Agitation After Desflurane and Dixon and Massey Up-and-Down Method : Anesthesia & Analgesia

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LETTERS TO THE EDITOR: Letters & Announcements

Agitation After Desflurane and Dixon and Massey Up-and-Down Method

Muñoz, Hernán R. MD; Ibacache, Mauricio E. MD

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Anesthesia & Analgesia 96(2):p 628, February 2003. | DOI: 10.1213/00000539-200302000-00062
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To the Editor:

We have read with interest the recent articles by Cohen et al. (1,2) on emergence agitation after general anesthesia in children. In the first of the studies, the authors used the Dixon and Massey (3) up-and-down method to determine the ED50 of fentanyl to reduce emergence agitation after desflurane in children who underwent otorhinolaryngologic surgery (1). We are a bit worried with regard to the use of this methodology in this study design. The Dixon and Massey up-and-down method has been thought to account for dichotomous variables or outcomes (i.e., agitation or no agitation), one of which should occur 100% of the time that the patient is not undergoing the appropriate intervention (i.e., adequate dose of fentanyl) (3). In the aforementioned study, however, the authors used the classic up-and-down method to define the ED50 of fentanyl to reduce the incidence of an outcome such as agitation that they expect to occur in no more than 80% of the cases and eventually in only half the number of patients (1). Thus, in the best scenario, at each dose and just by chance, 20% (but even up to 50%) of the cases will not present agitation resulting in a reduction of the dose for the next case, finally leading to an underestimation of the ED50. Although in a subsequent study the ED50 of fentanyl so determined seems to work (2), we think that the Dixon and Massey up-and-down method was incorrectly used.

Hernán R. Muñoz, MD

Mauricio E. Ibacache, MD


1. Cohen IT, Hannallah RS, Hummer KA. The incidence of emergence agitation associated with desflurane anesthesia in children is reduced by fentanyl. Anesth Analg 2001; 93: 88–91.
2. Cohen IT, Finkel JC, Hannallah RS, Hummer KA, Patel KM. The effect of fentanyl on the emergence characteristics after desflurane or sevoflurane anesthesia in children. Anesth Analg 2002; 94: 1178–81.
3. Dixon WJ, Massey FJ. Sensitivity experiments. In: Dixon WJ, Massey FJ Jr, eds. Introduction to statistical analysis. 4th ed. New York: McGraw-Hill, Inc, 1983: 426–41.
© 2003 International Anesthesia Research Society