Can CSM Monitor Depth of Anaesthesia Just as Good as BIS?

There is a considerable variation in the need of anaesthetics for the individual patient. For measuring the hypnotic component (i.e. sleep) during anaesthesia, no reliable monitoring system was available before Bispectral Index, BIS (Aspect Medical) was commercially launched about ten years ago. BIS is based on complex mathematical and statistical processing of the electroencephalogram, EEG.

A widespread use of BIS has been limited in part by high costs. Last year a considerably cheaper EEG monitor, Cerebral State Monitor, CSM (Danmeter), was launched into the marked. The validation of CSM is so far limited to very few cases comparing BIS and CSM offline. No large scaled clinical study has been performed to test whether CSM also reflects depth of hypnosis in a reliable way.

We set up a study on 60 relatively healthy patients, undergoing various kind of surgery in general anaesthesia. The study is approved by the Regional Committee of Ethics in Medicine, Health Region East, and all patients give written informed consent. Both monitors (BIS and CSM) are applied to the patients, but only information from BIS is available for the anaesthetist throughout surgery. Information from the two monitors and from the routine monitoring equipment as well as from the actual delivery of anaesthetics is sampled online into a designed data program (Rugloop, Demed, Belgium).

The output from BIS and CSM will afterwards be analyzed together with statistical experts, to see if CSM can predict the time for falling asleep and time for awakening just as good as BIS. The curves for the two monitors will also be compared, qualitatively and quantitatively, to see if they perform equally well.

Inclusion criterias: