|Ahead of print publication
A comparative evaluation of hemodynamic response and ease of intubation using Airtraq and McCoy laryngoscope
Alok Kumar Sahoo1, Kalpana Majhi2, Indraprava Mandal1
1 Department of Anaesthesiology, AIIMS, Bhubaneswar, Odisha, India
2 Department of Critical Care, Sunshine Hospital, Bhubaneswar, Odisha, India
Plot No – 437/3134, Flat No- 403, AIIMS Road, Patrapada, Bhubaneswar - 751 019, Odisha
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Background: Various airway gadgets have been devised to overcome difficult airway scenario in anesthesia practice. It includes simple rigid laryngoscope to complex fiber-optic intubating devices; however, there is weak evidence to support the superiority of one device over the other. Aims and Objective: The ease of intubation, time and the hemodynamic variability between two groups during intubation are considered as the primary outcome measures. Materials and Methods: In this prospective study, 60 patients of either sex undergoing elective surgery who required tracheal intubation were included. All the patients of age between 20 and 50 years with the American Society of Anesthesiologists Classes I and II were divided into the following two groups: Group AT (n = 30): the intubation was performed using AT laryngoscope and Group-MC (n = 30); the intubation was performed using MC laryngoscope. The following intubating parameters were recorded: ease of intubation (Grade-I–IV), mean time of laryngoscopy and intubation, Cormack–Lehane grade, and the percentage of glottis opening (POGO) score. The vital parameters such as heart rate (HR) and mean arterial blood pressure (MABP) were recorded only after premedication, and it was taken as the baseline value. These parameters were again recorded at 1 min, 3 min, 5 min, and 10 min after laryngoscopy and intubation. The incidences of sore throat were recorded just before discharge from the recovery room till 24 h of surgery. All these parameters were compared between these two groups using the Student's t-test and Chi-square test. Results: There was no significant difference in age, sex, weight, and Mallampati grading between the two groups. More than 30% of patients in Group AT were intubated without an external aid than the Group MC (P < 0.05). In Group AT, the mean time of intubation was 13.5 ± 5.72 s when compared to 15.63 ± 7.28 s in Group MC (P > 0.05). The Cormack–Lehane grade and POGO score were better in the AT group than that of the MC group. The HR at 1 min in Group AT was 101.83 ± 14.50 and in Group MC, it was 108.93 ± 12.86 (P < 0.05) and after 3 min, it was 98.66 ± 12.60 and 111.53 ± 11.67 (P < 0.05), respectively. The MABP was 107.17 ± 9.03 in Group AT compared to 116 ± 10.12 in Group MC (P < 0.05) at 1 min postintubation. The incidences of sore throat were similar in both the groups. Conclusion: The AT laryngoscope is better than MC in terms of the ease of intubation, better glottis view, and hemodynamic stability. However, the incidences of sore throat in both groups were comparable.
Keywords: Airtraq laryngoscope, Cormack–Lehane grade, ease of intubation, intubation, McCoy laryngoscope, percentage of glottis opening score, sore throat
|How to cite this URL:|
Sahoo AK, Majhi K, Mandal I. A comparative evaluation of hemodynamic response and ease of intubation using Airtraq and McCoy laryngoscope. Anesth Essays Res [Epub ahead of print] [cited 2019 Aug 20]. Available from: http://www.aeronline.org/preprintarticle.asp?id=260573
| Introduction|| |
Laryngoscopy and intubation though essential for general anesthesia were known to cause an exaggerated hemodynamic response., This response manifests as tachycardia, hypertension, and dysrhythmias. It may have deleterious respiratory, neurological, and cardiovascular effects. The above reflexes are of little concern in normal healthy controls but have deleterious effects in patients with comorbid conditions like coronary artery disease.,
The incidences of difficult intubation and failed intubation due to anatomical distortion of larynx are 1%–3% and 0.5%–2%, respectively. Failed and difficult endotracheal intubation thus remains an important cause of morbidity and mortality in general anesthesia; the absence of factors that can reliably predict the existence of difficult airway makes the situation hazardous.
Various airway gadgets have been introduced to ease laryngoscopy and intubation besides the original Macintosh's laryngoscope. The McCoy (MC) laryngoscope blade was introduced in 1993 and it was a modification of Macintosh laryngoscope blade to facilitate tracheal tube placement in case of nonvisualization of the larynx. The hinged blade controlled by a lever on the handle of laryngoscope allows elevation of the epiglottis and thus requiring lesser forces for application.
Indirect laryngoscope such as Airtraq™ Optical Laryngoscope (King Systems Corporation, Noblesville, IN 46060) is a highly appreciated intubation aid, introduced into clinical practice in 2005. It is designed to facilitate routine endotracheal intubation as well as in patients with difficult airways. The blade of the Airtraq (AT) consists of two side by side channels. One channel acts as a conduit through which a tracheal tube, whereas the other channel transfers the image from the illuminated tip to a proximal view finder. Because of the exaggerated blade curvature, an internal arrangement of the optical lenses and a mechanism to prevent fogging of the distal lens, a high-quality view of the glottis is provided without the need to align the oral, pharyngeal, and laryngeal axis. The advantage of this new device is that it does not obstruct the endoscopic view of the vocal cord during the act of laryngoscopy.,
Therefore, we planned this study to compare the laryngoscopic procedure and intubation during general anesthesia between AT laryngoscope and MC laryngoscope.
Aims and objective
The ease of intubation and the hemodynamic variability during intubation are considered as the primary outcome measures. The incidence of postoperative sore throat was evaluated as the secondary outcome.
| Materials and Methods|| |
This study was undertaken, at a tertiary care hospital, to look for the hemodynamic instability and ease of intubation between AT laryngoscope and MC laryngoscope. All patients of the American Society of Anesthesiologists (ASA) Classes I and II, between the age group of 20 and 50 years, Mallampati grading (I–IV), of either sex were considered for inclusion in this study [Figure 1]. The patients with pregnancy, ASA Class III/IV, ischemic heart disease, cervical spine injury, and restricted mouth opening were excluded from the study. The study was started after obtaining the Institutional Ethics Committee approval.
|Figure 1: Consort flow-diagram of patients' enrolment, randomization, allocation, and analysis|
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During pre-anesthetic check-up, the patients were investigated and examined as required, specifically for difficult airway such as Mallampati grading, thyromental distance with fully extended neck, temperomandibular joint stability, and cardiorespiratory reserve. Patients with any abnormalities were excluded from the study.
The patients were randomly divided into two groups based on the use of AT or MC laryngoscopes by sealed envelope techniques. Group AT patients were intubated using AT laryngoscope, and Group MC patients were intubated using MC laryngoscope.
All the patients received premedication with intravenous (i.v,) injection of injection glycopyrrolate 0.2 mg, midazolam 0.05 mg/kg i.v, and injection fentanyl 2.0 μg/kg i.v 15 min before the surgery. The technique of general anesthesia was the same for all patients. Immediately, after premedication, the heart rate (HR) and the mean arterial blood pressure (MABP) were recorded. These values were considered as the baseline value. Induction was done with injection. propofol 2 mg/kg i.v followed by succinylcholine 1. 5 mg/kg. Thereafter, the HR and the MABP were recorded at 1, 3, 5, and 10 min after laryngoscopy and intubation.
The laryngoscopy and intubation were tried with either AT or MC instrument by expert anesthesiologists. The laryngoscopy time was calculated from the introduction to the removal of the laryngoscope blade (AT and MC) from the mouth. The time was measured in seconds by an assistant using a stopwatch. The surgery was allowed to commence only after the collection of the last hemodynamic data at 10 min postintubation.
The percentage of glottis opening (POGO) scoring (100 = full glottic view, 0 = no portion of glottis visualized) was done by the attending laryngoscopist. The ease of intubation was graded as follows: Grade I: No extrinsic manipulation of the larynx is required, Grade II: External manipulation of the larynx is necessary to intubate, Grade III: Intubation possible only when aided by a stylet, and Grade IV: Failed intubation. The total time required for intubation was noted in both the groups. The difficult airway cart was kept ready for failed intubation.
In patients with failed intubation were excluded from the study. Nitrous oxide (66%) in oxygen (33%), isoflurane 1 minimum alveolar concentration (MAC), and intermittent doses of vecuronium bromide were used for the maintenance of anesthesia. At the end of the surgery, residual neuromuscular blockade was reversed by administering injection neostigmine (50 μg/kg) i.v. and injection glycopyrrolate (10 μg/kg) i.v. after respiratory effort was initiated by the patient and extubated accordingly.
Postoperatively, the sore throat was assessed using an independent observer blinded to the nature of the laryngoscopy. Any new pain or unpleasant sensation in the throat just before discharge from the recovery room and at 24 hours was considered as sore throat.
We based our sample size estimation on the previous study where AT reduced the duration of intubation. We considered that a clinically important improvement in the duration of intubation by reduction of time (expressed in mean ± standard deviation) by 10 sec will be clinically significant. Based on these figures, using an alpha error of 0.05 and power of the study at 80% for an experimental design having two equalsized groups we estimated that 29 patients would be required per group. Hence, 30 patients per group were selected.
Statistical analysis was performed using Microsoft Excel 2007 and GraphPad software (Graph Pad, San Diego, CA). The result was presented in number, percentage, mean, and standard deviation. The Student's t-test and Chi-square test without Yate's correction were used as per applicability to analyze the observations. P < 0.05 was considered as statistically significant.
| Results|| |
The demographic data and body mass index of both the groups were had no statistical significant difference [Table 1]. The Mallampati Grade of both groups was comparable (P > 0.05). The Cormack –Lehane grade was better in the AT Group than that of the Group MC (P < 0.05). In Group AT, 86.66% of patients had POGO score of 100, while in Group MC, 66.66% patients had POGO score of 100 (P < 0.05) [Table 2]. The mean time for laryngeal intubation was less in Group AT compared to Group MC. However, the difference was not statistically significant. In Group AT, 93% of patients were intubated without any external aid, while in Group MC, 56% of patients were intubated without any external aid (P < 0.05) [Table 2].
|Table 2: Comparison of observed airway parameters between the two groups|
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The baseline HR in Group AT was 83.8 ± 18.945 and it was 84.933 ± 14.75 in Group MC (P < 0.05). The HR after 1 min in Group AT was 101.83 ± 14.50 and in Group MC, it was 108.93 ± 12.86 (P < 0.05) and after 3 min, it was 98.66 ± 12.60 and 111.53 ± 11.67 (P < 0.05), respectively [Figure 2]. After 10 min, the HR became close to the baseline in both the groups.
|Figure 2: Changes in heart rate at various time intervals in both groups|
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The baseline MABP in Group AT and MC were 94.16 ± 6.35 94.2 ± 7.39, respectively (P > 0.05). After 1 min, in Group AT, the MABP was 107.17 ± 9.03 compared to 116 ± 10.12 in Group MC (P < 0.05). The fluctuations in MABP were more pronounced in the MC group compared to the AT group in the first and third minute readings (P < 0.05) [Figure 3].
|Figure 3: Changes in mean arterial blood pressure at the various time interval|
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The sore throat was observed in 9 of the patients in Group AT and 12 patients in Group MC after 24 h.
| Discussion|| |
Many studies have been conducted to know the laryngoscopic view, ease of intubation, hemodynamic changes during laryngoscopy and intubation, and associated complications with the evolution of the various type of laryngoscope. The present study is a similar attempt to compare two different types of laryngoscopes for intubation with regard to the various parameters discussed above. The present study demonstrated that the Airtraq™ laryngoscope performed better in relation to hemodynamic variability and ease of intubation as compared to MC laryngoscope.
In this study, the mean of POGO score in Group AT was 91% and in Group MC, it was 73% (P < 0.05). Better the POGO score, higher is the glottic view and lesser will be the failed intubation. The arrangements of the high definition optical fiber in AT laryngoscope gives a high quality, less fogging and wide-angle view of the glottis, the surrounding structures, and the tip of the endotracheal tube. The oxygen saturation was well maintained in both the groups during laryngoscopy. Moreover, ease of tracheal intubation was graded as Grade I, II, and III. In Group AT, 93.33% of patients were intubated without any external aid, while in Group MC, 66.67% of patients were intubated without any external aid. This finding was supported by a study entitled by Nasim et al. and Maharaj et al., The study by Kaki et al. also showed a better glottic view by AT in manikin by novice medical student. Abdelgalel and Mowa showed that the number of intubation attempts was significantly less in glidescope and AT groups than Macintosh group. The AT laryngoscope clearly provides superior intubating conditions both in normal and difficult airway situation with minimum external optimization maneuver which may be advantageous during intubation in the difficult airway.
The mean time for laryngeal intubation was less in Group AT (13.5 s) as compared to that of Group MC (15.63 s, P > 0.05) but is not statistically significant. This may be due to more familiar use of MC blade by our anesthesiologist and more number of patients may require achieving significant difference. The result is also supported by the results of other studies by Maharaj et al., Ndoko et al. in 2008, and by Hirabayashi and Seo in 2009.
The HRs and mean arterial pressure in patients from both the groups were increased in response to laryngoscopy, but in MC group, this was significantly higher. The patients in the AT group were closer to the baseline value after 5 min as compared to the MC group of patients (P = 0.054) which is a statistically significant difference. However, there was no obvious difference by the end of the 10th min (P > 0.05). These findings were comparable with other study., The optics and exaggerated curvature of blades of AT laryngoscope helps in alignment of oro-pharyngo-laryngeal axis alignment, thus reducing the lifting force and reduces the time of intubation. This leads to lessening of the hemodynamic response to laryngoscopy and intubation. The lower hemodynamic stimulations have potential benefit in patients with hypertension and ischemic heart disease.
The drawback in this study was smaller sample size, performer, and observer bias. The observer was also the performing anesthesiologists and thus cannot be blinded to type of laryngoscope and the Cormack–Lehan score, POGO score, and ease of intubations were observer dependent. We also restricted the age group >50 and difficult airway, and hence, the result may not extrapolated to the geriatric age group and difficult airway patients.
| Conclusion|| |
In this study, the AT laryngoscope seems superior to MC laryngoscope, irrespective of Mallampati grading for hemodynamic response and the Cormack and Lehane view is better in AT than MC laryngoscope. It also suggested that glottic view is better with AT and the ease of intubation is superior with AT than MC laryngoscope blade. Apart from this, time taken to intubate in AT group though less is not statistically significant. Moreover, for hemodynamic stability, AT seems to be superior over MC laryngoscope blade for laryngoscopy and intubation.
The author would like to thank Dr. K. Rout, Associate Professor, Department of Anaesthesiology.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2]