British Journal of Anaesthesia, 2004, Vol. 92, No. 2 159-161
© 2004 The Board of Management and Trustees of the British Journal of Anaesthesia
Editorial I
Entropy is blind to nitrous oxide. Can we see why?
1 Department of Anaesthetics, Waikato Clinical School, University of Auckland, Waikato Hospital, Hamilton, New Zealand
*Corresponding author. E-mail: sleighj{at}hwl.co.nz
Declaration of interest. J. W. Sleigh has received assistance to attend the 2003 ANZCA from Datex-Ohmeda.
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‘No one really knows what entropy is, so in a debate you will always have the advantage.’
J. von Neumann to Claude Shannon (Scientific American, 1971; 224: 178).
The word ‘entropy’ tends to cause cessation of rational thought in the reader, reflecting the difficulty we have in understanding this concept. It is therefore risky to base an editorial on the critical examination of why change in the spectral entropy of the EEG may be a useful indicator of consciousness.
In this issue of the journal, Anderson and Jakobsson demonstrate that the administration of incremental doses of propofol, to the point of loss-of-responsiveness, causes a concomitant decrease in the Spectral Entropy of the EEG compared with alert, baseline values.1 In contrast, the administration of nitrous oxide to the same endpoint results in no change in this entropy. In other words, the monitor seems to be blind to the
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