Recovery Following Desflurane Versus Sevoflurane for Outpatient Urologic Surgery in Elderly Females

Overview

Numerous studies demonstrate that patients have improved immediate recovery characteristics following desflurane anesthesia compared to other volatile agents, including sevoflurane. There is limited evidence in the literature to suggest that patients undergoing sevoflurane, compared to desflurane anesthesia, may suffer from limitation in function and cognitive ability for an undetermined, but prolonged period of time following surgery. These differences are not explained pharmacokinetically and may be a result of a direct neurotoxic effect of sevoflurane. An unresolved question is the time required for the ability to return to complex tasks, such as driving, following anesthesia. Commonly, patients are advised not to drive or make important decisions for 24 hours following anesthesia, but this is not well-studied and proscribed on an empiric, rather than scientific, basis with very limited data available.This study will better define recovery characteristics and characterize the severity and duration of cognitive impairment following sevoflurane or desflurane anesthesia after brief outpatient urologic surgery in elderly females using tests of cognitive ability coupled with performance on a driving simulator and cognitive task tests to objectively measure not only testing performance, but also cognitive effort in performing these tests.

Following IRB-approved consent, 60 patients were be randomized (63 patients to be enrolled accounting for a \<5% screen failure and \<5% dropped patient rates) to receive either a desflurane or sevoflurane-based anesthetic for pelvic floor repair. The selection of the anesthetic gas (sevoflurane or desflurane) was determined by computer generated randomization. Only the Anesthesiologist or the CRNA knows which gas has been administered to the subject. All the investigators and the co-investigator who collected the research data were blinded to the gas selection. Potential subjects were identified during the clinic visit in the Urology Department in Hahnemann University Hospital. On the morning of the surgery, the study investigator who is a medical doctor asked the subjects to perform a baseline cognitive task tests to determine the baseline thinking process. The detailed description of the cognitive task is as following; 1. Mini-Mental Status Exam (MMSE): (10-15 minutes) This is a 30-item measure of global cognition (Folstein, Folstein \& McHugh, 1975) that tests orientation to time and place, object naming, repetition, attention, recall, and following complex commands. 2. Trail Making Test Part A and Part B: Part A (3 minutes) of this measure (Army Individual Test Battery, 1944; Reitan \& Wolfson, 1985) is a test of visual attention where the subjects must draw lines on a page connecting 25 consecutive number as quickly as possible. Part B (5 minutes) requires the subject to alternately sequence numbers and letters randomly distributed on a page into their ascending and alphabetical order as quickly as possible. 3. Digit Symbol Coding: (2 minutes) This subtest of the WAIS-III (Wechsler, 1997) consists of nine digit-symbol pairs followed by a list of digits. Under each digit the subject must write down the corresponding symbol as quickly as possible. 4. Hopkins Verbal Learning Test-Revised (HVLT-R): (8 minutes) Memory for verbal information will be assessed with this list learning task assessing immediate and delayed recall. 5. Stroop Color and Word Test: (5 minutes) This test (Stroop, 1935; Golden, 2002) measures cognitive control by asking subjects to suppress a habitual response in favor of an alternate response. Participants are shown a word and asked to name the color in which the word is written Total time expected for cognitive task tests is 28-33 min. If the patients' were able to drive and have been driving for at least one year, they were required to perform driving simulation. After performing the baseline cognitive task tests, baseline driving simulation (15 minutes) on the driving simulator. After the baseline Cognitive Task Test and Virtual Driving Training session, the subjects underwent their planned surgery. The selection of the anesthetic gas was determined by a computer generated randomization list. The anesthesiologist or the CRNA in charge of the subject administered anesthesia. The investigators and the subjects were blinded to the anesthetic gas given. At the conclusion of the surgery, the anesthetic gas was shut down and the co-investigator was called into the OR to document the time the subjects take to open their eyes after the cessation of the gas. At 30 minutes after discontinuation of the anesthetic gas, the subjects were asked to repeat the same sets of cognitive task tests (28-33 min). And, at 2 hours after the surgery, the subjects repeated the cognitive tasks test (28-33 min) and the driving simulation (20 min) for patients who were able to drive. On the next day of the surgery, the co-investigator had a telephone conversation with the subjects who were discharged home after the surgery. Modified Telephone Interview for Cognitive Status (TICS-M) was used to collect data (10 minutes). This is a 13-item telephone interview (Welsh, Breitner, \& Magruder-Habib, 1993) for late-life cognitive assessment that includes tests of orientation, attention, working memory, praxis, sentence repetition, naming to verbal description, recent memory, word opposites, and an additional immediate and delayed recall of a 10-word list. The subjects' participation in the study ended after this follow-up telephone call. The participants were followed for the duration up to 28 hours. The follow-up and participation in this study ended after 24-28 hours. From date of randomization until the date of first documented progression, end of participation or date of death from any cause, whichever came first, assessed up to 30 days.