Anesth Analg 2000;91:250
© 2000 International Anesthesia Research Society
LETTERS TO THE EDITOR
Preoperative Anxiety and Intraoperative Anesthetic Requirements
Kiyoshi Nagase, MD, and
Kaori Ando-Nagase, MSc
Department of Anesthesiology & Critical Care Medicine Gifu University School of Medicine Gifu, 500-8705, Japan
Department of Psychology Faculty of Letters, Nagoya University Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan
We read Maranets and Kain’s article (1) with great interest. We’d like to pose a few questions regarding the article. First, it read that significant correlation was found between trait anxiety and intraoperative propofol infusion rate, but Figure 1B indicated that four outliers, which were over 210 µg · kg-1 · min-1 in propofol infusion, had a large impact on the result. If these outliers were omitted, the correlation would have less significance. Smith et al. (2) reviewed that less than 200 µg · kg-1 · min-1 was sufficient to achieve sedation in propofol infusion with opioid or nitrous oxide. Second, as for the theoretical issue, the authors claimed that it was trait anxiety rather than state anxiety that affected intraoperative anesthetic requirements, but sufficient discussion was not provided regarding its reason. The authors suggested that anesthesiologists should modify the initial induction dose based on the anxiety level of the patients, but the result indicated that anesthesiologists should pay attention to their character in their daily lives, rather than their anxiety level before the surgery. If so, the roll of premedication or preoperative visit to patients to relieve their anxiety will have less meaning.
References
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Maranets I, Kain ZN. Preoperative anxiety and intraoperative anesthetic requirements. Anesth Analg 1999;89:1346–51.[Abstract/Free Full Text]
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Smith I, White PF, Nathanson M, Gouldson R. Propofol: an update on its clinical use. Anesthesiology 1994;81:1005–43.[Web of Science][Medline]
Response
Zeev N. Kain, MD*, , , and
Inna Maranets, MD*
Departments of
*Anesthesiology,
\^Pediatrics, and
Child and Adolescent Psychiatry Yale University School of Medicine New Haven, CT 06510
At the onset of our investigation, we recognized that several potential confounding variables, such as patient population, surgical procedure, sedative premedication, and intraoperative anesthetic technique, must be controlled (1). Further, we realized that the most significant limitation of previous studies is their failure to control for anesthetic depth during the surgical procedure (2–4). That is, one can administer various doses of the same anesthetic agent to achieve "general anesthesia." In this investigation, we used the bispectral index monitor to control for the hypnotic component of the anesthetic depth.
Because of our careful control for all these variables, we do not agree with Nagase and Ando-Nagase’s suggestion that we should ignore 8% of our data because these subjects exhibited very high requirements for propofol. These four subjects did not differ from the larger sample population in any demographic respect, and because we controlled for the above variables, we believe that their high anesthetic requirements reflect a clinical phenomena and not a statistical error. These individuals may, in fact, represent a very interesting subgroup of patients who are highly anxious and who require high doses of propofol. Furthermore, the current trend in the biostatistical literature suggests incorporating all data in the final analysis and using fewer data-elimination methods. This is reflected in the intention-to-treat technique that has been adopted by major medical journals. For example, Lancet now requires from all authors submitting their work to indicate in their cover letter whether intention-to-treat was used for analysis of the data submitted.
As to the second point raised by Nagase and Ando-Nagase, on careful review of our article, one realizes that we recommend that anesthesiologists should modify their propofol dose based on the patient’s base-line anxiety (i.e., trait anxiety) and not state anxiety.
Finally, we reject Nagase and Ando-Nagase’s suggestion that because we did not demonstrate in this investigation that preoperative anxiety and intraoperative anesthetic requirements are strongly related, "the role of premedication or preoperative visit to patients to relive their anxiety will have less meaning." Increased preoperative anxiety is associated with a large number of adverse postoperative outcomes (5–7), and the lack of association between preoperative state anxiety and anesthetic requirements does not diminish the importance of preparation or premedication before surgery.
References
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Maranets I, Kain Z. Preoperative anxiety and intraoperative anesthetic requirements. Anesth Analg 1999;89:1346–51.
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Williams JG, Jones JR, Williams B. A physiological measure of preoperative anxiety. Psychosom Med 1969;31:522–7.[Abstract/Free Full Text]
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Williams JGL, Jones JR, Workhoven MN, Williams B. The psychological control of preoperative anxiety. Psychophysiology 1975;12:50–4.[Web of Science][Medline]
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Goldmann L, Ogg TW, Levey AB. Hypnosis and daycase anaesthesia: a study to reduce pre-operative anxiety and intra-operative anaesthetic requirements. Anaesthesia 1988;43:466–9.[Web of Science][Medline]
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Kain ZN, Mayes LC, O’Connor TZ, Cicchetti DV. Preoperative anxiety in children: predictors and outcomes. Arch Pediatr Adol Med 1996;150:1238–45.[Abstract/Free Full Text]
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Kiecolt-Glaser JK, Page G, Marucha P, et al. Psychological influences on surgical recovery. Am Psychol 1998;53:1209–18.[Medline]
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Johnston M. Pre-operative emotional states and post-operative recovery. Adv Psychosom Med 1986;15:1–22.
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