Cell Biochem Biophys DOI 10.1007/s12013-014-0415-5
ORIGINAL PAPER
Sevoflurane Used for Color Doppler Ultrasound Examination in Children Conghai Fan • Fengchao Zhang • Xiaomei Huang Cheng Wen • Chengjing Shan
•
Ó Springer Science+Business Media New York 2014
Abstract The objective of this study is to investigate the feasibility of sevoflurane inhalation in pediatric color doppler ultrasound examination. In this study, 30 cases of children under 1 year were selected. They were all I or II levels according to American Society of Anesthesiology. Children with severe cyanotic congenital heart disease or severe pneumonia were excluded. All the children received anesthesia with sevoflurane. The University of Michigan Sedation Scale was assessed and bispectral index (BIS) was recorded before induction (T0), after induction (T1), when maintaining (T2), and when waking-up (T3). Blood pressure and heart rate were monitored during the color doppler ultrasound examination, the time to receive sedation examination and anesthesia recovery time were also recorded. (1) Score for UMSS was zero at T0 and 3 at T1; (2) BIS value was 93.18 ± 2.94 at T0 and decreased to 87.6 ± 3.9 at T1; (3) Blood pressure or heart rate did not decline obviously; (4) The time to receive sedation examination was 46.4 ± 13.1 s and anesthesia recovery time was 7.8 ± 5.3 min. In conclusion, sevoflurane can be used in pediatric color doppler ultrasound examination safely and effectively. Keywords Sevoflurane Bispectral index (BIS) University of Michigan Sedation Scale (UMSS) Safe and effective Introduction Sevoflurane is a new kind of halogen inhalation anesthetic and has been widely used since 1990s in North C. Fan F. Zhang (&) X. Huang C. Wen C. Shan Department of Anesthesiology, Xuzhou Children’s Hospital, Xuzhou 221006, China e-mail: [email protected]
America. It smells slightly sweet and has no irritation to the respiratory tract; therefore, it is easy to accept for children. Sevoflurane has several advantages, such as low blood/gas partition coefficient, easy to control the induction of anesthesia, anesthesia depth and wake up velocity, low liver and renal side effects, and stable hemodynamics [1]. Sevoflurane has been widely used in pediatric anesthesia [2]. However, there are no reports about the application of sevoflurane in outpatient pediatric color doppler ultrasound examination. The current study was designed to assess the safety and effectiveness of sevoflurane in outpatient pediatric color doppler ultrasound examination and it can provide reference for the clinical application of sevoflurane.
Materials and Methods Clinical Data The present study was approved by the medical ethics review committee and all the children’s legal guardians signed the informed consent. Since most of the children who needed to be anesthetized were \1 year, 30 cases of children (18 female) under 1 year were selected. Their range of age was 9 days to 1 year old and the range of body weight was 3.8–9.2 kg. The examination time was 7.8 ± 5.3 min. There was one case with nausea and vomiting and two cases with body movement when examination. Children with severe cyanotic congenital heart disease or severe pneumonia were excluded. They were all levels I or II according to the American Society of Anesthesiology (ASA) and received cardiac ultrasonic examination.
123
Cell Biochem Biophys
Anesthetic Sedation Preparation and Methods
Results
Sevoflurane was used as an inhaled anesthetic and anesthesiologist administered the anesthesia on children using a special vaporizer (Sevoflurane Drager Vapor 2000; axter). The anesthesia apparatus in this study was the Drager series and it was equipped with an exhaust system. Routine fasting for 2 h was needed before the examination, and medication before anesthesia was not allowed. The air escape valve was opened before anesthesia and the joint between the breathing circuit and the outlet in the patients was closed by hand to avoid the anesthetic gas from escaping into the room. The breathing bag was emptied manually and the concentration of sevoflurane was adjusted to 8 % and the oxygen flow was 6 L/min. Release the breathing bag for about 60 s to fill it with a high concentration of sevoflurane. The mask was placed over the children’s nose and mouth with the tidal volume method until the eyelash reflex disappeared and there were no body movement when pinching the earlobe., Then, the concentration of sevoflurane was adjusted to 1–3 % and oxygen flow was 2 L/min. The inhalation was discontinued until the final inspection (suprasternal fossa check) in echocardiography.
None of the patients in the 30 cases had cough or breathholding phenomenon during anesthetic sedation. Respiratory secretions were less and airway tolerance was good. There were two cases with body movement and one case with vomiting. At T0, all the children were awake, so the score of UMSS was 0. At T1, the score of UMSS was 3. BIS values were significantly lower at T1 or T2 than that at T0 (P \ 0.05). There were no significant differences between BIS values at T3 and at T0 (P [ 0.05). When compared with T0, mean arterial blood pressure at T1 decreased by 5.91 % and heart rate decreased by 5.19 % (see Table 1). The duration between sedation and examination (t1) was 46.4 ± 13.1 s, and the duration between discontinue medication and waking-up (t3) was 7.8 ± 5.3 min.
Monitoring Items An invigilator (GOLDWAYVT4000F) was used to monitor blood pressure, heart rate, and oxygen saturation during the examination. AspectA-2000XPBIS monitor (Aspect, US) was used to monitor BIS before sedation (T0), after induction (T1), when maintaining (T2) and wakefulness (T3). The duration was recorded between sedation onset and being ready to receive examination (t1), the examination time (t2) and the duration between discontinue medication and waking-up (t3). The children were observed and recorded whether they had vomiting, increased secretions, body movement, cough, and breath during anesthesia. The state of consciousness was assessed with the University of Michigan Sedation Scale (UMSS): 0 = being awake or alert; 1 = sleep/responds appropriately; 2 = somnolent/arouses to light stimuli; 3 = deep sleep/arouses to deeper physical stimuli; 4 = unarousable to stimuli [3]. The status of children was assessed with UMSS.
Statistical Analysis All the data were analyzed with SPSS, version 17.0. Measurement data were shown as ± s. Paired t test was performed and an alpha level of 0.05 was used for all the statistical comparisons.
123
Discussion For pediatric outpatient echocardiography, children need to lie quietly. But due to the cool coupling agent, long examination time and the need of pressing, children’s sleep depth cannot reach the inspection requirements, so the inspection cannot be carried out smoothly, the efficiency of the color ultrasonic room significantly reduces, and the children’s check time is influenced. Therefore, chloral hydrate as one kind of sedation drug is widely used in pediatric out-patient examination for children \1 year who need sedation. But oral chloral hydrate could stimulate the gastric mucosa and cause problems such as nausea, vomiting, and abdominal discomfort. Chloral hydrate enema with larger resistance could easily cause mucosal damage and affect sedation. Therefore, it is particularly important to find a safe and efficient new outpatient sedation method. Sevoflurane is a new kind of inhalation anesthetic with blood/gas partition coefficient of 0.63 and brain/blood partition coefficient of 1.7. It works rapidly and children can wake up quickly. Sevoflurane is rapidly removed by pulmonary and has been widely applied in pediatric anesthesia. In this study, sevoflurane was used to anesthetize children and no one had cough or breath-holding phenomenon during anesthetic sedation. Respiratory secretions were less and airway tolerance was good, which was associated with small airway stimulation and the effects of expanding bronchus. Studies have indicated that nobody refuses breathing, cough, breath holding or laryngeal spasm happened even when the sevoflurane concentration reached 8 %, which was consistent with the current study [4]. High concentration (8 %) of sevoflurane was used in this study, and there were only two cases with body movement, which was due to sevoflurane’s characteristics of reaching to deep
Cell Biochem Biophys Table 1 BIS, blood pressure, and heart rate when anesthetic sedation (n = 30, ± s) Monitoring item
Before sedation (T0)
After sedation (T1)
Maintaining (T2)
Waking-up (T3)
BIS
93.0 ± 2.8
85.5 ± 3.7*
84.4 ± 7.3*
91.8 ± 4.0
SBP (mmHg)
81.9 ± 5.8
77.0 ± 4.8
78.3 ± 2.9
82.7 ± 6.9
HR (bpm)
148.6 ± 15.2
140.0 ± 10.3
137.4 ± 14.9
143.9 ± 13.0
BIS bispectral index; SBP systolic blood pressure; HR heart rate * Compared with T0, P \ 0.05
sedation quickly and avoiding excitement, salivation, cough, and body movement. The induction time in this study was 46.4 ± 13.1 s. However, one study showed that the time of tidal volume method with 8 % sevoflurane was 107.6 ± 27.5 s [5]. Our induction time was significant shorter, which may result from emptying manual breathing bag before anesthesia, being full of high concentration of sevoflurane in the ventilator circuit, or different levels of sedation. Sun et al. [6] showed that sevoflurane had little impact on the functions of lower esophageal sphincter in children and helped maintain stable functions. There was only one case with vomiting, which might be caused by insufficient fasting time or other factors causing high reflux. We must be more vigilant in clinical applications in future. Akazawa et al. [7] considered that sevoflurane affected the circulation in a dose-dependent manner: low concentration had no significant effects on myocardial contractility, myocardial blood flow, oxygen consumption, heart rate, mean arterial pressure, cardiac index, and stroke volume index; high concentration (more than 1.5 MAC) inhibited the myocardial contractility, expanded blood vessel, and cardiac index and mean arterial pressure decreased significantly. In our study, when compared with T0, mean arterial blood pressure at T1 decreased by 5.91 % and heart rate decreased by 5.19 %, but the differences were not statistically significant. This may be related to the fact that the total sevoflurane inhaled at high concentrations is not so much. At present, BIS is one accurate method with EEG to judge the level of sedation and monitor anesthesia depth. BIS value is presented with 0–100, and zero means no EEG signal and 100 means waking state. It is generally considered that BIS of 65–85 means sleep, 40–64 means anesthesia state, and \40 means cerebral cortex in erupted inhibitory state. There is significant correlation between BIS value with UMSS score and they could reflect the changes of the depth of sedation [8]. BIS monitoring has been widely used in anesthesia for children operation. Zhang et al. [9] studied bispectral index instrument in monitoring the depth of anesthesia amongst children of different ages, and their results were in accordance with ours. The results of the BIS monitoring technology reflect
the changes of the central electrical activity and monitor sedation level effectively. In this study, BIS values declined with the deepening of sedation depth. When compared with wakefulness, BIS value was lower than that at induction and maintaining phase when children were under sedation.
Conclusion In summary, sedation with sevoflurane inhalation in outpatient color doppler ultrasound examination has characteristics of waking-up quickly, with little effects on the respiratory and circulatory system. There is low incidence of adverse reaction and no pain. It has obvious advantages to enhance the color ultrasonic room work efficiency and significantly reduce the waiting time. Therefore, sevoflurane can be applied in pediatric outpatient color doppler ultrasound examination.
References 1. Klock, P. A., Czeslick, E. G., Klafta, J. M., Ovassapian, A., & Moss, J. (2001). The effect of sevoflurane and desflurane on upper airway reactivity. Anesthesiology, 94, 963–967. 2. Wang, Y. H., Zhang, Y., & Jin, Liu. (1999). Application of sevoflurane in pediatric cardiac operation anesthesia. Chinese Journal of Anesthesiology, 19, 574–576. 3. Power, K. S., Nazarian, E. B., Tapyrik, S. A., Kohli, S. M., Yin, H., van der Jagt, E. W., et al. (2005). Bispectral index as a guide for titration of propofol during procedural sedation among children. Pediatrics, 115, 1666–1674. 4. Peng, Z. H., Chang, K. Q., & Bi, H. S. (2003). Application of sevoflurane rapid inhalation induction in anesthesia of pediatric tetralogy of Fallot operation. Journal of Clinical Anesthesia, 11, 686–687. 5. Hu, B.Y. (2009). Study on strategy of general anesthesia induction of sevoflurane, Dalian Medical University. 6. Sun, Y. J., Chen, W. M., & Zhang, T. Z. (2003). The effects of sevoflurane on functions of lower esophageal sphincter in children. Journal of Clinical Anesthesia, 8, 452–453. 7. Akazawa, S., Shimizu, R., Nakaigawa, T., Ishii, R., Ikeno, S., & Yamato, R. (1997). Effects of magnesium sulphate on atrioventricular conduction times and surface electrocardiogram in dogs anaesthetized with sevoflurance. British Journal of Anaesthesia, 88, 214–217.
123
Cell Biochem Biophys 8. Mc Demott, N. B., Van Sickle, T., Motas, D., & Friesen, R. H. (2002). Validation of the bispectral index monitor during conscious and deep sedation in children. Anesthesia and Analgesia, 97, 39–43. 9. Zhang, J. M., Wang, F., Lv, H., et al. (2010). Use of bispectral index (BIS) monitor in inspecting the depth of anesthesia in
123
pediatric patients undergoing general anesthesia. Journal of Capital Medical University, 31(5), 664–667.
ORIGINAL PAPER
Sevoflurane Used for Color Doppler Ultrasound Examination in Children Conghai Fan • Fengchao Zhang • Xiaomei Huang Cheng Wen • Chengjing Shan
•
Ó Springer Science+Business Media New York 2014
Abstract The objective of this study is to investigate the feasibility of sevoflurane inhalation in pediatric color doppler ultrasound examination. In this study, 30 cases of children under 1 year were selected. They were all I or II levels according to American Society of Anesthesiology. Children with severe cyanotic congenital heart disease or severe pneumonia were excluded. All the children received anesthesia with sevoflurane. The University of Michigan Sedation Scale was assessed and bispectral index (BIS) was recorded before induction (T0), after induction (T1), when maintaining (T2), and when waking-up (T3). Blood pressure and heart rate were monitored during the color doppler ultrasound examination, the time to receive sedation examination and anesthesia recovery time were also recorded. (1) Score for UMSS was zero at T0 and 3 at T1; (2) BIS value was 93.18 ± 2.94 at T0 and decreased to 87.6 ± 3.9 at T1; (3) Blood pressure or heart rate did not decline obviously; (4) The time to receive sedation examination was 46.4 ± 13.1 s and anesthesia recovery time was 7.8 ± 5.3 min. In conclusion, sevoflurane can be used in pediatric color doppler ultrasound examination safely and effectively. Keywords Sevoflurane Bispectral index (BIS) University of Michigan Sedation Scale (UMSS) Safe and effective Introduction Sevoflurane is a new kind of halogen inhalation anesthetic and has been widely used since 1990s in North C. Fan F. Zhang (&) X. Huang C. Wen C. Shan Department of Anesthesiology, Xuzhou Children’s Hospital, Xuzhou 221006, China e-mail: [email protected]
America. It smells slightly sweet and has no irritation to the respiratory tract; therefore, it is easy to accept for children. Sevoflurane has several advantages, such as low blood/gas partition coefficient, easy to control the induction of anesthesia, anesthesia depth and wake up velocity, low liver and renal side effects, and stable hemodynamics [1]. Sevoflurane has been widely used in pediatric anesthesia [2]. However, there are no reports about the application of sevoflurane in outpatient pediatric color doppler ultrasound examination. The current study was designed to assess the safety and effectiveness of sevoflurane in outpatient pediatric color doppler ultrasound examination and it can provide reference for the clinical application of sevoflurane.
Materials and Methods Clinical Data The present study was approved by the medical ethics review committee and all the children’s legal guardians signed the informed consent. Since most of the children who needed to be anesthetized were \1 year, 30 cases of children (18 female) under 1 year were selected. Their range of age was 9 days to 1 year old and the range of body weight was 3.8–9.2 kg. The examination time was 7.8 ± 5.3 min. There was one case with nausea and vomiting and two cases with body movement when examination. Children with severe cyanotic congenital heart disease or severe pneumonia were excluded. They were all levels I or II according to the American Society of Anesthesiology (ASA) and received cardiac ultrasonic examination.
123
Cell Biochem Biophys
Anesthetic Sedation Preparation and Methods
Results
Sevoflurane was used as an inhaled anesthetic and anesthesiologist administered the anesthesia on children using a special vaporizer (Sevoflurane Drager Vapor 2000; axter). The anesthesia apparatus in this study was the Drager series and it was equipped with an exhaust system. Routine fasting for 2 h was needed before the examination, and medication before anesthesia was not allowed. The air escape valve was opened before anesthesia and the joint between the breathing circuit and the outlet in the patients was closed by hand to avoid the anesthetic gas from escaping into the room. The breathing bag was emptied manually and the concentration of sevoflurane was adjusted to 8 % and the oxygen flow was 6 L/min. Release the breathing bag for about 60 s to fill it with a high concentration of sevoflurane. The mask was placed over the children’s nose and mouth with the tidal volume method until the eyelash reflex disappeared and there were no body movement when pinching the earlobe., Then, the concentration of sevoflurane was adjusted to 1–3 % and oxygen flow was 2 L/min. The inhalation was discontinued until the final inspection (suprasternal fossa check) in echocardiography.
None of the patients in the 30 cases had cough or breathholding phenomenon during anesthetic sedation. Respiratory secretions were less and airway tolerance was good. There were two cases with body movement and one case with vomiting. At T0, all the children were awake, so the score of UMSS was 0. At T1, the score of UMSS was 3. BIS values were significantly lower at T1 or T2 than that at T0 (P \ 0.05). There were no significant differences between BIS values at T3 and at T0 (P [ 0.05). When compared with T0, mean arterial blood pressure at T1 decreased by 5.91 % and heart rate decreased by 5.19 % (see Table 1). The duration between sedation and examination (t1) was 46.4 ± 13.1 s, and the duration between discontinue medication and waking-up (t3) was 7.8 ± 5.3 min.
Monitoring Items An invigilator (GOLDWAYVT4000F) was used to monitor blood pressure, heart rate, and oxygen saturation during the examination. AspectA-2000XPBIS monitor (Aspect, US) was used to monitor BIS before sedation (T0), after induction (T1), when maintaining (T2) and wakefulness (T3). The duration was recorded between sedation onset and being ready to receive examination (t1), the examination time (t2) and the duration between discontinue medication and waking-up (t3). The children were observed and recorded whether they had vomiting, increased secretions, body movement, cough, and breath during anesthesia. The state of consciousness was assessed with the University of Michigan Sedation Scale (UMSS): 0 = being awake or alert; 1 = sleep/responds appropriately; 2 = somnolent/arouses to light stimuli; 3 = deep sleep/arouses to deeper physical stimuli; 4 = unarousable to stimuli [3]. The status of children was assessed with UMSS.
Statistical Analysis All the data were analyzed with SPSS, version 17.0. Measurement data were shown as ± s. Paired t test was performed and an alpha level of 0.05 was used for all the statistical comparisons.
123
Discussion For pediatric outpatient echocardiography, children need to lie quietly. But due to the cool coupling agent, long examination time and the need of pressing, children’s sleep depth cannot reach the inspection requirements, so the inspection cannot be carried out smoothly, the efficiency of the color ultrasonic room significantly reduces, and the children’s check time is influenced. Therefore, chloral hydrate as one kind of sedation drug is widely used in pediatric out-patient examination for children \1 year who need sedation. But oral chloral hydrate could stimulate the gastric mucosa and cause problems such as nausea, vomiting, and abdominal discomfort. Chloral hydrate enema with larger resistance could easily cause mucosal damage and affect sedation. Therefore, it is particularly important to find a safe and efficient new outpatient sedation method. Sevoflurane is a new kind of inhalation anesthetic with blood/gas partition coefficient of 0.63 and brain/blood partition coefficient of 1.7. It works rapidly and children can wake up quickly. Sevoflurane is rapidly removed by pulmonary and has been widely applied in pediatric anesthesia. In this study, sevoflurane was used to anesthetize children and no one had cough or breath-holding phenomenon during anesthetic sedation. Respiratory secretions were less and airway tolerance was good, which was associated with small airway stimulation and the effects of expanding bronchus. Studies have indicated that nobody refuses breathing, cough, breath holding or laryngeal spasm happened even when the sevoflurane concentration reached 8 %, which was consistent with the current study [4]. High concentration (8 %) of sevoflurane was used in this study, and there were only two cases with body movement, which was due to sevoflurane’s characteristics of reaching to deep
Cell Biochem Biophys Table 1 BIS, blood pressure, and heart rate when anesthetic sedation (n = 30, ± s) Monitoring item
Before sedation (T0)
After sedation (T1)
Maintaining (T2)
Waking-up (T3)
BIS
93.0 ± 2.8
85.5 ± 3.7*
84.4 ± 7.3*
91.8 ± 4.0
SBP (mmHg)
81.9 ± 5.8
77.0 ± 4.8
78.3 ± 2.9
82.7 ± 6.9
HR (bpm)
148.6 ± 15.2
140.0 ± 10.3
137.4 ± 14.9
143.9 ± 13.0
BIS bispectral index; SBP systolic blood pressure; HR heart rate * Compared with T0, P \ 0.05
sedation quickly and avoiding excitement, salivation, cough, and body movement. The induction time in this study was 46.4 ± 13.1 s. However, one study showed that the time of tidal volume method with 8 % sevoflurane was 107.6 ± 27.5 s [5]. Our induction time was significant shorter, which may result from emptying manual breathing bag before anesthesia, being full of high concentration of sevoflurane in the ventilator circuit, or different levels of sedation. Sun et al. [6] showed that sevoflurane had little impact on the functions of lower esophageal sphincter in children and helped maintain stable functions. There was only one case with vomiting, which might be caused by insufficient fasting time or other factors causing high reflux. We must be more vigilant in clinical applications in future. Akazawa et al. [7] considered that sevoflurane affected the circulation in a dose-dependent manner: low concentration had no significant effects on myocardial contractility, myocardial blood flow, oxygen consumption, heart rate, mean arterial pressure, cardiac index, and stroke volume index; high concentration (more than 1.5 MAC) inhibited the myocardial contractility, expanded blood vessel, and cardiac index and mean arterial pressure decreased significantly. In our study, when compared with T0, mean arterial blood pressure at T1 decreased by 5.91 % and heart rate decreased by 5.19 %, but the differences were not statistically significant. This may be related to the fact that the total sevoflurane inhaled at high concentrations is not so much. At present, BIS is one accurate method with EEG to judge the level of sedation and monitor anesthesia depth. BIS value is presented with 0–100, and zero means no EEG signal and 100 means waking state. It is generally considered that BIS of 65–85 means sleep, 40–64 means anesthesia state, and \40 means cerebral cortex in erupted inhibitory state. There is significant correlation between BIS value with UMSS score and they could reflect the changes of the depth of sedation [8]. BIS monitoring has been widely used in anesthesia for children operation. Zhang et al. [9] studied bispectral index instrument in monitoring the depth of anesthesia amongst children of different ages, and their results were in accordance with ours. The results of the BIS monitoring technology reflect
the changes of the central electrical activity and monitor sedation level effectively. In this study, BIS values declined with the deepening of sedation depth. When compared with wakefulness, BIS value was lower than that at induction and maintaining phase when children were under sedation.
Conclusion In summary, sedation with sevoflurane inhalation in outpatient color doppler ultrasound examination has characteristics of waking-up quickly, with little effects on the respiratory and circulatory system. There is low incidence of adverse reaction and no pain. It has obvious advantages to enhance the color ultrasonic room work efficiency and significantly reduce the waiting time. Therefore, sevoflurane can be applied in pediatric outpatient color doppler ultrasound examination.
References 1. Klock, P. A., Czeslick, E. G., Klafta, J. M., Ovassapian, A., & Moss, J. (2001). The effect of sevoflurane and desflurane on upper airway reactivity. Anesthesiology, 94, 963–967. 2. Wang, Y. H., Zhang, Y., & Jin, Liu. (1999). Application of sevoflurane in pediatric cardiac operation anesthesia. Chinese Journal of Anesthesiology, 19, 574–576. 3. Power, K. S., Nazarian, E. B., Tapyrik, S. A., Kohli, S. M., Yin, H., van der Jagt, E. W., et al. (2005). Bispectral index as a guide for titration of propofol during procedural sedation among children. Pediatrics, 115, 1666–1674. 4. Peng, Z. H., Chang, K. Q., & Bi, H. S. (2003). Application of sevoflurane rapid inhalation induction in anesthesia of pediatric tetralogy of Fallot operation. Journal of Clinical Anesthesia, 11, 686–687. 5. Hu, B.Y. (2009). Study on strategy of general anesthesia induction of sevoflurane, Dalian Medical University. 6. Sun, Y. J., Chen, W. M., & Zhang, T. Z. (2003). The effects of sevoflurane on functions of lower esophageal sphincter in children. Journal of Clinical Anesthesia, 8, 452–453. 7. Akazawa, S., Shimizu, R., Nakaigawa, T., Ishii, R., Ikeno, S., & Yamato, R. (1997). Effects of magnesium sulphate on atrioventricular conduction times and surface electrocardiogram in dogs anaesthetized with sevoflurance. British Journal of Anaesthesia, 88, 214–217.
123
Cell Biochem Biophys 8. Mc Demott, N. B., Van Sickle, T., Motas, D., & Friesen, R. H. (2002). Validation of the bispectral index monitor during conscious and deep sedation in children. Anesthesia and Analgesia, 97, 39–43. 9. Zhang, J. M., Wang, F., Lv, H., et al. (2010). Use of bispectral index (BIS) monitor in inspecting the depth of anesthesia in
123
pediatric patients undergoing general anesthesia. Journal of Capital Medical University, 31(5), 664–667.
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