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Monitoring Depth of Anaesthesia Using Auditory Brainstem Response: An Exploratory Clinical Study



Purpose: Various depth-of-anaesthesia monitors are available, but their trustworthiness is questioned. The aim of this study was to investigate brainstem auditory-evoked potentials during general anaesthesia using a specific audiometry method named SensoDetect Brainstem Evoked Response Audiometry (SD-BERA).
Awareness during general anaesthesia is a result of an inadequate
depth of anaesthesia (DoA) and the incidence is approximately 1-2%
in patients at high risk (1-5). Traditional clinical signs of depth of ana-
esthesia can be unreliable and various DoA monitors are commerci-
ally accessible but not all of them are validated to the same extent (6-
7). In previous studies, monitors like Bispectral Index (BIS) andAudi-
tory evoked potentials (AEP) have been questioned in different con-
texts (3, 8-14). A reliable way of measuring DoA is sought (15-18)
and thus, an improvement or further development of alternative means
for monitoring DoA is needed.
The latencies and amplitudes of the brainstem waves of AEP are
called the auditory brainstem response (ABR). ABR measures the
electrical activity of the subcortical nerve cells generated by neuronal
activity in the auditory pathways in the brainstem, within the first 10
milliseconds (ms) following acoustic stimulation. The wave pattern
consists of seven positive peaks, wave I is starting at the eight cranial
nerve and extending into medulla (wave II). Wave III represents
neuron activity at the level of auditory pons, and wave IV in the supe-
rior olivary complex (SOC). Wave V is believed to originate from the
inferior colliculus (19-20).
Available information about DoA and traditional ABR is limited. A
recent and further development of a digital ABR by SensoDetect AB
(Lund, Sweden), called SensoDetect Brainstem Evoked Response
Audiometry (SD-BERA), has been developed as a diagnostic tool for
psychiatric diseases, but has never been evaluated during general anaes-
thesia. Previous studies using traditional, analogue ABR show contra-
dictory results regarding the effects from general anaesthesia (8, 15, 21-
25). Therefore, the aim of this study was to investigate brainstem audi-
tory-evoked potentials during general anaesthesia using SD-BERA.
This prospective exploratory study was performed at Lund University
Hospital during spring of 2012. After approval by the Regional Ethics
Committee (Dnr: 2012/97, Lund, Sweden), seven consenting adult
patients scheduled for elective orthopaedic surgery with American
Society of Anesthesiologists (ASA) physical status I and II were assig-
ned. Patients were excluded if they had known or suspected neurolo-
gic disorder, or known or suspected hearing disabilities.
Standard monitoring of vital parameters was started, and electrodes
for monitoring with BIS and SD-BERA were placed before the induc-
tion of the anaesthesia. The surface electrodes were attached to the
skin over the mastoid bones behind both ears, with a ground electrode
placed on the forehead and a reference electrode placed on the vertex.
The attachment surface was prepared with disinfectant and scrub
before placement to optimize electrode contact and the stimuli were
presented through TDH-50P-headphones. Absolute impedance and
interelectrode impedance were measured before and after the experi-
ments to verify that electrode contact was maintained (below 5000)
during the whole procedure. No active participation from the patients
was required. Patients were instructed to close their eyes and relax
after the headphones were applied to reduce myogenic artefacts. After
a calm environment was achieved in the theatre, a stopwatch was star-
ted simultaneously with SD-BERA to match time with events in pro-
tocol and SD-BERA data. BIS were noted for the first time and sti-
muli were presented through the headphones to create a baseline in
alert state.
Stimuli were presented and evoked potentials recorded using SD-
BERA (SensoDetect, Lund, Sweden). A series of 1300 clicks of
acoustic stimuli was used. The sound was a square-shaped click tone
used in a standard ABR. The intensity of the tones did not exceed 70
dB. Divergent responses to stimuli, defined as the 10% of the 1300
responses with the largest range in volt, and the 10% with the narro-
west range, were excluded as outliers. This was done to remove arte-
facts, for instance breathing, coughs, and movements. The remaining
1040 responses were used to establish an average wave pattern. An
algorithm was also applied to filter specific artefacts like cardiac acti-
vity, and the frequency of adjacent electrical equipment (50Hz).
The anaesthesia apparatus Dräger PrimusTM (Dräger Medical)
with carbon dioxide absorber was used to perform the chosen anaes-
Sykepleievitenskap .Omvårdnadsforskning .Nursing Science
Monitoring depth of anaesthesia
using auditory brainstem response:
an exploratory clinical study
Catharina Larsson, CRNA, MSc, Emma Larsson, CRNA, MSc, Fredrik Åhlander, MD, John Jahr, MD, PhD, Anders Johansson,
RNAIC, associate professor*.
Purpose: Various depth-of-anaesthesia monitors are available, but their trustworthiness is questioned.The aim of this study was to investigate
brainstem auditory-evoked potentials during general anaesthesia using a specific audiometry method named SensoDetect Brainstem Evoked
Response Audiometry (SD-BERA).
Methods: Seven patients with American Society of Anaesthesiologists physical status I and II scheduled for elective orthopaedic surgery were
assigned. Brainstem auditory evoked responses were recorded at different stages of anaesthesia. Bispectral index and end-tidal tension of
Sevoflurane were measured at the same time.
Results: The index (%) from pre-anaesthesia to anaesthesia were significantly reduced 100 [0-0] vs. 53 [49-72], respectively (p=0.0156). At
extubation the index were set back to normal level with a significant increase from anaesthetized state, 102 [78-135] (p=0.0156). No signifi-
cant difference could be observed between pre-anaesthesia and at extubation (p=0.6875).
Conclusion: The findings imply that SD-BERA has a potential to measure depth of anaesthesia.
KEY WORDS: Anaesthesia, Brainstem Evoked Response Audiometry
thetic procedure and to monitor end tidal Sevoflurane concentration
(PETsevo). For the BIS monitoring a BISTM MONITOR Model A-
2000TM (Aspect Medical Systems, Newton, MA, USA) was used.
The chosen anaesthetic procedure was performed according to a
previously published study (26). Patients were monitored with 3-lead
ECG, SpO2, inspiratory oxygen partial pressure (FiO2) and sevoflu-
rane expiratory partial pressure (PETsevo) as analyzed by the ventila-
tor.At the induction, all patients were pre-oxygenated with 100% oxy-
gen for 3–4 minutes with fresh gas flow of 5 l/min. Anaesthesia was
induced with 2 µg/kg Fentanyl and 1.5–3.0mg/kg Propofol. Muscle
relaxant drugs used were Suxamethonium or Rocuronium bromide.
Manual ventilation was assisted with 100% oxygen until tracheal intu-
bation was performed. The Sevoflurane tension was regulated to 3%
on the vaporizer, and after five minutes, the fresh gas flow was adju-
sted to 1.0 l/min with an unchanged Sevoflurane tension throughout
the anaesthesia. Extra doses of Fentanyl (50-100 µg) were administe-
red if the mean arterial blood pressure (MAP) increased > 20% above
the initial baseline level. Hypotension was treated by head lowering,
crystalloid or colloid infusion and/or 5-10 mg Ephedrine intrave-
nously. All patients received 3-5 ml kg-1h-1of glucose 2.5 % with
sodium (70 mmol C-1), chloride (45 mmol C-1) and acetate (25 mmol
C-1) intravenously. Neuromuscular blockade was monitored.
During the anaesthesia, the recording with SD-BERA and parame-
ters as BIS and PETsevo were read simultaneously at specific time
points and documented. The time points were defined as: Baseline
(alert state, pre-anaesthesia =A), Anaesthetised I (ciliary reflex
gone=B), Anaesthetised II (preceding first incision=C) and Extuba-
tion (D). The stimuli generate an ABR during two minutes, which is a
mean of a continuous recording during this period of time. The ABR
closest to the time point of interest was chosen. BIS and PETsevo
were measured at the same time for depicting anaesthesia.
Statistical analysis
All recorded ABR waves were analysed in retrospect using GraphPad
Prism. The aberrations in the recordings were confirmed by a comp-
uterized algorithm patented by SensoDetect. The wave pattern was
analysed with respect to amplitudes and the data derived from the ana-
lysed amplitudes was indexed (SD-BERA Index) to specific values in
percent. The alert state for each patient was established at an indivi-
dual baseline set to 100%.
The data are presented as median and interquartile range, and ana-
lysed using the non-parametric Friedman test to examine the diffe-
rence between the matched data in the different time-points (A-D). A
Wilcoxon matched pair test was also applied to detect differences bet-
ween any matched data in the different time-points. A P-value < 0.05
was considered to indicate statistical significance.
A total of seven patients fulfilled the inclusion criteria and were enrol-
led in the study. The indexes derived from the brainstem activity and
BIS for each patient at the different time points (A-D) are presented in
table 1. However, one of the seven patients did not fulfil all the measu-
rement with BIS, because of BIS-monitoring failure.
The index and end-tidal sevoflurane concentrations (PetSevo) for all
the patients with the dispersion degree at the time points (A-D) is dis-
played in Table 2. At extubation (time point D) the median index was
set back to values round the baseline (time point A).
Measures from SD-BERA differed between anaesthetic (B and C) and
non-anaesthetic states (A and D), measures demonstrated statistical
differences between A:B (p=0.0156), A:C (p=0.0156), B:D
(p=0.0156) and C:D (p=0.0156) and no difference could be observed
between measures B:C (p=1.000) and A:D (p=0.6875), respectively.
Sykepleievitenskap .Omvårdnadsforskning .Nursing Science
VÅRD I NORDEN 4/2013. PUBL. NO. 110 VOL. 33 NO. 1 PP 0–0
Table 1. Individual index for each patientʼs brainstem
auditory response (SD-BERA) and BIS, at the different time
points A-D (N=7 SD-BERA and N=6 BIS).
Gender (age/yr)
Female (20)
Female (28)
Female (57)
Male (22)
Male (23)
Male (34)
Male (37)
Table 2. Indexes for SD-BERA, BIS and end-tidal sevoflurane
concentrations (PetSevo) at presented time points: Baseline
(alert state, pre-anaesthesia =A), Anaesthetised I (ciliary
reflex gone =B), Anaesthetised II (preceding first incision
=C) and Extubation (D). Values are expressed as median and
[interquartile range], N=7 SD-BERA, N=6 BIS and N=7
(Index %)
The main finding in the present study is a significant difference in
amplitudes of waveV between anaesthetised (time point B and C) and
defined alert state (time point A and D) (Table 2).This finding is con-
sistent with some of the existing literature and implies that SD-BERA
has a potential to measure depth of anaesthesia measuring differences
in the waveV amplitude (15, 21). Many studies has focused on the dif-
ferences in latencies with contradicting results (8, 24-25), but in this
study we focused on amplitudes and demonstrate significant changes
in wave V.
Interestingly, there is a wide distribution in individual indexes
around the baseline at extubation (Table 1 and 2). To our knowledge,
there is no existing data that indicates such variations (rebound effect)
in the context of using anaesthetic agents in humans. This phenome-
non may be explained in pharmacological or psychological terms. In
pharmacological terms it is known that a rebound effect could arise
following discontinuation of sedative substances (27). Furthermore,
the chosen anaesthetic procedure used sevoflurane for maintenance
after induction with propofol. Young-Shin and colleagues compared
emergency agitation between sevoflurane and propofol in adults and
the results demonstrates that 45% of the patients in the sevoflurane
group developed emergency agitation compared to 10% when using
propofol (28). It can´t be ruled out that this phenomenon occurred
during the present phase of extubation in the current study and that
this phenomenon is demonstrated with the values above 100%, detec-
ted by the SD-BERA. Further research has to be done to clarify this
According to other interferences with anaesthetic agents it is sugge-
sted that ABR are not influenced by central or peripheral muscle rela-
xants. To present authors this knowledge is only demonstrated in a few
animal studies. However, ABR is a commonly used method to deter-
mine hearing sensitivity in animals, using either isoflurane or keta-
mine anaesthesia. In an animal study designed by Ruebhausen et al.,
they concluded that hearing thresholds obtained with isoflurane were
on average elevated across a broad frequency range compared to
ketamine (29). This significant effect, generated from different anaes-
thetic agents, demonstrates a substantial difference between general
anaesthetics on ABR sensitivity. Therefore, potential mechanisms and
further implications for ABR during general anaesthesia to detect
DoA, had to be evaluated and discussed.
Table 1 depicts the observed relationship between SD-BERA and
BIS, including all time points. Validity is difficult to quantify in this
context, as there is no accepted gold standard measure of anaesthetic
depth (7). To be able to validate DoA monitoring, Bruhn and collea-
gues highlight the importance of comparing the actual instrument
with the states of unconsciousness and the plasma concentration of the
anaesthetic drug (7). In the present study PETsevo is utilized; howe-
ver, a more reliable and precise measurement would have been to use
arterial Sevoflurane tensions (Pasevo), as in the presented reference by
Enekvist et al (27). This may be considered in future studies. However,
BIS and PETsevo were used for depicting anaesthesia in correlation
with SD-BERA, demonstrating adequate levels according to used and
excepted values.
There are some important limitations of the present study. An ABR
is an average of two minutes of data recording and the SD-BERA
index will be an approximation if the patient is not in a steady state.
However, the aim of the present study was to explore the potential of
the method. In order to validate the method in further studies, more
exact time points should be chosen and eventually a real-time analysis
approach should be performed. The operative setting in which electro-
encephalographic data were collected could have affected the out-
come. Artefacts are a critical issue for the method. Interference of
other instruments used in the operating room, as well as the surgery
itself could potentially affect the outcome, as well as artefacts of
neuronal origin such as suppression of cortical activity during general
anaesthesia. Another limitation is that we don’t measure body tempe-
rature among the patients, even though studies indicate affected brain-
stem response in association with hypothermia. However, it’s been
reported that the body temperature must decrease below 28 ºC to
affect the ABR (30-33).
A possibility for decreasing the dispersion degree in time point D
would be if the extubation procedure occurred more standardised, in a
manner that the patients surely would be back at a similar alert state.
Another limitation is the small number of participants, but conside-
ring the design where intra-individual responses were studied, it was
still possible to achieve convincing results.
The fact that the technique is able to detect consistent differences of
amplitudes at certain time points during the procedure is promising. In
consideration to present and previous studies, further research is nee-
ded focusing on the use of SD-BERA to find further traits that can
support the results of this study, but also investigate if SD-BERA has
a potential of a more detailed quantification of DoA. Furthermore,
future research may show the potential to DoA in context with intrave-
nous agents alone. According to studies, BIS thresholds do not appear
to be independent of the combinations of anaesthetic agents adminis-
tered (10-13). Baas and colleagues also presents limitations with AEP
in association with opioids and peripheral analgesics, which as well
may motivate to further investigation of these findings in the same
context with SD-BERA (34).
The findings in this study imply that SD-BERA has a potential to
measure depth of anaesthesia.
Catharina Larsson, CRNA, MSc1, Emma Larsson, CRNA, MSc1,
Fredrik Åhlander, MD2, John Jahr3, MD, PhD, Anders Johansson,
RNAIC, associate professor1*.
1Department of Health Sciences, Faculty of Medicine, P.O. Box 157,
221 00 Lund, Sweden
2Clinical Memory Research Unit, Department of Clinical Sciences
Malmö, Lund University, Malmö, Sweden
3Department of Intensive- and Perioperative Care, Lund University
Hospital, S-221 85, Lund, Sweden
*Corresponding author: Anders Johansson, Department of Health
Sciences, Faculty of Medicine, P.O. Box 157, 221 00 Lund,
SwedenSweden. Phone: +46 46 2221930,
Special thanks to the staff at Department of Perioperative Care at
Lund University Hospital for assistance to make this study viable.
We would also like to thank SensoDetect for support and inspiration
and declare that the authors have no conflict of interest.
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Full-text available
In this prospective, randomized, double-blind, placebo-controlled trial, we investigated the effect of a single dose of esmolol on the bispectral index (BIS) to endotracheal intubation during desflurane anesthesia. After induction of anesthesia, 60 patients were mask-ventilated with desflurane (end-tidal 1 minimum alveolar concentration) for 5 min and then received either normal saline, esmolol 0.5 or 1 mg/kg, 1 min prior to intubation (control, esmolol-0.5 and esmolol-1 groups, n = 20/group). BIS, mean arterial pressure, and heart rate were measured prior to anesthesia induction and esmolol administration, immediately preceding intubation (time point 0), and every minute for 5 min after intubation (time point 1 to 5). At time point 0, 1 and 5, 5 ml of arterial blood was taken to measure plasma concentrations of norepinephrine and epinephrine. BIS increased significantly at 1 min after intubation when compared with pre-intubation values in all groups. Both mean arterial pressure and heart rate increased significantly 1 min after intubation when compared with preintubation values for all groups. Plasma epinephrine concentrations did not increase significantly after tracheal intubation in any of the groups. Norepinephrine increased at 1 min after intubation when compared with the preintubation values in the esmolol groups (P < 0.05). A single bolus of esmolol was unable to blunt the increase in BIS to endotracheal intubation during desflurane anesthesia.
Full-text available
Background Poor characterization of propofol pharmacokinetics and pharmacodynamics in the morbidly obese (MO) pediatric population poses dosing challenges. This study was conducted to evaluate propofol total intravenous anesthesia (TIVA) in this population. Methods After IRB approval, a prospective study was conducted in 20 MO children and adolescents undergoing laparoscopic surgery under clinically titrated propofol TIVA. Propofol doses/infusion rates, hemodynamic variables, times to induction and emergence, and postoperative occurrence of respiratory adverse events (RAE) were recorded, along with intraoperative blinded Bispectral Index/BIS and postoperative Ramsay sedation scores (RSS). Study subjects completed awareness questionnaires on postoperative days 1 and 3. Propofol concentrations were obtained at predetermined intra- and post-operative time points. Results Study subjects ranged 9 – 18 years (age) and 97 - 99.9% (BMI for age percentiles). Average percentage variability of hemodynamic parameters from baseline was ≈ 20%. Patients had consistently below target BIS values (BIS < 40 for >90% of maintenance phase), delayed emergence (25.8 ± 22 minutes), increased somnolence (RSS ≥ 4) in the first 30 minutes of recovery from anesthesia and 30% incidence of postoperative RAE, the odds for which increased by 14% per unit increase in BMI (p ≤ 0.05). Mean propofol concentration was 6.2 mg/L during maintenance and 1.8 mg/L during emergence from anesthesia. Conclusions Our findings indicate clinical overestimation of propofol requirements and highlight the challenges of clinically titrated propofol TIVA in MO adolescents. In this setting, it may be advantageous to titrate propofol to targeted BIS levels until more accurate weight-appropriate dosing regimens are developed, to minimize relative overdosing and its consequences.
Full-text available
Emergence agitation is associated with increased morbidity and hospital costs. However, there have been few reports in the medical literature on the occurrence of emergence agitation in adults. The aim of this study was to compare emergence agitation between sevoflurane and propofol anesthesia in adults after closed reduction of nasal bone fracture. Forty adults (ASA I-II, 20-60 yr) undergoing closed reduction of nasal bone fracture were randomly assigned to either sevoflurane or propofol group and anesthesia was maintained with sevoflurane or propofol. The bispectral index (BIS) was monitored and maintained within 40-60. At the end of surgery, patients were transported to the post anesthetic care unit (PACU) and agitation state scale was checked by Aono's four-point scale (AFPS). Emergence agitation was defined as and AFPS score of 3 or 4. Pain score were measured by numeric rating scale (NRS) on arrival and peak value at PACU. Nine (45.0%) patients in the sevoflurane group and 2 (10.0%) patients in the propofol group developed emergence agitation in the PACU (P = 0.031). There was no correlation between peak NRS and Aono's four-point scale. Propofol may decrease incidence of emergence agitation compared to sevoflurane in adults undergoing closed reduction of nasal bone fracture.
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The rate of uptake of volatile anesthetics is dependent on alveolar concentration and ventilation, blood solubility and cardiac output. We wanted to determine whether increased tidal volume (V(T)), with unchanged end-tidal carbon dioxide partial pressure (P(ET)CO(2)), could affect the arterial concentration of sevoflurane. Prospective, randomized, clinical study. ASA physical status (2) and II patients scheduled for elective surgery of the lower abdomen were randomly assigned to one of the two groups with 10 patients in each: one group with normal V(T) (NV(T)) and one group with increased V(T) (IV(T)) achieved by increasing the inspired plateau pressure 0.04 cmH(2)O/kg above the initial plateau pressure. A corrugated tube added extra apparatus dead space to maintain P(ET)CO(2) at 4.5 kPa. The respiratory rate was set at 15 min(-1), and sevoflurane was delivered to the fresh gas by a vaporizer set at 3%. Arterial sevoflurane tensions (P(a)sevo), F(i)sevo, P(ET)sevo, P(ET)CO(2), P(a)CO(2), V(T) and airway pressure were measured. The two groups of patients were similar with regard to gender, age, weight, height and body mass index. The mean P(ET)sevo did not differ between the groups. Throughout the observation time, arterial sevoflurane tension (mean ± SE) was significantly higher in the IV(T) group compared with the NV(T) group, e.g. 1.9 ± 0.23 vs. 1.6 ± 0.25 kPa after 60 min of anesthesia (P<0.05). Ventilation with larger tidal volumes with isocapnia maintained with added dead-space volume increases the tension of sevoflurane in arterial blood.
Background: Sedative drug administration is a challenging aspect of the management of mechanically ventilated patients in the out-of-hospital critical care medicine. We hypothesised that the bispectral index of the EEG (BIS) could be a helpful tool in evaluating the depth of sedation in this difficult environment. The main objective of the present study was to assess the agreement of BIS with the clinical scales in the out-of-hospital setting. Methods: This prospective study included mechanically ventilated patients. BIS values were blindly recorded continuously. A Ramsay score was performed every 5 min. The main judgement criterion was the correlation between BIS values and the Ramsay score. Results: 72 patients were included, mostly presenting with toxic coma (36%) or neurological coma (21%). The median (IQR) BIS value was 85 (84-86) when the Ramsay score was 3, 80 (76-84) when the Ramsay score was 4, 61 (55-80) when the Ramsay score was 5 and 45 (38-60) when the Ramsay score was 6. According to Receiver operating characteristic (ROC) curves, BIS was categorised into three classes (BIS<54 corresponding to Ramsay score 6, 54≤BIS<72 for Ramsay score 5 and BIS≥73 for Ramsay score ≤4). Based on these categories, the proportion of appropriate BIS values was 67% (217/323). The concordance correlation coefficient for repeated measurements was 0.54 (0.43-0.64). The agreement between BIS and the Ramsay score is moderate. Conclusions: Prehospital measured BIS values appear poorly correlated with clinical assessment of the depth of sedation. For this reason, the use of BIS to guide prehospital sedation cannot be recommended.
The auditory brainstem response (ABR) is an acoustically evoked potential commonly used to determine hearing sensitivity in laboratory animals. Both isoflurane and ketamine/xylazine anesthesia are commonly used to immobilize animals during ABR procedures. Hearing threshold determination is often the primary interest. Although a number of studies have examined the effect of different anesthetics on evoked potential waveforms and growth functions, none have directly compared their effect on ABR hearing threshold estimates. The present study used a within-subject comparison and typical threshold criteria, to examine the effect of isoflurane and ketamine/xylazine on ABR thresholds for clicks and pure-tone stimuli extending from 8 to 32 kHz. At comparable physiological doses, hearing thresholds obtained with isoflurane (1.7% in O(2)) were on average elevated across a broad frequency range by greater than 27 dB compared to ketamine/xylazine (ketamine HCl, 50mg/kg; xylazine, 9 mg/kg). This highly significant threshold effect (F(1,6) = 158.3403, p = 3.51 × 10(-22)) demonstrates a substantial difference between general anesthetics on auditory brainstem sensitivity. Potential mechanisms and implications for ABR threshold determination under anesthesia are discussed.
Intraoperative awareness is defined by both consciousness and explicit memory of surgical events. Although electroencephalographic techniques to detect and prevent awareness are being investigated, no method has proven uniformly reliable. The lack of a standard intraoperative monitor for the brain likely reflects our insufficient understanding of consciousness and memory. In this review, the authors discuss the neurobiology of consciousness and memory, as well as the incidence, risk factors, sequelae, and prevention of intraoperative awareness.
Desflurane in neurosurgery may be beneficial because it facilitates postoperative early neurologic evaluation. However, its use has been debated because of its capacity to promote cerebral vasodilatation. Sevoflurane has been extensively used in neurosurgical patients. In this prospective clinical trial, we compared early postoperative recovery and cognitive function in patients undergoing craniotomy for supratentorial expanding lesions and receiving sevoflurane or desflurane anesthesia. One hundred twenty patients, ASA physical status I-III (66 men), Glascow Coma Scale 15, undergoing craniotomy for supratentorial expanding lesions were enrolled in the study. Patients were randomly allocated to two anesthetic regimens. In Group S (60 patients, 52 +/- 16 yr), anesthesia was maintained using sevoflurane with end-tidal of 1.5%-2% and was age adjusted to obtain approximately 1.2 minimum alveolar anesthetic concentration. In Group D (60 patients, 60 +/- 14 yr), anesthesia was maintained using desflurane with end-tidal of 6%-7% and was age adjusted to obtain approximately 1.2 minimum alveolar concentration. Emergence time was measured as the time from drug discontinuation to the time at which patients opened their eyes; tracheal extubation time was measured as the time from anesthetic discontinuation and tracheal extubation. Recovery time was measured as the time elapsing from discontinuation of anesthetic and the time when patients were able to recall their name and date of birth. Cognitive behavior was evaluated with the Short Orientation Memory Concentration Test. In the postanesthesia care unit, a blinded observer monitored the patients for 3 h; the incidence of hemodynamic events, pain, nausea, and shivering requiring rescue medication was recorded. The mean emergence time (12.2 +/- 4.9 min in Group S vs 10.8 +/- 7.2 min in Group D; P = ns) was similar in the two groups, whereas the mean extubation time and recovery time were longer in Group S (15.2 +/- 3.0 min in Group S vs 11.3 +/- 3.9 min in Group D and 18.2 +/- 2.3 min in Group S vs 12.4 +/- 7.7 min in Group D, respectively; P < 0.001). The Short Orientation Memory Concentration Test score differed between the two groups only at the earliest assessment (15 min after extubation). No difference between the two groups was found in pain, shivering, nausea, vomiting, and incidence of postoperative hemodynamic events. Patients who received desflurane had a shorter extubation and recovery time but similar intraoperative and postoperative incidence of complications compared with those who received sevoflurane.