The Narcotrend monitor and the electroencephalogram in propofol-induced sedation

Consensus statement on continuous EEG in critically ill adults and children, part I: indications

INTRODUCTION

Critical Care Continuous EEG (CCEEG) is a common procedure to monitor brain function in patients with altered mental status in intensive care units. There is significant variability in patient populations undergoing CCEEG and in technical specifications for CCEEG performance.

METHODS

The Critical Care Continuous EEG Task Force of the American Clinical Neurophysiology Society developed expert consensus recommendations on the use of CCEEG in critically ill adults and children.

RECOMMENDATIONS

The consensus panel recommends CCEEG for diagnosis of nonconvulsive seizures, nonconvulsive status epilepticus, and other paroxysmal events, and for assessment of the efficacy of therapy for seizures and status epilepticus. The consensus panel suggests CCEEG for identification of ischemia in patients at high risk for cerebral ischemia; for assessment of level of consciousness in patients receiving intravenous sedation or pharmacologically induced coma; and for prognostication in patients after cardiac arrest. For each indication, the consensus panel describes the patient populations for which CCEEG is indicated, evidence supporting use of CCEEG, utility of video and quantitative EEG trends, suggested timing and duration of CCEEG, and suggested frequency of review and interpretation.

CONCLUSION

CCEEG has an important role in detection of secondary injuries such as seizures and ischemia in critically ill adults and children with altered mental status.

How best to approach endoscopic sedation?

Sedation is the drug-induced reduction of a patient's consciousness. The aim of sedation in endoscopic procedures is to increase the patient's comfort and to improve endoscopic performance, especially in therapeutic procedures. The most commonly used sedation regimen for conscious sedation in gastrointestinal endoscopy is still the combination of benzodiazepines with opioids. However, the use of propofol has increased enormously in the past decade and several studies show advantages of propofol over the traditional regimes in terms of faster recovery time. It is important to be aware that the complication rate of endoscopies increases when sedation is used; therefore, a thorough risk evaluation before the procedure and monitoring during the procedure must be performed. In addition, properly trained staff and emergency equipment should be available. The best approach to sedation in endoscopy is to choose a sedation regimen for the individual patient, tailored according to the clinical risk assessment and the anxiety level of the patient, as well as to the type of planned endoscopic procedure.

Spectral entropy as a monitor of depth of propofol induced sedation

OBJECTIVE

The aim of this prospective, observational study was to evaluate State and Response entropy (Entropy(TM) Monitor, GE Healthcare, Finland), indices as measures of moderate ("conscious") sedation in healthy adult patients receiving a low dose propofol infusion. Sedation was evaluated using: (I) the responsiveness component of the OAA/S scale (Observer's Assessment of Alertness/Sedation scale) and (II) multi-channel electroencephalogram (EEG) interpretation by a clinical expert.

METHODS

12 ASA I patients were recruited. A target-controlled infusion of propofol was administered (using Schnider's pharmacokinetic model) with an initial effect site concentration set to 0.5 microg ml(-1). A 4 minute equilibrium period was allowed. This concentration was increased at 4 minute intervals by 0.5 microg ml(-1) to a maximum of 2.0 microg ml(-1). State (SE) and Response (RE), entropy values were recorded for each 4 minute epoch together with clinical sedation scores (OAA/S) and continuous multi-channel EEG. The multi-channel EEG recorded during the final minute of each 4 minute epoch or "patient/time unit" was presented to a neurophysiologist who assigned a label "sedated/not sedated". SE/RE values were compared in patient/time units with clinical or EEG evidence of sedation versus those without.

RESULTS

Mean SE and RE values were less in patient/time units when clinical evidence of sedation was present, [mean = 86.8 (95% CI, 84.0-88.3) and 94.3 (95%CI, 92-96.1)], P = 0.002 and P = 0.001, respectively. In patient/time units assigned the label "sedated" by the clinical neurophysiologist assessing the multi-channel EEG, SE and RE values were less [mean = 87.5 (95% CI, 86.3-88.4) and 95.0 (95% CI, 93.8-96.1)] P = 0.001 and P < 0.001, respectively.

CONCLUSIONS

A statistically significant decrease in SE and RE values was demonstrated in patient/time units in which clinical or EEG evidence of sedation was present. We conclude that spectral entropy offers potential as a monitor of propofol induced sedation.