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Correspondence

Value of BIS-monitoring for electroconvulsive therapy

Wörden, tom R.1; Kreyig, M.

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European Journal of Anaesthesiology (EJA): January 2007 - Volume 24 - Issue 1 - p 95-96
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EDITOR:

We should like to comment on the article by Hanss and colleagues published in the European Journal of Anaesthesiology [1].

In Hamburg at Klinikum-Nord we have looked at more than 1500 ECT (electroconvulsive treatment) procedures over some decades. One of us (MK) has examined in total some 5000 ECT procedures with anaesthesia and neuromuscular blockade. The clinical impression without (electroencephalogram, EEG-monitoring) for this time has been that, if anything was a problem, then the inadequate seizure duration predictably resulted in less then the desired improvement of most depressive disorders after ECT treatment. In these 5000 procedures no fatal complications occurred and no other serious complications were seen.

If a bispectral index (BIS) value of 50 (why this number?) were mandatory or desirable to proceed with relaxation and ECT treatment, why is our clinical impression, based on several thousand treatments, that this is of no concern? No problems with awareness have been encountered. Even if awareness was not pro-actively searched for it appears reasonable to assume that this problem should have attracted attention. ECT treatment, in particular if successful in terms of seizure duration, does confer amnesia which according to all clinical experience reaches as far back as the application of the cranial shock current. So, as a corollary, if you increase your dose of hypnotics for induction prior to ECT, you will predictably decrease your protection against recall conferred by the seizure to a yet not measured extent. Moreover, as the author points out, in this patient group there is (even) less knowledge about the reliability and informative content of BIS-values than during conventional surgery. The authors fail to explain why BIS readings under these circumstances are valid for ECT treatment.

Studies [2] have shown that EEG-based monitoring of anaesthesia depth does not reliably predict response to noxious stimuli which should be decisive compared to prediction of lack of response to verbal command which might be better predicted by BIS. Even without studies this appears obvious based on clinical experience. Studies [3,4] showing there is a close link between discomfort relieving measures and EEG readings fail to prove that the EEG readings provide any safeguard against perceiving discomfort when the noxious stimulus is actually applied. It is well known that hypnotics produce different levels of EEG readings without necessarily reflecting different levels of hypnosis [5].

We believe that there is no reason why we should assume that the author’s suggestion for monitoring would to any extent improve quality of therapy and outcome in ECT. Little, if anything, suggests that BIS-values after induction for ECT are more significant than clinical experience. We were also surprised that the authors claimed that all 109 patients left the ECT suite basically with the same blood pressure as when they entered. This leaves us somewhat puzzled since there are blood pressure swings almost invariably associated with ECT treatment.

References

1. Hanss R, Bauer M, Bein B et al. Bispectral index controlled anaesthesia for electroconvulsive therapy. Eur J Anaesthesiol 2006; 23: 202–207.
2. Vanluchene A, Struys M, Meyse B, Mortier E. Spectral entropy measurement of patient responsiveness during propofol and remifentanil. A comparison with the bispectral index. Br J Anaesth 2004; 93(5): 645–654.
3. Schwary G, Litscher G, Wang L, Schoepfer A, Roetzer I. The effect of acupressure on the bispectral index and entropy parameters in mentally handicapped humans: a pilot study. Intern J Neuromonit 2005; 4(1).
4. Iannuzzi M, Iannuzzi E, Rossi F, Berrino L, Chiefari M. Relationship between bispectral index, electroencephalographic state entropy and effect-site EC50 for propofol at different clinical endpoints. Br J Anaesth 2005; 94(4): 492–495.
5. Hans P, Dewandre P, Brichant J, Bonhomme V. Comparative effects of ketamine on bispectral index and spectral entropy of the electroencephalogram under sevoflurane anaesthesia. Br J Anaesth 2005; 94: 336–340.
© 2007 European Society of Anaesthesiology