Comparison of Videolaryngoscope and Intubating Laryngeal Mask Airway for Tracheal Intubation with Manual-in-line Stabilization in Patients Undergoing Cervical Spine Surgery.

BACKGROUND: This prospective, randomized study compared CMAC® videolaryngoscope with intubating laryngeal mask airway (ILMA) for intubation under manual-in-line-stabilization (MILS) in patients undergoing cervical spine surgery. Settings and Design: Sixty-five ASA Physical Status Classes I and II patients aged 18-65 years undergoing elective cervical spine surgery were randomly allocated into two groups: group CM-intubation with CMAC® videolaryngoscope (n = 33) and Group IL-intubation using ILMA (n = 32).
MATERIALS AND METHODS: Intubation was performed in all patients after the application of MILS. The primary outcomes included first attempt and overall intubation success rate, intubation time, and apnea time. The secondary objectives were degree of head movement, hemodynamic response, incidence of desaturation, sore throat, and tissue injury. STATISTICAL ANALYSIS: Normality of data was tested by the Kolmogorov-Smirnov test. Quantitative variables were compared using the unpaired t-test or Wilcoxon Mann-Whitney test and qualitative variables were compared using the Chi-square test/Fisher's exact test. P < 0.05 was considered statistically significant.
RESULTS: CM group had a higher first attempt (96.97%, P = 0.054) and overall (100%, P = 0.053) intubation success rate than IL group (81.25% and 87.5%, respectively). Group CM had a significantly shorter (P < 0.0001) intubation time (33.13 ± 11.82 s) than IL group (55.71 ± 19.28 s), but group CM had significantly longer (P < 0.0001) apnea time (33.13 ± 11.82 s) than IL group (22.03 ± 7.14 s). The incidence of head movement was significantly lower in IL group (P = 0.011). Hypoxemia did not occur. Postintubation hemodynamic changes and tissue injury were significantly higher in ILMA group.
CONCLUSION: CMAC group had higher intubation success rate and significantly shorter intubation time. However, ILMA group had a significantly shorter apnea time and significantly lower incidence of head movements. Copyright:

INTRODUCTION

Stabilization of cervical spine by manual in-line stabilization (MILS) leads to increased risk of difficult laryngoscopy, increased intubation time, and an increased likelihood of failed intubation.[1] The current approach to airway management in these patients incorporates the use of alternative (to classic laryngoscope) airway devices, for example, videolaryngoscope, supraglottic airway devices, optical stylets, and fiberoptic intubation.[1] This prospective randomized study was conducted to compare the efficacy of CMAC® video laryngoscope (Karl Storz, Tuttligen, Germany) with intubating laryngeal mask airway (LMA-Fastrach ™; LMA North America, Inc., San Diego, CA, USA) for intubation while application of MILS in patients undergoing cervical spine surgery.

MATERIALS AND METHODS

This prospective, randomized comparative study was conducted after seeking clearance from the Institutional Ethics Committee. The trial was registered with ClinicalTrials.gov (CTRI/2018/07/015108) and adheres to the applicable CONSORT guidelines. To detect the difference of 16% in the success rate between two devices with alpha = 0.05 and power = 80%, the minimum required total sample size was 60 patients.[2] Assuming a dropout of 10%, total sample size taken was 65.

Patients aged 18–65 years, belonging to ASA physical status classes I or II and scheduled for elective cervical spine surgery under general anesthesia with endotracheal intubation and requiring application of MILS were enrolled for the study. Written informed consent was obtained from all the patients. The exclusion criteria included all patients with anticipated difficult airway as assessed using the following parameters: Modified Mallampati class 4, neck circumference >40 cm, mouth opening <4 cm, upper lip bite test class 3, and any swelling or pathology in the oral cavity or around the neck. The study patients were randomly allocated to two groups using the closed-envelope method: group CM-intubation done using CMAC video laryngoscope (n = 33), Group IL-intubation done using Intubating Laryngeal Mask Airway (ILMA) (n = 32).

All the patients were made to fast overnight and received premedication with tablet alprazolam 0.25 mg orally for anxiolysis. In the operation theater, electrocardiogram, noninvasive blood pressure, and pulse oximeter were attached and baseline readings noted. An adequate gauge intravenous (i.v.) cannula was secured and i.v. fluid started. The patient was preoxygenated with 100% oxygen for 3 min. General anesthesia was induced with fentanyl 2 μg.kg −1 body weight followed by propofol 2–2.5 mg.kg −1 body weight and vecuronium bromide 0.1 mg.kg −1 body weight to facilitate endotracheal intubation. Mask ventilation was done with oxygen (FiO2 1) and isoflurane (MAC 0.6). Patient's head and neck was then immobilized by an experienced anesthesiologist (who had already applied MILS at least 50 times) in the neutral position using MILS.[1] As per group allocation intubation was performed using one of the two devices.

In group CM, CMAC D blade was inserted in the midline in the oral cavity and advanced under its monitor vision till its tip reached vallecula. The epiglottis was then lifted to visualize the glottic opening. A styletted cuffed reinforced endotracheal tube (ETT) of internal diameter 7.0–7.5 mm for females and 7.5–8.0 mm for males was introduced. Correct placement of ETT was confirmed by the appearance of square wave capnographic trace, bilateral equal breath sounds, and absence of epigastric sounds. Oxygen was supplemented through nasal prongs at a rate of 12 L.min −1 during entire intubation process.

In group IL, the correct size of ILMA was selected according to patient's body weight: 30–50 kg: ILMA number 3, ILMA tube 7.0 mm; 50–70 kg: ILMA number 4, ILMA tube 7.5 mm; 70–100 kg: ILMA number 5, ILMA tube 8.0 mm. The cuff of ILMA was partially deflated using deflator and upper surface of its mask was lubricated. Mouth was opened using nondominant hand and ILMA inserted by dominant hand. The cuff of ILMA was inflated with the requisite amount of air (size 3: 20 ml, size 4: 40 ml, and size 4: 50 ml) and adjusted to get optimal ventilation.[3] After confirming the presence of bilateral equal entry and a square wave capnograph, intubation was done with lubricated ILMA ETT. The cuff of ILMA ETT was inflated and intubation confirmed by visualizing square wave capnograph and bilateral air entry. The ILMA cuff was deflated, and ILMA was swung out of the pharynx into the oral cavity while applying counter pressure to the tracheal tube using the stabilizing rod. The ETT connector was replaced and tube placement reconfirmed using a square wave capnograph. Either of the following maneuvers was used for troubleshooting any difficulty in intubation through the ILMA: rotation of ILMA ETT, reinsertion of ILMA ETT, and reinsertion of ILMA of same or smaller or larger size.[3]

Hypoxemia was defined as fall in SpO2 up to or below 92%. In case of failure to intubate with the given device in either CM group or IL group within two attempts, patient's trachea was intubated using fibreoptic bronchoscope as a rescue device. After rechecking the ETT position, patient was ventilated mechanically, and anesthesia was maintained with isoflurane (0.6–0.8 MAC) in oxygen and nitrous oxide (FiO2 0.33).

The primary objective of the study was to measure intubation success rate. The number of attempts of intubation was calculated as the number of times ETT was introduced into the oral cavity in CM group, and number of times ETT was introduced into the ILMA for IL group. Apnea time was also calculated in both groups. In CM group, apnea time was the time elapsed from the moment facemask was removed until the appearance of square wave capnograph through ETT. In the IL group, it was calculated as the time elapsed from the moment facemask was removed until appearance of square wave capnograph through ILMA. The total time to secure airway was calculated as time taken after removal of the face mask until appearance of capnographic trace through ETT in both the groups. The secondary objectives of the study were degree of head movement (using goniometer), hemodynamic parameters during the procedure, incidence of desaturation, incidence of postoperative sore throat, incidence of injury to lips, teeth, mucosa, and other soft tissues.

Categorical variables were presented in terms of frequency and percentage (%) and continuous variables as mean ± standard deviation and median under each group separately. Normality of data was tested by the Kolmogorov–Smirnov test. If the normality was rejected, then nonparametric tests were used. Quantitative variables were compared using unpaired t-test or Wilcoxon Mann–Whitney Test (when data sets were not normally distributed) between the two groups. Qualitative variables were compared using the Chi-square test/Fisher's exact test. P < 0.05 was considered statistically significant. Data were analyzed using the latest version of Statistical Package for Social Sciences, IBM, Chicago, United States of America.

RESULTS

A total of 70 patients were enrolled in the study of whom five patients got excluded on the basis of the exclusion criteria. Remaining 65 patients consented for the study and were randomly allocated into CM group (intubation done with CMAC® laryngoscope, n = 33) and IL group (intubation done using [ILMA, n = 32]) [Figure 1]. The results of all these patients were analyzed. The demographic characteristics of study population in both groups were comparable [Table 1]. The airway examination findings were also comparable between the groups [Table 2].

Figure 1

CONSORT flowchart

Table 1

Demographic characteristics of the study groups

	Group, n (%)		Total (n=65), n (%)	P
	CM (n=33)	IL (n=32)
Age distribution (years)
≤20	5 (15.15)	6 (18.75)	11 (16.92)	0.860
21- 30	11 (33.33)	12 (37.50)	23 (35.38)
31- 40	6 (18.18)	7 (21.88)	13 (20.00)
41- 50	5 (15.15)	4 (12.50)	9 (13.85)
51- 60	6 (18.18)	3 (9.38)	9 (13.85)
Mean±SD	35.52±13.09	32.59±11.65	34.08±12.39	0.346
Median (IQR)	35 (24.500- 45)	30 (23.500- 40)	30 (24.500- 43.250)
Gender distribution, number of patients (%)
Female	7 (21.21)	6 (18.75)	13 (20.00)	0.804
Male	26 (78.79)	26 (81.25)	52 (80.00)
ASA class, number of patients (%)
1	23 (69.70)	24 (75.00)	47 (72.31)	0.633
2	10 (30.30)	8 (25.00)	18 (27.69)

ASA=American Society of Anesthesiologists, SD=Standard deviation, CM=CMAC, IL=ILMA, ILMA=Intubating laryngeal mask airway, IQR=Interquartile range, CMAC=CMAC videolaryngoscope

Table 2

Airway parameters

	Group CM (n=33)		Group IL (n=32)		P
	Mean±SD	Median (IQR)	Mean±SD	Median (IQR)
Weight (kg)	57.64±8.78	60 (50- 63.250)	57.72±8.97	58 (50.500- 65)	0.97
Interincisor gap (cm)	4.78±0.5	4.7 (4.400- 5.100)	4.9±0.41	4.95 (4.650- 5.250)	0.266
Neck circumference (cm)	33.31±2.94	34.1 (31.575- 35.475)	32.19±2.54	32.2 (30.500- 33.850)	0.108
Thyromental distance (cm)	6.98±0.84	6.9 (6.500- 7.425)	7.09±0.8	7 (6.550- 7.450)	0.585
Upper lip bite test, number of patients (%)
Class 1	31 (93.94)		29 (90.63)		0.672
Class 2	2 (6.06)		5 (7.69)
MMPC, number of patients (%)
1	7 (21.21)		8 (25.00)		0.940
2	18 (54.55)		15 (46.88)
3	8 (24.24)		9 (28.13)

CM=CMAC, IL=ILMA, ILMA=Intubating laryngeal mask airway, SD=Standard deviation, IQR=Interquartile range, MMPC=Modified Mallampati Classification, CMAC=CMAC videolaryngoscope

The first attempt success rate for intubation was 96.97% in CM group (32 patients) as compared to 81.25% in IL group (26 patients) with P = 0.054. Intubation was possible in the second attempt in the remaining one patient of CM group and two patients of IL group. Hence, none of the patients in CM group needed rescue technique. The remaining four patients of IL group could not be successfully intubated using ILMA and were labeled as intubation failure. Their airway was secured using fibreoptic intubation. However, the incidence of intubation failure between the two groups was not significant (P = 0.053). These parameters are depicted in Figure 2. The mean value of number of intubation attempts in group CM (1.03 ± 0.17) was comparable (P = 0.054) to that in IL group (1.19 ± 0.4). To facilitate intubation, the incidence of patients who required alternative maneuvers was comparable in both the groups (P = 0.903). A total of 16 patients (48.48%) belonging to CM group required external laryngeal pressure or manipulation. However, no patient required a bougie for guiding ETT in CM group. Sixteen patients (50%) belonging to the IL group also needed alternative maneuvers to facilitate intubation. Of these patients in IL group, Chandy's maneuver was applied in 11 patients (34.38%) and ILMA size was changed in five patients (15.63%).

Figure 2

Intubation success and failure

Total time taken to secure airway with tracheal tube in group CM was 33.13 ± 11.82 s which was significantly shorter (P = 0.0001) as compared to time taken to secure airway in IL group (55.71 ± 19.28 s). The apnea time of patients in group CM was 33.13 ± 11.82 s which was significantly longer (P < 0.0001) as compared to apnea time in IL group (22.03 ± 7.14 s). These durations are shown in Table 3.

Table 3

Intubation and apnea times

	CM (n=33)		IL (n=32)		P
	Mean±SD	Median (IQR)	Mean±SD	Median (IQR)
Intubation time (s)	33.13±11.82	29.1 (26.725- 35.575)	55.71±19.28	50.5 (38- 71.500)	<0.0001
Apnea time (s)	33.13±11.82	29.1 (26.725- 35.575)	22.03±7.14	21 (17- 24)	<0.0001

CM=CMAC, IL=ILMA, ILMA=Intubating Laryngeal Mask Airway, IQR=Interquartile range, CMAC=CMAC videolaryngoscope

Degree of head movement (as measured by goniometer) was not seen in any patient in group IL and on the other hand, seven patients (21.21%) in CM group had some degree of head movement [Table 4]. Mean value of degree of head movement in group CM in patients in whom head movement was seen was 6.57 ± 2.07 degrees. Significant difference was observed in the incidence of patients with any degree of head movement between the both groups (P = 0.011). The heart rate was significantly higher at one and 3 min postintubation in ILMA group as compared to CMAC group [Figure 3]. The systolic blood pressure, diastolic blood pressure, and mean blood pressure were significantly higher at 3 min postintubation in the ILMA group than the CMAC group [Figure 4]. There was no episode of hypoxemia in either of the groups. Complication rate [Table 4] was significantly higher in IL group as compared to CM group. Incidence of soft-tissue trauma, trauma to lip, and blood on ILMA/blade was significantly higher in group IL as compared to group CM.

Table 4

Incidence of complications

	CM (n=33), n (%)	IL (n=32), n (%)	Total (n=65), n (%)	P
Degree of head movement	7 (21.21)	0 (0.00)	7 (10.77)	0.011
Sore throat	5 (15.15)	14 (43.75)	19 (29.23)	0.011
Soft-tissue trauma	3 (9.09)	10 (31.25)	13 (20)	0.032
Trauma to lip	4 (12.12)	11 (34.37)	15 (23.08)	0.042
Blood on ILMA/blade	1 (3.03)	7 (21.87)	8 (12.31)	0.027

CM=CMAC, IL=ILMA, ILMA=Intubating Laryngeal Mask Airway, CMAC=CMAC videolaryngoscope

Figure 3

Heart rate variation

Figure 4

Blood Pressure variation. DBP = Diastolic blood pressure, SBP = Systolic blood pressure, MBP = Mean blood pressure

DISCUSSION

The application of MILS during airway management is standard of care in cervical spine injury patients to prevent further neurological damage.[1] However, it leads to increase incidence of difficult laryngoscopy, worsens glottic exposure, increases difficulty in intubation, prolongs intubation time, and increases intubation failure rates necessitating use of various adjuncts and alternative airway devices.[1] Fibreoptic intubation offers advantages of minimizing cervical spine movements and providing optimum laryngeal exposure.[1] However, it requires skilled personnel, consumes time, is expensive, may not be readily available at all locations and may be difficult in emergency airway management of patients with hypoxia. The videolaryngoscopes improve laryngeal view and have high success rates for intubation in such patients.[245678910111213141516171819] ILMA allows ventilation and blind intubation with head and neck in neutral position.[2320212223] Different videolaryngoscopes have been compared with ILMA for intubation in cervical spine injury patients.[22425] This study compared C-MAC® videolaryngoscope with ILMA for intubation (with MILS) in patients undergoing cervical spine surgery.

The patients in CMAC (CM) group and ILMA (IL) group were found to be comparable for all airway examination parameters. The first attempt intubation rate was higher (96.97%) in CM group (32 out of 33 patients) as compared to 81.25% in IL group (26 out of 32 patients). Intubation was successful (completed in first or second attempt) in all the patients (100%) in CM group while it was successful in only 26 out of 30 patients (87.50%) even after two attempts in IL group (P = 0.054). It was evident that overall intubation success rate of CMAC was higher as compared to overall intubation success rate of ILMA. However, this result was not statistically significant. The use of alternative maneuvers to achieve the above success rates in either groups was found to be comparable (48.48% in group CM, 50% in group IL, P = 0.903). Özdil et al. published a study comparing ILMA with Glidecope videolaryngoscope for intubation in the presence of rigid neck collar and reported that total intubation success rate was similar (up to 96%) with the two devices.[24] Different videolaryngoscope usage and different way of immobilization of neck might explain their better success rate.

Furthermore, statistically significant difference was found between both the groups regarding total time taken to secure the airway with tracheal tube. It was significantly shorter (P < 0.0001) in the CM group (33.13 ± 11.82 s) as compared to IL group (55.71 ± 19.28 s). Özdil et al. also reported significantly longer total intubation times for ILMA than glidescope (85.6 ± 13 s vs. 43.5 ± 13 s; P < 0.001).[24]

The use of ILMA has also been compared with videolaryngoscopes in other anticipated difficult airway situations such as morbid obesity.[2627] In one study, King Vision laryngoscope yielded 100% first attempt intubation success rate as compared to 86.6% with ILMA. The time taken to secure airway with ETT was significantly longer with ILMA group (133.7 ± 44.12 s) as compared to Kings vision videolaryngoscope (17.96 ± 5.12 s).[26] In another study, glidescope yielded a first attempt intubation success rate of 92% compared to 84% with ILMA in morbidly obese patients undergoing bariatric surgery. However, time to secure airway using ETT was found to be comparable between glidescope and ILMA (49 s using the glidescope and 61 s using ILMA, P = 0.86).[27] The results of our present study are broadly consistent with these studies between videolaryngoscopes and ILMA. However, the mean time for tracheal intubation varied between the studies. The reason behind this difference could be different patient population in which these studies were conducted, different videolaryngoscopes used, and different methodologies used.

Mean apnea time was also calculated in the present study. Mean apnea time of patients in group CM was 33.13 ± 11.82 s which was significantly longer as compared to 22.03 ± 7.14 s in group IL. In CM group, patient remained apneic throughout the laryngoscopy time, while in IL group patient was apneic only till the time of insertion of ILMA. Oxygenation and ventilation were commenced through ILMA even before intubation. Majority of airway morbidity occurs from failure to oxygenate and not from failure to intubate. Hence, although total intubation duration is longer, but a significantly shorter apnea time with use of ILMA is a relevant and useful finding for the anesthesiologist. This is useful in patients with low oxygen reserves who are prone to desaturate fast since they can be ventilated through the ILMA first and then intubation can be attempted. The patient can also be ventilated in between intubation attempts.

Degree of head movement was not seen in any of the patient in Group IL, and on the other hand, in 21.21% of patients in Group CM had some degree of head movement. Mean value of degree of head movement in Group CM of patients in whom head movement was seen was 6.57 ± 2.07degrees. Significant difference was observed in the incidence of degree of head movement between the both groups (P < 0.05). Ozkan. et al. compared cervical motion during intubation with C-MAC D blade and ILMA radiologically and reported that the change in angulation between occiput-C1 during intubation was significantly lower with ILMA than with CMAC D blade (2.780 ± 2.10 vs. 6.040 ± 4.10, P = 0.007). The above finding of our present study is broadly in accordance with the study done by Ozkan D et al. However, the mean degree of head movement was less in our study. This could be because degree of head movement was measured using goniometer which is an easy and practical method; however, in the above study, it has been measured using X-rays. Although radiological evaluation may give more accurate results, it also exposes the patient to radiations and also is not very feasible.

The hemodynamic response to intubation process was comparable between the two groups at all times except heart rate being significantly higher in ILMA group at 1-and 3-min postintubation [Figure 3] and blood pressure (systolic, diastolic, and mean) being statistically higher in ILMA group at 1-min postintubation [Figure 4] as compared to CM group. This could be due to more manipulation required to obtain adequate ventilation after insertion, a greater number of attempts, and more time taken to secure the airway in ILMA group.

There was no episode of desaturation in either group. This could be because, all the patients were well preoxygenated, and maximum of only two attempts were allowed with these devices. Furthermore, oxygen was supplemented using nasal prongs throughout the intubation process. No major complication was seen in either of the two groups. However, minor complications such as sore throat, soft-tissue trauma, trauma to lip, and presence of blood on device were significantly higher in IL group as compared to CM group. This could be because of more manipulations required to get adequate ventilation after insertion, a greater number of attempts with ILMA or as a consequence of downfolding of epiglottis during blind intubation. Our results are broadly in accordance with the previous study done by Marouf et al. in obese patients.[26]

The results obtained in the present study indicate that both the devices, namely CMAC videolaryngoscope (D blade) and ILMA are efficacious in tracheal intubation of patients with cervical spine injury after the application of MILS. Intubation success rate was higher with CMAC videolaryngoscope. Although intubation time with CMAC videolaryngoscope was significantly lower than ILMA, ILMA offered the advantage of significantly shorter apnea time and is known to allow for simultaneous ventilation. ILMA caused a significantly lower degree of head movement in comparison to CMAC videolaryngoscope. It is also less expensive and can be a useful device when C-MAC videolaryngoscope is not available.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.