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Departments of *Anesthesiology and Intensive Care and
Urology, Meir Hospital, Kfar Saba, Israel, and the Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel; and the
Department of Anesthesiology and Pain Management, University of Texas Southwestern Medical Center, Dallas, Texas
Address correspondence and reprint requests to Brian Fredman, MB BCh, Department of Anesthesiology and Intensive Care, Meir Hospital, Kfar Saba 44281, Israel. Address e-mail to bdfgls{at}netvision.net.il
| Abstract |
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IMPLICATIONS: Geriatric outpatients undergoing brief urologic procedures more rapidly achieve fast-tracking discharge criteria after desflurane (versus isoflurane and propofol) anesthesia. Use of isoflurane was also associated with an increased need for nursing interventions in the early recovery period compared with desflurane and propofol.
| Introduction |
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Anesthesiologists are beginning to examine novel approaches to facilitating the perioperative process (3,4). Use of shorter-acting anesthetic drugs (e.g., propofol, desflurane, and sevoflurane) (5) and improved titration techniques (e.g., electroencephalographic [EEG] bispectral index [BIS] monitoring) (6,7) can provide for a more rapid emergence from anesthesia and thereby facilitate postanesthesia care unit (PACU) bypassing (i.e., the fast-tracking concept) (8). However, the results of studies involving young ambulatory patients may not be extrapolated directly to the geriatric population undergoing short surgical procedures. Furthermore, because of the effects of the aging process, geriatric patients may require more intensive monitoring in the early postoperative period.
To investigate the effect of different maintenance anesthetic techniques on fast-track eligibility, recovery profiles should be assessed from comparable depths of anesthesia-induced hypnosis. Because intraoperative blood pressure and heart rate (HR) responses can be influenced by underlying cardiovascular disease in the elderly, the EEG-BIS monitor was used to ensure that comparable levels of intraoperative anesthesia-induced hypnosis were achieved (9,10). Therefore, the objective of this prospective, randomized, double-blinded study was to evaluate fast-track eligibility of geriatric outpatients after maintenance of general anesthesia with isoflurane, desflurane, or propofol at comparable EEG-BIS values during short urologic surgical procedures.
| Methods |
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Upon arrival in the operating room, noninvasive blood pressure, electrocardiogram, and arterial hemoglobin oxygen saturation (SpO2) were placed. An A-2000TM Bispectral IndexTM monitoring system (Aspect Medical Systems, Natick, MA) was used to record perioperative EEG-BIS values. After baseline values were obtained, all patients received fentanyl 0.51 µg/kg IV and breathed 100% oxygen for 23 min before the induction of anesthesia with fentanyl 0.51 µg/kg IV and propofol 1.02.0 mg/kg IV. After the induction of anesthesia, a laryngeal mask airway (LMA) was inserted, and 70% nitrous oxide in oxygen was administered.
By use of a computer-generated randomization table, patients were assigned to one of three maintenance anesthetic treatment groups: Group 1 received a variable-rate propofol infusion, Group 2 was maintained with isoflurane, and Group 3 was administered desflurane. The inspired oxygen and end-tidal (ET) concentrations of CO2, isoflurane, desflurane, and nitrous oxide were continuously measured with an infrared gas analyzer (AS/3TM; Datex, Helsinki, Finland).
Hemodynamic and anesthetic variables, as well as EEG-BIS values, were recorded at 3-min intervals from the induction of anesthesia until the patient was admitted to the PACU. The primary maintenance anesthetic was titrated to maintain an EEG-BIS value of 6065. Increases in BIS values, HR, or mean arterial blood pressure (MAP) more than 20% of the preinduction (baseline) recordings were treated by an increase of the inspired isoflurane or desflurane concentration or the propofol infusion rate. Supplemental doses of fentanyl 2550 µg IV were administered to treat persistently increased HR or MAP values not responding to increasing the dose of the primary anesthetic.
The induction time was defined as the time from the initial fentanyl injection until the LMA was inserted. The number of patients requiring assisted ventilation and the occurrence of coughing, breath-holding, laryngospasm, or bronchospasm during the operation were recorded. Upon completion of the surgical procedure, the EEG-BIS value, as well as the ET isoflurane and desflurane concentrations and propofol infusion rates, was recorded. Subsequently, the maintenance anesthetics were discontinued, and 100% oxygen was administered at 8 L/min until the LMA was removed.
The early recovery end points recorded at 1-min intervals after discontinuing the maintenance anesthetics included emergence time (from discontinuation of anesthetics until spontaneous eye opening), command time (from discontinuation of anesthetics until responding to verbal commands), extubation time (from discontinuation of anesthetics until the LMA was removed), orientation time (from discontinuation of anesthetics until patients were able to correctly state their name, age, and identification number), anesthetic time (from first fentanyl dose until removal of the LMA), and the time to achieve fast-track eligibility criteria (i.e., from LMA removal until achieving a fast-track score of 14) (11). Supplemental oxygen was administered only if the SpO2 <96% on admission to the PACU. The need for therapeutic interventions (e.g., supplemental oxygen, analgesic, or antiemetic rescue medications) in the PACU was recorded. The occurrence of intraoperative recall was assessed at the time of discharge from the PACU.
On the basis of the results of previous studies (5,11,12), a power analysis (
= 0.05, ß = 0.8) revealed that 30 patients per group would be required to detect a 3-min difference in the times from discontinuation of anesthesia to achieving fast-track eligibility. Data are expressed as mean values ± SD. In all cases, normality was assessed with the Kolmogorov-Smirnov test (with the Lilliefors modification). Depending on the results of the Kolmogorov-Smirnov analysis, either a parametric or nonparametric analysis was performed. Demographic, hemodynamic, anesthetic, and recovery data; EEG-BIS and ETCO2 values; and the time required to achieve a fast-track score of 14 were analyzed with one-way analysis of variance (Bonferronis multiple comparison). Drug dosages were analyzed with one-way analysis of variance (Dunns multiple comparison). Therapeutic interventions, as well as the number of patients eligible for PACU bypass and incidence of rescue medication administration, were analyzed with the
2 test. In all cases, P < 0.05 was considered statistically significant.
| Results |
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| Discussion |
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In earlier studies involving young women undergoing laparoscopic tubal ligation procedures (5,13), a significantly larger percentage of patients who received desflurane (versus sevoflurane or propofol) for maintenance of general anesthesia were fast-track eligible upon arrival in the PACU. However, unlike in the earlier studies by Apfelbaum et al. (14) and Van Hemelrijck et al. (15), immediate recovery milestones were similar among the groups. These differences may be related to the fact that in these earlier studies, the amount of maintenance anesthetic drug administered was based on cardiovascular variables rather than EEG-BIS values. In addition, fast-tracking was not an option at the time these earlier studies were performed.
In geriatric patients, the physiologic reduction in organ function can decrease the rate of volatile anesthetic elimination. Therefore, use of desflurane for maintenance of general anesthesia would seem to offer advantages because of its lower tissue solubility and lack of dependence on metabolic breakdown for elimination. In addition to its less favorable early recovery profile, isoflurane was associated with an increased need for interventions in the PACU. Despite the economic pressures to use less costly drugs (e.g., isoflurane), pharmacoeconomic analyses should also consider the indirect costs associated with the need for increased nursing interventions in the early postoperative period (16). In our study, desflurane anesthesia was associated with a significantly infrequent incidence of postoperative therapeutic interventions when compared with both isoflurane and propofol. This factor is important in implementing a PACU bypass paradigm because the patient/nurse ratio is higher in lower acuity recovery areas, and it is important to avoid increasing the need for nursing interventions if the benefits of fast-tracking on nursing staffing are to be realized (11,17).
In our study, the EEG-BIS monitor was used to ensure comparable depths of intraoperative hypnosis (9,10). However, although improved technology has minimized the effect of surgical artifacts, the BIS value can increase in conjunction with increased electromyographic (EMG) activity (18). Because these patients did not receive any muscle relaxant medication, it is possible that EMG activity contributed to higher BIS measurements. However, EMG interference is not drug specific, and all patients were breathing spontaneously throughout the operative procedures. Therefore, any EMG-induced "contamination" of the BIS calculation should have been similar in all three anesthetic groups.
In conclusion, the use of desflurane for the maintenance of general anesthesia resulted in a larger percentage of geriatric outpatients being eligible for PACU bypass after short urologic procedures compared with maintenance of anesthesia with either isoflurane or propofol. Despite age-related physiologic changes in organ function, these data suggest that advanced age alone is not a contraindication to fast-tracking outpatients undergoing minor surgical procedures with general anesthesia.
| Acknowledgments |
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| References |
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