Comparison of King Vision and Truview Laryngoscope for Postextubation Visualization of Vocal Cord Mobility in Patients Undergoing Thyroid and Major Neck Surgeries: A Randomized Clinical Trial.

BACKGROUND: Visualization of vocal cords following extubation after thyroid and major neck surgeries is highly desirable for the surgeon as well as the anaesthesiologist to rule out vocal cord palsy or oedema. As the patient is emerging from general anaesthesia, it may be challenging for the anaesthesiologist to optimally visualise and grade vocal cord movement following extubation.
SETTING: Randomized clinical trial at a tertiary care centre.
METHODOLOGY: After obtaining institutional ethics committee approval, 60 patients posted for thyroid and major neck surgeries under American Society of Anesthesiologists (ASA) grade I and II were recruited for the study. Written informed consent was obtained. Pre-operatively indirect laryngoscopy was performed in all the patients to assess baseline vocal cord function. All patients were premedicated and induced and maintained as per standardized anaesthesia protocol. Patients were randomized using a sealed envelope technique to either Group K where intubation was performed using Kings vision laryngoscope or Group T where intubation was performed using True view laryngoscope. Glottis visualization was graded in all patients and intubated. Ten minutes prior to extubation injection. dexmedetomidine 1 μg/kg was administered. Once patients satisfied extubation criteria, laryngoscopy was performed using respective video-laryngoscope in each group, patient extubated under vision and assessed for vocal cord visualization and mobility grade (VMG) and patient reactivity score (PRS). Heart rate, systolic blood pressure, diastolic blood pressure and mean arterial pressure was also noted. Total intraoperative morphine consumption was recorded. Vocal cord function was assessed again before the day of discharge by indirect laryngoscopy.
RESULTS: Age (P = 0.27), sex (P = 0.08), body mass index (P = 0.70), ASA (P = 0.39), mallampati class (P = 0.72) and morphine used (P = 0.39) were comparable in both groups. There was no statistically significant difference among the two groups with respect to VMG (P = 0.18). There was no statistical difference in the PRS (P = 0.06) in both groups. Increase in heart rate or mean arterial pressure from baseline was not significant statistically in both groups. Time taken for laryngoscopy during extubation was significantly less with group T as compared to group K (P = 0.000).
CONCLUSION: Both Kings Vision and Truview Video-laryngoscopes provide comparable laryngoscopic view with similar patient comfort, although clinically Truview may be a better choice due to less time consumed for visualisation and rating vocal cord movement during extubation.

RCT Entities:   Population Interventions Outcomes

INTRODUCTION

Visualization of vocal cords following extubation after thyroid and major neck surgeries is highly desirable for the surgeon as well as the anesthesiologist to rule out vocal cord palsy or edema.[12] The two major challenges faced by the anesthesiologist to achieve this are first to optimally visualize vocal cords as well as demonstrate it to the surgeon and second to ensure adequate patient comfort without producing any respiratory complication such as local trauma, coughing, desaturation, breath holding, laryngospasm, and aspiration.[3] Direct laryngoscopy with Macintosh laryngoscope does not provide optimum visualization and poses significant discomfort to patients.[4]

Video laryngoscopes are not new to the difficult airway armamentarium of anesthesiologists and have been widely studied and utilized for intubation of difficulty airways.[567] However, their utility in visualizing the vocal cords at the time of extubation has not been explored much.

Hence, this study was conducted to compare postextubation laryngoscopic view, vocal cord mobility, and patient comfort during laryngoscopy using King Vision and Truview video laryngoscopes in patients undergoing thyroid and major neck surgeries.

MATERIALS AND METHODS

After obtaining approval from the Institutional Ethics Committee, sixty American Society of Anesthesiologists (ASA) physical status Class I and II patients posted for thyroid and major neck surgeries under general anesthesia were recruited for the study. Patients of ASA physical status III and IV and hypertensive patients were excluded from the study. Preoperatively, indirect laryngoscopy was performed in all the patients to assess the baseline vocal cord function. All patients received a standardized anesthesia protocol. They were premedicated with tablet diazepam 10 mg in the night and tab ranitidine 150 mg on the morning of the surgery.

On arrival in the operating room, intravenous access was established, and patients monitored for continuous electrocardiogram, noninvasive blood pressure, oxygen saturation, end-tidal carbon dioxide, and baseline parameter were noted. Injection midazolam 1 mg and injection ondansetron 4 mg were given, and analgesia was provided with morphine 0.1 mg/kg. After preoxygenation with 100% oxygen for 3 min, all patients were induced with injection propofol 2 mg/kg, and injection vecuronium 0.1 mg/kg was used to facilitate laryngoscopy. Patients were randomized using a closed envelope technique to one of the two groups [Figure 1], Group K where laryngoscopy was performed using King Vision video laryngoscope (KVL03C, King Systems Corporation, Germany) or Group T where laryngoscopy was performed using Truview video laryngoscope (Truview PCD™ 4150, Truphatek International Ltd., Israel). Glottis visualization was noted in all patients as (1) full glottic opening visible and (2) partial glottic opening visible.

Figure 1

Consort diagram.

Patients were intubated with appropriate size endotracheal tube. Low-flow anesthesia (600 ml) was maintained with oxygen:nitrous oxide (50:50), and isoflurane and a total minimum alveolar concentration of one was ensured throughout the surgery. Additional morphine 0.1 mg/kg was administered based on hemodynamic alterations.

Fifteen minutes before expected last surgical suture, isoflurane was cutoff, and injection dexmedetomidine 1 µg/kg was administered 10 min before extubation to increase patients comfort during postextubation laryngoscopy. Residual neuromuscular blockade was reversed with a mixture of neostigmine 2.5 mg and glycopyrrolate 0.4 mg, and assessment of airway reflexes was done. Once patients satisfy extubation criteria (arousable, fully reversed, regular breathing and no coughing on the tube), extubation was planned.

Laryngoscopy was performed during extubation in Group K using King Vision scope and Group T using Truview scope to assess vocal cord visualization and mobility grade as follows: 1 (a) - Full glottis visualized with normal abduction of both vocal cords. 1 (b) - Full glottis visualized with partial immobility. 1 (c) - Full glottis with complete immobility. 2 (a) - Partial glottis visualized with normal abduction of both vocal cords. 2 (b) - Partial glottis visualized with partial immobility. 2 (c) - Partial glottis with complete immobility. Patient discomfort was assessed using patient reactivity score as follows: (1) - No grimace. (2) - Grimacing facial expression. (3) - Discomforting head movements. (4) - Protective head and limb movements. (5) - Coughing and gagging. Time taken for laryngoscopy during extubation was defined as time starting from introduction of video laryngoscope into the patient's mouth, till complete visualization of vocal cords followed by removal of the scope.

Heart rate, systolic blood pressure, diastolic blood pressure, and mean arterial pressure (MAP) were noted just before extubation and every 1 min thereafter for 5 min. Total intraoperative morphine consumption was recorded. Vocal cord function was assessed again before the day of discharge by indirect laryngoscopy.

Sample size was calculated based on a pilot study conducted in the institute. Considering the Alfa value 0.05 with power of 80% to get 15% difference in the proportion of patients with good vocal cord visualization between the two airway devices, sample size was calculated as 30 in each group. Statistical analysis was done using SPSS version 20 (IBM Corporation). Age, height, weight, body mass index (BMI), and morphine consumed were compared using Student's t-test. Chi-square test was used to analyze ASA grade, Mallampati classification and Mann–Whitney test to analyze vocal cord mobility grading, and patient reactivity score.

RESULTS

Mean age, BMI, ASA grade, and sex ratio were statistically comparable in both the groups [Table 1]. There was no statistically significant difference among the two groups with respect to modified Mallampati grade [Table 1]. Intraoperative consumption of morphine was found to be comparable between both the groups (P = 0.39).

Table 1

Comparison of demographic data among the two groups

Comparison of vocal cord mobility grade by direct laryngoscopic assessment showed similar visualization in Group K and Group T with no statistically significant difference in both groups [Figure 2]. Patient reactivity score was also comparable in both the groups [Figure 3].

Figure 2

Comparison of vocal cord mobility grade among the two groups.

Figure 3

Comparison of patient reactivity score among the two groups.

Variation of heart rate [Figure 4] and MAP [Figure 5] was not statistically significant between the two groups.

Figure 4

Heart rate variation during laryngoscopy and extubation between the two groups.

Figure 5

Mean arterial pressure variation during laryngoscopy and extubation between the two groups.

Time taken for visualization of vocal cords was shorter in Group T as compared to Group K. This was found to be statistically significant [Figure 6].

Figure 6

Time taken for laryngoscopy in both groups.

Four patients (two in each group) were found to have unilateral incomplete recurrent laryngeal nerve palsy on postoperative indirect laryngoscopic evaluation, for which patients were reassured and managed appropriately.

DISCUSSION

Recurrent laryngeal nerve injury is a major concern in patients undergoing thyroid and major neck surgeries. The incidence of temporary unilateral vocal cord palsy following thyroid surgery is 3%–4% and permanent unilateral palsy in <1% of patients.[89] Accurate assessment of postoperative vocal cord function by laryngoscopic examination is recommended for patients undergoing thyroid surgery.[10]

Fiber-optic laryngoscopy has been considered the gold standard for detecting postoperative vocal cord palsy[11] as it can also be used through a laryngeal mask airway to maintain the airway patent during this procedure.[1213] However, its availability, setup, and skill of the operator are major drawbacks in using fiber-optic laryngoscopy on a routine basis for all thyroid and major neck surgeries.

Video laryngoscopes are easy to use, and skills involved are easy to master.[14] The greater effectiveness of video laryngoscopes associated with multiperson visualization makes them suitable for visualization of vocal cords by anesthesiologist and his much anxious surgical counterpart.

In the present study, we have found that both Truview and King Vision laryngoscopes are equally effective in visualization of vocal cords during extubation following thyroid and major neck surgeries. This is reflected by the statistical comparability between the two groups with regard to vocal cord visualization and grading. Previous studies have also found the efficacy of Truview laryngoscope comparable with fiber-optic laryngoscopy.[11] This could be explained by the technical fact that the Truview laryngoscope has an integral optical lens system and unique blade tip angulation that provide optimal sight of vision.[15] There are no data available regarding efficacy of King Vision laryngoscope to visualize vocal cords during extubation. Although researchers have compared Truview and King Vision video laryngoscopes for intubation and found that both the video laryngoscopes were comparable with respect to laryngoscopic view.[16]

We found that patient comfort during laryngoscopy was acceptable and comparable in both the groups. This could be attributed to the lesser lifting force required for glottis visualization with both the laryngoscopes under study. These findings are similar to those in previous studies on Truview laryngoscope as compared to Macintosh laryngoscope.[17] There are several case reports and case series on awake intubation with King Vision video laryngoscope which is well tolerated due to its plastic blade and small diameter.[18]

Increase in heart rate and mean blood pressure during laryngoscopy in both the groups was not statistically significant from preextubation value. Previous studies have also found decreased stress response to laryngoscopy with video laryngoscopes as compared to the Macintosh laryngoscope.[19] This finding could be because laryngoscopy can be performed with less lifting force required with video laryngoscopes as discussed previously.

Numerous drugs have been used to ensure patient comfort and attenuate stress response to extubation, including fentanyl, lignocaine, nitroglycerine, esmolol, clonidine, and magnesium.[20212223] We have used dexmedetomidine infusion (1 mcg/kg) because of its sympatholytic, sedative, amnestic, and anesthetic sparing property without causing any respiratory depression which is highly desirable during emergence.[2425]

Time taken for laryngoscopy was significantly more with King Vision as compared to Truview video laryngoscope in our study despite using channeled blade King Vision video laryngoscope, which has been found to be superior to nonchanneled blade by some researchers.[26]

CONCLUSION

Both King Vision and Truview video laryngoscopes provide comparable laryngoscopic view with similar patient comfort although clinically Truview may be a better choice due to less time consumed for visualization and rating vocal cord movement during extubation.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.