Anesth Analg 2003;96:890-895
© 2003 International Anesthesia Research Society
GENERAL ARTICLES
Hemodynamic Responses Among Three Tracheal Intubation Devices in Normotensive and Hypertensive Patients
S. Kihara, MD,
J. Brimacombe, FRCA MD,
Y. Yaguchi, MD,
S. Watanabe, MD PhD,
N. Taguchi, MD, and
T. Komatsuzaki, MD
Department of Anaesthesia, Pain Clinic, and Clinical Toxicology, Mito Saiseikai General Hospital, Ibaraki, Japan
Address correspondence and reprint requests to J. Brimacombe, MD, University of Queensland and James Cook University, Department of Anaesthesia and Intensive Care, Cairns Base Hospital, The Esplanade, Cairns 4870, Australia. Address e-mail to jbrimacombe{at}austarnet.com.au
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Abstract
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We compare hemodynamic responses in normotensive and hypertensive anesthetized paralyzed patients among three intubation devices: the Macintosh laryngoscope (LS), the TrachlightTM lightwand (LW), and the intubating laryngeal mask airway FastrachTM (ILM). Seventy-five normotensive and 75 hypertensive patients were randomly assigned to each intubation device (n = 25). Noninvasive systolic blood pressure (SBP) and diastolic blood pressure (DBP) and heart rate (HR) were recorded immediately preinduction, immediately preintubation, and every minute for the first 5 min after the successful intubation. The number of intubation attempts, the time to successful intubation, and any airway injuries were recorded. Pharyngolaryngeal morbidity was assessed 18–24 h after surgery by a blinded investigator. In all groups, there was a reduction in SBP and DBP but no change in HR immediately preintubation compared with baseline values. In all groups, HR increased, but there were no increases in SBP and DBP other than in DBP in the LS/hypertensive group after intubation compared with baseline values. In normotensive patients, there were no differences in any hemodynamic variables among the three devices. In hypertensive patients, SBP and DBP in the LS group were significantly higher than the ILM and LW groups for 2 min after intubation, but there were no differences in HR among the devices. The number of intubation attempts was similar among groups, but intubation time was longer for the ILM group. The incidence of airway injury was more frequent for the ILM than the LS and LW groups (16% versus 0% versus 0%). There were no differences in pharyngolaryngeal morbidity among groups. We conclude that both the ILM and the LW attenuated the hemodynamic stress response to tracheal intubation compared with the LS in hypertensive, but not in normotensive, anesthetized paralyzed patients.
IMPLICATIONS: Both the intubating laryngeal mask airway FastrachTM and the TrachlightTM lightwand attenuate the hemodynamic stress response to tracheal intubation compared with the Macintosh laryngoscope in hypertensive, but not in normotensive, anesthetized paralyzed patients.
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Introduction
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The hemodynamic stress response to tracheal intubation can precipitate adverse cardiovascular events in patients with (1) and without (2) cardiovascular disease. Laryngoscopic stimulation of oropharyngolaryngeal structures may be an important factor in the hemodynamic stress response associated with tracheal intubation (3,4). In principle, tracheal intubation techniques that avoid or minimize oropharyngolaryngeal stimulation might attenuate the hemodynamic stress response or reduce the incidence of airway morbidity. However, published studies have provided little or conflicting evidence of an attenuated response for a variety of nonlaryngoscopic intubation devices including fiberoptic orotracheal intubation (5), the mask adapter (6), the Augustine guideTM (7), the TrachlightTM lightwand (Laerdal Medical Corporation, Wappingers Falls, NY) (8–10), and the intubating laryngeal mask airway FastrachTM (Laryngeal Mask Company, Henley-on-Thames, United Kingdom) (11,12). In addition, hemodynamic responses after laryngoscope-guided tracheal intubation are more pronounced in hypertensive patients (13,14), and there is only one study comparing hemodynamic responses between different intubating devices in hypertensive patients (10). In the following randomized prospective study, we compare hemodynamic stress responses in normotensive and hypertensive patients among three intubation devices: the Macintosh laryngoscope (LS), the TrachlightTM lightwand (LW), and the intubating laryngeal mask airway FastrachTM (ILM).
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Methods
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With ethics committee approval and written informed consent, we studied 75 normotensive (ASA physical status I) and 75 controlled hypertensive (ASA physical status II) patients scheduled for elective surgery under general anesthesia requiring tracheal intubation. Patients were eligible to be in the normotensive group if they had no history of hypertension and their admission blood pressure on three occasions was <160 mm Hg systolic and <95 mm Hg diastolic. Patients were eligible to be in the hypertensive group if they had a history of hypertension for which they were being treated and the admission blood pressure on three occasions was <180 mm Hg systolic and <105 mm Hg diastolic. General exclusion criteria were age <18 yr old, a history of pulmonary, cardiac, central nervous system, or cervical spine disease, a history of difficult intubation or an intercisal distance <2 cm, gastroesophageal reflux, or head and neck surgery. All hypertensive patients received their antihypertensive medication approximately 3 h before the induction. Normotensive and hypertensive patients were randomly assigned (by opening a sealed envelope) to three equal-sized groups (n = 25) for tracheal intubation: the LS group, the LW group, and the ILM group.
Mallampati score, thyromental, and sternomental distances were measured before surgery. The type of antihypertensive medication was noted. Premedication was with diazepam 5 mg per os and roxatidine 75 mg per os approximately 1.5 h before surgery. An electrocardiograph, pulse oximeter, gas analyzer, noninvasive blood pressure monitor (BP608, Nippon Colin Corporation, Aichi, Japan), and peripheral nerve stimulator were applied preinduction. Patients were in the supine position with the head on a standard firm pillow 7 cm in height. Oxygen was administered via a face mask for 5 min. Lidocaine 0.5 mg/kg was given IV to reduce propofol injection pain. Anesthesia was induced 30 s later with propofol 2.5 mg/kg IV and maintained with sevoflurane 2% in oxygen and nitrous oxide 66%. Muscle relaxation was with vecuronium 0.1 mg/kg IV. Patients were ventilated via a face mask until the train-of-four count was zero. All tracheal intubations were by a single anesthesiologist with considerable experience with all three techniques of intubation (approximate number of uses, LS >1000; ILM >500; and LW >200). A well-lubricated 7.5-mm internal diameter silicone straight tracheal tube (ILM endotracheal tube, Euromedical Industries, Kedah, Malaysia) was used in all patients. In the LS group, tracheal intubation was with a size 3 Macintosh LS, and the tracheal tube was stiffened with a wire stylet. If the vocal cords were not seen, external laryngeal pressure was applied. The Cormack and Lehane (15) grade without laryngeal pressure was recorded. Care was taken to avoid excessive force with the LS. In the ILM group, an ILM was inserted using a single-handed rotational technique. A size 3 ILM was used for patients <160 cm, a size 4 ILM for those 160–170 cm, and a size 5 ILM for those >170 cm in height. The cuff was inflated with air (size 3, 20 mL; size 4, 30 mL; and size 5, 40 mL), and an anesthesia circuit was connected. The position of the ILM was adjusted until optimal ventilation was obtained. This position was maintained by holding the handle firmly. The tracheal tube was inserted through the ILM and advanced to 9 cm beyond the epiglottic elevating bar if no resistance was felt. If resistance was felt through the tracheal tube, the ILM was readjusted in the patient’s mouth before the second attempt of tracheal tube insertion. If tracheal intubation was unsuccessful at the second attempt, the following adjusting maneuvers were performed before a further attempt depending on the depth of resistance: 1.5–2.0 cm, withdrawal of the ILM by 5 cm followed by reinsertion; 0–1.5 or >4 cm, smaller size ILM was used; and 2–4 cm, larger size ILM was used (16). The ILM was removed from the pharynx after cardiovascular data were collected. In the LW group, a LW was introduced into the endotracheal tube, and the proximal end of the tube was bent to a 90-degree angle. Room illumination was reduced during the intubation, and signs of the light were observed at the patients’ anterior neck. The detection of a distinct central point of light without a halo at the cricothyroid membrane was taken as evidence that the tip of the tracheal tube was correctly placed around the laryngeal inlet. The tracheal tube was then advanced until the glow disappeared behind the sternum as the stylet was withdrawn. In all groups, failed intubation was defined as the inability to intubate after 3 min. Successful intubation was determined by capnography. In the LS and LW groups, face mask ventilation was permitted between attempts, if required. In the ILM group, ventilation using the ILM was permitted between attempts, if required.
The following data were collected by an unblinded observer: (a) grade of face mask ventilation (easy, Guedel airway not required; moderate, Guedel airway required; difficult, Guedel airway plus jaw thrust required; and failed, failure to ventilate and alternative technique required); (b) number of intubation attempts (a failed attempt was defined as removal of the tracheal tube from the oral cavity or the ILM); (c) esophageal intubation (lack of capnograph trace after tracheal tube insertion); (d) intubation time (from insertion of the intubating device into the mouth to capnographic confirmation); (e) mucosal trauma (blood detected on the intubation device after use); (f) lip or dental injury; and (g) episodes of hypoxia during intubation (SpO2 < 95%). Noninvasive blood pressure and heart rate were recorded immediately preinduction, immediately preintubation, and every min for the first 5 min after successful intubation. End-tidal sevoflurane and CO2 concentrations were recorded immediately before intubation.
Pharyngolaryngeal morbidity was assessed 18–24 h after surgery by an investigator blinded to the method of intubation. Sore throat and hoarseness were graded on an established 4-point scale (9,17). Sore throat was graded as: none, no sore throat; mild, less severe than with a cold; moderate, similar to that noted with a cold; and severe, more severe than with a cold. Hoarseness was graded as: none, no hoarseness; mild, noted by a patient; moderate, obvious to observer; and severe, aphonia.
Sample size was selected to detect a 20 mm Hg or 20 bpm difference in blood pressure and heart rate, respectively, for a type I error of 0.05 and a power of 0.8 and was based on data from a pilot study of 30 patients. Descriptive data were tested using a factorial analysis of variance. Heart rate and blood pressure values were tested using analysis of variance repeated measures. Pair-wise comparison of the mean values was assessed by Bonferroni-Dunn test. The Kruskal-Wallis test was used for the scored data. The Pearson correlation and the Spearman rank correlation were used to determine the relationship between the degree of change of the hemodynamic variables (from the baseline values to those of 1 min after intubation) and the intubation time and number of intubation attempts, respectively. Unless otherwise noted, data are presented as mean ± SD. Significance was taken as P < 0.05.
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Results
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There were no differences in demographic and airway assessment data among groups (Table 1). Face mask ventilation was graded as easy in all patients. End-tidal sevoflurane and CO2 concentrations immediately preintubation were similar among groups (Table 1). There were no failed intubations. The number of intubation attempts was similar among groups, but intubation time was significantly longer for the ILM group than the LS and LW groups (Table 1). Hemodynamic data are presented in Table 2. In all groups, there was a reduction in systolic and diastolic blood pressure, but no change in heart rate immediately preintubation compared with baseline values. In all groups, heart rate increased, but there were no increases in blood pressure other than in diastolic blood pressure in the LS/hypertensive group after intubation compared with baseline values. In normotensive patients, there were no differences in any hemodynamic variables among the three devices. In hypertensive patients, systolic blood pressure and diastolic blood pressure in the LS group were significantly higher than the ILM and LW groups for 2 min after intubation, but there were no differences in heart rate among the devices. There was no correlation between hemodynamic changes and intubation time or number of intubation attempts for any group. There was no correlation between hemodynamic changes and the type of antihypertensive medication. The incidence of airway injury was more frequent for the ILM group than the LS group (8 of 50 versus 0 of 50; P = 0.003) and LW group (8 of 50 versus 0 of 50; P = 0.003), but otherwise, there were no differences in the incidences of intraoperative and postoperative airway complications among groups (Table 3).
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Discussion
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We found that both the ILM and the LW attenuate the hemodynamic stress response to tracheal intubation compared with the LS in hypertensive patients but not in normotensive patients. This suggests that the ILM and LW cause less oropharyngolaryngeal stimulation than the LS but that this is only clinically detectable in hypertensive patients. The reduction in stimulation is related to a lack of distortion of sensitive extraglottic structures by the ILM and LW. Hypertensive patients have an exaggerated hemodynamic stress response (13,14) compared with normotensive patients. This is probably related to increased catecholamine levels (18) and increased sensitivity of peripheral vessels to catecholamines (19).
There are conflicting data about the influence of the LW and ILM on hemodynamic stress response compared with the LS. Hirabayashi et al. (8) found that the LW did not attenuate hemodynamic responses compared with the LS in normotensive patients. Nishikawa et al. (10) found that LW did attenuate responses in normotensive patients but not in hypertensive patients. Joo and Rose (11) found that the ILM attenuated hemodynamic stress responses compared with the LS in normotensive patients; however, Kihara et al. (12) found no attenuation of hemodynamic responses. It is likely that these contrasting results are related to factors such as the duration and force during laryngoscopy and the number of attempts taken. Nishikawa et al. (10) found that the hemodynamic stress response with the LW correlated with the number of attempts. Shribman et al. (3) found that plasma catecholamine levels and hemodynamic stress responses to 10-second laryngoscopy were only similar to laryngoscopy followed by tracheal intubation; however, Bucx et al. (4) reported that hemodynamic stress responses to three-second laryngoscopy were only significantly less than those by laryngoscopy followed by tracheal intubation. Together, these studies suggest that prolonged laryngoscopy causes an increased hemodynamic stress response. Unfortunately, we did not record the duration of laryngoscopy, but it was probably closer to 10 seconds than 3 seconds.
In our study, the number of attempts was similar among devices, but the time taken was longer with the ILM. This is probably because intubation with the ILM is a two-stage process of ILM placement and then intubation. The clinical importance of these hemodynamic changes is unknown. There are only two reports where the hemodynamic response to tracheal intubation precipitated adverse cardiovascular events (1,2). Fox et al. (1) reported two cases: a 28-year-old woman with chronic hypertension who developed pulmonary edema after the systolic blood pressure increased from 240 to 300 mm Hg and a 37-year-old chronic hypertensive man who ruptured a cerebral aneurysm after the systolic blood pressure increased from 140 to 240 mm Hg. Forbes and Dally (2) reported acute ischemic changes in a healthy normotensive man when his blood pressure increased to 190/130 mm Hg. In our study, 3 patients (two in the LW group and one in the LS group) had systolic blood pressures more than 190 mm Hg, and no adverse events were noted.
We found no differences in pharyngolaryngeal complaints among groups. There are conflicting data about the influence of the LW on pharyngolaryngeal complaints compared with the LS. Friedman et al. (9) found that there was a reduced incidence of sore throat, hoarseness, and dysphagia with the LW, but Nishikawa et al. (10) found no difference. The data for the ILM are less conflicting with Kihara et al. (12) and Joo and Rose (11) reporting no difference between the ILM and LS. We found that airway injury was more common with the ILM than the LS and LW. This may reflect a genuine increase in injury, perhaps because of high mucosal pressures (20) or because of easier detection of bleeding with the ILM, because of the cuff collecting supra-cuff material.
Our study has four limitations. First, all insertions were conducted by a single anesthesiologist with variable experience with airway devices and could have biased the results. However, the success rate for all intubation techniques was similar, suggesting that performance was comparable. Nonetheless, our findings may not apply to users with less skill with a particular airway device. Second, collection of hemodynamic data was not blinded to the device used. However, the hemodynamic data were stored in the memory of the monitor, printed out, and verified by two individuals, reducing bias and error. Third, our study population had an average age of approximately 60 years old and did not have difficult airways. Our results may not apply to different age groups and to patients with difficult airways. Fourth, our results are specific to the anesthetic administered and might not apply for other anesthesia regimes such as the use of large-dose narcotics.
We conclude that both the ILM and the LW attenuate the hemodynamic stress response to tracheal intubation compared with the LS in hypertensive patients but not in normotensive patients. The ILM and LW may be preferable to LS in hypertensive patients where attenuation of hemodynamic stress responses is desired.
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References
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Accepted for publication October 21, 2002.
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Abstract
Introduction
