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Department of Anesthesiology and Reanimation, Hacettepe University, Ankara, Turkey
To the Editor:
Because of our previous studies on the cognitive function in the elderly patients, we read the study by Chen et al. (1) with great interest.
Postoperative cognitive dysfunction is especially hazardous for the patient when discharged after day-case surgery. Tests such as Mini-Mental State may show a decline in memory efficiency, but may not reflect highly practiced everyday memory skills. Using Broadbent Cognitive Failures Questionnaire (CFQ), a standard measure of mistakes that commonly occur in everyday life (2), we previously compared the cognitive failures over 3 days after halothane, isoflurane, sevoflurane or propofol anesthesia for day-case cystoscopic surgery and found that 50% of 115 patients had worse CFQ scores after anesthesia compared with the preoperative scores without any difference between groups (3).
Although Chen et al. (1) also hoped that the recently introduced short-acting drugs would further improve cognitive outcome by providing fast exit and early return to normal daily activities, they failed to show any clinically significant effect of the anesthetics used. Cognitive complaints after surgery may reflect both actual changes in cognitive performance and other factors such as anxiety, stress of the surgery, and depression (4). We think various factors such as age, limited education, second operation, and rocky postoperative course (5) rather than the type of the anesthetic may explain the relative success of the patients’ adaptations to surgical stress, perioperative anxiety, and ultimately the cognitive function after surgery, so further studies should evaluate these factors more closely.
References
Professor and Holder of the Margaret Milam McDermott Distinguished Chair in Anesthesiology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas
In Response:
Basgul and Akinci have correctly pointed out that nonanesthetic factors can affect the cognitive functioning of the elderly after surgery. Although it is virtually impossible to control all of these potentially confounding factors, the patients in our two anesthetic study groups had very similar demographic characteristics (1). Our study was designed to test the hypothesis that the use of a less soluble volatile anesthetic (e.g., desflurane) would be associated with less residual impairment of cognitive function than a more highly soluble compound (e.g., sevoflurane) in elderly patients undergoing major orthopedic surgical procedures. Even though desflurane was associated with a faster emergence from anesthesia than sevoflurane in this patient population, we found no clinically significant differences in recovery of cognitive function between these two relatively insoluble anesthetic agents. In fact, neither of these volatile anesthetics produced significant impairment beyond the immediate postoperative period, confirming the suggestion that modern inhaled anesthetics do not significantly contribute to "cognitive failures" after surgery.
We would seriously question the statement that "postoperative cognitive dysfunction is especially hazardous for the patient when discharged after day-case surgery." The study by Tzabar et al. (2) utilized a "cognitive failures questionnaire" to evaluate outpatients after general versus local anesthesia. These investigators reported a significantly more frequent incidence of cognitive failures persisting beyond 24 h in the general (versus local) anesthesia group. However, if these two study groups were undergoing different types of surgical procedures, it would not be appropriate to ascribe their findings to general anesthesia per se. In fact, most of the published studies that have alleged to demonstrate long-lasting postoperative cognitive dysfunction have involved elderly patients undergoing major surgery procedures (3,4). If a cognitive function study fails to demonstrate differences between a highly soluble (e.g., halothane) and a highly insoluble anesthetic (e.g., desflurane), the cognitive failures were presumably attributable to nonanesthetic related factors.
In a recent publication involving elderly outpatients undergoing outpatient urologic procedures (5), use of desflurane for maintenance of anesthesia facilitated early cognitive recovery compared with both isoflurane and propofol. Clearly, the increasing use of volatile anesthetics (e.g., desflurane, sevoflurane), which are rapidly eliminated, has minimized the impact of general anesthesia on postoperative cognitive impairment in the elderly. Future cognitive function studies should focus on the contribution of nonanesthesia related factors to postdischarge cognitive problems in the elderly surgical population.
References
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