In Europe and North America, nearly half of the total health care resources are expended on the elderly. As our population ages, an increasing number of elderly patients will be undergoing anesthesia (1). Because of the physiologic changes associated with aging, elimination of anesthetic drugs is slowed, and therefore, geriatric patients are at an increased risk for drug-induced postoperative complications. Furthermore, in the geriatric patient, the effects of residual anesthesia can delay postoperative mental and psychomotor recovery and consequently prolong the recovery stay (1,2).
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.
After obtaining written, informed consent, 90 geriatric patients were enrolled in this prospective, randomized, double-blinded, IRB-approved study. All participants were 65 yr of age or older and undergoing short elective transurethral surgical procedures. Patients with a history of unstable cardiovascular, pulmonary, hepatic, renal, neurologic, psychiatric, or metabolic diseases were excluded from the study. Patients receiving chronic benzodiazepine or tricyclic antidepressant therapy were also excluded. All perioperative data were collected by a research assistant blinded to the anesthetic treatment group. No preanesthetic medication was administered.
Upon arrival in the operating room, noninvasive blood pressure, electrocardiogram, and arterial hemoglobin oxygen saturation (Spo2) were placed. An A-2000™ Bispectral Index™ monitoring system (Aspect Medical Systems, Natick, MA) was used to record perioperative EEG-BIS values. After baseline values were obtained, all patients received fentanyl 0.5–1 μg/kg IV and breathed 100% oxygen for 2–3 min before the induction of anesthesia with fentanyl 0.5–1 μg/kg IV and propofol 1.0–2.0 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/3™; 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 60–65. 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 25–50 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 (α = 0.05, β = 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 (Bonferroni’s multiple comparison). Drug dosages were analyzed with one-way analysis of variance (Dunn’s 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 χ2 test. In all cases, P < 0.05 was considered statistically significant.
The three study groups were comparable with respect to demographic variables and types of surgical procedures (Table 1). The induction doses of propofol and fentanyl, as well as surgical and anesthetic times, were also similar in all three groups. However, intraoperative boluses of fentanyl were required more frequently in the Desflurane (versus Propofol) group (17 vs 5, respectively) (Table 2). During the induction and maintenance periods, MAP, HR, ETco2, and BIS values (Fig. 1) were comparable among the three groups. At the end of anesthesia, the ET isoflurane and desflurane concentrations and the propofol infusion rate were 0.6% ± 0.2%, 3.2% ± 1.4%, and 86 ± 43 μg · kg−1 · min−1, respectively.
Although the times to LMA removal, emergence, following commands, and orientation were consistently shorter in the Desflurane group, the differences were not statistically significant. However, the time to achieve a fast-track score of 14 was significantly shorter in the Desflurane group (Table 3). On arrival in the PACU, a significantly larger percentage of patients receiving desflurane were judged to be fast-track eligible compared with those receiving isoflurane or propofol (73% vs 43% and 44%, respectively).
The need for therapeutic interventions in the PACU was significantly higher in the Isoflurane group compared with the Propofol and Desflurane groups (86% vs 36% and 20%, respectively). Supplemental oxygen was administered to three (10%), four (13%), and two (7%) patients in the Propofol, Isoflurane, and Desflurane groups, respectively. Furthermore, significantly more patients in the Isoflurane (versus Propofol and Desflurane) group required postoperative opioid analgesics. Although the incidence of postoperative nausea and vomiting was most frequent in the Isoflurane group, this difference did not achieve statistical significance. No intraoperative recall was reported in any of the anesthetic groups.
These data suggest that a large percentage of geriatric outpatients undergoing general anesthesia for short transurethral procedures may be able to safely bypass the PACU. As reported earlier in younger outpatients (5,13), fast-tracking eligibility is influenced by choice of the maintenance anesthetic. Compared with isoflurane and propofol, significantly more patients were fast-track eligible on PACU admission when desflurane was used for maintenance anesthesia. Furthermore, the time required to achieve the fast-track discharge criteria was significantly shorter in the Desflurane group. Finally, the need for therapeutic interventions in the PACU was significantly less among geriatric patients who received desflurane for maintenance of general anesthesia. However, it should be remembered that our favorable results may be specific to the anesthetic technique used, the type of surgery performed, or the short anesthetic and surgical times. Therefore, our results may not apply to other surgical procedures.
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.
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