The availability of less soluble inhalation anesthetics such as sevoflurane and desflurane has led to a reassessment of the use of volatile anesthetics for outpatient surgical procedures. Given the low blood-gas partition coefficients of sevoflurane (0.69) and desflurane (0.42) [1,2], a more rapid emergence from anesthesia is expected compared with traditional inhalation anesthetics. Not surprisingly, both drugs have shorter emergence times compared to isoflurane-based techniques [3-8]. Although it has been suggested that desflurane is the volatile drug of choice for ambulatory surgery , its use is associated with a high incidence of coughing and laryngospasm during inhalation induction of anesthesia , and desflurane-induced sympathetic stimulation can result in transient hypertension and tachycardia [11,12]. Although both desflurane and sevoflurane have been investigated extensively , no direct comparison has been published to date.
The objective of this preliminary study was to test the hypothesis that the maintenance and recovery profiles of sevoflurane and desflurane are equivalent when used as part of a standardized balanced technique for outpatient anesthesia.
After review board approval, 42 healthy consenting (ASA class I or II) outpatients scheduled for laparoscopic tubal ligation procedures were studied. After a standardized induction sequence, patients received either sevoflurane or desflurane for maintenance of anesthesia using an open (nonblinded) study design. Patients with clinically significant cardiovascular, respiratory, hepatic, renal, neurologic, psychiatric, or metabolic disease were excluded. Pregnant women, or those who had undergone a recent anesthetic (within the previous 7 days), were also excluded.
No preanesthetic medication was administered. In the preoperative holding area, patients completed a baseline digit-symbol substitution test (DSST), and 100-mm visual analog scales (VAS) for sedation, energy, confusion, coordination, nausea, and pain, with scores from 0 = none to 100 = maximum effect. During the procedure, routine monitoring included esophageal temperature, electrocardiogram (lead II), hemoglobin oxygen saturation (SpO2), and noninvasive mean arterial pressure (MAP) and heart rate (HR) values. The inspired oxygen concentration and end-tidal concentrations of N2 O, CO2, sevoflurane, and desflurane were recorded at 5-min intervals (and upon discontinuation of the inhaled drug). Volatile anesthetic concentrations were determined using an infrared gas analyzer (Datex Ultima; Datex Medical Instrumentation, Tewksbury, MA) for sevoflurane and a Raman spectroscopy analyzer (Ohmeda Rascal Trademark; Ohmeda, Madison, WI) for desflurane. Sevoflurane was administered using a Sevotec IV Trademark vaporizer (Ohmeda) and desflurane was administered using an Ohmeda TEC Trademark vaporizer (Ohmeda).
All patients received fentanyl, 1-2 micro gram/kg intravenously (IV), and then breathed 100% oxygen for 3 min prior to induction of anesthesia. Anesthesia was induced with propofol, 1.5-2.0 mg/kg, IV. After loss of consciousness, ventilation of the lungs was manually assisted. Neuromuscular block was achieved with vecuronium, 0.1 mg/kg IV. The trachea was intubated after the loss of all four twitches to a train-of-four stimulus, and patients subsequently received either sevoflurane 1%-2% or desflurane 3%-6% with N2 O 60% in O2. The inspired concentration of the volatile anesthetic was adjusted to maintain MAP within 20% of baseline values. Additional bolus doses of fentanyl, 0.5-0.75 micro gram/kg IV, were administered to control acute hemodynamic changes that did not respond to a 50% increase in the inspired concentration of the volatile drug. During the maintenance period, ventilation was controlled to maintain normocarbia with a fresh gas flow of 3.0 L/min, using a semiclosed circle system. Incremental doses of vecuronium, 0.5-1 mg IV, were given for increases in peak inspiratory pressure which did not respond to an increase in the inspired concentration of the inhaled drug. MAP, HR, SpO2, esophageal temperature, and end-tidal CO2, N2 O, and volatile anesthetic concentrations were recorded every 1-2 min after induction for 15 min, then every 5 min from skin incision until the end of the operation.
Upon completion of surgery, residual neuromuscular block was reversed with neostigmine (40-80 micro gram/kg IV) and glycopyrrolate (8-16 micro gram/kg IV). The volatile anesthetic and N2 O were discontinued after reversal of neuromuscular block, and the lungs were ventilated with 100% O2 at a fresh gas flow rate of 10 L/min. The following emergence times were evaluated at 30- to 60-s intervals by an observer who was blinded to the maintenance anesthetic: spontaneous eye opening, tracheal extubation, responding to verbal commands ("Squeeze my fingers"), and time to orientation ("What is your name?" "What is your date of birth?"). The trachea was extubated when a regular spontaneous breathing pattern had been reestablished and when patients were able to open their eyes on command.
At 30, 60, 90, and 120 min after the end of anesthesia, the patients were asked to repeat the DSST and VAS for sedation, energy, confusion, coordination, nausea, and pain. Times to transfer from Phase I to Phase II recovery, to sit, to walk unaided (to the bathroom), and to being judged fit for discharge home were assessed at 15-min intervals by the recovery room staff who were unaware of which maintenance anesthetic had been administered during the operation. On the first postoperative day, patients were interviewed by telephone and asked to indicate the occurrence of postdischarge nausea and vomiting (using a scale of none, mild, moderate, or severe) and to state their preference for receiving a similar anesthetic in the future.
Data are reported as mean values, with variability expressed as SD in the text and in the tables, or as the SEM in the figures. Continuous variables were analyzed using analysis of variance, with Bonferroni's correction for multiple comparisons. Descriptive (categorical) variables were analyzed using chi squared tests or Fisher's exact test when appropriate. In all cases, P values < 0.05 were considered statistically significant.
The two treatment groups were comparable with respect to demographic characteristics, duration of anesthesia and surgery, as well as adjunctive drug doses Table 1. The end-tidal sevoflurane and desflurane concentrations were 0.86% +/- 0.58% and 2.78% +/- 1.52%, respectively, 10 min after induction, and averaged 1.3% +/- 0.35% and 4.07% +/- 1.03%, respectively, from incision to the end of the procedure. Intraoperative changes in MAP and HR are summarized in Figure 1 and Figure 2. After induction of anesthesia, MAP decreased in both groups and the minimum values were recorded immediately prior to skin incision. In the period prior to skin incision, HR also decreased in both groups but was significantly lower in the sevoflurane group. During the maintenance period, MAP and HR were satisfactorily maintained within +/- 20% of baseline values with both anesthetics. The end-tidal concentrations of sevoflurane and desflurane were 1.5% +/- 0.4% and 4.5% +/- 1.5%, respectively, at the end of the operation.
After discontinuation of the volatile drug, patients in the desflurane group opened their eyes and were extubated earlier than those in the sevoflurane group Table 2. However, there were no statistically significant differences in the times to stating their name and date of birth, to transfer from Phase I to Phase II recovery areas, to sitting up in a chair, to walking unaided, or to being judged fit for discharge Table 2. The overall percentage of patients unable to complete the postoperative VAS and DSST tests were 55%, 34%, 34%, and 26% at 30, 60, 90, and 120 min, respectively. There was no difference between the two groups with respect to the patients' ability to complete these tests. Similarly, no significant differences were found between the two groups with respect to the various VAS scores (data not reported). The DSST scores showed an initial decrease from baseline values in both groups and progressively improved during the recovery period Figure 3. In addition, there was no difference in the incidence of postoperative nausea and/or emesis during the first 24 h in the two treatment groups (33% and 38% in the sevoflurane and desflurane groups, respectively). Finally, patients in both groups stated a high preference (>90%) for receiving the same anesthetic in the future.
Early recovery (emergence) from anesthesia was more rapid after desflurane compared to sevoflurane. However, intermediate recovery times, including time to discharge, as well as recovery of psychomotor and cognitive function, were similar after desflurane and sevoflurane. Since doses of the adjuvant drugs were similar in the two groups, differences in later recovery times may have been masked by the use of these supplemental drugs (e.g., opioid analgesics). Furthermore, times to ambulation and discharge are also influenced by the rigid recovery protocols used at Parkland Memorial Hospital, Dallas, Texas.
Previous studies have confirmed more rapid early recovery after both desflurane and sevoflurane anesthesia compared with isoflurane [3-8]. However, the practical benefit of earlier emergence from anesthesia leading to more rapid discharge from the postanesthesia care unit has been demonstrated in only one comparative study involving desflurane and isoflurane . The present findings are similar to those of Fraizer et al.* who compared sevoflurane and desflurane for maintenance of outpatient anesthesia in children after an inhaled induction with halothane. In their preliminary study, awakening (4.7 vs 8.0 min) and early recovery (9.3 vs 17.1 min) times were more rapid with desflurane compared to sevoflurane. However, they also found that later recovery times (the times to walking and to being judged fit for discharge) did not differ between the two inhaled anesthetics.
*Fraizer LJ, Welborn LG, Hannallah RS, Norden J. Emergence and recovery characteristics of sevoflurane, halothane, and desflurane in pediatric ambulatory patients. Abstract presented at the 1994 annual meeting of the Society for Ambulatory Anesthesia.
Intraoperative cardiovascular stability was easily achieved with both sevoflurane and desflurane, with MAP and HR maintained within +/- 20% of baseline values during the entire maintenance period. Although HR decreased below baseline levels 10 min after induction of anesthesia in both groups, the reduction was less in the desflurane group. This difference may have been a result of the sympathetic stimulation associated with the introduction of desflurane after induction of anesthesia with an IV drug [11,15]. In contrast to previous volunteer studies [11,12], desflurane did not produce an increase in HR above baseline levels, nor the tachycardia which has been reported after a sudden increase in the inspired concentration of desflurane. An alternative explanation for these findings is that sevoflurane may lead to a small reduction in HR, analogous to the findings reported in comparisons with isoflurane and propofol-based anesthetic techniques [15,16]. The cardiovascular stability during the maintenance period and the lack of any difference between the two groups was predictable, since the study was designed to maintain MAP within 20% of the baseline values by varying the inspired concentration of the volatile anesthetics.
The minimum alveolar anesthetic concentration (MAC) of desflurane in oxygen in 18- to 30-yr-old woman was estimated to be 6%-7%, and is reduced to 3%-4% by the addition of fentanyl (3 micro gram/kg) and N2 O 60% in O2[17,18]. The MAC of sevoflurane in young adults is reported to be approximately 2% [19,20]. If fentanyl and N2 O produce a similar decrease in the sevoflurane MAC value, the sevoflurane MAC with N2 O would be approximately 1.2%. Thus, end-tidal concentrations of desflurane and sevoflurane at the end of surgery were approximately equipotent.
This study can be criticized because the design did not permit a double-blind comparison of the two volatile anesthetics. As a result of the registration status of the two inhaled drugs at the time that the study was performed, it was not possible to perform a random assignment of the anesthetic treatments. However, all patients were undergoing identical procedures by the same group of surgeons and anesthesiologists. The anesthesiologists attempted to maintain a similar depth of anesthesia with both volatile drugs until the end of surgery such that recovery would be assessed from similar clinical end-points. Furthermore, the recovery assessments were performed by blinded observers. Finally, it was not possible to perform a cost comparison because sevoflurane had not been marketed in the United States at the time the study was performed.
In conclusion, sevoflurane and desflurane provided similar intraoperative conditions during the maintenance period. Although early recovery was more rapid after desflurane, there were no differences in later recovery end-points. Thus, recovery from sevoflurane is no better than desflurane when used for maintenance of outpatient anesthesia.
The authors would like to thank Doctors Jun Tang and Dae Woo Kim for their assistance in the final stages of the project and Joyce Mandujano for her assistance in preparing the manuscript.
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© 1995 International Anesthesia Research Society
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