European Journal of Cardiovascular Medicine

Anaesthesiologists face a formidable obstacle while administering general anaesthesia: safeguarding the airway, especially in individual who are known to have trouble with this procedure. (1, 2) Effective management of the airway is critical to avoid life-threatening scenarios such as “can’t intubate, can’t ventilate”. (3) Awake fiberoptic bronchoscope-assisted nasotracheal intubation (FOI) is often recommended in these situations to ensure optimal operating conditions for various head, neck, and upper respiratory tract surgeries. (4)

However, the prospect of awake nasotracheal manipulations can be highly intimidating for patients, necessitating thorough mental and pharmacological preparation. (5,6) Adequate sedation and opioid use are essential to maintain patient comfort while keeping the airway patent. (7) Patient cooperation, achieved through detailed procedural explanations, is vital for the success of awake FOI. (8)

Several studies have documented excellent hemodynamic stability with FOI when mild sedation and local anaesthetics are used in combination. (9) Nonetheless, anxiety can trigger undesirable autonomic responses, complicating the intubation process through elevated heart rate (HR), blood pressure (BP), excessive secretions, and heightened protective reflexes. (6,7) Comprehensive knowledge of airway innervation and anatomy is crucial for effective anaesthesia during intubation.

To reduce these reflexes by desensitizing certain areas of the airway, researchers have used a variety of topical and regional approaches. (10) Topical anaesthesia can be achieved via sprays, nebulization, atomization, gargles, and direct application. (10) Ultrasonic nebulizers, which produce a fine mist with a lower dose of medication, offer uniform distribution but carry a risk of systemic toxicity if dosages exceed recommended limits (British Thoracic Society Bronchoscopy Guidelines Committee, 2001). Additionally, inadequate topical anaesthesia can lead to laryngospasm, jeopardizing airway patency during FOI. (10)

On the other hand, when done by skilled anaesthesiologists, airway nerve blocks provide better airway anaesthetic despite the increased risk of problems including bleeding and nerve injury. (7) The transtracheal injections for the recurrent laryngeal nerve, the glossopharyngeal nerve (GPN), and the superior laryngeal nerve (SLN) are the usual components of an effective airway block. (10)

AIMS & OBJECTIVES OF THE STUDY

Primary objective

• To check efficacy of airway topicalization to achieve upper airway anaesthesia for awake fiberoptic bronchoscope assisted nasotracheal intubations.
• To compare airway topicalization with airway nerve blocks to achieve upper airway anaesthesia for awake fiberoptic bronchoscope assisted nasotracheal intubations.

Secondary objective

•             To compare the hemodynamical response between airway nerve blocks group and airway topicalization group.

Study design: Single blinded randomized controlled trials Study setting: The study was conducted in the Department of Anaesthesiology, in Sri Devaraj urs Medical College, Tamaka, Kolar, in Karnataka. Study duration: The study was conducted from September 2022 to February 2024. Study participants: The study looked at 50 people at the R. L. Jalappa Hospital and Research Centre in Tamaka, Kolar, who were going to have planned treatments while under general anaesthesia and were expected to have trouble breathing. Sampling Method: Universal sampling. Randomization will be done by software with 1:1 allocation using block randomization with unequal block size. Sample Size: The sample size is estimated as 25 per each group The sample size is calculated through G power 3.1.9.6 software by taking the Ease of Intubation Score in patients with Airway Nerve block and Airway topicalization for awake fibreoptic bronchoscope assisted Naso-tracheal intubation as reported in a study done by the input values taken for the calculation are, Number of groups = 2 Calculated Mean (as reported in the study) Group UAB = 2.64 Calculated Mean (as reported in the study) Group LA = 5.96 Standard deviation for Group UAB= 1.25 Standard deviation for Group LA= 1.27 α error probability = 0.05 Power (1-β power probability) = 0.95 Allocation Ratio = 1:1 Effect size f = 1.10 The minimum sample size needed for the study amounted to be = 45 (including both groups) So, for this study we considered 50 patients in total, and divided them 25 per each group for better statistical representation. INCLUSION CRITERIA: Patients over 18 years old, over 50kg, and ASA grade I II and III planned for elective procedures under general anaesthesia with expected airway difficulty. EXCLUSION CRITERIA: • Uncooperative patients • Local anaesthetic allergy • Pregnancy • Deranged coagulation • Skull base fracture • Epilepsy • Raised Intracranial pressure and Intraocular pressure Study procedure: The study was started after Institutional Ethical Clearance (IEC). Prior to the treatment, the patients were given thorough explanations in their native language and informed permission was acquired. The study was conducted on adult patients more than 18 years of age and requiring fiberoptic bronchoscope assisted nasotracheal intubations. A detailed preoperative evaluation was performed on each patient. This evaluation comprised a thorough check of their airway, which included a dental inspection, mouth opening, Mallampati grade, thyromental distance, and neck movements. Additionally, the standard operating procedure for fasting was included in this evaluation. In the preoperative room the following medications was administered after securing IV cannula half an hour before intubation: • Inj. Ranitidine 50mg IV • Inj. Ondansetron 4mg IV • Inj. Glycopyrrolate 0.2mg IV. Inside the operating room, standard monitors are connected to monitor i.e., electrocardiogram (ECG), HR, BP and oxygen saturation. Continuous end tidal carbon dioxide (EtCO2) will be monitored following intubation. Airway nerve block (N) and airway topicalization (T) were the two groups that patients were assigned to using a computer-generated random sequence of numbers and the closed-envelope technique. Nerves supplying the nose are blocked using nasal packs soaked with 2% lignocaine with 1:200000 adrenaline in both the groups. Group N (n-25): Patients received following nerve blocks 1. Bilateral Superior Laryngeal Nerve block - with 2ml of 2% lignocaine (each side) injected approximately 2-4 mm inferior to the greater cornu of the hyoid bone. 2. Recurrent laryngeal nerve block – trans laryngeal injection with 2ml of 4% Lignocaine injected after aspirating air at the level of cricothyroid membrane. Group T (n-25): 1. Patients receive 10ml of 4% Lignocaine for topicalization using Modified McKeinzie Technique with infant feeding tube. Both the groups receive 4- 5 liters of supplemental oxygen through nasal cannula throughout the procedure. Appropriate size flexometallic endotracheal tube was loaded on to Fibre Optic Bronchoscope. The following parameters are recorded: • The length of time required for intubation, measured in seconds, beginning with the insertion of the fiberoptic scope into the nose and ending with the confirmation of tracheal intubation via capnography • Ease of intubation – cough and gag score, intubation score • Cough and gag reflex • Any other complications. After securing the airway, general anaesthesia was delivered by intravenous administration of fentanyl at a rate of 2 mcg/kg, propofol at a rate of 2 mg/kg, and vecuronium at a rate of 0.06 mg/kg. For maintenance, isoflurane, 50% oxygen, and 50% nitrous oxide were supplied. Methods of data collection Data was collected using a pre-tested proforma after taking the informed consent from the participants. Study variables Hemodynamics – Heart rate, blood pressure, oxygen saturation, respiratory rate. Cough and gag score 1 = None, 2 = Minimal coughing and gagging, <3 times, 3 = Mild cough and gag lasting for <1 min, 4 = Persistent coughing and gagging Intubation score 1 = no reaction 2 = slight grimacing 3 = severe grimacing 4 = verbal objection 5 = defensive movement of head, hands, or feet Ease of intubation – quality of awake fiberoptic intubation Grading of the score was done as below: - 1-2 score – grade 1 (excellent) 3-4 score – grade 2 (good) 5-6 score – grade 3 (satisfactory) 7-9 score – grade 4 (poor) Comfort score 1 = Good 2 = Moderately comfortable 3 = Poor, uncomfortable Lignocaine toxicity – ECG changes, seizures, bronchoconstriction Time taken for intubation (minutes) Airway complications - The following are examples of airway complications: sore throat, throat spasms, hoarse voice, inflammation, hematoma of vocal cords, epistaxis, symptoms similar to influenza, tracheal perforation, and changes in ETCO2 before and after intubation. Gastric complications – aspiration Drug complications – lignocaine toxicity Statistical considerations: Collected data was coded and entered into an excel data base. The data was analyzed in Stata version 18.0. All the quantitative measures were provided in either the mean and standard deviation (SD) or the median and inter-quartile range (IQR), depending on the distribution of the variable. The categorical variables were provided in the form of frequency and percentage (%), together with the corresponding confidence interval (CI). To compare the two groups, independent sample t-test was done for the continuous variables. In the case of categorical variables, the Mann-Whitney U test, the chi square test, and Fisher's exact test will be deemed suitable for the purpose of interpreting the findings. A p-value < 0.05 was considered as statistically noteworthy for all statistical tests. It was necessary to acquire authorization from the institutional ethics committee before beginning the research. Consent to participate was sought from each and every participant in a prospective manner.

We recruited a total number of 50 participants in the study. The mean age of the participants was 44.3 years (SD 15.6 years).

Baseline characteristics of the two groups

The following table illustrates the differences between the two groups:

Age distribution: In the T group, the average age was 46.2 years old, with a standard deviation of 15.4 years. In the N group, the average age was 46.3 years old, with a standard deviation of 13.9. Table 1 show that statistical analysis did not find any noteworthy differences (p = 0.36).

Gender distribution: Overall, there were 22 (44%) males and 28 (56%) females. There were 14 men and 11 ladies in group N, making it 56% male and 44% female. Eight (13.2%) men and seventeen (68.0%) ladies made up the T group. With a p-value of just 0.08 (Table 1), the disparity passed muster.

Distribution of comorbidity: As a whole, there were 12 (48%) patients in the N group had any comorbidity, while 9 (36%) patients in the T group was diagnosed with any comorbidity. The variance was not statistically noteworthy (p=0.73) (Table 1).

Distribution of diabetes mellitus (DM): While 7 (28%) patients in the N group had DM, 6 (24%) patients in the T group was diagnosed with DM. There was no statistically noteworthy change (p=0.1) (Table 1).

Distribution of hypertension: While 9 (36%) patients in the N group had hypertension, 8 (32%) patients in the T group was diagnosed with hypertension. With a p-value of just 0.1, there was no statistically noteworthy change. (Table 1)

Distribution of hypothyroidism: 3 (12%) patients in each groups had hypothyroidism. There was no variance of the groups in terms of hypothyroidism proportion (p=1.0) (Table 1).

INR distribution: The mean INR of group N was 1.12 (SD 0.14) in the N group and 1.14 (SD 0.11) in the T group. The variance was not statistically noteworthy (p=0.53) (Table 1).

Pre-operative heart rate distribution: In the group N, the mean pre-operative HR was 83 beats per minute (standard deviation: 12 beats per minute), whereas in the group T, the mean heart rate was 79 beats per minute (standard deviation: 15 beats per minute). Due to the fact that the change was statistically insignificant (p=0.3), (Table 1)

Pre-operative MAP distribution: The pre-operative mean arterial pressure (MAP) of group N was 78 mm Hg (standard deviation: 9 mm Hg), whereas the MAP of group T was 77 mm Hg (standard deviation: 10 mm Hg). The deviation did not meet the criteria for statistical significance (p = 0.65; Table 1).

Pre-operative SpO2 distribution: The mean pre-operative SpO2 of group N was 98% (SD 1%) in the N group and 98% (SD 2%) in the T group. Statistically, the change was insignificant (p=0.39). (Table 1).

Pre-operative respiratory rate (RR) distribution:

The mean pre-operative RR of both the groups was 18/min (SD 2/min). There was no variance between the groups (p=0.42) (Table 1)

Table 1: Baseline characteristics of the two groups

Intra-operative clinical differences between the two groups

Difference in heart rates (HR):

The mean HR was 78/min (13/min) in the N group, while it was 81/min (SD 11/min) in the T group at the end of 3 minutes. The variance was not statistically noteworthy (p=0.43). While the heart rate remained static for the N group over the time till the end of 15 minutes, the heart rate steadily increased for the T group. The difference in mean HR was 10 (95% CI: 4 to 15; p=0.02) at 9 minutes, 12 (95% CI: 6 to 18; p=0.001) at the end of 12 minutes, and 17 (95% CI: 8 to 25; p=0.001) at the end of 15 minutes between the two groups (Table 2).

Table 2: Distribution of intra-operative in HR between the two groups

*Statistically significant

Difference in MAP:

The mean MAP was static for the N group. The MAP was static for the T group till 9 minutes but surged marginally after that. The difference between the two groups was not noteworthy till 9 minutes; however, the MAP was high by 8 mm HG (95% CI: 1 to 14 mm HG; p=0.03) at the end of 12 minutes and 10 mm HG (95% CI: 4 to 15 mm Hg; p=0.006) at the end of 15 minutes. (Table 3).

Table 3: Distribution of intra-operative MAP between the two groups

*Statistically noteworthy

Difference in SpO2:

The mean SpO2 was static for the both groups till 9 minutes. For the T group, SpO2 reduced marginally at 12 and 15 minutes. However, the difference was not statistically noteworthy. (see Table 4).

Table 4: Distribution of intra-operative SpO2 between the two groups

*Statistically noteworthy

Difference in RR: (Table 5).

Table 5: Distribution of intra-operative RR between the two groups

*Statistically noteworthy

Cough GAG score: The cough and GAG score was relatively high (score 3) in the T group (n=10, 40%) than the N group (n=3, 12%). The difference was statistically noteworthy (p=0.02) (Table 6)

Table 6: Cough GAG score distribution among the two groups

*Statistically significant

Intubation score: According to the intubation score, group T had a higher score than group N. Only two patients, or eight percent, obtained a score of three in the N group, while nine patients, or thirty-six percent, received a score of three in the T group. There was a variation that was statistically noteworthy (p = 0.03). (table 7).

Table 7:  Intubation score distribution among the two groups

*Statistically significant

Comfort score: While 8 (32%) patients had a good comfort score in the N group, only 2 (8%) patients in the T group had a good comfort score. The disparity was identified via statistical analysis (p=0.03). (Table 8).

Table 8: Comfort score distribution among the two groups

*Statistically significant

Ease of intubation: The median ease of intubation score

Only 8% of patients in group T reported intubation ease of 2 or higher, but 32% (n=8) of patients in group N said the same. A statistical test revealed a noteworthy difference (p=0.03). (Table 9).

Table 9: Ease of intubation among the two groups

*Statistically significant

Intubation time: While 16 patients (64%) in the group N took 6 minutes or less for intubation, only 7 (28%) patients took 6 minutes or less for intubation in the T group. On the other hand, one patient (4% of the N group) required twelve minutes for intubation, while three patients (12%) in the T group required twelve minutes. A statistical test revealed a noteworthy difference (p=0.04).  (Table 10).

Table 10: Time taken for intubation among the two groups

*Statistically significant

Lignocaine toxicity: The administration of lignocaine did not cause any adverse effects in either group of patients.

Gastric complication: No patients in either group had gastrointestinal toxicity, including aspiration, according to the reports.

Airway complication: When it came to opening their mouths, every single patient in both groups had difficulties with their airways. Eighteen patients in the N group had one finger opening, whereas nineteen patients in the T group had such a condition. The N group included 18 patients with this issue. The difference did not meet the criteria for statistical significance (p = 0.53) (Table 11).

Table 11: Airway complications in both the groups

Drug complications: None of the patients in either group reported to have any drug-related complications.

Baseline characteristics:

Age Distribution: The mean ages of the participants in the airway nerve block (N) group and the airway topicalization (T) group were 46.3 years and 42.2 years, respectively, with no statistically noteworthy difference (p=0.36).

Comorbidity Distribution: Co-morbid conditions can have a marked effect on the response to anaesthesia as well as procedure safety. The distribution of comorbidities including DM, hypertension (HTN), and hypothyroidism was similar in both groups (p>0.1 for all).

INR Distribution: International Normalized Ratio is a measure of blood clotting. Mean INR values of 1.12 for the N group and 1.14 in the T group (P =0.53) suggest comparable coagulation profiles.

Pre-operative Vital Signs: Pre-operative HR and MAP are similar in the two groups of patients, as well SpO2 %. The respiratory rate was also not statistically significantly different between both groups.

The two groups in this study were homogeneous at baseline without noteworthy differences in their characteristics (Table 1). In summary, baseline characteristics establish no major differences between groups that subsequently allows a strong basis for comparison in the efficacy and hemodynamic effects.

Clinical differences:

Heart rate: Results show that there was no noteworthy variance in the HR between the two groups at the end of three minutes. A noteworthy difference was noticed subsequently. Initially, the mean HR was 78 beats per minute (bpm) in the N group and 81 bpm in the T group (p=0.43), indicating similar baseline heart rates.

After this period, HR in the N group showed little extra variation until time of shock emerged but progressively increased within T group. By minute 9 of there was a mean HR difference between groups by 10 bpm (95% CI:4-15; p=0.02) that widened to 12bpm (6-18; p=0.001) at minute-12and17bpm (8-25, p =0.03) at end-exercise. This suggests that over time, the T group has a noteworthy increased change in heart rate compared to the N group.

Mean Arterial Pressure (MAP) Analysis: Both nerve block group and topicalization experienced different trends of mean arterial pressure throughout the procedure. Initially, there was no noteworthy difference in MAP between the two groups up to 9 minutes. At the end of 12 minutes, the MAP in the T group was 8 mm Hg higher than in the N group (95% CI: 1 to 14 mm Hg; p=0.03). By the end of 15 minutes, this difference increased to 10 mm Hg (95% CI: 4 to 15 mm Hg; p=0.006).

Difference in SpO2

In this study, the oxygen saturation (SpO2) was unchanged with time during 9 min in N and T groups. The only change we observed was a small reduction of SpO2 at 12 and 15 min in the T group. However, this lower rate did not reach statistical significance. With respect to SpO2, it can be deduced from the results that both approaches are largely similar in terms of oxygenation preservation as the variance was not statistically noteworthy. The slight decrease in SpO2 for the T group at latter stages is not clinically important enough to be of concern and as such, both anaesthetic techniques are overall effective in preserving respiratory function throughout this procedure. Similarly, there were no large and clinically meaningful changes in SpO2 after rebreathing other than posttreatment sedation of around 91% that is insignificant.

Difference in Respiratory Rate (RR)

In the current study, overall mean respiratory rate (RR) remained constant for both groups nerve block N and topicalization T till 12th minute. After 15 minutes the mean RR increased significantly in group T to 20 breaths per minute (SD=4), compared with N at just16 breathes/min (SD-3)]; P<0.05). This difference was statistically noteworthy, with a mean difference of 4 bpm (95% CI:1 to 9; P=0.03).

Cough and Gag Scores: The incidence of higher cough and gag scores (score 3) was notably higher in the T group, with 40% of patients (n=10) experiencing severe responses compared to only 12% (n=3) in the N group. This difference was statistically noteworthy.

Comfort Scores: Patient comfort was rated as good in 32% (n=8) patients within the N group compared to only 8% (n=2) within the T group. The variance was not statistically noteworthy (p=0.03).

The combined analysis of following three parameters highlights the nuanced outcomes of the two anaesthetic techniques:

Intubation Score: The high intubation scores in the T group clearly suggest that airway nerve block is superior in achieving adequate conditions for intubation over topicalization.

Ease of Intubation: As reflected from the intubation score, intubation was significantly better in the nerve block group, indicating that nerve blocks facilitate a smoother intubation process, potentially reducing the stress and effort required by the clinician.

Intubation Time: The less intubation time for the nerve block group suggests that the duration of the procedure is an additional advantage for the nerve block group apart from the understanding that ease of performing the intubation is better with nerve blocks.

Complications: In the present study, none of the patient reported lignocaine toxicity, and gastric Complications. However, airway complications in terms of mouth opening were observed in almost all the patients, with no significant difference (p=0.53).

LIMITATIONS

Airway topicalization – Incidence of incomplete anaesthesia is not well defined. Available evidence suggests that it may be considerable, especially in anatomically less accessible regions of airway, and the technique in question requires careful and often clumsy administraton.

Airway nerve blocks – The procedure is technically demanding and requires a high degree of precision, more sophisticated, and more disorderly, with a higher chance of unintentional intravascular drug injection, hematoma, or nerve damage. Consequently, a skilled doctor and an intuitive grasp of airway anatomy are necessities. (11)

The present study focuses on the effectiveness and complications of airway local anaesthetic nerve blocks in comparison with topicalization during awake fibre-optic bronchoscope naso-tracheal intubation. Both techniques were useful in creating optimal intubation conditions for the patients. Airway nerve blocks had better results in terms of patient’s tolerance, intubation process, time for intubation, and cough and gag reflexes, as well as less variability in the patients heamodynamics.

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