Abstract
Die Registrierung der Hirnströme (Elektroenzephalogramm, EEG) eignet sich zur Patientenüberwachung im Operationssaal und auf
der Intensivstation (Freye u. Levy 2005).
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Continuous electroencephalography (cEEG) seems a suitable modality to detect both cerebral ischaemia and epileptic seizures. In this review we will provide background information on EEG monitoring, discuss features of cerebral ischaemia and epileptiform activity and describe the pitfalls and caveats in performing and interpreting cEEG in the Intensive Care Unit. Copyright © 2008, Nederlandse Vereniging voor Intensive Care. All Rights Reserved.
Due to technological advances, it is now feasible to record continuous digital EEG (CEEG), with or without video, in critically ill patients and review recordings remotely. Nonconvulsive seizures (NCSzs) are more common than previously recognized and are associated with worse outcome. The majority of seizures in ICU patients are nonconvulsive and will be missed without CEEG. Factors associated with an increased risk for NCSzs include coma, prior clinical seizures, CNS infection, brain tumor, recent neurosurgery, and periodic epileptiform discharges. In addition to detecting seizures, CEEG is also useful for characterizing paroxysmal spells such as posturing or autonomic changes, detecting ischemia, assessing level of sedation, following long-term EEG trends, and prognosticating. Most NCSzs will be detected in the first 24 hours of CEEG in noncomatose patients, but longer recording periods may be required in comatose patients or in those with periodic epileptiform discharges. EEG patterns in encephalopathic or comatose patients are often equivocal. How aggressively to treat NCSzs and equivocal EEG patterns in these patients is unclear and requires further research. Real-time detection of ischemia at a reversible stage is technologically feasible with CEEG and should be developed into a practical form for prevention of in-hospital infarction in the near future.
Das EEG-Monitoring bietet als mobil durchführbare Untersuchungsmethode wertvolle Informationen für die Therapiegestaltung bei Intensivpatienten und ist durch neuere technische Entwicklungen inzwischen recht einfach durchführbar. Im vorliegenden Artikel werden Indikationen für das EEG-Monitoring bei plastisch-chirurgischen Intensivpatienten vorgestellt, wie der Einsatz zur Sedierungssteuerung, bei der Hirndrucktherapie, zum Koma-Screening, im Rahmen der Epilepsiediagnostik und -therapie und bei der Herddiagnostik. Außerdem wird über Erfahrungen mit dem neuentwickelten EEG-Monitor Narcotrend® berichtet.
Summary
EEG monitoring can be performed at the patients' bedside and it is a valuable support in therapeutic decision making providing unique information about the functional state of the brain. Due to newer technical developments, EEG monitoring can be conducted rather easily. In this article, indications for EEG monitoring in plastic surgical patients are presented: controlling the level of sedation, use in states of increased intracranial pressure, screening the cerebral state in comatous patients, diagnosis and therapy of epileptic seizures, and the search for circumscribed cerebral abnormalities. Furthermore, practical experience with the use of the new EEG monitor Narcotrend®, which is provided with an automatic EEG classification, is described.
Einleitung: Es sollte geprüft werden, ob das EEG-Monitoring das Dosierverhalten bei Propofolnarkosen beeinflusst, unter besonderer Berücksichtigung von Alter, Geschlecht, Propofol-Applikationsform und Opioidauswahl.
Methodik: In 32 Zentren erhielten 3 542 Patienten Narkosen entweder als total-intravenöse Anästhesie (TIVA) oder target-controlled infusion (TCI). Die Steuerung erfolgte bei 472 Anästhesien nach klinischen Kriterien mit verblindet registriertem EEG, bei 3 070 Anästhesien mithilfe des EEG. Als EEG-Monitor wurde der Narcotrend® verwendet, der eine Einteilung des Narkose-EEG von Stadium A (wach) bis F (sehr tiefe Hypnose) vornimmt.
Ergebnisse: Ohne EEG-Monitoring lagen 5,9% der Narkosen im sehr flachen B/C-Bereich (erhöhtes Awareness-Risiko), 18,7% dagegen im Burst-Suppression-Bereich (individuelle Überdosierung der Allgemeinanästhesie, Stadium F). 67,2% hatten mit D/E ein dem Tiefschlaf entsprechendes Stadium. Durch das EEG-Monitoring änderte sich in den Zentren die Propofoldosierung um −28,4% bis +86,2%. Bei EEG-gesteuerten Narkosen erhielten Frauen im Mittel mehr Propofol als Männer und hatten kürzere Aufwachzeiten. Zudem nahmen die Propofoldosierungen mit zunehmendem Alter stärker ab als ohne EEG, wobei sich die Dosierungen von Frauen und Männern mit steigendem Lebensalter anglichen. Das kurzwirksame Opioid Remifentanil führte im Vergleich zu Fentanyl zu einer signifikanten Reduzierung von Propofolbedarf und Aufwachzeit. Das EEG-Monitoring bewirkte bei der TCI eine deutliche Abnahme des Propofolverbrauchs.
Diskussion: Nach klinischen Kriterien geführte Narkosen waren in erheblicher Zahl zu flach oder zu tief. Das EEG-Monitoring führte zu wesentlichen Änderungen im Dosierverhalten der Zentren.
Schlussfolgerung: Mithilfe des EEG-Monitorings lässt sich der individuelle Propofolbedarf in Abhängigkeit von Geschlecht, Alter und der Opioidauswahl ermitteln.
Einleitung: Bei neurochirurgischen Patienten wurden Narkosen mit und ohne EEG-Monitoring verglichen, um den Einfluss des EEG-Monitorings, des Patientenalters und des Geschlechts auf die Propofoldosierungen zu untersuchen.
Methodik: Es wurden Anästhesien mit Propofol (Disoprivan 2%) bei 76 Patienten (16–78 Jahre alt) mit Tumorkraniotomien untersucht. Bei 50 Patienten erfolgte die Narkosesteuerung unter Zuhilfenahme des EEG-Monitorings (Gruppe 1), bei 26 Patienten allein anhand klinischer Kriterien (Gruppe 2). Die Patienten beider Gruppen erhielten entweder 0,25 μg/kg KG/min (ohne Lachgas) oder 0,15 μg/kg KG/min (mit Lachgas) Remifentanil. Der angestrebte EEG-Stadienbereich während der Narkoseaufrechterhaltung war D2/E0, der einer tiefen Hypnose entspricht [EEG-Monitor: Narcotrend® (MT MonitorTechnik, Bad Bramstedt, Deutschland)].
Ergebnisse: Das EEG-Monitoring führte zu einer niedrigeren (p<0,001) und altersspezifischen (p=0,016) Propofoldosierung. Mit EEG-Monitoring wurde eine Tendenz zu höheren Dosierungen bei Frauen im Vergleich zu Männern beobachtet (Differenz: 15%, p=0,19). Patienten mit EEG-Monitoring wurden früher extubiert als Patienten ohne EEG-Überwachung (p<0,001). Bei Patienten ohne EEG-Überwachung ergab sich keine Korrelation zwischen dem Patientenalter und der Propofoldosierung.
Schlussfolgerung: Das EEG-Monitoring unterstützt eine individuelle Dosierung von Propofol. Die signifikante Propofoleinsparung und der hohe Anteil von frühen Extubationen implizieren einen gesundheitsökonomischen Vorteil des EEG-Monitorings.
Einleitung: In der vorliegenden Untersuchung sollte geprüft werden, ob der Einsatz des EEG-Monitorings zum Zweck der Kontrolle der Sedierungstiefe bei beatmeten Intensivpatienten einen Beitrag zur Verkürzung der Liegezeiten auf der Intensivstation leistet.
Methodik: Daten von beatmeten Patienten einer anästhesiologisch-chirurgischen Intensivstation aus zwei Zeiträumen wurden verglichen: Es handelte sich um ein Jahr, in dem Analgosedierungen ohne EEG-Kontrolle durchgeführt wurden (154 Patienten), und um ein Jahr mit EEG-Kontrollen bei analgosedierten Patienten (161 Patienten). Ziel der EEG-Kontrollen war die Vermeidung von individuellen Überdosierungen, die sich im EEG als Burst-Suppression-Muster darstellen. Zur Sedierung wurden die Substanzen Midazolam und Propofol jeweils in Kombination mit Fentanyl eingesetzt. Das Sedierungsschema oblag den Intensivmedizinern.
Ergebnisse: Im Vergleich zum ersten Jahr ohne EEG-Kontrollen waren in dem Jahr mit regelmäßigen EEG-Kontrollen die Jahrespflegetage aufgrund der signifikanten Reduzierung der Beatmungstage (p<0.001) vermindert. Bei vergleichbarer Gesamtzahl der Patienten (1284 vs. 1280) reduzierten sich die Jahrespflegetage der beatmeten und nicht beatmeten Patienten von 3771 auf 3423.
Diskussion: Mithilfe des EEG-Monitorings lassen sich individuelle Überdosierungen bei der Analgosedierung vermeiden und Liegezeiten von Patienten auf der Intensivstation verkürzen.
Schlussfolgerung: Das EEG ist eine sinnvolle Ergänzung des Sedierungsmonitorings von Intensivpatienten.
Einleitung: Es sollte geklärt werden, inwieweit eine Dosierung des Hypnotikums Propofol entsprechend dem Alter und dem Allgemeinzustand der Patienten mithilfe einer EEG-gestützten Narkoseüberwachung individuell vorgenommen werden kann. Methodik: Während Narkosen mit dem Opioid Remifentanil und dem Hypnotikum Propofol wurde das EEG bei 92 Patienten im Alter von 16 - 84 Jahren (ASA I - IV, 39 m., 53 w.) kontinuierlich mit dem EEG-Monitor Narcotrend® registriert. Die Propofolzufuhr erfolgte mittels einer TCI-Pumpe Diprifusor® und richtete sich nach dem EEG. Angestrebt waren EEG-Stadien im Bereich D2/E0, welche der tiefen Narkose zugeordnet werden. Untersucht wurden Propofoldosierungen und Aufwachzeiten in Abhängigkeit vom Alter und der ASA-Gruppe. Ergebnisse: Der Propofolbedarf nahm pro Lebensdekade um 4,1 % ab (20-Jährige: 3,13 µg/ml, 80-Jährige: 2,45 µg/ml). Die Zeiten vom Ende der Propofolzufuhr bis zum Öffnen der Augen und bis zur Extubation unterschieden sich weder in den ASA-Gruppen I, II und III/IV noch in den Altersgruppen ≤ 50, 51 - 70 und > 70 Jahre signifikant. Bei einer mittleren Remifentanildosierung von 0,22 ± 0,07 µg/kg KG/min betrug der mittlere TCI-Propofolblutspiegel 2,74 ± 0,51 µg/ml. Diskussion: Mithilfe des EEG-Monitorings lässt sich bei der Propofol/Remifentanil-Anästhesie eine altersgerechte und dem Allgemeinzustand angepasste Propofoldosierung ermitteln. Schlussfolgerung: Die routinemäßige Anwendung der EEG-gestützten Narkoseüberwachung kann hinsichtlich einer Optimierung perioperativer Abläufe, sowohl bei Eingriffen mit geplantem postoperativen stationären Aufenthalt als auch bei ambulanten Anästhesien, einen wesentlichen Beitrag leisten.
Seit April 1997 ist in Deutschland ein TCI-System für Propofol (Disoprifusor-TCI®) kommerziell erhältlich. Wir haben Prädiktivität und Präzision dieses Systems untersucht und mit dem Bias, der Präzision, dem Propofolverbrauch und dem Blutspiegelverlauf einer manuell gesteuerten Infusion verglichen. Methode: 21 Patienten erhielten randomisiert eine intravenöse Anästhesie mit Propofol entweder als manuell gesteuerte Infusion oder als TCI. Blutplasmaspiegel wurden mittels HPLC bestimmt. Ergebnisse: Für das untersuchte TCI-System ergab sich eine Präzision von 27,5% und ein Bias von 6,7%. In der manuellen Gruppe betrug der Bias 44,2% und die Präzision 50%. Die durchschnittlich infundierte Propofolmenge (9,0 ± 1,2 vs. 6,6 ± 1,2 mg/kg/h, p p Schlußfolgerung: Die in dieser Studie ermittelte Präzision und der Bias des untersuchten TCI-Systems ist nur unwesentlich größer als die Variabilität der pharmakokinetischen Parameter selbst, und kann somit als akzeptabel angesehen werden.
Gender-related differences in the pharmacology of drugs used in anaesthesiology have been reported by different authors. The aim of this study was to compare propofol dosages in a greater number of male and female patients who had received electroencephalogram (EEG) monitoring to maintain a defined depth of anaesthesia. Data from an EEG-controlled study were analysed with regard to gender differences in the consumption of the short-acting hypnotic propofol during maintenance of total intravenous anaesthesia and with regard to recovery times. The 656 patients (239 male, 417 female) were 15 to 97 years old, underwent different surgical procedures, and received propofol in combination with remifentanil, a short-acting opioid. During the steady-state of anaesthesia the EEG stage D(2)/E(0), which corresponds to deep hypnosis, was the target level (EEG monitor: Narcotrend). Propofol dosages were calculated as mg/kg body weight/h and as mg/kg lean body mass/h. Significantly higher propofol dosages were observed in female patients compared to male patients, especially with lean body mass as a reference parameter. The dosages were characterised by a high interindividual variability. The time from stop of propofol until extubation was significantly shorter in women than in men. The propofol dosage for maintenance of anaesthesia at the EEG level D(2)/E(0) decreased with increasing age.
Electroencephalographic (EEG) recordings were made using a "Narkograph", which performs an automatic on-line interpretation of electroencephalographic data obtained during anesthesia. The EEG was classified into one of 13 stages from A (awake) to F (very deep narcosis). In 20 of roughly 600 patients EEG changes were observed that could not be explained by the effects of anesthetics. Slowing of the EEG occurred during the transition from controlled to spontaneous ventilation and disappeared after minute ventilation increased. The alterations seen during hypoventilation were similar to the effects of hypoxia described in the literature. During the slowing in the rough EEG, waves appeared that were very regularly formed and corresponded to sharp peaks in the power spectrum. These features are rather atypical of the effects of anesthetics such as thiopental, propofol, halothane, isoflurane, and enflurane and were not observed when patients went back to sleep after extubation. If depth of anesthesia is monitored by EEG recording, clinical circumstances should be taken into account because conditions such as hypoxia may cause alterations of the EEG that bear a resemblance to the effects of anesthetics.
Intracranial hypertension is a dangerous condition and is common in patients suffering from a severe head injury or from a variety of pathological problems. Measurement of intracranial pressure (ICP) is considered by many to be a valuable aid in the management of such patients. Despite the invasive nature of the more widely-used measurement techniques, and hence their associated risks, results from many centres have convincingly shown that ICP measurement enables management of intracranial hypertension to be rationally approached, and a direct measure of the progress and outcome of treatment to be obtained. This paper begins with a description of normal cerebrospinal fluid (c.s.f.) pressure. This is followed by an account of the pressure-volume relationship of the intracranial system, and the control mechanisms that regulate the ICP during limited increases in mass volume within the cranium. The consequences of these for patient management are discussed. Reasons why ICP is monitored, and the benefits arising, are described. The paper then concentrates upon the methods of measuring ICP and discusses their relative merits and limitations. A selection of typical pressure sensors is described. Finally, methods that have been devised to monitor ICP and to anticipate intracranial hypertension are reviewed, and the direction of work in this area is assessed.
SUMMARY Depth of anaesthesia and tendency to sleep were assessed by means of electroencephalography in healthy volunteers following
the administration of different intravenous anaesthetics. Graphs of sleep depth were constructed from the records. Characteristic
differences were observed in the postanaesthetic course between methohexitone, thiobarbiturates, neuroleptanalgesics, and
propanidid. Whereas the effects of propanidid rapidly diminished, this was not the case with the other drugs, and even after
12 hours the potentiating effect of a small quantity of alcohol was discernible after methohexitone, thiopentone and thiobutobarbitone.
The results suggest that after intravenous barbiturate anaesthesia for out-patient procedures the patient should be cautioned
against driving or drinking alcohol for 24 hours, but after propanidid a 2-hour period is sufficient.
Within the last two decades, the measurement of intracranial pressure (ICP) advanced from basic research to a useful method in clinical practice. The recording of ICP in clinical diagnosis and therapy requires the knowledge of physical, anatomical and pathophysiological fundamentals, of the different measurement principles and of typical, pathognomonic intracranial pressure patterns. This data will be described in this article. The ICP, and its effects, are based on the anatomy of the almost closed rigid skull which is divided into three "compartments" by pressure-resistent septa (falx, tentorium), and which opens into the spinal dura cavity as a 4th compartment. The pressure is distributed by the CSF, whereby hydrostatic laws must be considered. The brain itself is visco-elastic, and its physical characteristics change in pathological conditions. The pathophysiological effects of intracranial hypertension must be divided into generalized pressure effects and directed pressure actions. The generalized pressure effects are caused by the disturbance of the cerebral blood flow (CBF); their understanding requires the knowledge of the characteristic Pressure-Volume (P/V)-Diagram of the craniospinal space, which can be described by mathematical approximations. The directed actions of an elevated ICP are based on pressure gradients (unequal pressure distribution), which are produced by more rapidly growing local intracranial lesions. These pressure differences cause cerebral mass movements with brain stem incarceration, whereby the "pressure = force per area" - rule must be considered. These anatomical and functional basics are of great importance for the measurement technique; for reliability and safety of ICP registration, the elastic forces of the dura and the brain, the pressure distribution as well as the operative procedure and invasivity of the measurement technique have to be regarded. For clinical routine, less invasive methods using miniaturized transducers for epi- or subdural implantation are favorized above the registration of ventricular pressure, which, however, has its special indications. These problems will be described. Besides a registration of the spontaneous ICP fluctuations, a quantitative determination of the P/V-diagram (compliance, elastance, PVI) and of parameters of the CSF dynamics (resistance, CSF production, Pss) may be useful in clinical practice. In diagnosis, invasive methods with artificial volume load may be used, the techniques will be explained.(ABSTRACT TRUNCATED AT 400 WORDS)
Etomidate was injected i.v. within 10 or 60s at various doses. After etonudate 0.3 mg kg−1 the plasma concentration was 1.6 μg ml at 1 min after the end of injection. For about 7min a good hypnotic effect (stages
C0−D2) was observed on the e.e.g. recording. For surgical procedures, however, a combination with analgesic drugs appeared to
be necessary. When the dose of etomidate was increased (0.1 –0.4 mg kg−1 ) a linear increase in plasma concentration and slow e.e.g activity was observed concomitantly. Anaesthesia could be prolonged
with additional injections or with continuous infusion. Each additional injection produced a steep increase in concentration
of short duration with marked deepening of hypnosis. The infusion induced only a moderate increase in plasma concentration,
whereas the depth of sleep during the period of infusion remained nearly the same. E.e.g. changes induced by etomidate are
similar to those after barbiturates and other i.v. anaesthetics
Unlabelled:
Pain on injection is the most commonly reported adverse event after propofol injection. In a randomized, cross-over study in two groups of 12 healthy male volunteers (24-42 yr), we compared the pharmacokinetics and pharmacodynamics of two new propofol formulations (1% and 2% concentrations) in a fat emulsion consisting of medium- and long-chain triglycerides with the standard propofol formulation. After a single intravenous bolus injection of 2 mg/kg, propofol blood levels were measured for 24 h and evaluated according to an open three-compartment model. The derived pharmacokinetic variables were not different among formulations. Additionally, electroencephalographic recordings of the onset and duration of hypnotic action were comparable with all formulations. After propofol 1% in the new formulation, fewer volunteers reported severe or moderate pain on injection (9%) than after the standard formulation (59%) (P < 0.05). We attribute this result to a lower concentration of free propofol in the aqueous phase of the new formulation.
Implications:
Changing the composition of the carrier fat emulsion for propofol does not have an impact on the pharmacokinetics and efficacy of propofol, but it promises to provide better patient acceptance by lowering the incidence of moderate and severe pain on injection.
We studied 30 female patients undergoing elective surgery, to assess the reliability of electroencephalogram spectral edge frequency and median frequency to predict loss of consciousness and movement in response to skin incision during total intravenous anaesthesia. Each patient received a different combination of propofol (1, 2, 3, 4, 5 or 6 micrograms.ml-1) and sufentanil (0.1, 0.2, 0.3, 0.5 or 1.0 ng.ml-1) target concentrations for induction of anaesthesia using target controlled infusions, assigned randomly. In a logistic regression model, spectral edge frequency was a significant determinant of both loss of consciousness (p = 0.0006) and movement to skin incision (p = 0.0044), whereas for median frequency no significant prediction model could be established. The probabilities of 50% and 95% no response for spectral edge frequency were 13.4 Hz and 6.8 Hz, respectively. The variability of the data limited the predictive value, so that spectral edge frequency was a poor predictor and median frequency was no predictor of response in the individual patient during total intravenous propofol/sufentanil anaesthesia.
This review considers the main principles and indications of EEG and evoked potential (EP) neuromonitoring in the operating room. Neuromonitoring has a threefold purpose: to warn the surgeon that he has to adjust his strategy, to confirm his decision, and to help him improve subsequent procedures. The pathophysiology of intraoperative events liable to alter the EEG or the EPs is first considered. The usefulness of neuromonitoring in preventing neurological complication relies on its ability to detect neurological dysfunction at a reversible stage. This applies especially to ischemia and compressive damage. The anesthetic influences on EEG and EPs are then considered. Knowledge of them is essential to disentangle these neurophysiological alterations due to intraoperative events from those merely due to anesthesia and to use neurophysiological parameters to evaluate the depth of anesthesia. Third, the main indications and limitations of neuromonitoring are considered: prevention of ischemic brain or spinal cord damage, prevention of mechanical injuries of the brain, spinal cord or peripheral nerve, and localization of the motor cortex in cortical neurosurgery or of cranial nerves in posterior fossa surgery. Finally, the 3 levels of neuromonitoring (neurophysiological feature extraction, neurophysiological pattern recognition, clinical integration of the neurophysiological patterns) are discussed together with the rules that should guide the dialogue between the surgeon, the anesthesiologist, and the neurophysiologist.
The Narcotrend is a new EEG monitor designed to measure the hypnotic component of anaesthesia; however, a major clinical evaluation is still missing. This prospective multicentre study was designed to investigate the feasibility of Narcotrend monitoring in a large number of patients under different clinical conditions and to define its impact on recovery times after propofol-based total intravenous anaesthesia.
After legal authority approval and patients'informed consent had been obtained, total intravenous anaesthesia was induced and maintained with propofol and an opioid analgesic at the discretion of the attending anaesthesiologist. In the first 10-15 patients of each centre the anaesthesiologist was blinded to the Narcotrend recordings and propofol was dosed according to clinical needs. In the following patients propofol was infused at a rate sufficient to achieve a target Narcotrend stage of D or E. With termination of propofol infusion,recovery times were recorded and analysed for the patients with or without Narcotrend monitoring; in addition, recovery times were analysed depending on the Narcotrend stage at the moment of termination of propofol infusion.
In total, 4,630 adult patients were studied at 46 institutions, 521 without and 4,109 with Narcotrend monitoring. Demographic data and duration of anaesthesia were comparable. Emergence from anaesthesia was significantly shorter in Narcotrend monitored patients, e.g.opening eyes after 9.8+/-5.9 (mean+/-SD) vs.11.8+/-7.1 min. In addition,awakening was significantly more rapid when the propofol infusion was stopped at a lower level of hypnosis as indicated by Narcotrend monitoring, e.g.opening eyes after 7.1+/-4.5 min with stage C instead of 17.0+/-7.4 min with stage F.
The EEG monitor Narcotrend can be used for adult patients of different ages and during various surgical procedures.Narcotrend monitoring facilitates a reduction of recovery times after propofol-based total intravenous anaesthesia,presumably by allowing for an individual titration of the propofol dosage. Moreover, it appears that the profile of recovery can be optimised when at the end of surgery,the propofol infusion is controlled to Narcotrend stage C instead of D, E, or F.
The Narcotrend is a new electroencephalographic monitor designed to measure depth of anesthesia, based on a six-letter classification from A (awake) to F (increasing burst suppression) including 14 substages. This study was designed to investigate the impact of Narcotrend monitoring on recovery times and propofol consumption in comparison to Bispectral Index (BIS) monitoring or standard anesthetic practice.
With institutional review board approval and written informed consent, 120 adult patients scheduled to undergo minor orthopedic surgery were randomized to receive a propofol-remifentanil anesthetic controlled by Narcotrend, by BIS(R), or solely by clinical parameters. Anesthesia was induced with 0.4 micro x kg-1 x min-1 remifentanil and a propofol target-controlled infusion at 3.5 microg/ml. After intubation, remifentanil was reduced to 0.2 micro x kg-1 x min-1, whereas the propofol infusion was adjusted according to clinical parameters or to the following target values: during maintenance to D(0) (Narcotrend) or 50 (BIS); 15 min before the end of surgery to C(1) (Narcotrend) or 60 (BIS). Recovery times were recorded by a blinded investigator, and average normalized propofol consumption was calculated from induction and maintenance doses.
The groups were comparable for demographic data, duration of anesthesia, and mean remifentanil dosages. Compared with standard practice, patients with Narcotrend or BIS monitoring needed significantly less propofol (standard practice, 6.8 +/- 1.2 mg x kg-1 x h-1 vs. Narcotrend, 4.5 +/- 1.1 mg x kg-1 x h-1 or BIS(R), 4.8 +/- 1.0 mg x kg-1 x h-1; P < 0.001), opened their eyes earlier (9.3 +/- 5.2 vs. 3.4 +/- 2.2 or 3.5 +/- 2.9 min), and were extubated sooner (9.7 +/- 5.3 vs. 3.7 +/- 2.2 or 4.1 +/- 2.9 min).
The results indicate that Narcotrend and BIS monitoring are equally effective to facilitate a significant reduction of recovery times and propofol consumption when used for guidance of propofol titration during a propofol-remifentanil anesthetic.
Cochlear implantation is a widely used means of treating deafness and severe hearing disorders. The surgical procedure includes inserting the cochlear implant electrode array into the cochlea and embedding the corresponding signal receiver in the mastoid bone behind the ear. Postoperative fitting of the externally worn speech processor is very important for successful use of the cochlear implant. For this purpose, electrically elicited stapedius reflex threshold values can be used. However, stapedius reflex threshold values measured intraoperatively are influenced by anaesthetics. The goal of this retrospective study was to find out whether electroencephalogram (EEG) control of anaesthesia produces more reliable reflex threshold values as a basis for the fitting of the speech processor.
Three groups of children, after surgery for cochlear implantation, were analysed with regard to the magnitude of intraoperative electrically elicited stapedius reflex threshold values and their deviations from postoperatively determined maximum comfortable levels (group 1: methohexital/remifentanil with EEG monitoring, n = 10; group 2: isoflurane/fentanyl with EEG monitoring, n = 9; group 3: isoflurane/fentanyl without EEG monitoring, n = 11).
Children with EEG monitoring had significantly lower electrically elicited stapedius reflex threshold values and also significantly lower differences between intraoperative stapedius reflex threshold values and postoperatively determined maximum comfortable levels.
Electroencephalogram monitoring in cochlear implantation is of considerable value in controlling anaesthesia and improving speech processor fitting based on more reliable intraoperative neurophysiological data.
Age-related differences in the spectral composition of the EEG in induction and emergence times, and in drug consumption during propofol anaesthesia were investigated.
The EEGs of 60 female patients between 22 and 85 years of age were monitored continuously during standardized induction of anaesthesia with 2 mg of propofol kg(-1)60 s(-1). The EEGs were visually assessed in 20-s epochs according to a scale from A (awake) to F (very deep hypnosis). Visual EEG classifications, spectral parameters, and induction times were compared between different age groups. Additionally, data of 546 patients included in a multicentre study with 4630 patients (EEG monitor Narcotrend, MT MonitorTechnik, Bad Bramstedt, Germany) were analyzed with regard to age-dependent changes of propofol consumption using target-controlled infusion (TCI).
During induction, patients older than 70 years reached significantly deeper EEG stages than younger patients, needed a longer time to reach the deepest EEG stage, and needed more time until a light EEG stage was regained. In patients aged 70 years and older, the total power, mainly in deep EEG stages, was significantly smaller due to a distinctly smaller absolute power of the delta frequency band. No single spectral parameter was able to reliably distinguish all EEG stages. During the steady state of anaesthesia, older patients needed less propofol for the maintenance of a defined stage of hypnosis than younger patients.
Older patients differ from younger ones regarding the hypnotic effect of propofol and the spectral patterns in the EEG. For an efficient automatic assessment of the EEG during anaesthesia a multivariable approach accounting for age-effects is indispensable.
The Narcotrend performs an automatic interpretation of the electroencephalogram (EEG) during anaesthesia. The classification algorithms have been developed on the basis of visually classified EEG epochs. The classification scheme which was used for these visual assessments has its origin in sleep analysis and was adapted for the EEG during anaesthesia. From the awake state to very deep anaesthesia, 15 stages (A, B(0-2), C(0-2), D(0-2), E(0-2), F(0-1)) are distinguished. The transformation of these stages into a numerical scale from 100 to 0 is a further refinement for a differentiated presentation of EEG effects. For the automatic classification multivariate discriminant functions are used. Age-related changes of the EEG were incorporated. The device contains functions for the identification of artifacts. The EEG can be recorded from a frontal channel using standard ECG electrodes, other electrode positions and types can be chosen. The device has been clinically and scientifically validated.
The Narcotrend Index (NI) of anesthetic depth is potentially a pharmacodynamic measure of the effects of sevoflurane on the brain.
In this prospective observational study of 30 pediatric surgical patients (1-11 years), we investigated the correlation between nonsteady-state endtidal sevoflurane (eT(Sevo)), NI, mean arterial pressure (MAP), and heart rate (HR). The performance of the Narcotrend for differentiation between consciousness and unconsciousness was evaluated using prediction probability (P(K)).
Spearman correlation analysis showed significant correlations (P < 0.01) between eT(Sevo) and NI (r = -0.85) and MAP (r = -0.43). P(K)-values for differentiation between consciousness and unconsciousness were 1.0 for NI and <0.85 for MAP and HR. During the surgical procedure, NI-values showed a constant rise with each 0.5% step of lowering eT(Sevo) (P < 0.03), whereas MAP remained unaltered and HR showed a constant decline (P < 0.03), except between 1.5 and 1%.
In children, nonsteady-state eT(Sevo) concentrations are more closely related with NI than with MAP or HR. In this study, only NI reliably differentiated consciousness from unconsciousness.
While there is an increasing body of knowledge in regard to central nervous system function and/or the mode of action of centrally active agents on neuronal function, little is done to develop new techniques on how to measure such changes. Also, monitoring of the cardiovascular system in the past has made extensive progress especially when it comes to evaluate the failing heart. In contrast monitoring of the central nervous system is only done in rare cases where operative procedures likely impede nervous function integrity. Since in the past decade the aging population undergoing operation has rise considerably, the risk of cerebral malperfusion or minute signs of degradation of the aging central nervous system (CNS) to anesthetics and agents being used in the operation room (OR) or the intensive care unit (ICU), needs continuous monitoring of an organ which presents the highest vulnerability and is likely to deteriorate faster than the cardiovascular system. In spite the rapid improvement in technology regarding the electroencephalogram (EEG) and evoked potential monitoring, physicians still are reluctant to use a technology on a routine base, which will give them insight information into brain function and activity. Such “windows to the brain” now not just are reserved to specialists working in the area of neurology and/or psychiatry. More so, cerebral monitoring is getting an integrated part in the overall therapy in patients undergoing operation or who need ventilatory support in the ICU as it effects the well-being and the outcome. The present book therefore, is intended for the practitioners who work with the patient, guide the clinician in his decision making and outlining those situations where cerebral monitoring presents an integrated part in the diagnosis and therapy of patient care. Without going too much into the technical details, representative cases underline the potential use of cerebral monitoring in the underlying clinical situation where either the patient presents borderline perfusion of the CNS, undergoes vascular surgery, or where monitoring of cerebral function in the intensive care in a head trauma patients is an integrated part in therapy.
The book therefore is meant for all those clinicians who have to deal with the CNS in a day-to-day situation. This may be the anesthesiologist, the surgeon, the intensive care therapist, the nurse anesthetist as well as all other medical personal involved in intensive care therapy. The aim of the book therefore is to outline the possibilities, the limitations, and the options for therapy when the windows to the brain are opened, how to interpret the data in the light of other physiological parameters and aid the user in the technical details of how to avoid artifacts in recording which may have an impact on final decision making. Therefore, emphasis is placed on the electrode placement, artifact and electrical noise reduction, as well as data interpretation so that cerebral function diagnosis can be made on reliable grounds. The following serves as an introduction to and as a reference guide for Cerebral Monitoring in the OR and the ICU:
Gives complete coverage of EEG power spectra analysis.
Describes in detail the EEG machines available to be used in the OR and ICU setting.
Describes in detail the major features of EEG power spectra and evoked potential measurements, including amplifiers, filter setting and microprocessor algorithm for data reduction.
Gives suggestions for assessing and improving signal quality, including noise and artifact rejection, which usually are encountered in the operation room and the intensive care unit, both of which can be considered as electrically contaminated.
Gives examples of EEG power spectra and evoked potential monitoring related to different types of anesthesia, in coma, after head trauma, and for the detection of ischemic events.
In addition, gives complete coverage of those machines being available for the OR and the ICU, including a list of parameters regarding latency and amplitude in evoked potential
As an introductory, recommendations are given for the novice to start cerebral monitoring and guide the beginner in setting up cerebral monitoring in the clinical environment.
Background and objective:
The electroencephalographic Narcotrend Index (NI) is a measure of the hypnotic component of general anaesthesia. The purpose of this study was to evaluate the impact of Narcotrend guidance on propofol consumption and emergence times in children receiving total intravenous anaesthesia with propofol and remifentanil.
Methods:
Thirty children, aged 1-11 yr, scheduled for paediatric urological surgery were enrolled. Remifentanil was given to all patients at a constant infusion rate of 0.3 microg kg [-1] min[-1] throughout anaesthesia. Patients were randomly allocated to receive a continuous propofol infusion adjusted either according to a conventional clinical practice (Group C: n=15) or guided by Narcotrend monitoring (Group NI: n=15; target NI 60+/-5). All patients were connected to the Narcotrend Monitor, but in Group C the anaesthetist was blinded to the screen of the monitor. Propofol consumption (mg kg[-1]h[-1]) and emergence times (min) were the primary and secondary outcome measures.
Results:
Propofol consumption (median [inter-quartile range]) was significantly lower in Group NI compared to Group C (NI: 7.0 [6.4--8.2] vs. C: 9.3 [8.3--11.0] mg kg[-1]h[-1]; P<0.001), whereas Log-Rank-analysis revealed no intergroup difference in emergence times (Group NI: mean [95% confidence interval (CI)] 12.8 [11.2--14.4] min; Group C: 16.4 [12.6--20.2] min; P=0.10). Haemodynamic variables remained stable within age-related limits, and there were no observations of adverse events, especially no clinical signs of intraoperative awareness in any patient.
Conclusion:
Narcotrend monitoring for guidance of propofol/remifentanil anaesthesia in children results in reduced propofol consumption compared to a conventional clinical practice.
The concept of entropy, originally derived from thermodynamics, has been successfully applied to EEG analysis. Various entropy algorithms have been used in clinical studies, but until now a commercially available monitor exists only for spectral entropy. By calculating two distinct values for the EEG dominated part of the spectrum (state entropy, SE) and the total spectrum (response entropy, RE), the M-Entropy module claims to provide useful information regarding the cortical state of the patient as well as an indirect measure of adequacy of analgesia. Generally, entropy has been studied for quantification of anaesthetic drug effect for various GABA-ergic i.v. induction agents and volatile anaesthetics like propofol and sevoflurane and overall was found comparable to the current clinical gold standard bispectral index (BIS). Entropy guidance may not be used during ketamine or nitrous oxide administration, since there is no reliable correlation to the patient's state of consciousness. The usefulness of RE as a surrogate for increased EMG activity due to painful stimulation has not been proven so far.
Since 1997, bispectral index (BIS; Aspect Medical Systems Inc., Natick, MA) has been in clinical practice and a wealth of experimental research has accumulated on its use. Originally, the device was approved only for monitoring hypnosis and has now received an indication for reducing the incidence of intraoperative awareness during anesthesia. Numerous studies have documented the ability of BIS to reduce intermediate outcomes such as hypnotic drug administration, extubation time, postoperative nausea and shortened recovery room discharge. Two recent large-scale outcome studies using BIS (one randomized controlled trial and one prospective, nonrandomized historical cohort study) identified an approximately 80% reduction in the incidence of recall after anesthesia. BIS provides clinicians with unique information that can be used to tailor hypnotic drug doses to individual patient requirements. BIS does not predict movement or hemodynamic response to stimulation, nor will it predict the exact moment consciousness returns. This review will also discuss other BIS applications including use in pediatrics, intensive care and for procedural sedation. Some limitations exist to the use of BIS and it is not useful for some individual hypnotic agents (ketamine, dexmedetomidine, nitrous oxide, xenon, opioids). BIS technology is moving out of the operating room and into diverse environments where conscious and deep sedation are provided. Anesthesiologists need to be actively involved in promoting patient safety and helping transition this technology into broader use.
The use of processed electroencephalography (EEG) using a simple frontal lead system has been made available for assessing the impact of anesthetic medications during surgery. This review discusses the basic principles behind these devices. The foundations of anesthesia monitoring rest on the observations of Guedel with ether that the depth of anesthesia relates to the cortical, brainstem and spinal effects of the anesthetic agents. Anesthesiologists strive to have a patient who is immobile, is unconscious, is hemodynamically stable and who has no intraoperative awareness or recall. These anesthetic management principles apply today, despite the absence of ether from the available anesthetic medications. The use of the EEG as a supplement to the usual monitoring techniques rests on the observation that anesthetic medications all alter the synaptic function which produces the EEG. Frontal EEG can be viewed as a surrogate for the drug effects on the entire central nervous system (CNS). Using mathematical processing techniques, commercial EEG devices create an index usually between 0 and 100 to characterize this drug effect. Critical aspects of memory formation occur in the frontal lobes making EEG monitoring in this area a possible method to assess risk of recall. Integration of processed EEG monitoring into anesthetic management is evolving and its ability to characterize all of the anesthetic effects on the CNS (in particular awareness and recall) and improve decision making is under study.
Central nervous system monitoring in anesthesia and intensive care
- Schulte
- J Esch
- E Kochs
Multivariable nicht-invasive Intensivüberwachung. Fischer
- G Litscher
Neuromonitoring in Anästhesie und Intensivmedizin
- E Rügheimer
- M Dinkel
Therapie des Schädel-Hirn-Traumas-aktueller Stand
- K Steinbereithner
- W Mauritz
- P Sporn
Monitoring der Narkosetiefe: Monoparametrischer oder multivariater Ansatz? Bildschirm aktuell
- A Schultz
- I Pichlmayr
Visual EEG analysis to measure depth of anesthesia. Comparison with an automatic classification
- Aw Doenicke
- Mf Roizen
- J Kugler
- H Bromber
- Ji Lichtor
EEG-gesteuerte Narkosen bei Tumorkraniotomien
- A Schultz
- E Lüllwitz
- B Schultz
- U Grouven
- G Korsch
Narkose-EEG-Stadien bei Einleitung mit 4 mg Propofol/kgKG und Aufrechterhaltung mit 4 mg Propofol
- A Schultz
- U Rohde
- U Grouven
- G Korsch
- J Hausdörfer
- B Schultz
Validierungsuntersuchungen zum EEG-Monitor Narcotrend
- A Schultz
- B Schultz
- U Grouven
The value of EEG-monitoring during cochlear implant surgery in children
- B Schultz
- E Lüllwitz
- A Schultz
Propofoldosierungen und Aufwachzeiten bei Carotis-OPs ohne und mit EEG-Monitoring (Narcotrend)
- G Kraus
- F Mogendorf
- M Bartlog
- U Grouven
- B Schultz
EEG-Monitoring auf der Intensivstation
- B Schultz
- W Wilhelm
- J Bruhn
- S Kreuer
DRGs: Fast-Track-Anästhesie in der Thoraxchirurgie-total intravenöse Anästhesie (TIVA) mit EEG-Monitoring
- K Schulze
- G Kraus
- R Nordhausen
Women need more propofol than men during EEG-monitored total intravenous anaesthesia
- K Haensch
- A Schultz
- T Krauß
Hat die EEG-gestützte Narkoseführung einen Einfluss auf die Erholung der psychomotorischen Funktionen in der frühen postoperativen Phase?
- I Rundshagen
- I Dressier
- N Thattamanil