European Journal of Cardiovascular Medicine

Majority of cardiac surgeries are done under general anaesthesia wherein endotracheal intubation as a part of general anaesthesia is essential and as anesthesiologists it becomes a part of responsibility to secure airway safely with minimal manipulation whether airway difficulty is anticipated or not. Intubation in difficult cases have been made easy with the use of video laryngoscopes (VLS) which provided better Laryngoscopic view with high success rate though more effective but it was time consuming than intubation with conventional Macintosh laryngoscope which was comparable to the previous study with TAS Scope ^[1]. The alignment of oropharyngolaryngeal axis which is provided best sniffing position is essential ^[2,3] during DLS for successful intubation which need not be the case with video laryngoscopes which was proved by studies wherein conventional sniffing and didn’t improve intubation success compared to neutral position ^[4]. So video laryngoscopes and their usages were studied extensively in difficult airway cases and found very useful ^[5,6,7]. Most VLS available are expensive so we took up the study comparing a new Indigenous TAS scope and conventional macintosh laryngoscope for Cormack Lehane grading of  the larynx , ease of intubation and hemodynamic changes with each device , TASCOPE  (Figure-1,2) is a video intubation device to help passage of tube ,involves the use of endoscope or borescope camera (5.5 mm diameter HD camera) which is either connected to laptop/or even compatible mobiles or tablet, Customized initial TASCOPE blades were made of metal , now available in ABS (Acrylonitril butadlene styrene) A thermoplastic polymer .This was innovated by respected member of the anaesthesia society (TAS) and named after society which is available at affordable price ,and can be easily sterilised using  2.4% glutaraldehyde (cidex). A preliminary study was done showing the usefulness of the device ⁽¹⁾. We took up this study with more experience in the usage of the instrument in our institute prior to do our study.

Ethical committee approval

The study was approved by Institutional Human Ethical Committee with refrence number (SJICR/EC/2019/042).

Inclusion criteria

• 120 ASA II and III patients undergoing elective cardiac surgery requiring general anaesthesia and endotracheal intubation.

Exclusion criteria

• Morbidly obese
• Patients at risk of aspiration
• Patients undergoing emergency surgery
• Patients having cervical spine pathology were excluded

Procedure

Patients were randomly allocated to one of the two groups TAS or MAC depending on the instrument which was used for intubation, and anesthesiologists who had performed at least 50 intubations with TAS scope were assigned for the study. Each patient was premedicated with alprazolam 0.25 mg and pantoprazole 40 mg per orally with sips of water on the night and morning on the day of surgery. In the operation theatre after connecting standard monitors pulse oximeter, 5 lead electrocardiogram (SPO2, 5L ECG) to the patient radial artery catheterization and peripheral venous cannulation done under sterile technique and local anaesthesia, then invasive blood pressure was calibrated to atmosphere and recorded. All patients were placed in intubating position and preoxygenated with 100% oxygen before induction. patients were induced with inj. midazolam 0.03 mg/kg, inj. fentanyl 3 mic/kg, inj. etomidate 0.1 mg/kg, Muscle relaxation was achieved with inj. vecuronium 0.1 mg/kg then patients were ventilated with oxygen and up to 2% of sevoflurane while hemodynamics were monitored, inj. lignocaine 2% xylocard) was given 90 seconds before the scheduled time of laryngoscopy. The patients were randomized by close envelope technique to either one of the groups, Group TAS or Group MAC (60 each). In TAS group

Intubated with TAS after initial laryngoscopy with Macintosh for CLG (1-visualization of entire glottis, 2-visualization of posterior laryngeal aperture but not anterior portion, 3-visualization of epiglottis but not any part of larynx, 4-visualization of soft palate but not epiglottis) and spray the vocal cord with 10 % lignocaine then the patient was ventilated with 100% oxygen sevoflurane up to 3% and till the hemodynamics reduce to 10% of the baseline before intubation with TAS. In MAC group, Intubated with Macintosh after initial laryngoscope with TAS scope. No external laryngeal manipulation was used to improve the Laryngoscopic view to improve Cormack Lehane grading during initial scopy in both groups. The Intubation duration (T1 OR T2) was measured from the time Laryngoscope Blade past the teeth to ETCO2 confirmation.

Ease of intubation was noted and graded as follows:

Grade I Good: Easy tracheal intubation as Glottis visualized adequately without external maneuvers

Grade II Satisfactory: Tracheal intubation possible but required external manipulation in the form of backward pressure on larynx, increased force of laryngoscope for visualization

Grade III Difficult: Tracheal intubation not possible even with maneuvers

Number of intubation attempts was also noted. Invasive Blood pressure (systolic blood pressure [SBP], diastolic blood pressure [DBP], heart rate (HR), and SpO 2 were measured at baseline, before and after Laryngoscopic device Also before and after the Intubating device.

Statistics analysis

The data was analysed using R-4.1.1 for windows software. Parametric data were analysed with unpaired t-test and nonparametric data were analysed with Mann Whitney test P value< 0.05 was considered statistically significant.

Patients demographic characteristics and preoperative airway features of the two groups are showed in (Table-1). Both groups were comparable with respect to age, height, weight, and sex. Cormack Lehane grading (Table-2) showing grade I visualisation  was found in 57 and 55 patients  when we used TAS scope as Laryngoscopic and intubating  respectively, it was grd I 36 and 39 when we used macintosh as Laryngoscopic and intubating respectively which is statically significant (p=0.001), observed no higher CLG (GRD 3 AND 4) while TAS scope was used either for laryngoscopy  OR  for intubation, but CLG 3  was noticed in 4 patients  and 6 patients when macintosh (MAC) was used as laryngoscopy and intubation respectively. And CLG 4 was in 3 and 2 when macintosh was used for laryngoscopy and for intubation respectively and all CLG 4 patients were visualised as grade 2 and intubated with TAS as we expected lot of manipulation and haemodynamics fluctuation during instrumentation. Time taken for intubation (Table 3) was significantly shorter 12.50±2.50 s in macintosh laryngoscope group (MAC) compared to TAS group was 23.73± 3.48s. Ease of intubation (Table 4) was assessed as gradings which was Gr 1 (good) in 59 patients (98.33%) in TAS gp compared to 52 of 60 patients when macintosh (86.66%) found to be statistically significant, and of 8 patients (MAC) whose CLG grd 3 grd 4 (n=6 and n=2) respectively. We intubated 56 of 60 TAS patients in first attempt (93.3%) and succeeded in 52 of 60 patients in MAC group 86% (p=0.224). External laryngeal manueres in the form of backward pressure were not required in 55 of 60 (91.6%) TAS patients and 51 of 60 (85%) MAC patients (p=0.285). There was mucosal trauma in   2 and 4 patients of TAS and MAC   group respectively (p=0.143) and no incidence of dental or severe airway injury of concern.

Table-1: Comparison of demographic data between TAS and MAC

Table-2: Cormack lehane grading

Table-3: Comparison of time taken intubation between TAS and MAC

Table-4: Comparison of ease of intubation, number of attempts, external laryngeal manueres required, trauma during intubation with each device

Figure-1: TAS SCOPE showing scope with boroscope cable and usb port to connect to mobile or tab

Figure-2: Front view showing camera head and lcd lights around the camera eye

Figure-3: Viewing angle for TAS scope

We observed that TAS Scope was associated with better glottic exposure when compared to Macintosh laryngoscope (P = 0.001). One hundred and twelve out of 120 (93%) patients had CLG 1 visualization with TAS scope whereas in MAC gp using macintosh laryngoscope 75 of 120 patients (62%) had grade I visualization. Seven   patients in DLS had grd 3 ( n=4 ) and grd 4 (n=3) CLG  were visualised as  grd 1  and grd 2 respectively  when TAS SCOPE was used as a first device( for laryngoscope)  and  eight  patients had grd 3 ( n =6 ) and grd 4 (n=2) had better visualisation with TAS scope  as grd 1 and grd 2 respectively when TAS was used as second device  this can be due  to better viewing angle with TAS SCOPE (70 deg) than macintosh laryngoscope  (MAC) where in viewing angle is 22 deg (Fig 2) and camera head becomes the eye to visualise the field near larynx where in distance is reduced from 30-40 cm (distance from larynx to laryngoscopist eye in conventional macintosh laryngoscopy ) to less than 5 cm in  case of videolaryngscopes ^[9]. This was comparable with the preliminary study done by Kaur et.al., ^[1] Observed Higher grades of C L laryngeal view (1and2) were observed in patients with group TAS as compared to DLS (90% vs 53.3% of patients, P < 0.05) and study with other videolaryngoscopes like glidescope, pentax airway scope, C MAC ^{[5 ,6,7,8]}. Improved visualisation and securing of airway in this study also could be due to good learning curve done by anaesthesiologists before assigning for the study.

In our present study Time to intubate was considerably longer with TAS scope (23.73± 3.48s.) compared to MAC (12.50±2.50 S) and extended period can be explained by one of reasons mentioned below included procedural steps involved during TAS laryngoscopy , mandatory passage of  bougie since inline arrangement of intubating axis is lost , negotiation of ETT upon bougie secondly it needed good eye to hand coordination due to indirect visualisation of larynx and finally it’s a midline procedural approach which needed manipulation of tongue especially in edentulous patients as in other video laryngoscopes  but considerably quick compared to preliminary study on TAS ^[1] 38.3±6.7 S, and it could be due to update in the model of TAS scope with change in handle and modified channel in recent one  and all anaesthesiologist participated in the study had done with minimum of 50  successful first attempt intubations prior. Mean Time to intubate are comparable to the use of Tas scope in preliminary study where it was 38.26 ± 6.7s and with other video laryngoscopes like C MAC, glidescope, Mc grath and airtrac in previous publication where in mean time to intubate were 56s, 60s, 53s and 47s respectively ^[6] and in other study with true view glide scope and macintosh time to intubate was 39s,44s, 23s ^[11]. The improvement with mean time to intubate (23.73±3.48s) could be explained by experience of the investigator on this new instrument handling before the conduction of study. We observed easier intubation with TAS scope 59/60 (98.33%) than with Macintosh laryngoscope 49 /60 (81%) which is statistically significant (p=0.04) remaining patient in TAS group was edentulous requiring pulling of right corner of mouth which was comparable to other studies showing improved visualisation and easier intubation as with the other video laryngoscopes. ^[5,6,7,10] 

We intubated 56 of 60 TAS patients in first attempt (93.3%) and succeeded in 52 of 60 patients  DLS 86% ( p=0.224 ), 3 of 52 patients needed external larynygeal pressure though it was first attempt,  the remaining patients were intubated in next attempt. In a study using GlideScope®, it was observed that 93% patients could be intubated successfully in first attempt with GlideScope as compared to 51% patients via direct laryngoscopy(p<0.01) but time to intubate was considerably longer in their study probably because they were untrained ^[12], and The first-attempt success rate was less than 50% in novice operators (1–5 previous experiences with videolaryngoscope, independently of airway expertise with direct laryngoscopies) and 87% in expert operators (>15 previous experiences with video laryngoscope) ^[13] but in our study we enrolled only the clinician who had an experience of minimum 50 successful intubation with TAS scope which could explain increased first attempt intubation here. As, explained earlier ,The mean difference systolic blood pressure (SBP1 ) to SBP2  in TAS grp (where TAS is the used for intubation) was significantly higher after direct laryngoscope  compared to after TAS laryngoscopy ( indirect) (p=0.001) as direct laryngoscope needs higher pressure to view the larynx than TAS scope , but during intubation the mean difference from SBP3 to SBP4 is significantly higher (p=0.001) in the group where TAS is used for intubation   which could be explained by the time duration taken by TAS to introduce the bougie and  negotiation of ETT followed by confirmation, this is in contrast with a study of glidescope ^[14] wherein systolic pressure variations were lesser with glidescope compared to macintosh could be explained by time taken for intubation was lesser with glidescope compared to macintosh l scope and they monitored noninvasive blood pressure timed to specific intervals in contrast with our study where we monitored continuous invasive blood pressure recordings, other study⁽¹⁵⁾ did not show any difference with hemodynamic when glide and macintosh were studied on elective surgery patients.

External laryngeal manoeuvres were required more when direct laryngoscope was used for intubation in the form of backward pressure which was statistically insignificant(p=0.285). There were Limitations in the present study which included inability to blind the intubating anaesthesiologist and the observer regarding the device being used, recording manoeuvres, hemodynamic changes and Cormack- Lehane grade.

Conflicts of interest: Nil

Funding: Self

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