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LETTER TO THE EDITOR

Is Depth of Anesthesia, as Assessed by the Bispectral Index, Related to Postoperative Cognitive Dysfunction and Recovery?

Department of Pharmacology, The University of Melbourne, Victoria 3010 Australia, colin.royse{at}unimelb.edu.au, http://www.pharmacology.unimelb.edu.au/echocourse/faq.html, http://www.Heartweb.com.au

To the Editor:

Farag et al. (1) reported less postoperative cognitive dysfunction (POCD) in patients who received a greater depth of anesthesia using isoflurane as the maintenance anesthetic. Their work, however, is not consistent with two consensus statements for use of POCD testing in cardiac surgery, where there is the greatest experience with POCD testing (2,3). Specifically, they used 3 rather than 10 tests, and have used group means rather than tracking individual changes, as their primary method of analysis. For studies in cardiac surgery, it is recommended to either use >1 standard deviation (SD) change from baseline in at least 2 of 10 tests, or >20% decline in at least 20% of tests, and individual changes rather than group means are to be used (4). Their power analysis was based on a 0.5 SD change and upon continuous data (group means) rather than categorical data (presence or absence of POCD). To detect 1 SD difference in each of the tests would require a test score difference of 15, and the maximal difference between groups was less than this. I am also concerned that the raw baseline and postoperative data were not shown, and we are not able to determine whether there were group differences in POCD scores at baseline, which could, in part, reflect changes seen in the postoperative setting. I question, from the data presented, whether there were actual differences in POCD between the groups.

REFERENCES

1. Farag E, Chelune GJ, Schubert A, Mascha EJ. Is depth of anesthesia, as assessed by the Bispectral Index, related to postoperative cognitive dysfunction and recovery? Anesth Analg 2006;103:633–40.[Abstract/Free Full Text]
2. Murkin JM, Baird DL, Martzke JS, Yee R. Cognitive dysfunction after ventricular fibrillation during implantable cardiovertor/defibrillator procedures is related to duration of the reperfusion interval. Anesth Analg 1997;84:1186–92.[Abstract]
3. Murkin JM, Newman SP, Stump DA, Blumenthal JA. Statement of consensus on assessment of neurobehavioral outcomes after cardiac surgery. Ann Thorac Surg 1995;59:1289–95.[Free Full Text]
4. Royse AG, Royse CF, Ajani AE, et al. Reduced neuropsychological dysfunction using epiaortic echocardiography and the exclusive Y graft. Ann Thorac Surg 2000;69:1431–8.[Abstract/Free Full Text]

This article has been cited by other articles:

				A. Schubert, E. Farag, and E. J. Mascha Is Depth of Anesthesia, as Assessed by the Bispectral Index, Related to Postoperative Cognitive Dysfunction and Recovery? Anesth. Analg., May 1, 2007; 104(5): 1297 - 1298. [Full Text] [PDF]

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a colleague Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (1) Citing Articles via Google Scholar Google Scholar Articles by Royse, C. Search for Related Content PubMed PubMed Citation Articles by Royse, C.