ABSTRACT
Background and Aims:
Endotracheal intubation (ET) in infants is considered a challenging task over the decades. Infants have short safe apnoea time, and this difficulty has been vanquished to some extent by using the videolaryngoscopes (VLs), but there exists a dearth of research particularly in this vulnerable subset. Therefore, this trial was conducted to evaluate intubation times obtained with C-MAC VL and conventional Miller laryngoscopes in infants.
Methods:
A total of 80 infants aged between 1 month and 1 year with American Society of Anesthesiologists physical status I-II requiring ET were randomised in two groups; the C-MAC VL or Miller laryngoscope ML. Anaesthesia was induced with sevoflurane 1–8% and atracurium 0.5 mg/kg IV. The primary outcome was evaluated as the total time taken to intubate. Secondary outcomes were time to achieve best glottic view (TBGV), tube insertion time (TIT), percentage of glottic opening (POGO) score, number of attempts and intubation difficulty score (IDS).
Results:
The median (interquartile range) of time taken for ET was less in VL; 22.5 (20.75–26) compared to ML; 26 (21.75–31). TBGV was achieved early in VL group than the ML group (6.03 ± 1.33s/7.88 ± 2.44) respectively (P-value < 0.001). POGO was better in VL (99.12 ± 4.795s) compared to ML (85.50 ± 31.13s). IDS was less in the VL group (0.07 ± 0.27) than in ML (0.70 ± 1.14). Other parameters, such as the number of attempts, bougie usage, adverse effects and TIT, were comparable across the two groups.
Conclusion:
When compared to the ML group, the C-MAC VL group exhibited a decreased intubation time, early TBGV, better POGO score, reduced IDS and subjective intubation difficulty. As a result, we consider VL to be a more efficacious device for intubating the trachea in infants.
Keywords: Infant, intubation, laryngoscopes, time
INTRODUCTION
Airway-related complications and their management have an exalted perioperative critical incidence in the paediatric age group, and in infants, these incidences are fourfold more prevalent, compared to older children. The paediatric airway is certainly not a mimeograph of the adult airway and mandates, both knowledge and training.[1] Owing to their distinct anatomical and physiological characteristics, this vulnerable subset faces unique challenges in airway management.[2] The limited time for intubation due to increased oxygen consumption, multiple attempts for intubation and allied cardio-respiratory consequences during infant anaesthetic induction are significant and preventable forerunners of perioperative censorious events. As a result, amelioration in airway management in this subset remains to be emphasised.[3]
Direct laryngoscopy using Miller (straight) blade is considered a gold standard technique to directly lift the floppy and long epiglottis out of view during laryngoscopy. However, due to the unique anatomy in infants, direct laryngoscopy may offer a poor glottic view unexpectedly.[4] A videolaryngoscope (VL) has recently been investigated as a pivotal tool for difficult airway scenario management by a paediatric anaesthesiologist.[5] There exists substantial literature insinuating a better glottic visualisation in adults and older children. Albeit, the data referring to the time to intubation (TTI) and intubation success rate in infants is negligible and inconclusive.[6-8] We thus carried out this study to assess the relative efficacy of the C-MAC Miller blade (Karl Storz GmbH & Co. KG, Tuttlingen, Germany) and conventional Miller blade direct laryngoscope (DL) in infants with the total time taken for successful endotracheal intubation as the primary objective.
METHODS
After being approved by the Institutional Ethics Committee (IEC/VMMC/SJH/Thesis/2019-10/72 dated 2019 Oct 30) and clinical trial registration (CTRI/ 2020/07/026731), 80 infants (40 in each group) aged between one month and one year weighing 3–10 kg, belonging to the American Society of Anesthesiologists (ASA) grades I and II undergoing elective surgery were enroled in this prospective randomised controlled trial (RCT). Infants with an anticipated difficult airway, upper respiratory tract infection, raised intracranial pressure, congenital anomalies of the head, face and neck, and cardiovascular and respiratory systems were excluded from the study. Written informed consent was taken from all the parents or legal guardians included in the study. The study was conducted in accordance with the principles of the Declaration of Helsinki from July 2020 to December 2022 in a tertiary healthcare centre.
After pre-anaesthetic check-up and nil-per-oral status confirmation, infants were randomised using computer-generated randomisation into two groups, each consisting of 40. In group VL, infants were intubated with a C-MAC Miller VL, and in group ML, patients were intubated using a Miller DL. Standard ASA monitors were attached on arrival at the operation theatre. All intubations were done by an anaesthesiologist who had performed at least 50 intubations with C-MAC Miller VL and more than 50 with Miller DL in children before starting the study cases.
General anaesthesia was induced in all patients using 1%–8% sevoflurane in nitrous oxide and oxygen (2:1). Intravenous (IV) cannulation was performed with an appropriately sized IV cannula, and IV fluid was started as calculated. IV fentanyl 1.5 μg/kg was administered. After checking ventilation, neuromuscular blockade was achieved by IV atracurium 0.5 mg/kg. Nitrous oxide was then discontinued. All the patients were ventilated with 100% oxygen and sevoflurane maintaining a minimum alveolar concentration (MAC) value of 1.3 and an end-tidal oxygen concentration >90% before all tracheal intubations. Tracheal intubation was performed with appropriately sized uncuffed styletted endotracheal tube (ETT) as per group allocation.
The primary outcome of the study was to compare the total time taken (it is defined as the time from the laryngoscope blade tip passing the lip of the patient up to the appearance of the first capnography trace) for successful endotracheal intubation (TTI). Time for achieving the best glottic view (TBGV), tube insertion time (TIT), percentage of glottic opening (POGO), number of attempts and intubation difficulty score (IDS) were recorded as the secondary outcomes.
TBGV is defined as the time from the laryngoscope blade tip passing the lip of the patient till the laryngoscopist’s verbal declaration of obtaining the best glottic view. TIT is defined as the time between acquiring the best glottic view and the laryngoscopist’s vocal declaration of the endotracheal tube’s passage into the glottis. POGO score was noted for successful attempts without external laryngeal manipulation and with external laryngeal manipulation (if applied for intubation). A 100% POGO score is a full view of the glottis from the anterior commissure to the interarytenoid notch. A POGO score of 0 means that even the interarytenoid notch is not seen. The degree of difficulty in intubation was evaluated using the IDS. The larynx view was noted on the basis of Cormack and Lehane (CL) grading (Grade 1-visualisation of entire glottis, Grade 2a-visualisation of parts of laryngeal aperture, Grade 2b-visualisation of arytenoids only or the very posterior origin of cords, Grade 3a-visualisation of epiglottis only and it is liftable, Grade 3b-visualisation of epiglottis only and it is not liftable, Grade 4-both epiglottis and glottis are absent). In case of suboptimal visualisation of vocal cords in the first attempt, external laryngeal manipulation was applied and any optimising manoeuvres were noted. Failed attempt was defined as any time the laryngoscope had to be withdrawn from the mouth either due to oxygen desaturation (peripheral oxygen saturation <95%), or if the tracheal tube could not be passed successfully into the trachea. If more than one attempt to intubate was required, the patient was mask ventilated with 100% oxygen and sevoflurane in between the attempts. Any change in blade size or use of bougie was noted. If successful intubation was not achieved in two attempts of laryngoscopy, the device would be declared a failure, and intubation was done using an alternative device. At baseline, before induction, shortly before intubation, at 1, 3 and 5 minutes after intubation, heart rate and blood pressure (systolic, diastolic and mean) were recorded and then monitored continuously throughout the surgery. Any adverse effect such as blood on the blade/trauma/technical snag/failed intubation/oesophageal intubation was noted. The presence of any hoarse cry, cough or stridor in the postoperative room was noted till 2 hours after reversal.
The sample size was calculated based on a previous study,[9] wherein the mean [standard deviation (SD)] time for successful endotracheal intubation with Miller DL was 26.3 (11.5) seconds. With α-error of 0.05 and a power of 80%, the minimum sample size required was 33 patients in each group. To reduce the margin of error, we decided to recruit a total of 80 patients (40 in each group). The data was analysed using the Statistical Package for Social Sciences (SPSS) (International Business Machines, Inc., version 21.0, Chicago, United States of America). Categorical variables were presented as frequency and percentage (%) and continuous variables as mean ± SD. Quantitative variables were compared applying the Wilcoxon Mann–Whitney/unpaired t-test. The Chi-square test and Fisher’s exact test were used for comparing qualitative variables. A P value of <0.05 was considered statistically significant.
RESULTS
A total of 100 infants were assessed for eligibility, wherein 80 infants were randomised following the exclusion of 20 neonates as per the study protocol [Figure 1]. The C-MAC group (n = 40) and the Miller group (n = 40) were comparable in terms of demographic characteristics [Table 1]. The TTI for C-MAC VL and ML was 22.5 s (20.75–26) versus 26 s (21.75–31), respectively; P =0.013 [Figure 2]. The median [interquartile range (IQR)] time taken for best glottic view (TTBGV) for an infant undergoing C-MAC intubation was significantly shorter than the Miller DL group 8s (6–9.25); P =0.684 [Figure 3]. The mean difference in glottic view time between the two groups, with 95% confidence intervals surrounding the difference, was -1.85 (-1.50 to -2.44), while the mean difference in the ETT intubation time was -3.85 (3.26 to -4.14). The time taken for successful tracheal tube insertion using C-MAC (9.32 ± 3.8) versus Miller DL (10.15 ± 4.81) was comparable, and no statistically significant difference was found between the two modalities (P = 0.684). POGO scores were significantly better with C-MAC as compared to Miller DL (99.12 ± 4.79/85.50 ± 31.13; P = 0.019). 100.0% of the participants in both the groups, VL and ML, were intubated in a single attempt [Figure 4]. The mean IDS was significantly less with the C-MAC VL group (0.07 ± 0.270) in comparison with the ML group (0.70 ± 1.14) (P-value < 0.005) [Figure 5].
Figure 1.
Consolidated Standards of Reporting Trials (CONSORT) Flow chart
Table 1.
Demographic data of the infants
| Variables | C-MAC | Miller | P |
|---|---|---|---|
| Age (months) | |||
| Mean (SD) | 6.56±3.40 | 7.26±3.53 | 0.329 |
| Median (IQR) | 7 (4-9) | 7.5 (3.75-10) | |
| Weight (kg) | |||
| Mean (SD) | 6.41±2.27 | 6.39±2.03 | 0.992 |
| Median (IQR) | 6 (5-8) | 6 (5-8) | |
| Gender | |||
| Male/Female | 26:14 | 26:14 | 1.000 |
| Duration (minutes) | |||
| Mean (SD) | 97.88±25.42 | 101.62±26.20 | 0.518 |
SD; Standard deviation; IQR; Interquartile range. Data of gender expressed as absolute number
Figure 2.
The means of Time for Successful Endotracheal Intubation (s) in the 2 different groups. Box-and-whisker plots demonstrating time for tracheal intubation (in seconds) with C-MAC Miller videolaryngoscope and conventional Miller laryngoscope. The inner horizontal line within the box illustrates the median time for tracheal intubation, and the outer horizontal lines of the box illustrate the 25th and 75th quartiles. The horizontal lines of the whiskers display the 95% confidence intervals
Figure 3.
Time taken for best glottic view. Box-and-whisker plots demonstrating time to achieve best glottic view (in seconds) with C-MAC Miller videolaryngoscopes and conventional Miller laryngoscope. The inner horizontal line within the box illustrates the median time for the glottic view, and the outer horizontal lines of the box demonstrate the 25th and 75th quartiles. The horizontal lines of the whiskers illustrate 95% confidence interval
Figure 4.
Comparison of POGO without external laryngeal manipulation. POGO: Percentage of glottic opening; ELM: External laryngeal manipulation
Figure 5.
Comparison of Total IDS between the groups. IDS: Intubation difficulty score
DISCUSSION
The results of our prospective RCT demonstrated a decrease in the TTI reduced TTBGV, clinically and statistically better glottic view (POGO), and lesser subjective intubation difficulty scoring with C-MAC VL in contrast to the ML group, during infant intubation. The median intubation time in the present study was 23.2 seconds, which closely correlates with the recommended 20 seconds for an attempt by the neonatal resuscitation council.[10] A retrospective analysis highlighted that multiple and increased times to intubation with DL can exaggerate the incidence of bradycardia and hypoxia in infants. In order to improve intubation time and success rate, a number of intubation techniques and devices have been investigated.[11] The assertion of a lesser time for tracheal intubation using C-MAC VL as compared to DL in our study is consistent with the existing literature.[3,6] Saran et al. also concluded a short time for intubation with VL.[3] Jain et al. in their RCT found the decreased time taken for endotracheal intubation with C-MAC VL (32.1 ± 5.5s) compared with Miller direct laryngoscope (38.2 ± 10.7s).[6] These findings were attributed to the fact that C-MAC VL exhibits a larger angle (visual) of up to 80° in comparison to 15° with the traditional ML and is usually not affected by the anatomical variation.[12] Furthermore, non-angulation of the C-MAC blade can provide direct and indirect views of the glottic opening. The congregation of all these parameters decreases the requirement of ETT negotiation and thereby less TTI with the antecedent. Gupta A et al., in a RCT, concluded that the C-MAC VL reduced the time for intubation (median = 22 s, IQR = 19-24.5 s) similar to the observations that we made in the C-MAC group (median = 22.5s, IQR = 20.75-26s) in our study.[13] Mutlak H et al., in their study of 65 children, found the time taken for endotracheal intubation with a C-MAC VL to be 28 s (8-93 s), which is more than what we found in our study. This may be because their definition of time for intubation was taken from the time the face mask was taken off the mouth till the first detection of end-tidal carbon dioxide.[14] On the other hand, a meta-analysis comprising of 14RCTs compared DL with VL and deduced prolonged TTI in the background of necessary hand-eye coordination to manipulate and pass the ETT through the vocal cords.[8] Vlatten et al. compared 56 children (<4 years) and found increased time for intubation with C-MAC VL (median = 27 s, IQR = 22-37 s) compared to direct laryngoscope (median = 21 s, IQR = 17-29 s).[15] Our results differ from their results as the anaesthesiologist doing the intubations with C-MAC VL had done only 10 mannequin and 3 human intubations before the study, whereas in our study, the anaesthesiologist had performed 50 intubations with C-MAC VL before starting the study cases. This resulted in better hand-eye coordination and faster intubation. Overall time to intubation is a cardinal factor for the prevention of desaturation in infants as they have a low functional residual capacity and higher oxygen consumption as compared to adults which can expedite shorter tolerance.[16]
The visualisation of the glottis and TTBGV is a pre-eminent step for successful endotracheal intubation. In a recent meta-analysis, the authors observed improved glottic visualisation in paediatric patients with VL. However, they suggested that further studies are required to clarify the safety and efficacy of VL in this vulnerable age group. Concordant with our findings, Goel et al. also found improved glottic view and TTBGV.[2] In prior research, C-MAC VL explicated better glottic view in comparison to the traditional Miller blade.[6,17] Fiadjoe compared the time to best view (TTBV) between GlideScope and DL in 60 neonates and infants. They inferred that the GlideScope yielded faster TTBV than DL.[18] Vlatten et al. compared C-MAC with DL in 56 children and found that TTBGV with C-MAC VL (median = 7 s, IQR = 4.2-9 s) was more than direct laryngoscope (median = 5.5 s, IQR = 4-8 s); P value = 0.769.[15] The result differs from our study, which may be due to the involvement of the less experienced anaesthesiologist with C-MAC performing the intubation. The anaesthesiologist performing intubation in their study had less experience with the C-MAC videolaryngoscope as compared to the anaesthesiologist in our study. Inconsistent with our findings, Riveros concluded poor glottis views with GlideScope compared with DL. The author attributed these findings to limited size options in GlideScope affecting the glottis views.[19] Our results are in harmony with few other authors (Vlatten and Das B et al.) who found a statistically significant better POGO score with VL compared to DL (P-value = 0.003, P value = 0.004, respectively).[15,20] Results similar to ours have been reported by Saran et al. who found a higher first-attempt intubation success rate in the VL group when compared with the DL group (83.3% versus 44.4%).[3] In congruence with our findings, Gupta A et al., found that out of 40 infants in the C-MAC VL group, only 1 patient (3%) had to undergo a second intubation attempt, so the first attempt success rate was 97%.[13] A multicentric randomised VISI (acronym for videolaryngoscopy in small infants) trial concluded that VL with a standard blade improved the first attempt success rate.[21]
In our study, IDS was significantly higher in the Miller DL group compared to VL. Concordant to our findings, Jain et al. found higher IDSs in the Miller DL group Median IQR = 2[0-1] when compared to C-MAC VL Median IQR = 0[0-1].[6] In a recent multicentric registry, numerous laryngoscopies with C-MAC VL have reported a low incidence of airway complications.[22,23] It is noteworthy that higher difficulty with the device during intubation could lead to various adverse effects. Hence, the inclusion of IDS could render the assessment of the complex intubation process more comprehensive.[24] Yadav et al. in 74 children also found similar results with the Miller blade (0.6 ± 0.7) compared with the conventional Miller blade in our study.[25] We also inferred in our study that the number of patients requiring external laryngeal manipulation was more in the Miller DL group compared to C-MAC VL. The possible explanation for this could be attributed to the fact that the inline view of the glottic aperture is not required in the C-MAC VL, as a camera at the tip of the blade gives a wider visual angle.[6]
There were some limitations associated with the present study. Firstly, inability to bind the assigned laryngoscope may lead to observer bias. However, the time focuses to measure our essential result, and the total time taken for intubation was adequately characterised, to decrease the individual bias. We also incorporated the IDS to measure the intricacy of the tracheal intubation for the identification of ease of intubation, which assimilates various indicators of difficult intubation. The operator’s experience was better with the Miller DL; however, this could not alter our findings because VL has a steep learning curve with fast learning skills,[26,27] and our anaesthesiologist had an experience with more than fifty intubations using C-MAC VL. Lastly, the results of this study cannot be extrapolated in infants with difficult airways or anomalies, thereby demanding future research to explicate the efficacy of C-MAC VL in infants.
CONCLUSION
To summarise, this RCT demonstrated that compared to Miller DL, the C-MAC VL-aided intubation in infants not only provided the best CL, and POGO score but also the time taken to achieve the best glottic view and intubate the trachea in infants was less. Furthermore, decreased IDSs and subjective operative difficulty were noticed with C-MAC VL. Due to shorter safe times in infants, we recommend C-MAC VL over Miller DL to achieve faster intubation.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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