Airway

ORIGINAL ARTICLE
Year
: 2020  |  Volume : 3  |  Issue : 3  |  Page : 127--134

Midline versus paraglossal laryngoscopic approach using the Miller blade in small children: A randomised, controlled, cross-over study


Swarupa Roychoudhury1, Ratul Kundu2, Rituparna Murmu1, Tuhin Mistry3, Dipten Paul4, Amalendu Bikash Chatterjee5,  
1 Department of Anaesthesiology, ESI-PGIMSR, ESIC Medical College and Hospital, Joka, Kolkata, West Bengal, India
2 Department of Anaesthesiology, Ruby General Hospital, Kolkata, West Bengal, India
3 Department of Anaesthesiology, All India Institute of Medical Sciences, Raipur, Chhattisgarh, India
4 Department of Otorhinolaryngology, Diamond Harbour Government Medical College and South 24 pgs District Hospital, Diamond Harbour, India
5 Department of Anaesthesiology, Bankura Sammilani Medical College and Hospital, Bankura, West Bengal, India

Correspondence Address:
Dr. Tuhin Mistry
Flat No. 304, Tower 11, Surya Vihar, Junwani, Bhilai, Chhattisgarh
India

Abstract

Background: Airway management in children is different from that of adults and needs special consideration. Laryngoscopy in children with the Miller straight blade can be performed via midline (MID) or paraglossal (PGL) approach. This study aimed to find out whether there was any advantage of one approach over the other in small children. Patients and Methods: After obtaining parental consent and approval from the Institutional Ethical Committee, this randomised, controlled, cross-over study was conducted in 110 children aged 2–24 months belonging to the American Society of Anesthesiologists Physical Status I or II. Children scheduled for elective surgeries under general anaesthesia were allocated randomly into one of the following two groups: A (PGL/MID) or B (MID/PGL) with 55 patients in each group. Following induction of anaesthesia and neuromuscular blockade, laryngoscopy was performed in a cross-over manner with either the PGL or MID approach first. The tip of the blade was placed at the vallecula. Intubation was performed following the second laryngoscopy. Glottic views with and without optimal external laryngeal manipulation (OELM) and ease of intubation were observed. Data were analysed, and P < 0.05 was considered statistically significant. Results: Both the approaches provided the same view in 81/110 children. In the remainder, a better view was obtained with the MID and PGL approaches in 14/110 and 15/110 children respectively. Laryngoscopy was easy in 93/110 children with both the approaches. OELM was required to improve the laryngoscopic view in 37/110 and 40/110 children with the MID and PGL approaches respectively. Conclusion: Using the Miller blade, both the MID and PGL approaches provided comparable laryngoscopic views and intubating conditions for young children in the age group between 2 and 24 months. When a restricted view is obtained, a change of approach may provide a better view.



How to cite this article:
Roychoudhury S, Kundu R, Murmu R, Mistry T, Paul D, Chatterjee AB. Midline versus paraglossal laryngoscopic approach using the Miller blade in small children: A randomised, controlled, cross-over study.Airway 2020;3:127-134


How to cite this URL:
Roychoudhury S, Kundu R, Murmu R, Mistry T, Paul D, Chatterjee AB. Midline versus paraglossal laryngoscopic approach using the Miller blade in small children: A randomised, controlled, cross-over study. Airway [serial online] 2020 [cited 2021 Jun 20 ];3:127-134
Available from: https://www.arwy.org/text.asp?2020/3/3/127/304842


Full Text



 Introduction



Laryngoscopy and orotracheal intubation are two fundamental airway management skills that every anaesthesiologist must learn in the early phase of his/her career. The success and ease of the procedure depend on the design and technique of using the laryngoscope blade, patient's airway anatomy and the skill of the laryngoscopist. The paediatric airway is different from that of an adult, necessitating technical modification during laryngoscopy to achieve successful intubation.[1] The differences in airway anatomy are more pronounced until 2 years of age, and become less marked as the child grows older. In 1941, Robert Miller designed a straight blade with a curved distal tip, which is now popularly known as the Miller blade.[2] The straight Miller blade is generally used to obtain a view of the larynx in children aged <2 years due to the large size and floppy nature of the infant epiglottis.[3]

There are several approaches to expose the glottis in infants using a Miller blade.[4] The midline (MID) approach is commonly performed during laryngoscopy with the Miller blade to directly lift the large-sized epiglottis. In the MID approach, the straight blade is inserted down the middle of the tongue and the tip of the blade is placed in the vallecula. The blade is then pivoted or rotated to the right to sweep the tongue to the left and lift it to expose the glottic opening. If this is unsuccessful, then the laryngoscopist may directly lift the epiglottis with the tip of the blade. In 1930, Magill suggested the paraglossal (PGL) approach, but at present, this technique is rarely used or taught.[5] In the PGL approach, the blade is inserted into the mouth at the right commissure and advanced along the right gutter of the mouth to sweep the tongue across to the left. Once the tip of the blade reaches under the epiglottis, the epiglottis is lifted to expose the glottic opening. Right PGL laryngoscopy with the straight Miller blade was found to be an effective approach in routine anaesthesia practise as well as in anticipated difficult intubation.[6],[7]

The PGL approach with the straight blade improves visualisation due to reduction of soft-tissue compression, which is a central component of the line of sight.[8] The Miller laryngoscope blade with PGL approach is reported to provide an improved view of the larynx compared to that obtained with the Macintosh blade in the adult population.[9] The PGL approach does require diligence to master the technique and the recent modification of the Miller blade by Henderson facilitates this approach because of the width and overall design of the blade.[10] Available literature has supported the use of the PGL approach with Miller straight blade and has raised the question as to why this technique is not being included in routine practice.

No prospective, randomised, controlled study has been published to date which has directly evaluated and compared the MID and PGL approaches during laryngoscopy with Miller blade in the paediatric population. Hence, this study was designed to compare the laryngoscopic views and intubating conditions obtained with the Miller straight blade using both these approaches in small children undergoing elective surgery under general anaesthesia.

 Patients and Methods



This study was conducted at a tertiary care centre over an 18-month period between February 2015 and July 2016. Prior permission was obtained from the Institutional Ethical Committee (Inst/IEC/2015/006 dated 12 January 2015). This prospective, randomised, cross-over study included 110 American Society of Anesthesiologists (ASA) Physical Status I and II children of either gender aged 2–24 months scheduled to undergo elective surgeries under general anaesthesia with endotracheal intubation. Children with an anticipated difficult airway, those with a full stomach and those weighing <3 kg were excluded from the study. Children whose parents refused to participate in the study were also excluded. The Consort diagram indicating the enrolment and progress of our children through the study is shown in [Figure 1].{Figure 1}

After a thorough preanaesthetic checkup, children satisfying the inclusion criteria were selected. Written informed consent was obtained from the parents/guardians of each child after explaining the cross-over nature of the study and the procedures in detail. Demographic data such as age, gender, weight and ASA Physical Status were recorded. The children were randomised to be included in one of the following two groups – A (PGL/MID) or B (MID/PGL) with 55 patients in each group by using a computer-generated random number table. As it was a cross-over study, each child acted as his/her own control.

On arrival in the operation theatre, fasting status and consent were checked. Standard monitoring consisting of a 5-lead electrocardiogram, noninvasive blood pressure, oxygen saturation (SpO2), capnography (ETCO2), precordial stethoscope and temperature probe was established. All children were premedicated with intravenous (IV) fentanyl 1.5 μg/kg and glycopyrrolate 10 μg/kg. Children were placed in the supine position, and anaesthesia was induced with IV propofol (2.5 mg/kg) and paralysed with atracurium (0.5 mg/kg) after confirming the ability to mask ventilate. Following IV induction, children were manually ventilated with sevoflurane in oxygen via the paediatric circle system and facemask. An end-tidal concentration of sevoflurane of 2.5% was ensured before laryngoscopy. Laryngoscopy was attempted 4 min after the administration of muscle relaxant with the head in neutral position. All children were intubated following direct laryngoscopy with Miller blade via the PGL or MID approach. To maintain uniformity and as per recommendation, we used a 103 mm long Miller blade size 1 in all children. An anaesthesiologist with a minimum of 1 year experience of endotracheal intubation performed the laryngoscopy and intubation in the presence of a consultant anaesthesiologist.

In the MID approach, the blade was inserted down the middle of the tongue and the tip was placed at the vallecula. The blade was pivoted to sweep the tongue to the left and then lifted to expose the glottic aperture [Figure 2]a. In the PGL approach, the blade was introduced at the right commissure of the mouth, advanced along the right gutter to sweep the tongue towards the left [Figure 2]b. However, the tip of the blade was placed at the vallecula. Direct lifting of the epiglottis to improve visualisation or to facilitate the passage of the endotracheal tube was done in either method only if required.{Figure 2}

In Group A, the initial laryngoscopy was done by right PGL approach followed by a second laryngoscopy by the MID approach. The reverse sequence was followed in Group B. During each laryngoscopy, the tip of the blade was placed in the vallecula and Cook's modification of Cormack–Lehane (CL) grading of laryngoscopic view was noted.[11] Optimal external laryngeal manipulation (OELM) was performed by the laryngoscopist if the CL grading was 2a or worse and any improvement in laryngoscopic grading was noted.[12] Following each laryngoscopy, adequate depth of anaesthesia was ensured by maintaining an end-tidal concentration of 2.5% sevoflurane with manual ventilation. Following the second laryngoscopy, intubation was performed with an appropriate-sized endotracheal tube. Laryngoscopy was interrupted or delayed in any event of hypoxaemia (SpO2 <94%) or bradycardia (heart rate <100 beats/min).

Data were collected by an independent unblinded observer. Other than CL grading and use of OELM, the grade of difficulty during intubation, the time for laryngoscopy, the time for intubation, the need for direct lifting of the epiglottis, the need for retraction of the angle of mouth, the number of attempts for intubation and the need for stylet were also recorded. The time taken for laryngoscopy and intubation was noted. The time for laryngoscopy (T1) was defined as the time taken from opening the mouth until the best glottic view could be achieved, with/without OELM or after inclusion of epiglottis. The time for intubation (T2) was defined as the time taken from obtaining the best laryngoscopic view to the achievement of successful intubation (as evidenced by auscultation of bilateral equal breath sounds). The laryngoscopist was asked to complete a 5-point Likert-scale survey to assess ease of intubation with both techniques: 1 = extremely easy, 2 = easy, 3 = somewhat easy, 4 = not very easy and 5 = most difficult.[13]

Any complication occurring during laryngoscopy and intubation such as a fall in saturation (SpO2 <94%), dental trauma, oesophageal intubation, laryngospasm or mucosal trauma was noted.

The sample size was estimated using the formula applicable for randomised controlled trial with a dichotomous outcome and having equal sample size in both the arms. Based on a previous study in adults by Achen et al.,[9] and assuming a confidence interval (CI) of 95%, Type I error (alpha) of 0.05, power of study of 80% and Type II error (beta) of 0.20, the calculated sample size was 104 participants or 52 children in each group. To account for attrition, 55 children were included in each group for our study.

Raw data were entered into Microsoft Excel Spreadsheet (version 2019) and analysed using IBM SPSS Statistics for Windows, version 27 (IBM Corp., Armonk, New York, USA). Categorical variables were expressed as number of patients and compared across the groups using Pearson's Chi-square test for independence of attributes. Continuous variables were expressed as mean, median and standard deviation and compared across the groups using unpaired t-test. The kappa test was used to analyse the grades of laryngoscopic view observed between the PGL and MID approaches using the Miller blade. McNemar test was used to analyse the comparison of easy and restricted laryngoscopy between the two approaches. With an alpha level of 5%, any P < 0.05 was considered statistically significant.

 Results



We recruited 55 children in each group and did not have any dropouts. Laryngoscopic views were observed in 110 children with both the approaches (PGL and MID), and intubation was performed in 55 children with either PGL or MID approach. Thus, final data analysis was performed on 110 patients.

Both the groups were comparable in terms of demographic profiles (age, gender, weight and ASA Physical Status) [Table 1].{Table 1}

The details of laryngoscopic grades obtained with the two approaches are shown in [Table 2]. There was no statistically significant difference in overall laryngoscopic views with both the approaches (P > 0.05). The laryngoscopic view was similar with both approaches in 81 out of the 110 (73.64%) children and differed in the remaining 29 (26.36%) children. Among those children for whom the laryngoscopic views differed, MID approach provided a better view than PGL approach in 14 out of the 110 (12.73%) children. The PGL approach provided a better view than MID approach in 15 out of the 110 (13.64%) children. The statistical analysis revealed a kappa value of 0.493, indicating a moderate agreement between the two approaches (95% CI = 0.347–0.639).{Table 2}

Cook's classification of laryngoscopic grades of easy (1 and 2a), restricted (2b and 3a) and difficult (3b and 4)[11] was compared between the two approaches [Table 2]. Easy laryngoscopy was noted in 96 out of the 110 children and restricted laryngoscopy was observed in the remaining 14 children with either of the two approaches. The difference was found to be statistically insignificant (P = 0.6831). Difficult laryngoscopy grades (3b and 4) were not observed in any child.

OELM was required in 37 and 40 children with the MID and PGL approaches respectively. Improvement of laryngoscopic grading was observed in all children with OELM. A two-tailed P value using the McNemar test was found to be 1.000; hence, no significant difference was seen in the requirement of OELM in either approach [Table 3].{Table 3}

The mean time for laryngoscopy, as well as time for intubation via MID and PGL approaches, was comparable (P = 0.859 and P = 0.410, respectively) [Table 4].{Table 4}

Intubation was possible in the first attempt in 55/55 children with the MID approach and 54/55 children with the PGL approach. One child in the PGL approach was intubated in the second attempt.

In MID approach, intubation of 49/55 children was easy (scale 2) while somewhat easy (scale 3) in the remaining 6/55. Intubation via PGL approach was assessed to be easy (scale 2) in 47/55 children and somewhat easy (scale 3) in the remaining 8/55 children [Table 5].{Table 5}

The requirement of additional manoeuvres such as direct lifting of the epiglottis with the tip of the Miller blade or retraction of the angle of the mouth is shown in [Table 6].{Table 6}

We observed no complication associated with the MID approach of Miller blade laryngoscopy and intubation. One patient had desaturated during the PGL approach of Miller blade laryngoscopy which was managed with mask ventilation followed by PGL approach of laryngoscopy, and successful intubation in the second attempt.

 Discussion



In the present study, we compared the laryngeal views using a MID or PGL approach with Miller size 1 blade in children with normal airways aged between 2 and 24 months. Laryngeal views obtained with both the approaches were similar in 81/110 children. The PGL approach provided a better view than the MID in 15/110 children, whereas a better view was observed with MID in 14/110 children. Other parameters such as time for laryngoscopy, time for intubation, ease of intubation and need for additional manoeuvres (lifting of epiglottis/retraction of angle of mouth) were found to be similar.

Varghese and Kundu compared the MID approach using Miller blade with PGL approach using Macintosh blade in children aged 1–24 months.[14] They observed that both the laryngoscopes provided similar laryngoscopic views and intubating conditions. Achen et al. did a similar study in adult patients and demonstrated that the PGL approach using the Miller blade provided a better laryngeal view than the conventional Macintosh blade.[9] Both studies compared different approaches with different laryngoscope blades. The present study was conducted to compare the two different approaches with the Miller straight blade laryngoscope. We observed comparable findings in our study.

As the present study was of a cross-over design, the same laryngoscopist observed both laryngoscopic views with the MID and PGL approaches. In our study, a Grade 1 view was noted in 73/110 children with the MID approach and 70/110 children with PGL approach. Jindal et al. obtained CL Grade 1 view in 97.1% (68) of participants in PGL Miller approach as compared to 67.1% (47) in conventional Macintosh approach.[6] Henderson observed CL Grade 3 or 4 in all the ten cases of difficult intubation with traditional Macintosh laryngoscopy. Using the PGL approach with the Miller blade in these patients provided Grade 1 laryngeal view in all of them.[10]

Our study provided the same laryngoscopic view in 81/110 children with either approach. In the remainder, a better view was obtained with MID and PGL approaches in 14/110 and 15/110 children respectively. However, this is different from the literature where PGL has yielded a better view than MID approach in the difficult airway or syndromic child. Kose et al. reported successful intubation of a 2-month-old child with Walker–Warburg syndrome by PGL approach using the Miller blade, in which the first attempt by the traditional MID approach had failed to provide a view of the larynx.[15] Saxena et al. used the PGL approach with Miller blade in a 14-month-old boy with Pierre Robin syndrome to obtain Grade 2b laryngoscopic view when MID approach had yielded a Grade 4 view.[16] Semjen et al. had failed to obtain a Grade 1 or 2 view using MID approach with Miller blade in six infants with Pierre Robin syndrome. However, the PGL approach yielded a better view.[17] Because children with an anticipated difficult airway were excluded from our study, it would not be possible for us to conclude which one of the approaches would have been superior in the difficult airway.

Our study highlights the fact that the MID approach does not necessarily provide a better view of the larynx in small children and that the PGL approach with a straight blade is equally effective. Anaesthesiologists need to be familiar with both the approaches and in the event of difficulty with one approach, switching to the other may provide a better view.

Benumof and Cooper demonstrated a significant improvement in the laryngoscopic view with the use of OELM in adult patients.[12] In our study, OELM was found to effectively improve laryngoscopic grade with both the approaches, which is similar to other studies. Varghese and Kundu demonstrated that OELM improved the laryngoscopic grading using MID approach with the Miller blade and PGL approach with the Macintosh blade in children. With the application of OELM in the case series by Sharma et al., the incidence of Grade 3 laryngoscopic view for MID, left molar and right molar approaches was reduced to 0, 0 and 17% respectively in OELM versus non-OELM scores (P = 0.000).[18] Mukharjee et al. also reported similar improvement of grade of laryngoscopic view with the application of OELM during laryngoscopy using Miller blade via the PGL approach.[19]

In our study, the difference between the mean time for laryngoscopy and time for intubation with MID and PGL approaches was statistically insignificant. However, Jindal et al. reported that the time taken for laryngoscopy and intubation in adult patients had significantly reduced in the PGL approach in comparison to the conventional Macintosh blade laryngoscopy.[6]

Retraction of the angle of mouth was mostly required with PGL approach (10/55) in our study. It was also required in a few children (2/55) for the MID approach where the mouth was too small. Despite the MID introduction of the blade in these two children, additional space was needed to be created for the introduction of the endotracheal tube by retracting the angle of the mouth. Huang et al., Sharma et al. and Potdar et al. also reported the need for assistance with retraction of angle of mouth during laryngoscopy using the Miller blade via PGL approach.[5],[18],[20] With the right PGL approach, retraction of the angle of the mouth created more space for visualisation of the endotracheal tube and the path along which it traverses.

In both the approaches, the tip of the blade was placed in the vallecula to lift the epiglottis indirectly. However, many anaesthesiologists are taught to place the tip of the Miller blade on the posteroinferior surface of the epiglottis, which may result in stimulation of the vagus nerve, laryngospasm, bronchospasm and bradycardia.[14] In our study, the inclusion of epiglottis was required mostly in MID approach (6/55), but this did not result in vagal stimulation. We thereby proposed to place the tip of the Miller blade at the vallecula and to tense the hyoepiglottic fold to facilitate the upward movement of the epiglottis. If the larynx is still difficult to visualise, application of OELM may be resorted to. Should this also fail to provide a view of the larynx, the epiglottis may be lifted directly to improve laryngeal visualisation.

Although laryngoscopy was the primary aim of the study, the ease of intubation with the two approaches was also observed. The ease of intubation has very high interobserver variability and depends a lot on the practice and experience of the individual performing laryngoscopy and intubation. Successful intubation with the PGL approach in the first attempt was achieved in 98% of children. Both laryngoscopy and intubation were reported to be easy for the majority of the trainee anaesthesiologists even though they were more familiar using the MID approach with the Miller blade in children. The ease of intubation in our study was similar to the PGL approach in a study by Jindal et al.[6] Though the findings of a study by Sharma et al.[18] state that the left PGL approach was easier, this needs to be evaluated in children. There was no requirement of a bougie or stylet to facilitate intubation in our study.

Our study has a few limitations. We did not include children with a difficult airway or syndromic children. It would have been interesting to see the influence of the PGL approach in children with an anticipated difficult airway. We also did not compare between the left and right PGL laryngoscopic approaches with the Miller blade in children.

 Conclusion



We conclude that both MID and PGL laryngoscopic approaches with the Miller #1 blade provide similar laryngoscopic views and intubating conditions in children aged between 2 and 24 months. The anaesthesiologist should be familiar with and skilled in using both the approaches. Placing the tip of the Miller blade in the vallecula provides satisfactory intubating conditions in this age group. OELM was found to be effective in improving laryngoscopic grade in children. Intubation of small children requires retraction of the angle of the mouth, more so in the PGL approach.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

References

1Harless J, Ramaiah R, Bhananker SM. Pediatric airway management. Int J Crit Illn Inj Sci 2014;4:65-70.
2Burkle CM, Zepeda FA, Bacon DR, Rose SH. A historical perspective on use of the laryngoscope as a tool in anesthesiology. Anesthesiology 2004;100:1003-6.
3Passi Y, Sathyamoorthy M, Lerman J, Heard C, Marino M. Comparison of the laryngoscopy views with the size 1 Miller and Macintosh laryngoscope blades lifting the epiglottis or the base of the tongue in infants and children<2 yr of age. Br J Anaesth 2014;113:869-74.
4Loepke AW, Shank ES. The pediatric airway. In: Cote CJ, Lerman J, Anderson BJ, editors. A Practice of Anesthesia for Infants and Children. 6th ed.. Philadelphia: Saunders Elsevier; 2019. p. 1437-8.
5Huang YF, Ting CK, Chang WK, Chan KH, Chen PT. Prevention of dental damage and improvement of difficult intubation using a paraglossal technique with a straight Miller blade. J Chin Med Assoc 2010;73:553-6.
6Jindal P, Khurana G, Gupta D, Chander U. Can paraglossal approach be an effective alternative to the conventional laryngoscopy in routine anesthesia practice – A comparative study. J Anesth Clin Res 2014;5:406.
7du Toit MA, Gray RM. Paraglossal straight blade intubation in syndromic children. South Afr J Anaesth Analg 2018;24:118-21.
8Agrawal S, Asthana V, Meher R, Singh DK. Paraglossal straight blade intubation technique – An old technique revisited in difficult intubations: A series of 5 cases. Indian J Anaesth 2008;52:317-20.
9Achen B, Terblanche OC, Finucane BT. View of the larynx obtained using the Miller blade and paraglossal approach, compared to that with the Macintosh blade. Anaesth Intensive Care 2008;36:717-21.
10Henderson JJ. The use of paraglossal straight blade laryngoscopy in difficult tracheal intubation. Anaesthesia 1997;52:552-60.
11Cook TM. A new practical classification of laryngeal view. Anaesthesia 2000;55:274-9.
12Benumof JL, Cooper SD. Quantitative improvement in laryngoscopic view by optimal external laryngeal manipulation. J Clin Anesth 1996;8:136-40.
13Mandal AP, Kumar N, Kumar R. Comparative evaluation of conventional approach versus paraglossal approach for routine anesthesia. Ann Int Med Den Res 2019;5:22-5.
14Varghese E, Kundu R. Does the Miller blade truly provide a better laryngoscopic view and intubating conditions than the Macintosh blade in small children? Paediatr Anaesth 2014;24:825-9.
15Kose EA, Bakar B, Ates G, Aliefendioglu D, Apan A. Anesthesia for a child with Walker-Warburg syndrome. Braz J Anesthesiol 2014;64:128-30.
16Saxena KN, Nischal H, Bhardwaj M, Gaba P, Shastry BV. Right molar approach to tracheal intubation in a child with Pierre Robin syndrome, cleft palate, and tongue tie. Br J Anaesth 2008;100:141-2.
17Semjen F, Bordes M, Cros AM. Intubation of infants with Pierre Robin syndrome: The use of the paraglossal approach combined with a gum-elastic bougie in six consecutive cases. Anaesthesia 2008;63:147-50.
18Sharma S, Sehgal R, Kumar R, Sharma K, Agrawal N. The left molar approach, the right molar approach and midline approach for direct laryngoscopy and intubation using Macintosh blade. J Anaesthesiol Clin Pharmacol 2007;23:41-6.
19Mukharjee S, Mitra D, Sen A, Chattopadhyay A, Kajal S, Dhankhar M. Intubation of a neonate with glossopalatine ankylosis using a paraglossal approach and a laryngoscope with a straight blade. South Afr J Anaesth Analg 2014;20:218-9.
20Potdar M, Patel RD, Dewoolkar LV. Molar intubation for intra oral swellings: Our experience. Indian J Anaesth 2008;52:861.