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Effect-site concentration of remifentanil for
nasotracheal versus orotracheal intubation during
propofol target-controlled infusion
by
Effect-site concentration of remifentanil for
nasotracheal versus orotracheal intubation during
propofol target-controlled infusion
by
Yi Hwa Choi
A Dissertation Submitted to The Graduate School of Ajou University
in Partial Fulfillment of the Requirements for the Degree of
Master of Medical Sciences
Supervised by
Jong Yeop Kim, M.D., Ph.D.
Major in Medicine
Department of Medical Sciences
The Graduate School, Ajou University
This certifies that the dissertation
of Yi Hwa Choi is approved.
SUPERVISORY COMMITTEE
J Yeop Kim
_________________________________
J Soo Kim
S Kee Min
- ABSTRACT –
Effect-site Concentration of Remifentanil for Nasotracheal versus
Orotracheal Intubation during Propofol Target-controlled Infusion
Background: The purpose of this study was to determine the effect-site concentrations ofremifentanil required for acceptable nasotracheal (NT) intubation in adults after propofol target-controlled infusion (TCI) without neuromuscular blocking agent, and whether or not these concentrations differ from those for orotracheal (OT) intubation.
Methods: Fifty patients were assigned to receive either OT intubation (OT group, n = 25)
or NT intubation (NT group, n = 25). Anaesthesia was induced with propofol TCI at the effect-site concentration of 5.0 μg/ml. Two minutes later, the predetermined effect-site concentration of remifentanil was started (from 4.5 ng/ml) using Dixon’s up-and-down method. Tracheal intubation was performed during the remifentanil infusion 2 min after beginning. Acceptable intubation was defined as excellent or good intubating conditions.
Results: EC50 ± SD of remifentanil in the OT and NT groups was 5.58 ± 0.75 ng/ml and
6.08 ± 0.75 ng/ml, respectively; there was no statistical significance between the groups (P = 0.277). Using isotonic regression, EC50 (95% CI) of remifentanil in the OT and NT groups was 5.00 (3.34-7.46) ng/ml and 5.75 (3.66-7.84) ng/mlv, respectively (P = 0.592).
Conclusion: The effect-site concentration of remifentanil for acceptable NT intubation was
6.08 ng/ml in 50% of adults during propofol TCI at an effect-site concentration of 5.0 μg/ml without neuromuscular blocking agent. The predicted effect-site concentration of remifentanil for NT intubation was not different from OT intubation.
TABLE OF CONTENTS
ABSTRACT --- ⅰ TABLE OF CONTENTS --- ⅱ LIST OF FIGURES --- ⅲ LIST OF TABLES --- ⅳ TEXT ---ⅴ Ⅰ. INTRODUCTION --- 1 Ⅱ. METHODS --- 2 Ⅲ. RESULTS --- 6 Ⅳ. DISCUSSION --- 9 V. CONCLUSION--- 17 REFERENCES --- ⅵ 국문요약 --- ⅶLIST OF FIGURES
Fig.1. Sequences of effect-site concentration of remifentanil for acceptable
intubation in the OT group using the up-and-down methods. EC50 of remifentanil in the OT groups was 5.58 ± 0.75 ng/ml.
--- 7
Fig.2. Sequences of effect-site concentration of remifentanil for acceptable
intubation in the NT group using the up-and-down methods. EC50 of remifentanil in the NT groups was 6.08 ± 0.75 ng/ml.
LIST OF TABLES
Table 1. Assessment of intubation conditions --- 13 Table 2. Patient characteristics and induction profiles.--- 14 Table 3. Intubation conditions and causes of unacceptable intubating conditions
--- 15 Table 4. Haemodynamic and bispectral index (BIS) data from patients with
Ⅰ. INTRODUCTION
Propofol and remifentanil have been shown to provide good intubating conditions without the use of neuromuscular blocking drugs (Stevens, 1998; Alexander, 1999). Target-controlled infusions (TCI) of propofol and remifentanil can provide satisfactory conditions for intubation without the use of muscle relaxants, and allow for easy adjustment of anaesthetic depth, and can attenuate the haemodynamic response to laryngoscopy (Troy, 2002).
Nasotracheal (NT) intubation is often necessary in elective or emergency maxillofacial surgery and can stimulate the nasal cavity and nasopharynx, which does not occur during orotracheal (OT) intubation. Findings from a previous study demonstrated that circulatory responses to laryngoscopic NT intubation are greater than those produced by OT intubation (Smith, 1991). Therefore, the depth of anaesthesia required for achievement of ideal NT intubating conditions without muscle relaxant may be increased. To date, there are no reports on the dose of remifentanil for acceptable NT intubation during propofol induction. The purpose of this study was to determine the effect-site concentrations of remifentanil required for acceptable NT intubation in adults after propofol TCI without neuromuscular blocking agent, and whether or not these concentrations differ from those for OT intubation.
Ⅱ. Methods
This study was approved by the institutional review board, and written informed consent for the study was obtained from all patients. We enrolled ASA I or II, aged 18-50 years, undergoing general anaesthesia for short dental and ENT surgery. Exclusion criteria included a history of hypertension, reactive airway disease, and a suspected difficult airway. No premedication was administered prior to surgery. For drug injection, a 20-gauge cannula was inserted into the forearm or dorsum of the hand, and connected to a T-connector prior to arrival in the operating theatre. Upon arrival in the operating theatre, all patients were monitored with electrocardiogram, pulse oximeter, noninvasive blood pressure, and bispectral index (BIS) (BIS VISTATM monitor, four electrode sensor; Aspect Medical Systems, Norwood, MA, USA).
Patients were assigned to one of two groups according to the type of surgery: NT intubation for dental surgery (NT group) or OT intubation for ENT surgery (OT group). Following injection of 30 mg lidocaine, anaesthesia was induced with propofol TCI at the effect-site concentration of 5.0 μg/ml. Two minutes later (i.e. when the intended target effect-site concentration of propofol was reached), the predetermined effect-site concentration of remifentanil was started. A commercially available two-channel TCI pump (Orchestra®, Fresenius Vial, Brezins, France) was used for effect-site TCI of propofol and remifentanil. Pharmacokinetic sets used in calculation of target effect-site concentrations for propofol and remifentanil were Marsh et al (Marsh, 1991) and Minto et al (Minto, 1997). models, respectively. The ke0 value used for propofol was 1.21/min (Struys, 2000). Infusions of propofol and remifentanil were prepared in 50 ml syringes using 2% propofol and remifentanil 2 mg (diluted with normal saline to make a 40 μg/ml solution). When remifentanil is administrated using the integrated Minto model, the infusion pattern shows that initial bolus is infused for 10 s, and thereafter pseudo-equilibrium state reaches, then varying rates of continuous infusion are maintained about 1.6 min after the start of TCI. So, Tracheal intubation was performed during the remifentanil infusion 2 min after beginning. All intubations were carried out using direct laryngoscopy with a Macintosh
(Portex® tube, Smith Medical International, Hythe, UK) was used. The nasal RAE tube was put into the warm saline bottle and lubricated with a jelly immediately before intubation. For OT intubation, the chosen size of the tracheal tube was 7.0 mm for females and 7.5 mm for males, and for NT intubation, the size was 6.0 mm for females and 6.5 mm for males.
The effect-site concentration of remifentanil for each patient was determined by the response of the previously tested patient using the modified Dixon’s up-and-down method (0.5 ng/ml as a step size) (Dixon, 1991). The first patient was tested at an effect-site concentration of remifentanil 4.5 ng/ml. This was a target concentration close to the predicted remifentanil concentration at which there was a 50% probability of acceptable tracheal intubation (EC50) (Ithnin, 2009). If intubation was unacceptable, the target effect-site concentration of remifentanil for the next patient was increased by 0.5 ng/ml. If intubation was acceptable, the target effect-site concentration of remifentanil was decreased by the same amount. Intubating conditions were evaluated according to a scoring system described by Viby-Mogensen (Table 1) (Viby-Mogensen, 1996). Acceptable intubation was defined as excellent or good intubating conditions. A single measurement was obtained from each patient. The anaesthesiologist who performed and assessed the intubating conditions was unaware of the effect-site concentration of remifentanil. For the patients’ safety, if intubation failed due to strong movement by the patient, inadequate jaw relaxation, or closed vocal cords, rocuronium 0.3 mg/kg was administered and intubation was attempted. Clinically significant hypotension and bradycardia were defined as a mean arterial pressure (MAP) of < 55 mmHg and a heart rate (HR) of < 45 beats/min, respectively. Patients were treated with atropine or ephedrine where appropriate. MAP, HR, SpO2, and BIS were recorded at anaesthetic induction, 2 min after propofol infusion, before, and 1 min after
estimates of the optimal concentration of remifentanil using the modified Dixon’s up-and-down method (Dixon, 1991). This study ended when data from six independent pairs of patients were collected in each group. Statistical analyses were performed using SPSS 13.0 for windows (SPSS Inc, Chicago, IL, USA) and R for windows (version for R 2.9.0.). Data are expressed as mean ± SD or number of patients. The 50% effective concentration (EC50) of remifentanil that enabled acceptable tracheal intubation was determined by calculating the average of the midpoint dose of all independent pairs of patients after six crossover points were obtained in each group. For backup analysis, the data were also subjected to isotonic regression estimators for calculation of EC50 and 95% confidence interval (CI). An adjusted response probability was easily calculated by the pooled adjacent-violators algorithm (PAVA), and the CI was estimated by a bootstrapping approach (Pace, 2007). For comparison of two groups EC50, a two sample Z-procedure was used. Patient characteristics and induction profiles were compared using a Student’s t-test. Changes in haemodynamic data were compared by repeated measures ANOVA. A P value < 0.05 was considered statistically significant.
Ⅲ. Results
Fifty patients were enrolled in this study. Three patients could not meet the time schedule of this study due to unexpected difficult intubation and technical problems (1 in the OT group and 2 in the NT group). A total of 47 patients completed the study. No significant differences in patient characteristics were observed between the two groups (Table 2). However, intubation time was significantly longer in the NT group than in the OT group (Table 2). Intubating conditions were good or excellent (acceptable intubation) in 12/24 and 11/23 patients in the OT and NT groups. Excellent intubating conditions were present in 4/24 patients in the OT group and in 4/23 patients in the NT group (Table 3). Table 3 shows observed causes of unacceptable intubating conditions. Table 4 lists haemodynamic data on patients with acceptable intubation during induction of anaesthesia. No significant differences in MAP, HR, SpO2, and BIS were observed between the two groups.
Figure 1 shows the sequences of effect-site concentration of remifentanil for acceptable and unacceptable tracheal intubation in the two groups. Using the Dixon’s up and down methods, EC50 ± SD of remifentanil in the OT and NT groups was 5.58 ± 0.75 ng/ml and 6.08 ± 0.75 ng/ml, respectively. EC50 of the NT group was higher than that of the OT group, but did not reach statistical significance (P = 0.277). Using isotonic regression estimated from the PAVA response rate, EC50 (95% CI) of remifentanil in the OT and NT groups was 5.00 (3.34-7.46) ng/ml and 5.75 (3.66-7.84) ng/ml, respectively (P = 0.592). Adverse respiratory events, such as laryngospasm, were not observed, and SpO2 remained above 90% in all patients. No patient suffered clinically significant bradycardia or hypotension.
E ff ec t-si te c on ce nt ra tio n of r em if en ta ni l ( ng /m l) Consecutive patients Orotracheal
Fig.1. Sequences of effect-site concentration of remifentanil for acceptable intubation in the OT group using the up-and-down methods. EC50 of remifentanil in the OT
E ff ec t-si te c on ce nt ra tio n of r em if en ta ni l ( ng /m l) Consecutive patients Nasotracheal
Fig.2. Sequences of effect-site concentration of remifentanil for acceptable intubation in the NT group using the up-and-down methods. EC50 of remifentanil in the NT
Ⅳ. DISCUSSION
This study demonstrated that EC50 ± SD of remifentanil for OT and NT intubation was 5.58 ± 0.75 ng/ml and 6.08 ± 0.75 ng/ml, respectively, in adults during propofol TCI at an effect-site concentration of 5.0 μg/ml without neuromuscular blocking agent, and no statistical difference was observed between the groups.
Acceptable NT intubation without neuromuscular blockade during propofol anaesthesia has been reported, although no previous report has evaluated NT intubation conditions using propofol and remifentanil TCI. Andel et al (Andel,2000). demonstrated the minimal propofol dose in combination with fentanyl required for NT intubation. They reported that intubation of all patients without neuromuscular blockade is possible, and that median value of the required propofol dose in combination with 3 μg/kg of fentanyl was 2.74 mg/kg. Another previous study in adults has demonstrated acceptable NT intubation in 83% of patients receiving propofol 2.5 mg/kg and alfentanil 20 μg/kg (Coghlan,1993). In our study using isotonic regression estimated from the PAVA response rate, EC50 and EC95 of remifentanil for NT intubation during propofol TCI was 5.75 ng/ml and 7.42 ng/ml, respectively.
Because the tracheal tube has to be inserted through the nasal passage, NT intubation is a more time-consuming and more invasive airway procedure than OT intubation. As a result, NT intubation can cause greater haemodynamic response than OT intubation. Findings from a previous study have demonstrated that the hypertensive response after NT intubation is significantly greater than that after OT intubation under comparable conditions (Smith, 1991; Fassoulaki, 1990). In our study, we assumed that NT intubation may be more stimulating, and that the dose of remifentanil required for NT intubation without neuromuscular blockade may be increased. However, our results have shown that EC50 of remifentanil for OT and NT intubation was 5.58 ± 0.75 ng/ml and 6.08 ± 0.75 ng/ml, respectively, during propofol TCI, and that there was no strong evidence that the target
A possible explanation for our results may be that tracheal intubation was the most potent stimulus of the airway during nasotracheal intubation (Singh, 2003), which typically comprises three distinct stages: (i) nasopharyngeal intubation; (ii) direct laryngoscopy for identification of the vocal cords; and (iii) passage of the tracheal tube into the trachea (tracheal intubation). Singh and Smith (Singh, 2003) suggested that the third stage produced a marked pressor response that was significantly greater than that of the first two stages. This implies that NT intubation resulted in a comparable magnitude of airway manipulation to the OT intubation, and thus required a similar depth of anaesthesia. And, this finding concurs with evidence that tracheal stimulus, not stimulus to the oropharyngeal structure, is the primary cause of the stress response to OT intubation (Takahashi,2002; Hirabayashi, 1998). Takahashi et al.(Takahashi, 2002) reported that the magnitude of haemodynamic changes associated with tracheal intubation using the lightwand device (Trachlight) is almost the same as that which occurs with the direct laryngoscope. And, they suggested that haemodynamic changes are likely to occur as a result of direct tracheal irritation rather than direct stimulation of the larynx. Our haemodynamic results are consistent with these previous studies showing that cardiovascular responses to tracheal intubation with lightwand did not differ from those with Macintosh laryngoscope (Takahashi, 2002; Hirabayashi, 1998).
Propofol TCI and adjuvant remifentanil have been shown to provide acceptable intubation conditions for OT intubation in adults without the use of a neuromuscular blocking agent (Troy, 2002; Ithnin, 2009). Troy et al.(Troy, 2002) suggested that an effect-site concentration of remifentanil 8 ng ml-1 along with an effect-site concentration of propofol 3 μg/ml could provide acceptable conditions for OT intubation in 95% of adult patients. In addition, another previous study reported that EC50 and EC95 of remifentanil
min after propofol TCI. Johansen et al. (Johansen, 2000) suggested that anaesthetic maintenance at BIS values between 50 and 65 was associated with shortened emergence and recovery from general anaesthesia.
We utilized isotonic regression to estimate EC50 and EC95 values. However, when small samples, such as the present one, are evaluated, accuracy of the parameter estimates has been questioned. Despite this criticism, isotonic regression has been suggested as a more favorable backup analysis for obtaining EC50 with a smaller bias and tighter CIs compared to standard probit or logit regression, which is likely to produce biased estimators (Pace, 2007). And, the EC50 calculated with the isotonic regression analysis from the up-and-down data in each group was similar to EC50 values obtained by crossover points in our study.
In conclusion, the required effect-site concentration of remifentanil at which acceptable NT intubation is possible in 50% of adults was 6.08 ng/ml during a TCI of 5.0 μg/ml propofol without neuromuscular blockade, using the modified Dixon’s up-and-down method. Concentration of remifentanil for acceptable intubating conditions might not differ according to the route of intubation.
Table 1
Assessment of intubation conditions
Intubating conditions
Acceptable unacceptable
Variables Excellent Good Poor
Ease of laryngoscopy
(jaw relaxation) Easy Fair Difficult
Vocal cord position Abducted Intermediate Closed Vocal cord movement None Moving Closing Airway
reaction(coughing) None Diaphragm Sustained Movement of the limbs None Slight Vigorous
Excellent: all criteria are excellent. Good: all criteria are either excellent or good. Poor: presence of a single criterion listed under ‘Poor’
Table 2
Values represent mean ± SD or number of patients.
* P < 0.05 compared with the OT group.
OT, patients with orotracheal intubation; NT, patients with nasotracheal intubation; LOC, loss of consciousness.
Patient characteristics and induction profiles
OT (n = 24) NT (n = 23) Sex (M/F) 13/11 14/9 Age (yr) 37.6 ± 10.4 33.5 ± 10.3 Weight (kg) 63.3 ± 12.1 59.1 ± 9.2 Height (cm) 165.5 ± 9.1 168.7 ± 7.5 ASA (I/II) 21/3 18/5 LOC time (s) 64.3 ± 27.2 68.9 ± 35.2 Intubation time (s) 23.6 ± 8.1 50.7 ± 18.5*
Table 3
Intubation conditions and causes of unacceptable intubating conditions
OT (n = 24) NT (n = 23) Excellent 4 4 Good 8 7 Poor 12 12
Causes of unacceptable intubation
Poor jaw relaxation 2 3
Closed vocal cord position 3 4
Closing vocal cord movement 0 2
Sustained coughing 7 3
Vigorous limb movement 3 4
Table 4
Values represent mean ± SD.
No significant differences between the groups were noted. MAP, mean arterial blood pressure; HR, heart rate.
Haemodynamic and bispectral index (BIS) data from patients with acceptable intubation during anaesthesia induction
Group Baseline 2 min after propofol infusion Prior to intubation 1 min after intubation MAP (mmHg) OT 85.0 ± 7.9 73.6 ± 5.9 60.5 ± 5.5 74.9 ± 10.3 NT 84.5 ± 7.8 72.0 ± 10.5 64.2 ± 12.3 76.3 ± 9.0 HR (beats min-1) OT 71.3 ± 11.5 69.9 ± 10.5 61.3 ± 9.3 67.4 ± 10.1 NT 74.0 ± 11.2 71.0 ± 9.1 62.8 ± 7.9 68.4 ± 9.9 SpO2 (%) OT 99.2 ± 0.8 100 ± 0.0 99.9 ± 0.3 99.8 ± 0.4 NT 99.6 ± 0.7 99.8 ± 0.4 99.9 ± 0.3 99.8 ± 0.4 BIS OT 97.4 ± 0.7 48.5 ± 18.1 54.0 ± 12.0 56.9 ± 13.5 NT 97.7 ± 0.5 44.9 ± 8.3 46.8 ± 8.2 52.0 ± 9.5
V. CONCLUSION
The effect-site concentration of remifentanil for acceptable NT intubation was 6.08 ng/ml in 50% of adults during propofol TCI at an effect-site concentration of 5.0 μg/ml without neuromuscular blocking agent. The predicted effect-site concentration of remifentanil for NT intubation was not different from OT intubation.
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Anaesthesia 54: 1037-40, 1999
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3. Coghlan SF, McDonald PF, Csepregi G. Use of alfentanil with propofol for nasotracheal intubation without neuromuscular block. Br J Anaesth 70: 89-91, 1993
4. Dixon WJ. Staircase bioassay: the up-and-down method. Neurosci Biobehav Rev 15: 47-50, 1991
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6. Hirabayashi Y, Hiruta M, Kawakami T, Inoue S, Fukuda H, Saitoh K, Shimizu R. Effects of lightwand (Trachlight) compared with direct laryngoscopy on circulatory responses to tracheal intubation. Br J Anaesth 81: 253-5, 1998
7. Ithnin F, Lim Y, Shah M, Shen L, Sia AT. Tracheal intubating conditions using propofol and remifentanil target-controlled infusion: a comparison of remifentanil EC50 for Glidescope and Macintosh. Eur J Anaesthesiol 26: 223-8, 2009
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- 국문요약 –
Propofol 목표농도조절주입 중 경비 또는 경구
기관내삽관을 위한 remifentanil 의 효과처농도 비교
아주대학교 대학원 의학과 최 이 화 (지도교수: 김 종 엽) 배경 : Propofol 과 Remifentanil 은 근이완제 없이 쉬운 기관삽관이 가능하다고 알려져 있다. 경비기관삽관술은 상악 및 안면부 수술에서 많이 이루어지고 있는데, 이 때 경구기관 삽관술에서와 달리 비강 내와 비 인두부에 자극을 주게 된다. 본 논문은 성인에서 근이완제 없이 propofol target – controlled infusion (TCI) 동안 경비기관삽관술을 가능하게 하는 remifentail 의 효과처 농도를 결정하고 경구기관 삽관술과의 차이를 알아보았다.방법 : 50 명의 환자를 대상으로 각각 경구삽관 25 명, 경비기관삽
25 명에서 시행하였다. 마취 induction 시 propofol TCI 효과처 농도는 5.0 μg/ml 으로 하였고, 2 분후 remifentanil 효과처 농도 4.5 μg/ml 에서 시작한 후 Dixon’s up-and-down method 를 사용하였다. 기관삽관은 remifentanil 주입시작 2 분후 시행하였고, 성공적인 삽관은 excellent or good intubating conditions 으로 결정하였다.
결과 : 경구삽관군과 경비기관삽관군의 remifentanil 의 EC50 ± SD 은
후 경구삽관군과 경비기관삽관군 사이 remifentanil 의 EC50 (95% CI) 은 각각 5.00 (3.34-7.46) ng/ml 과 5.75 (3.66-7.84) ng/ml (P = 0.592) 으로 나타났다. 결론 : 50%의 어른에서 근이완제 없이 propofol TCI 5.0 μg/ml 동안 경비 기관삽관술을 가능하게 하는 remifentanil 의 효과처 농도는 6.08 ng/ml 였으며, 이는 경구 기관삽관술에서 기대 되어지는 remifentanil 의 효과처 농도와 큰 차이가 없었다. --- 핵심어 : Remifentanil, Propofol, 경구삽관, 경비기관삽관
