通过插管型喉罩与直接喉镜行经口气管插管对血流动力学影响的比较

Original articleComparative study of hemodynamic responses to orotra- cheal intubation with intubating laryngeal mask airway and direct laryngoscopeZHANG Guo-hua, XUE Fu-shan, SUN Hai-yan, LI Cheng-wen, SUN Hai-tao, LI Ping and LIU Kun-peng Keywords: intubating laryngeal mask airway; general anesthesia; orotracheal intubation;hemodynamic responsesBackground Intubating laryngeal mask airway (ILMA) offers a new approach for orotracheal intubation and is expected to produce less cardiovascular stress responses. However, the available studies provide inconsistent results. The purpose of this study was to identify whether there is a clinically relevant difference in hemodynamic responses to orotracheal intubation by using ILMA and direct laryngoscope (DLS).Methods A total of 53 adult patients, ASA physical status I－II, scheduled for elective plastic surgery under general anesthesia requiring the orotracheal intubation, were randomly allocated to either DLS or ILMA groups.After a standard intravenous anesthesia induction, orotracheal intubation was performed. Noninvasive blood pressure and heart rate were recorded before (baseline values) and after anesthesia induction (post-induction values), at intubation and every minute for the first 5 minutes after intubation. The data were analyzed using Chi-square test, paired and unpaired Student's t test, and repeated-measures analysis of variance as appropriate.Results The mean intubation time in the ILMA group was longer than that in the DLS group (P<0.05). The blood pressure and heart rate increased significantly after intubation in the two groups compared to the post-induction values (P<0.05), but the maximum value of blood pressure during the observation did not exceed the baseline value, while the maximum value of heart rate was higher than the baseline (P<0.05). During the observation, there were no significant differences in blood pressure and heart rate among each time point and in the maximum values between the two groups.Conclusions Orotracheal intubations by using ILMA and DLS produce similar hemodynamic response. ILMA has no advantage in attenuating the hemodynamic responses to orotracheal intubation compared with DLS.Chin Med J 2006; 119 (11 ):899-904ntubating laryngeal mask airway (ILMA) is a new device specially designed for blind orotracheal intubation.1-2 It offers several advantages over direct laryngoscope (DLS). In order to bring the glottis into the line of sight, tracheal intubation by using DLS requires distortion of surrounding oropharyn- golaryngeal structures inevitably. However, as we all know, it is impossible to distort oropharyngolaryngeal structures adequately and to exposure the glottis clearly in some cases. Anatomically curved ILMA may overcome the limitation of DLS, because it facilitates guidance of tracheal tube towards the glottis, and does not need a line of sight from the mouth to glottis. Moreover, ILMA-guided orotracheal intubation may avoid or alleviate the mechanical stimuli to the oropharyngolaryngeal structures, which are inevitable by using a rigid DLS. Theoretically, ILMA-guided orotracheal intubation leads to less severe hemodynamic responses than that by using DLS. However, some studies provide conflicting data on this issue.3-7 For example, Baskett and colleagues3 found that the tracheal intubation using ILMA produced insignificantly less hemodynamic responses, than that by using DLS. But another study showed that ILMA provided more constant blood pressure than that by DLS. Kahl etDepartment of Anesthesiology, Plastic Surgery Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100041, China (Zhang GH, Xue FS, Sun HY, Li CW, Sun HT, Li P and Liu KP)Correspondence to: Prof. XUE Fu-shan, Department of Anesthesiology, Plastic Surgery Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100041, China (Tel: 86-10-88703936. Fax: 86-10-88964137. Email: fruitxue@)Ial8 demonstrated that tracheal intubation- associated reduction of cardiovascular and endocrine stress response was more pronounced by using ILMA than that by using DLS. It is likely that these conflicting results are resulting from different duration of laryngoscopy, the times of attempts and methods of operation during ILMA-guided orotracheal intubation, and anesthetics and subject selection. In this study, we observed the hemodynamic responses to orotracheal intubation by using DLS or ILMA in adult patients under standard general anesthesia to further explore whether there is clinically relevant difference in hemodynamic response between the two intubation methods.METHODSPatientsAfter obtaining institutional ethics committee approval and written informed consent, we studied 53 adult patients, ASA physical status I－II, scheduled for elective plastic surgery under general anesthesia requiring orotracheal intubation. Of these patients, 23 were men and 30 women. Their age, weight and height ranged from 18 to 57 years, 45 to 87 kg, and 145 to 178 cm, respectively. Those who were younger than 18 or older than 60 years, taking long-term medications that may affect heart rate (HR) and blood pressure (BP), or having difficult airway, were excluded from this study.Study designPatients involved in this study were divided, on a random number basis (stratified by sex), into either DLS or ILMA groups. The hypothesis of this study was that there would be a clinically meaningful difference in hemodynamic responses to intubation between the groups. The number of patients for each group was determined by using an appropriate power calculation. Assuming a 1 type error of 5%, an 80% chance to detect a difference, 7 mmHg as the standard deviation in change of systolic BP (SBP), and a 50% reduction in change of SBP as being clinically significant (15 mmHg) to detect a difference between the two intubation methods, 16 patients in each group are required at least. For more reliable statistical results, a larger sample size (25 patients in each group) was used in this study. Random assignment of 25 successfully intubated patients to each group was achieved as follows: 50 index cards were placed in a box；25 cards were labeled for each group. Before each patient entered the operating room, a card was selected randomly and the patient was assigned to the indicated group. If the intubation was accomplished, the patients were included in this study, and the card was destroyed. If the intubation failed, the patient was excluded from the trial and his/her card was returned to the box.Anesthesia and intubation procedureAll the patients were fasted overnight and kept normothermic. Midazolam 0.1 mg/kg (maximum 5 mg) and scopolamine 0.01 mg/kg (maximum 0.3 mg) were given intramuscularly one hour before anesthesia. After entering the operating room, the patients was intubated with an intravenous cannula, and their BP, HR, and pulse oxygen saturation (SpO2) were monitored invasively with a multifunction monitor continuously (Datex-Ohmeda F-CU8, Datex Instrumentarium, Finland). Baseline values of BP and HR were recorded after a stabilization period of 5 minutes. In the DLS group, PVC Murphy-type cuffed tracheal tube (Hudson Respiratory Care Inc., USA) was used. In the ILMA group, ILMA (Laryngeal Mask Co. Ltd., UK) and specially designed straight silicone tubes (Accusil Inc., USA) were used. Tracheal tubes with internal diameter of 7.5 mm and 7.0 mm were used for male and female patients, respectively.After preoxygenation of 5 minutes, anesthesia was induced with fentanyl (2 µg/kg), vecuronium (0.1 mg/kg), and propofol (2 mg/kg) injected intrave- nously. The orotracheal intubation was started 2 minutes after vecuronium injection. All the intubations were performed by a single experienced anesthetist. In the DLS group, the tracheal tube was inserted into the trachea under a Macintosh laryngoscope according to the conventional methods, and the optimal external laryngeal manipulation was used to improve the laryngoscopic view if necessary. In the ILMA group, ILMA with suitable size was inserted using the technique described previously1 that consists of one-handed rotational movement in the sagittal plane with the head supported by a pillow to achieve a neutral position. Then, the cuff was inflated with air to reach an intracuff pressure of 60 cmH2O, and the position of the ILMA was examinedwith bag ventilation. When the ventilation was confirmed, a specially designed straight silicone tube was inserted into the ILMA immediately, and the intubation was attempted by gently advancing the tube beyond the epiglottic elevator bar. If resistance was felt, a predetermined sequence of adjusting maneuvers was performed as that recommended previously.1,2 If no resistance was felt after the tube was advanced 7 cm beyond the epiglottic elevator bar, the tube cuff was inflated and the circuit was connected to confirm correct ventilation through the tube with bag ventilation and capnography. When successful tracheal intubation was confirmed, the ILMA was removed under the help of a stabilizing rod.After the successful intubation, the tracheal tube was connected to the anesthesia breathing system for intermittent positive-pressure ventilation. Anesthesia was maintained with isoflurane and 60% nitrous oxide in oxygen. During the observation, a fresh gas flow of 1.5 L/min was used, and the ventilator settings were adjusted to maintain an end-expired carbon dioxide level of 35－40 mmHg and the isoflurane vaporizer was adjusted to maintain the end-tidal isoflurane concentration at 1%. Inspired concentrations of oxygen, nitrous oxide and isoflurane, and end-tidal concentration of carbon dioxide were measured and displayed digitally with a multifunction monitor (Datex-Ohmeda F-CU8). Lactated Ringer's solution was infused at a constant rate of 15 ml·kg-1·h-1 throughout the observation.Measuring variablesBP and HR were recorded after anesthetic induction (post-induction values), at intubation and every minute for the first 5 minutes after intubation. The maximum values of BP and HR during the observation were also noted. The intubation time, namely the period from termination of manual ventilation using a facemask to restarting of ventilation through the tracheal tube, was recorded using a stopwatch. Because the intubation time can significantly affect the hemodynamic response to tracheal intubation,9 patients requiring more than 120 seconds to achieve successful intubation were excluded from this study.Statistical analysisAll the data were analyzed by using SPSS 10.1 and a POMS statistical software (Version 5.0, Shanghai Scientific and Technical Publishers, China). Demographic and clinical data from the two groups were compared using two tailed t test and Chi-square test as appropriate. Inter- and intra-group differences among the hemodynamic variables recorded over time were analyzed by using two-way analysis of variance for repeated measures, and paired and unpaired t tests with Bonferroni post-test analysis as appropriate. All quantitative data are expressed as mean±standard deviation (SD). A P value less than 0.05 was considered statistically significant.RESULTSQuality of orotracheal intubationTwenty-seven patients received ILMA-guided orotracheal intubation, which was completed at the first attempt in 24 cases, the second attempt in 3, and the third attempt in 1. In 3 patients, the intubation time was more than 120 seconds, because it was difficult to seek an optimal position of ILMA or insert the tracheal tube through ILMA. The other 25 patients received laryngoscopic orotracheal intubation, which was successfully performed at the first attempt in all of them with an intubation time less than 120 seconds.The 3 patients with intubation time longer than 120 seconds in the ILMA group were excluded, and then the general and hemodynamic data of the other 50 patients in the two groups were analyzed statistically. Except for intubation time, no significant difference was found between the two groups. (Tables 1 and 2)Table 1. Clinical data of patients in the two groups(n=25 in each group; mean±SD)DLS: direct laryngoscope; ILMA: intubating laryngeal mask airway.*P＜0.05, compared with the DLS group. Hemodynamic changesAfter anesthetic induction, the patients' BP decreased significantly compared to the baseline value in the two groups (P<0.05), but HR remained stable. Both ILMA-guided and laryngoscopic orotracheal intubations resulted in a significant increase in BP compared to the post-induction value Groups M/F Age (y) Weight(kg)Height(cm)Intubationtime (s)DLS 10/1533.6±11.463.1±14.7 165.5±7.728.5±9.7 ILMA 11/1429.5±6.857.6±10.7 163.4±7.991.8±8.6*Table 2. Hemodynamic changes associated with the orotracheal intubation in the two groups(n =25 each; mean ±SD)DLS: direct laryngoscope; ILMA: intubating laryngeal mask airway; SBP: systolic blood pressure; DBP: diastolic blood pressure; HR: heart rate.*P ＜0.05 compared with the baseline values ；#P ＜0.05 compared with the post-induction values.(P <0.05) which, nonetheless, did not exceed the baseline value. In the DLS group, HR at intubation and 1 minute after intubation increased significantly compared to the post-induction value (P <0.05), but did not exceed the baseline values. While in the ILMA group, HR at 1 minute after intubation was significantly higher than the post-induction and baseline values (P <0.05). The maximal BP during the observation in both groups were not significantly different from the baseline values, but the maximal HR were significantly higher than the baseline values (P <0.05). There were no significant differences in BP and HR among each time point and in their maximum values during the observation between the two groups. No patient developed severe bradycardia (HR ≤50 beats/min) or severe hypotension (SBP ≤60 mmHg), and SpO 2 in all the patients were maintained at 100% in this study.DISCUSSION Laryngoscopy and tracheal intubation can cause significant pressor and tachycardiac responses by enhancing sympathetic activity. Although these are only transient cardiovascular stress responses, they are life threatening dangers to the patients suffering from the cardiocerebral vascular diseases. It has been proved that such hemodynamic responses are associated with instrument procedures through the airway, anesthetics, cardiovascular agents, patients' underlying diseases, and even their race.10-14 Because mechanic stimuli to oropharyngolaryngealstructures caused by a direct laryngoscope are considered as major causes of the hemodynamic responses to laryngoscopy and tracheal intubation,15,16 many studies have focused on an intubation method that is able to attenuate or avoid the mechanic stimuli.ILMA is a new airway-securing device recently applied to clinical practice.1-2 Not only does it offer the same advantage in facilitating lung ventilation as that with standard LMA, but also it provides the superior function as an aid to the orotracheal intubation. ILMA can also be used for difficult intubation and airway management on emergencies to ventilate the patients timely and effectively.One of the prominent advantages of ILMA-guided orotracheal intubation is that it will not stimulate the base of the tongue, epiglottis, and the receptors in the pharyngeal muscles mechanically. Therefore, theoretically, ILMA-guided orotracheal intubation produces less adverse cardiovascular stress responses. However, our results showed thatorotracheal intubations by using ILMA and DLSunder general anesthesia lead to similar pressor andtachycardiac responses, which is consistent with the results of other studies on adults,5-7,10 suggesting that ILMA has no advantage in attenuating the hemodynamic responses to orotracheal intubation. Whereas, some studies showed different data. Baskett and colleagues 3 found that ILMA-guided orotracheal intubation produced statistically but not clinically significant less hemodynamic responses. In the study of Joo and Rose,4 mean arterial pressure was higher in the patients received laryngoscopicorotracheal intubation than that in those received ILMA-guided orotracheal intubation. Nevertheless, Baskett did not conduct a comparative study involving laryngoscopic intubation.3 Joo and Rose 4 did not apply the routine clinical practice becauseAfter intubation (min) Index Baseline Post- inductionAtintubation1 2 3 4 5Maximumvalues SBP (mmHg) DLS 115.6±10.8 90.8±14.5* 106.3±23.4#105.8±20.8*# 96.3±11.9* 92.4±10.9*89.2±8.8* 88.0±8.5* 113.0±23.6#ILMA 109.9±10.2 86.1±13.2* 103.3±13.2#100.0±13.6*# 92.6±13.1*89.9±12.0*87.1±10.4*86.3±11.1*106.7±13.3#DBP (mmHg)DLS 69.1±9.8 50.1±10.2* 67.1±17.7#59.7±10.87*#52.8±7.9* 50.0±7.8* 48.5±9.0* 48.0±9.1* 69.9±17.4#ILMA69.5±8.449.0±9.2*62.3±11.1*#57.2±11.25*#51.4±9.9* 47.8±8.5* 45.6±9.6* 46.1±8.3* 67.8±13.4#HR (bpm) DLS 79.5±9.4 78.3±10.4 85.2±12.0#84.1±10.0#83.9±10.9 82.7±10.4 81.2±10.5 79.0±11.8 92.4±8.6*#ILMA 84.8±11.9 84.1±12.8 89.3±15.0 92.3±12.5*#90.0±11.3 86.3±14.1 84.0±14.0 81.7±13.0 97.2±13.4*#orotracheal intubation was performed 5 minutes after the insertion of ILMA in their study.The results of our study may be caused by multiple factors. First, ILMA-guided orotracheal intubation, which includes three steps (insert and confirm the position of ILMA, insert and confirm the position of tracheal tube, and then remove the ILMA), is a time consuming procedure compared to the intubation using DLS. In our study, the mean intubation time in the ILMA group was approximately three times greater than that in the DLS group. The longer apnea and repeated airway manipulation may enhance the hemodynamic responses.9,17-19 Second, as compared with laryngoscopic intubation, ILMA- guided orotracheal intubation may impose a greater pressure on the oropharyngeal structures and cervical vertebrae, which even exceeds capillary perfusion pressure of the pharyngeal structures, resulting in backward shifting of the cervical vertebrae,20,21 thus producing more stimuli to the local structures. Third, in order to obtain an optimal position of ILMA to facilitate the insertion of tracheal tube, it is often required to move the ILMA back and forth, grasp and lift the jaw, adjust the patient's head-neck position, and increase the volume of ILMA cuff inflation or change the size of ILMA. These auxiliary maneuvers may cause additional stimuli to the oropharyngeal structures. Previous study found that grasping and lifting the jaw upwards can cause hemodynamic responses similar to those observedin conventional laryngoscopic intubation.22 Fourth, before inserting tracheal tube into the trachea via ILMA, epiglottic elevating bar of the ILMA is lifted to elevate the epiglottis and approach the glottis, that results in stimuli to the epiglottis and periepiglottic structures. Previous work suggested that mechanical stimulus to the supralaryngeal area rich in nociceptive receptors can cause strong hemodynamic responses.23 Fifth, ILMA-guided orotracheal intubation is actually a blind procedure, and tracheal tube is likely blocked off by the down folding epiglottis, anterior commissure, vocal cords and anterior tracheal wall. When the tracheal tube is blocked off, it is necessary to rotate the tracheal tube, move the ILMA up and down, and adjust patients' head-neck position, which may further stimulate the oropharyngolaryngeal structures. We believe that these maneuvers may bring longer time or even failure in tracheal intubation by using ILMA. Sixth, it has been shown that removal of the ILMA after successful intubation is a more severe stimulus than the insertion of the ILMA and tracheal tube, and can produce more significant hemodynamic responses because of stronger frictions.24 Finally, in order to avoid accidental extubation, anesthetists often use stabilizing rod to further advance the tracheal tube that may results in more frictions against the tracheal wall and even stimulating the carina when the tracheal tube is inserted too deeply. It was demonstrated that the tracheal stimulus is another main cause of hemodynamic responses to tracheal intubation.11,22,25Based on the statements above, orotracheal intubations using ILMA and DLS lead to similar hemodynamic responses. Considering the possible more attempts or even failure in tracheal intubation, ILMA is preferred to be used as a rescue means rather than a routine method for tracheal intubation in clinical anesthesia practice.In addition, our results also showed no significant difference in the maximum values of BP and HR between the two groups, further supporting the conclusion that orotracheal intubations using ILMA and DLS result in similar hemodynamic responses. Since the maximum value of BP was not significantly different from the baseline value, and the maximum increase of HR was less than 20% of the baseline value, general anesthesia could effectively attenuate the pressor and tachycardiac responses to orotracheal intubations by using the two methods.In conclusion, orotracheal intubations by using ILMA and DLS produce similar hemodynamic responses. ILMA has no advantage in attenuating the hemodynamic responses compared to DLS.REFERENCES1. Brain AI, Verghese C, Addy EV, Kaplia A. The intubatinglaryngeal mask, I: Development of a new device forintubation of the trachea. Br J Anaesth 1997; 79:699-703.2. Brain AI, Verghese C, Addy EV, Kaplia A, Brimacombe J.The intubating laryngeal mask, ii: A preliminary clinicalreport of a new means of intubating the trachea. Br JAnaesth 1997; 79: 704-709.3. Baskett PJ, Parr MJ, Nolan JP. The intubating laryngealmask. Results of a multicentre trial with experience of500 cases. Anaesthesia 1998; 53: 1174-1179.4. Joo HS, Rose DK. The intubating laryngeal mask airwaywith and without fiberoptic guidance. Anesth Analg 1999;88: 662-666.5. Kihara S, Yaguchi Y, Watanabe S, Brimacombe J,Taguchi N, Yamasaki Y. Haemodynamic responses tothe intubating laryngeal mask and timing of removal. EurJ Anaesth 2000; 17:744-750.6. Ihara S, Watanabe S, Taguchi N, Suga A, BrimacombeJR. Tracheal intubation with the Macintosh laryngoscope vs intubating laryngeal mask airway inadults with normal airways. Anaesth Intensive Care2000; 28:281-286.7. Choyce A, Avidan MS, Harvey A, Patel C, Timberlake C,Sarang K, et al. The cardiovascular response toinsertion of the intubating laryngeal mask airway.Anaesthesia 2002; 57:330-333.8. Kahl M, Eberhart LH, Behnke H, Sanger S, Schwarz U,Vogt S, et al. Stress response to tracheal intubation inpatients undergoing coronary artery surgery: directlaryngoscopy versus an intubating laryngeal maskairway. J Cardiothorac Vasc Anesth 2004; 18:275-280.9. Stoelting RK. Circulatory changes during directlaryngoscopy and tracheal intubation: influence ofduration of laryngoscopy with or without prior lidocaine.Anesthesiology 1977; 47: 381-383.10. Imai M, Matsumura C, Hanaoka Y, Kemmotsu O.Comparison of cardiovascular responses to airwaymanagement: fiberoptic intubation using a new adapter,laryngeal mask insertion, or conventional laryngoscopicintubation. J Clin Anesth 1995; 7:14-18.11. Takahashi SJ, Mizutani T, Miyabe M, Toyooka H.Hemodynamic responses to tracheal intubation withlaryngoscope versus lightwand intubating device (Trachlight) in adults with normal airway. Anesth Analg2002; 95: 480-484.12. Helfman SM, Gold MI, DeLisser EA, Herrington CA.Which drug prevents tachycardia and hypertensionassociated with tracheal intubation: lidocaine, fentanylor esmolol? Anesth Analg 1991; 72:482-486.13. Kirvela M, Scheinin M, Lindgren L. Haemodynamic andcatecholamine responses to induction of anaesthesiaand tracheal intubation in diabetic and non-diabeticuraemic patients. Br J Anaesth 1995; 74:60-65.14. Houghton IT, Low JM, Lau JT, OH TE. An ethniccomparison of the sympathetic response to trachealintubation. Anaesthesia 1993; 48: 965-968.15. Shribman AJ, Smith G, Achola KJ. Cardiovascular andcatecholamine responses to laryngoscopy with and without tracheal intubation. Br J Anaesth 1987;59:295-299.16. Bucx MJ, Scheck PA, Van Geel RT, Den Ouden AH,Niesing R. Measurement of forces during laryngoscopy.Anaesthesia 1992; 47: 348-351.17. Shribman AJ, Smith G, Achola KJ. Cardiovascular andcatecholamines responses to laryngoscopy with andwithout tracheal intubation. Br J Anaesth 1987;59:295-299.18. Shinji T, Taro M, Masayuki M, Hidenori T. Hemodynamicresponses to tracheal intubation with laryngoscope versus lightwand intubating device (Trachlight) in adultswith normal airway. Anesth Analg 2002; 95:480-484.19. Singh S, Smith JE. Cardiovascular changes after thethree stages of nasotracheal intubation. Br J Anaesth2003; 91: 667-671.20. Keller C, Brimacombe J. Pharyngeal mucosal pressures,airway sealing pressures, and fiberoptic position with theintubating versus the standard laryngeal mask airway.Anesthesiology 1999; 90:1001-1006.21. Keller C, Brimacombe J, Keller K. Pressures exertedagainst the cervical vertebrae by the standard andintubating laryngeal mask airway:a randomized, controlled, cross-over study in fresh cadavers. AnesthAnalg 1999; 89:1296-1300.22. Hirabayashi Y, Hiruta M, Kawakami T, Inoue S, FukudaH, Saitoh K, et al. Effects of lightwand (Trachlight)compared with direct laryngoscopy on circulatory responses to tracheal intubation. Br J Anaesth 1998;81:253-255.23. Hamaya Y, Dohi S. Differences in cardiovascularresponse to airway stimulation at different sites andblockade of the responses by lidocaine. Anesthesiology2000; 93:95-103.24. Shimoda O, Yoshitake A, Abe E, Koga T. Reflexresponses to insertion of the intubating laryngeal maskairway, intubation and removal of the ILMA. AnaesthIntensive Care 2002; 30:766-770.25. Adachi YU, Takamatsu I, Watanabe K, Uchihashi Y,Higuchi H, Satoh T. Evaluation of the cardiovascularresponses to fiberoptic orotracheal intubation with television monitoring: comparison with conventional direct laryngoscopy. J Clin Anesth 2000; 12:503-508.(Received June 20, 2005)Edited by LUO Dan。