Abstract
OBJECTIVE:
The end-tidal concentration of inhalation anesthetics is a clinical indicator for predicting the emergence from anesthesia. This study was conducted to assess the relationship between arterial blood and end-tidal sevoflurane concentrations during emergence.
METHODS:
Thirty-two female American Society of Anesthesiologists physical status I-II patients receiving general anesthesia for elective gynecologic surgery were included. A fixed dose of 3.5% inspiratory sevoflurane in 6 L min-1 oxygen was maintained until the end of surgery. At 20 and 10 minutes before and 0, 5, 10, 15, and 20 minutes after discontinuing sevoflurane, as well as at the time of eye opening by verbal command, defined as awakening, 1 ml arterial blood was obtained to measure its sevoflurane concentration by gas chromatography. Simultaneous inspiratory and end-tidal concentrations of sevoflurane were detected by an infrared analyzer and tested by Bland-Altman agreement analysis.
RESULTS:
The arterial blood concentrations of sevoflurane were similar to the simultaneous end-tidal concentrations during emergence: 0.36% (0.10) and 0.36% (0.08) sevoflurane at awakening, respectively. The mean time from discontinuing sevoflurane to eye opening was 15.8 minutes (SD 2.9, range 10-26) and was significantly correlated with the duration of anesthesia (52-192 minutes) (P = 0.006) but not with the body mass index or total fentanyl dose.
CONCLUSION:
The mean awakening arterial blood concentration of sevoflurane was 0.36%. The time to awakening was prolonged in accordance with the anesthetic duration within 3 hours. With well-assisted ventilation during emergence, the sevoflurane end-tidal concentration was nearly equal to its arterial blood concentration, which could be a feasible predictor for awakening.
Inhalation anesthetics; Sevoflurane; Emergence; Anesthesia recovery period; Monitoring
INTRODUCTION
Sevoflurane, with its properties of a lower blood-gas partition coefficient of 0.69
(11 Behne M, Wilke HJ, Harder S. Clinical pharmacokinetics of
sevoflurane. Clin Pharmacokinet. 1999;36(1):13-26,
http://dx.doi.org/10.2165/00003088-199936010-00002.
http://dx.doi.org/10.2165/00003088-19993...
) and a less irritating odor, allows
for rapid and smooth anesthetic induction (22 Lee SY, Cheng SL, Ng SB, Lim SL. Single-breath vital capacity
high concentration sevoflurane induction in children: with or without nitrous
oxide? Br J Anaesth. 2013;110(1):81-6.,33 Lin TC, Lu CC, Kuo CK, Hsu CH, Huang GS, Liu JY, et al. Single
vital-capacity and successive tidal-volume breathing of sevoflurane in induction
of anesthesia for tracheal intubation in gynecologic patients. Acta Anaesthesiol
Taiwan. 2008;46(2):66-70,
http://dx.doi.org/10.1016/S1875-4597(08)60028-4.
http://dx.doi.org/10.1016/S1875-4597(08)...
) and less coughing during
emergence (44 White PF, Tang J, Wender RH, Yumul R, Stokes OJ, Sloninsky A, et
al. Desflurane versus sevoflurane for maintenance of outpatient anesthesia: the
effect on early versus late recovery and perioperative coughing. Anesth Analg.
2009;109(2):387-93,
http://dx.doi.org/10.1213/ane.0b013e3181adc21a.
http://dx.doi.org/10.1213/ane.0b013e3181...
). However, with a higher
fat-blood partition coefficient of 47.5 (55 Yasuda N, Targ AG, Eger EI 2nd. Solubility of I-653, sevoflurane,
isoflurane, and halothane in human tissues. Anesth Analg.
1989;69(3):370-3.),
the extubation time with sevoflurane is prolonged up to 20-25% compared with
desflurane (66 Dexter F, Bayman EO, Epstein RH. Statistical modeling of average
and variability of time to extubation for meta-analysis comparing desflurane to
sevoflurane. Anesth Analg. 2010;110(2):570-80,
http://dx.doi.org/10.1213/ANE.0b013e3181b5dcb7.
http://dx.doi.org/10.1213/ANE.0b013e3181...
). In addition, emergence and
airway reflex recovery may be delayed by a greater body mass index (77 McKay RE, Malhotra A, Cakmakkaya OS, Hall KT, McKay WR, Apfel CC.
Effect of increased body mass index and anaesthetic duration on recovery of
protective airway reflexes after sevoflurane vs desflurane.
Br J Anaesth. 2010;104(2):175-82.).
During the elimination phase, sevoflurane washout progresses from the brain and body
to the alveolar space and can be detected by the end-tidal concentration.
Clinically, the end-tidal concentration of inhalation anesthetics has been a
feasible indicator for predicting the emergence from general anesthesia, especially
after desflurane anesthesia (88 Lin TC, Lu CC, Hsu CH, Wu GJ, Lee MS, Ho ST. Duration effect of
desflurane anesthesia and its awakening time and arterial concentration in
gynecologic patients. Clinics. 2013;68(10):1305-11,
http://dx.doi.org/10.6061/clinics/2013(10)03.
http://dx.doi.org/10.6061/clinics/2013(1...
). However,
irregular respiration before awakening usually results in fluctuations of the
end-tidal concentrations of inhalation anesthetics. Alternatively, the arterial
blood concentration provides a steadier and closer representation of the brain
concentration during uptake (99 Lu CC, Tsai CS, Ho ST, Chueng CM, Wang JJ, Wong CS, et al.
Pharmacokinetics of desflurane uptake into the brain and body. Anaesthesia.
2004;59(3):216-21,
http://dx.doi.org/10.1111/j.1365-2044.2003.03654.x.
http://dx.doi.org/10.1111/j.1365-2044.20...
10 Lu CC, Tsai CS, Ho ST, Chen WY, Wong CS, Wang JJ, et al.
Pharmacokinetics of sevoflurane uptake into the brain and body. Anaesthesia.
2003;58(10):951-6,
http://dx.doi.org/10.1046/j.1365-2044.2003.03346.x.
http://dx.doi.org/10.1046/j.1365-2044.20...
11 Lu CC, Ho ST, Wong CS, Wang JJ, Tsai CS, Hu OY, et al.
Pharmacokinetics of isoflurane: uptake in the body. Pharmacology.
2003;69(3):132-7, http://dx.doi.org/10.1159/000072665.
http://dx.doi.org/10.1159/000072665...
12 Lu CC, Ho ST, Wang JJ, Wong CS, Hu OY, Chang SY, et al.
Pharmacokinetics of isoflurane: uptake in the brain. Pharmacology.
2003;69(2):102-7, http://dx.doi.org/10.1159/000072363.
http://dx.doi.org/10.1159/000072363...
-1313 Lin TC, Lu CC, Li CY, Chang CC, Ho ST. Arterial blood
concentration of sevoflurane during single-breath induction and tracheal
intubation in gynecologic patients. J Clin Anesth. 2008;20(7):496-500,
http://dx.doi.org/10.1016/j.jclinane.2008.05.011.
http://dx.doi.org/10.1016/j.jclinane.200...
) and recognizes the time-dependent
elimination of inhaled anesthetics from the brain and blood to the alveolar cavity
(1414 Lu CC, Tsai CS, Hu OY, Chen RM, Chen TL, Ho ST. Pharmacokinetics
of isoflurane in human blood. Pharmacology. 2008;81(4):344-9,
http://dx.doi.org/10.1159/000122960.
http://dx.doi.org/10.1159/000122960...
15 Lu CC, Tsai CS, Hu OY, Chen RM, Chen TL, Ho ST, et al.
Pharmacokinetics of desflurane elimination from respiratory gas and blood during
the 20 minutes after cardiac surgery. J Formos Med Assoc.
2013;112(4):185-92,
http://dx.doi.org/10.1016/j.jfma.2012.01.017.
http://dx.doi.org/10.1016/j.jfma.2012.01...
-1616 Lu CC, Lin TC, Hsu CH, Tsai CS, Sheen MJ, Hu OY, et al.
Pharmacokinetics of sevoflurane elimination from respiratory gas and blood after
coronary artery bypass grafting surgery. J Anesth.
2014;28(6):873-9.). Our previous study (1010 Lu CC, Tsai CS, Ho ST, Chen WY, Wong CS, Wang JJ, et al.
Pharmacokinetics of sevoflurane uptake into the brain and body. Anaesthesia.
2003;58(10):951-6,
http://dx.doi.org/10.1046/j.1365-2044.2003.03346.x.
http://dx.doi.org/10.1046/j.1365-2044.20...
)
revealed no further uptake of sevoflurane into the brain after 40 minutes but
near-constant uptake into the body until the end of the study (60 minutes). Thus, we
hypothesized that sevoflurane would accumulate in the body and/or blood during an
increased anesthetic duration and that this accumulation could be verified by
analyzing the arterial blood concentrations during emergence and the time to
awakening. The aims of this study were to examine the arterial blood concentrations
of sevoflurane during emergence and the effect of the anesthetic duration, as well
as the validity of non-invasively measuring the end-tidal concentration to assess
the simultaneous arterial blood concentration.
MATERIALS AND METHODS
Patients
After obtaining IRB approval (TSGHIRB-097-05-189) and written informed consent, 32 20-60-year-old ASA I or II gynecologic patients undergoing elective surgery were included. Those patients with severe cardiopulmonary diseases, hepatic diseases (1717 Singhal S, Gray T, Guzman G, Verma A, Anand K. Sevoflurane hepatotoxicity: a case report of sevoflurane hepatic necrosis and review of the literature. Am J Ther. 2010;17(2):219-22.), or neuropathy or who were receiving regular hypnotics or sedatives were excluded.
Anesthetic Management
In the operating room, after the administration of 100 mcg intravenous fentanyl and 0.5 ml subcutaneous 2% lidocaine, a 20-gauge catheter was placed into the radial artery for blood sampling and perioperative blood pressure monitoring. General anesthesia was induced with 1.5 mg kg-1 propofol and 1.5 mg kg-1 succinylcholine for endotracheal intubation and was maintained with 0.1 mg kg-1 cisatracurium and fixed 3.5% inspiratory sevoflurane in 6 L min-1 oxygen throughout the entire procedure. Nitrous oxide was not used. To suppress the patient's painful responses beyond the ability of sevoflurane alone, 25 or 50 mcg fentanyl was titrated. An Ohmeda-Datex anesthetic machine was used with soda lime (CO2 absorber), and the minute ventilation was adjusted to keep the end-tidal CO2 between 38-42 mmHg. The leakage of each system was assessed by using constant-pressure ventilation with a test lung. The sampled gases (approximately 210 ml min-1) were redirected into the circuit. Both the inspiratory and end-tidal sevoflurane concentrations were detected by an infrared multi-gas analyzer (Datex AS/5 Anesthesia system; Datex, Helsinki, Finland), calibrated according to the manufacturer's recommendations. A Finometer (FMS, Finapres Measurement Systems, Arnhem, Netherlands) was used to assess cardiac output. Hypotension, defined as a decrease in blood pressure by 25% from baseline, was treated with intravenous fluid and/or ephedrine (5 mg bolus). After the operation was completed, we turned off the vaporizer and then intravenously administered 2 mg neostigmine and 0.4 mg glycopyrrolate to reverse the neuromuscular blockade. The end-tidal CO2 was maintained between 38 and 42 mmHg with manually assisted ventilation in quiet conditions without any other stimulation during sevoflurane elimination. Awakening was defined as eye opening to verbal command and was tested every 30 seconds after discontinuing sevoflurane until the appropriate response was observed. Extubation was accomplished after brief endotracheal suction. The time from the discontinuation of sevoflurane to awakening and the duration of anesthesia were recorded. The inspiratory and end-tidal sevoflurane concentrations, end-tidal CO2, blood pressure, heart rate, and body temperature were recorded every 30 seconds using commercial software until 20 minutes after stopping sevoflurane.
Determination of Sevoflurane Blood Concentrations
Before induction, 10 ml of each patient's arterial blood without sevoflurane
was collected to calculate the blood/gas partition coefficient (λ) of
sevoflurane for each patient (1313 Lin TC, Lu CC, Li CY, Chang CC, Ho ST. Arterial blood
concentration of sevoflurane during single-breath induction and tracheal
intubation in gynecologic patients. J Clin Anesth. 2008;20(7):496-500,
http://dx.doi.org/10.1016/j.jclinane.2008.05.011.
http://dx.doi.org/10.1016/j.jclinane.200...
).
Sevoflurane in each blood sample was converted to the corresponding
concentration based on gas chromatographic measurements and the blood/gas
partition coefficient of sevoflurane (λ) measured in each patient.
Gas Chromatography Conditions
The HP 6890 series GC system (Hewlett-Packard, Wilmington, DE) comprised a
headspace sampler (Agilent G1888), an oven, a flame-ionization detector and an
integrator. The oven temperature was set at 40°C, increased to 200°C
at a rate of 25°C per minute and maintained at this level for 2.60 min.
Both the injection and detection temperatures were set at 250°C. The inlet
pressure was set at 349 kPa. Injection was performed in the direct injection
mode. The carrier gas (helium) flow was 25.0 ml min-1. Separation was
achieved with a capillary column (HP-5; 30.0 m × 0.32 mm ID, 0.25-μm
film thickness; Restek, Bellefonte, PA). An integrator and a data acquisition
system were provided by Agilent CHEMOSTATION software. The method used to create
a calibration curve for measuring the blood sevoflurane concentration was
modified according to our previous publication (1313 Lin TC, Lu CC, Li CY, Chang CC, Ho ST. Arterial blood
concentration of sevoflurane during single-breath induction and tracheal
intubation in gynecologic patients. J Clin Anesth. 2008;20(7):496-500,
http://dx.doi.org/10.1016/j.jclinane.2008.05.011.
http://dx.doi.org/10.1016/j.jclinane.200...
). The mean (SD) of the blood/gas partition coefficient of
sevoflurane (λ) for 32 patients was 0.65 (0.01).
Statistical Analysis
The mean, range and median (time to eye opening) were used to describe the patients' characteristics. Clinical parameters were presented as the mean (SD) over time. Bivariate relationships between variables were analyzed by simple linear regressions and Pearson's correlations. Moreover, we used the Bland-Altman agreement analysis to determine the degree of agreement between the simultaneous arterial blood and end-tidal sevoflurane concentrations at three time points relative to awakening using MedCalc¯ statistical software (Version 12.2.1.0). A P value <0.05 was considered statistically significant.
RESULTS
The demographic data are summarized in Table 1. The mean time from discontinuing sevoflurane to eye opening by verbal command was 15.8 minutes (2.9) (range 10-26, median 15), with a 95% confidence interval of 14.5-16.6 min.
Table 2 shows the arterial blood, inspiratory and end-tidal concentrations of sevoflurane before and during emergence. The mean arterial and end-tidal concentrations were 2.09% (0.19) and 3.01% (0.11) before discontinuing and decreased to 0.36% (0.10) and 0.36% (0.08) at awakening, respectively. The end-tidal concentrations decreased more prominently in the initial 5 minutes after discontinuation and then remained nearly equal to the arterial concentrations until awakening. The end-tidal CO2 concentrations were kept steady during emergence, whereas the cardiac output and cardiac index increased by less than 15% after discontinuing sevoflurane, without significant differences (Table 3).
As shown in Figure 1, the arterial concentrations, as well as the awakening end-tidal concentrations, before discontinuing sevoflurane and at awakening were not significantly correlated with the duration of general anesthesia (P = 0.162, 0.277 and 0.295, respectively).
The correlation between the duration of anesthesia and the arterial concentrations of sevoflurane before discontinuation and at awakening. The arterial concentrations just prior to discontinuing 3.5% sevoflurane (upper) and at awakening (middle), as well as the awakening end-tidal concentration (lower), were not correlated with the anesthetic duration (52-192 minutes) (P = 0.323, 0.520 and 0.880, respectively), indicating both saturated blood contents and fast alveolar washout of sevoflurane.
The Bland-Altman plot (Figure 2) displays the differences between the arterial concentration and end-tidal concentration at awakening. The differences between the two concentrations ranged from -0.15 to 0.18%, with a mean (SD) of 0.01% (0.09). After grouping, the differences fell into the acceptable range (±1.96 SD), regardless of the length of the awakening time.
The Bland-Altman plot displays the differences between the arterial and end-tidal concentrations at awakening plotted against the average of the two concentrations. The differences ranged from -0.15 to 0.18, all of which were within the SD range of ±1.96. The two methods may be used interchangeably.
Figure 3 depicts that the time to awakening was prolonged according to the duration of anesthesia from 52 to 192 minutes (P = 0.006) but was not correlated with the body mass index (range 18-29) or the total fentanyl dose (P = 0.971 and 0.850, respectively).
The time to awakening after discontinuing 3.5% sevoflurane in gynecologic surgical patients was prolonged by the duration of anesthesia (P = 0.006) but was not correlated with the body mass index (P = 0.971) or total fentanyl dose (P = 0.850).
DISCUSSION
This study first quantitatively demonstrated that the awakening arterial blood concentration of sevoflurane was 0.36% (0.10) in surgical gynecologic patients. An increased duration of sevoflurane anesthesia within 3 hours did not elevate the arterial concentration before discontinuing sevoflurane but did prolong the awakening time. With well-assisted ventilation, the end-tidal concentration of sevoflurane was nearly equal to the arterial concentration and could be a reliable predictor for eye opening during the emergence from general anesthesia.
The total body uptake and elimination of inhaled anesthetics should be proportional
to the duration of general anesthesia (1818 Bailey JM. Context-sensitive half-times and other decrement
times of inhaled anesthetics. Anesth Analg. 1997;85(3):681-6.,1919 Eger EI, 2nd, Shafer SL. Tutorial: context-sensitive decrement
times for inhaled anesthetics. Anesth Analg.
2005;101(3):688-96.). Compared with desflurane,
the higher blood-gas and tissue-blood partition coefficients of sevoflurane
theoretically increase total body uptake and detain elimination in patients with a
longer anesthetic duration and higher body mass index (77 McKay RE, Malhotra A, Cakmakkaya OS, Hall KT, McKay WR, Apfel CC.
Effect of increased body mass index and anaesthetic duration on recovery of
protective airway reflexes after sevoflurane vs desflurane.
Br J Anaesth. 2010;104(2):175-82.,2020 La Colla L, Albertin A, La Colla G, Mangano A. Faster wash-out
and recovery for desflurane vs sevoflurane in morbidly obese patients when no
premedication is used. Br J Anaesth.
2007;99(3):353-8.). Mckay et al.
(77 McKay RE, Malhotra A, Cakmakkaya OS, Hall KT, McKay WR, Apfel CC.
Effect of increased body mass index and anaesthetic duration on recovery of
protective airway reflexes after sevoflurane vs desflurane.
Br J Anaesth. 2010;104(2):175-82.) demonstrated that the time from
anesthetic discontinuation to the first response to verbal command and the time to
recover the ability to swallow after sevoflurane exceeded those after desflurane. In
addition, the contribution of the body mass index to this delay of airway reflex
recovery was more pronounced after sevoflurane anesthesia. Sevoflurane has been
clearly proven to prolong the extubation time compared with desflurane (20-25%)
(66 Dexter F, Bayman EO, Epstein RH. Statistical modeling of average
and variability of time to extubation for meta-analysis comparing desflurane to
sevoflurane. Anesth Analg. 2010;110(2):570-80,
http://dx.doi.org/10.1213/ANE.0b013e3181b5dcb7.
http://dx.doi.org/10.1213/ANE.0b013e3181...
) but to reduce the mean extubation
time by 13% relative to isoflurane (2121 Agoliati A, Dexter F, Lok J, Masursky D, Sarwar MF, Stuart SB,
et al. Meta-analysis of average and variability of time to extubation comparing
isoflurane with desflurane or isoflurane with sevoflurane. Anesth Analg.
2010;110(5):1433-9,
http://dx.doi.org/10.1213/ANE.0b013e3181d58052.
http://dx.doi.org/10.1213/ANE.0b013e3181...
). In
our study, the arterial concentration before discontinuing sevoflurane was not
correlated with the duration of anesthesia (55-192 min), indicating that a limited
content of sevoflurane was present in the blood (lower blood-gas partition
coefficient, 0.65). However, the time to awakening was proportionally prolonged by a
longer duration of anesthesia, further indicating increased body uptake (higher
muscle-blood and fat-blood partition coefficients, 3.1 and 47.5, respectively)
(55 Yasuda N, Targ AG, Eger EI 2nd. Solubility of I-653, sevoflurane,
isoflurane, and halothane in human tissues. Anesth Analg.
1989;69(3):370-3.). By measuring arterial blood
concentrations during the emergence period, this study provided convincing evidence
for sevoflurane elimination that should be taken into consideration in cases of a
prolonged duration of anesthesia.
The rate of uptake of inhaled anesthetics depends on the alveolar concentration and
ventilation (2222 Enekvist B, Bodelsson M, Sturesson LW, Johansson A. Larger tidal
volume increases sevoflurane uptake in blood: a randomized clinical study. Acta
Anaesthesiol Scand. 2010;54(9):1111-6,
http://dx.doi.org/10.1111/j.1399-6576.2010.02291.x.
http://dx.doi.org/10.1111/j.1399-6576.20...
23 Lu CC, Lin TC, Hsu CH, Yu MH, Chen TL, Chen RM, et al.
Hyperventilation accelerates the rise of arterial blood concentrations of
desflurane in gynecologic patients. Clinics. 2012;67(9):1029-34,
http://dx.doi.org/10.6061/clinics/2012(09)08.
http://dx.doi.org/10.6061/clinics/2012(0...
24 Lu CC, Lin TC, Hsu CH, Yu MH, Ku CH, Chen TL, et al.
Hyperventilation accelerates rise in arterial blood concentrations of
sevoflurane in gynecologic patients. J Anesth.
2013;27(1):35-42.-2525 Lu CC, Lin TC, Yu MH, Chen TL, Lin CY, Chiang JS, et al. Effects
of changes in alveolar ventilation on isoflurane arterial blood concentration
and its uptake into the human body. Pharmacology. 2009;83(3):150-6,
http://dx.doi.org/10.1159/000187719.
http://dx.doi.org/10.1159/000187719...
), blood solubility (55 Yasuda N, Targ AG, Eger EI 2nd. Solubility of I-653, sevoflurane,
isoflurane, and halothane in human tissues. Anesth Analg.
1989;69(3):370-3.) and cardiac output (2222 Enekvist B, Bodelsson M, Sturesson LW, Johansson A. Larger tidal
volume increases sevoflurane uptake in blood: a randomized clinical study. Acta
Anaesthesiol Scand. 2010;54(9):1111-6,
http://dx.doi.org/10.1111/j.1399-6576.2010.02291.x.
http://dx.doi.org/10.1111/j.1399-6576.20...
).
Similarly, sevoflurane washout commences from the brain and body via the circulating
blood into the alveolar space during elimination, allowing the lungs to ventilate it
into the air. When the brain or arterial concentration decreases to a certain level,
the patient awakens enough to follow the verbal command for eye opening. In this
study, the end-tidal concentrations of sevoflurane decreased more prominently in the
initial 5 minutes after discontinuation, indicating a rapid alveolar washout, and
then became consistently close to the arterial concentrations. Our previous study
demonstrated that the end-tidal concentrations of desflurane are generally lower
than the arterial blood concentrations during elimination in gynecologic patients
(88 Lin TC, Lu CC, Hsu CH, Wu GJ, Lee MS, Ho ST. Duration effect of
desflurane anesthesia and its awakening time and arterial concentration in
gynecologic patients. Clinics. 2013;68(10):1305-11,
http://dx.doi.org/10.6061/clinics/2013(10)03.
http://dx.doi.org/10.6061/clinics/2013(1...
); this effect is related to the lower
blood-gas partition coefficient of 0.42 and tissue/blood partition coefficients of
desflurane (55 Yasuda N, Targ AG, Eger EI 2nd. Solubility of I-653, sevoflurane,
isoflurane, and halothane in human tissues. Anesth Analg.
1989;69(3):370-3.). By determining the arterial
blood concentration, we therefore identified that the end-tidal concentration of
sevoflurane, which is close to 0.36%, is a reliable indicator for predicting
emergence from general anesthesia.
There are two limitations in the current study. First, all of our patients were
female, had BMIs less than 29 and received a maximum 3-hour duration of anesthesia.
The minimum alveolar concentration (MAC) value of sevoflurane varied from 2.6% in
young adults (age 18-35 yrs) to 1.58% to 2.05% in middle-aged adults (age 16-59
yrs), to 1.45% in elderly people (age over 70 yrs) (11 Behne M, Wilke HJ, Harder S. Clinical pharmacokinetics of
sevoflurane. Clin Pharmacokinet. 1999;36(1):13-26,
http://dx.doi.org/10.2165/00003088-199936010-00002.
http://dx.doi.org/10.2165/00003088-19993...
). The MAC-awake of sevoflurane in children ranged from 0.43 to 0.66%
(2626 Davidson AJ, Wong A, Knottenbelt G, Sheppard S, Donath S,
Frawley G. MAC-awake of sevoflurane in children. Paediatr Anaesth.
2008;18(8):702-7,
http://dx.doi.org/10.1111/j.1460-9592.2008.02664.x.
http://dx.doi.org/10.1111/j.1460-9592.20...
), whereas the awakening time was
significantly shorter in male patients than in females (2727 Tercan E, Kotanoglu MS, Yildiz K, Dogru K, Boyaci A. Comparison
of recovery properties of desflurane and sevoflurane according to gender
differences. Acta Anaesthesiol Scand. 2005;49(2):243-7,
http://dx.doi.org/10.1111/j.1399-6576.2004.00559.x.
http://dx.doi.org/10.1111/j.1399-6576.20...
). In our study, the relatively lean body size and shorter
duration of general anesthesia may not demonstrate the BMI effect of sevoflurane
compared with previous studies (77 McKay RE, Malhotra A, Cakmakkaya OS, Hall KT, McKay WR, Apfel CC.
Effect of increased body mass index and anaesthetic duration on recovery of
protective airway reflexes after sevoflurane vs desflurane.
Br J Anaesth. 2010;104(2):175-82.,2020 La Colla L, Albertin A, La Colla G, Mangano A. Faster wash-out
and recovery for desflurane vs sevoflurane in morbidly obese patients when no
premedication is used. Br J Anaesth.
2007;99(3):353-8.). The clinical inference should be adjusted
for the patient's characteristics. Second, the minute ventilation could hardly
be controlled by a ventilator after the reversal of spontaneous breathing during
emergence. We therefore manually assisted the ventilation to keep the end-tidal
CO2 concentrations as close to 38-42 mmHg as possible before
extubation. The end-tidal CO2 depicts the status of minute ventilation
and cardiac output. Hyperventilation may decrease the PaCO2 and cerebral
blood flow and then depress cardiac output, which reverses and decelerates the
elimination of inhaled anesthetics. In our study, the minute ventilation and cardiac
index of all patients was kept steady before extubation, which revealed a good
agreement between the awakening arterial blood and end-tidal sevoflurane
concentrations. By investigating both arterial blood and end-tidal concentrations,
the clinical influence of minute ventilation and cardiac output can be further
clarified during the elimination of inhaled anesthetics.
In conclusion, we have demonstrated the awakening arterial concentration of sevoflurane in gynecologic patients. An increased duration of sevoflurane anesthesia (1-3 hours) did not significantly elevate arterial concentrations before discontinuation and at awakening but did prolong the time to awakening, indicating limited blood uptake but increased body uptake of sevoflurane. With well-assisted ventilation during emergence, the end-tidal concentration of sevoflurane can be a reliable indicator for predicting awakening from general anesthesia.
ACKNOWLEDGMENTS
We gratefully acknowledge Ms Yi-Fon Roa, who assisted with the gas chromatography headspace sampler system for blood sevoflurane determination, and the research assistant, Ms Yi-Ru Chen. This study was funded by a grant (NSC98-2314-B-016-007-MY3) from the Taiwan National Council of Science. This work was performed in the Tri-Service General Hospital/National Defense Medical Center in Taipei, Taiwan.
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Publication Dates
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Publication in this collection
Mar 2015
History
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Received
24 Sept 2014 -
Reviewed
27 Nov 2014 -
Accepted
5 Jan 2015