Publicité
Les langues disponibles
Les langues disponibles
14.1 Introduction
The Cerebral State Monitoring (CSM) is intended for use in monitoring the hypnotic state of the brain by
data acquisition of EEG signals of the anaesthetized or sedated patient in all areas of the hospital. CSM is a
non-invasive measurement tool to be used by a trained professional to measure the level of consciousness
during general anaesthesia and sedation by use of variations in the frequency content of the spontaneous
EEG. It analyses the frequency shifts that take place in the EEG signal as the level of consciousness changes.
Based on this principle, the device calculates the Cerebral State Index (CSI), which is used to estimate the
level of consciousness of the patient.
14.2 Safety Information
Warning
If used with High Frequency (HF) surgery please pay attention to the positioning of CSM
electrodes. In order to reduce the hazard of burns, the electrodes should not be located
between the surgical site and the electro-surgical unit return sensor.
The conductive parts of sensors and their connectors, including the neutral sensor, should
not contact other conductive parts including earth and ground.
The monitor will not render accurate reading when used on patients with severe
neurological disorders and patients under 2 years old.
The use of pacemakers might cause either long periods of artefacts or elevated CSI
values.
If skin rash or other unusual symptoms are developed, remove sensors from patient.
Ethanol is not recommended as a skin cleanser, for it leaves a film layer that may cause
high sensor impedance.
If used with High Frequency surgery during CSM monitoring, then artefacts or elevated
CSI value may be caused.
14.3 Understanding CSM Parameters
CSI
The performance of the CSM is based on the analysis of the frequency content of the EEG signal.
The energy of the EEG is evaluated in specific frequency bands. These are used to define two energy ratios
called alpha (α) and beta (β). Both of these show a shift in energy content from a higher to the lower
frequencies during anaesthesia. The relationship between these quantities is also analysed as a separate
parameter (β-α).
Chapter 14 Monitoring CSM
α
=ln(E
30-42.5Hz
ratio
/E
)
6-12Hz
96
Publicité
