The efficacy of combined regional nerve blocks in awake orotracheal fiberoptic intubation

Abstract

Aims of Study:

To evaluate the efficacy, hemodynamic changes, and patient comfort during awake fiberoptic intubation done under combined regional blocks.

Materials and Methods:

In the present observational study, 50 patients of American Society of Anesthesiologists ( ASA) Grade I–II, Mallampati Grade I–IV were given nerve blocks - bilateral glossopharyngeal nerve block, bilateral superior laryngeal nerve block, and recurrent laryngeal nerve block before awake fiberoptic intubation using 2% lidocaine.

Results:

Procedure was associated with minimal increases in hemodynamic parameters during the procedure and until 3 min after it. Most of the intubations were being carried out within 3 min. Patient comfort was satisfactory with 90% of patients having favorable grades.

Discussion:

The most common cause of mortality and serious morbidity due to anesthesia is from airway problems. One-third of all anesthetic deaths are due to failure to intubate and ventilate. Awake flexible fiberoptic intubation under local anesthesia is now an accepted technique for managing such situations. In awake patient's anatomy, muscle tone, airway protection, and ventilation are preserved, but it is essential to sufficiently anesthetize the upper airway before the performance of awake fiberoptic bronchoscope-guided intubation to ensure patient comfort and cooperation for which in our study we used the nerve block technique.

Conclusion:

A properly performed technique of awake fiberoptic intubation done under combined regional nerve blocks provides good intubating conditions, patient comfort and safety and results in minimal hemodynamic changes.

INTRODUCTION

The largest class of causes leading to serious morbidity and mortality in anesthesia are from airway complications.[1] It has been estimated that failure to intubate and ventilate constitute one-third of all anesthetic deaths. The incidence of difficult tracheal intubation due to various reasons during routine anesthesia has been estimated to be 3–18%.[2,3] Newer technologies such as video laryngoscopes[4] and fiberoptic intubation[5] in which intubation can be done under vision have been introduced to tackle such situations.

It can be performed either awake or under general anesthesia. The American Society of Anesthesiologists (ASA) and many European authors recommend awake fibreoptic intubation[6] where difficult intubation is anticipated, which can lead to the life-threatening “can't intubate, can't ventilate scenario.” As while awake patient can sustain ventilation and oxygenation without assistance, pharyngeal muscle tone, and phonation are preserved, can swallow its secretions thus keeping the pharynx clear and other alternatives to deal with the difficult airway can still be used.

The stress and discomfort associated may lead to undesirable elevations in the patient's sympathetic and parasympathetic outflow thus it is essential to anesthetize the upper airway adequately and suppress the gag, swallow, and cough reflexes[7] prior to awake fibreoptic bronchoscope (FOB) guided intubation to ensure patient comfort. This can be achieved by either (a) Topical administration of local anesthetic (LA) or (b) blockade of neural supply to oropharynx and larynx. Trivedi and Patil in 2009 conducted a study[8] on 100 patients of laryngeal carcinoma randomly dividing them into two groups receiving combined regional blocks (Group 1) (bilateral glossopharyngeal block, superior laryngeal block, and recurrent laryngeal nerve block) or general anesthesia (Group 2). The results obtained showed a significant increase in mean arterial pressure and pulse rate in Group 2 as compared to Group 1. Postoperative analgesia was higher; patients were less agitated and calm, lesser requirement of postoperative nebulization in Group 1 as compared to Group 2. Gupta et al.[9] in 2014 conducted study on 50 patients with cervical spine injury allocated in two groups one receiving airway anesthesia through ultrasonic nebulization of 10 ml of 4% lignocaine and other receiving airway nerve blocks (bilateral superior laryngeal, transtracheal, and recurrent laryngeal nerve). Nerve block group showed less time taken for intubation, less number of coughing/gagging episodes, more vocal cord visibility and more ease of intubation and less use of extra LA as compared to the nebulized group.

Thus taking into consideration the above studies and the life-saving advantages of awake intubation, especially in difficult airway conditions this study was undertaken to evaluate the intubating conditions, patient comfort, and hemodynamic changes during awake orotracheal fiberoptic intubation done under common regional nerve blocks.

MATERIALS AND METHODS

After approval of the protocol by the ethical committee of the hospital, a prospective observational was done on 50 adult patients with ASA Grade I–II and Mallampati Grade I–IV. A written informed consent was obtained from each patient. Uncooperative patients, those allergic to LAs, epileptics, asthmatics and those with deranged coagulation, hemodynamic instability, bradyarrhythmias, or infection at the local site were excluded from the study.

A preoperative evaluation including a complete airway evaluation (mouth opening, Mallampati grading, thyromental distance, and evaluation of dentition) was performed. Standard fasting guidelines along with anti-aspiration prophylaxis with tablet ranitidine 150 mg were prescribed. The patients were explained about the awake FOB guided intubation during preoperative assessment.

Eutectic mixture of lignocaine and prilocaine cream (2.5 g over 20–25 cm²) was applied on the sites on the skin where the needle had to be inserted for the nerve blocks at least 60 min before the surgery over which occlusive dressing was applied.

On the operation table, standard monitoring, including electrocardiography, noninvasive blood pressure (BP), and pulse oximetry were applied in all patients. An intravenous (IV) line was secured, and ringer lactate was started. After recording the baseline heart rate (HR), BP and oxygen saturation (SpO₂). All patients received injection glycopyrrolate (0.2 mg) IV 5 min before surgery and injection midazolam (1 mg) IV 5 min before surgery and injection butorphanol (2 mg) IV just before intubation.

After the premedication on the operation table four aliquots (40 mg) of 10% lidocaine were sprayed into the oropharynx. After this airway blocks[8] were given to the patient which included.

Bilateral glossopharyngeal nerve block

The glossopharyngeal nerve was anesthetized using extraoral (peristyloid) approach. To perform the peristyloid approach in the glossopharyngeal nerve block, the patient was placed supine, and a line was drawn between the angle of the mandible and the mastoid process. Using deep pressure, the styloid process was palpated just posterior to the angle of the jaw and along this line, and a 1.5″ 23-gauge, the needle was inserted against the styloid process to a depth of 2–2.5 cm. The needle was then withdrawn slightly and directed posteriorly off the styloid process. As soon as bony contact was lost, 2 ml of LA solution 2% lignocaine was injected after careful negative aspiration for blood. Same procedure was repeated on opposite side [Figure 1].

Figure 1.

Glossopharyngeal nerve block

Superior laryngeal nerve block

After topicalization, superior laryngeal nerve block involving bilateral injections at the level of the greater cornu of the hyoid bone were given. The patient's head was extended as much as possible. The patient's skin was cleaned with an appropriate antimicrobial solution (e.g. betadine). The cornu of the hyoid bone was located below the angle of the mandible. The nondominant hand was used to displace the hyoid bone with contralateral pressure, bringing the ipsilateral cornu and the internal branch of the superior laryngeal nerve towards the anesthesiologist.

A 1.5″, 23-gauge needle was inserted in an antero infero medial direction until the lateral aspect of the greater cornu was contacted. The needle was walked downward toward the midline (1–2 mm) off the inferior border of the greater cornu, the thyrohyoid membrane was pierced and the internal branch was blocked. The syringe was then aspirated, and if aspiration was negative for air and blood, 2 ml of LA (2% lidocaine) without epinephrine was injected. Same procedure was repeated on opposite side [Figure 2].

Figure 2.

Superior laryngeal nerve block

Recurrent laryngeal nerve block

Technique for blocking the sensory input of the recurrent laryngeal nerve was the transtracheal block. In this technique, the cricothyroid membrane was located in the midline of the neck. It was located by palpating the thyroid prominence and proceeding in a caudal direction. The cricothyroid membrane was identified as the spongy fibromuscular band between the thyroid and cricoid cartilages. After sterile skin preparation, the overlying skin was anesthetized by raising a small skin wheal of LA. Then a 22-gauge needle on a 10 ml syringe with 3 ml of 2% lidocaine was passed perpendicular to the axis of the trachea piercing the membrane. While the needle was advanced, the syringe was continuously aspirated. The needle was advanced until air was freely aspirated, signifying that the needle was in the larynx. Instillation of LA at this point invariably lead to coughing. Through coughing, the LA was dispersed diffusely blocking the sensory nerve endings of the recurrent laryngeal nerve [Figure 3].

Figure 3.

Recurrent laryngeal nerve block

After this along with supplemental oxygen through nasal prongs, FOB guided orotracheal intubation was performed. If this precipitated coughing, “spray as you technique” using lignocaine 4%, 3–3 ml was sprayed through the working channel of the bronchoscope.

Vital parameters (HR, BP, SpO₂) were recorded at an interval of 1 min until intubation was done followed by every 2 min until 10 min after intubation. Other parameters recorded were intubation score [Table 1], patient's comfort score [Table 2], intubation time, intubation attempts, intraoperative complications, and finally patient's satisfaction score postoperatively [Table 2].

Table 1.

Intubation score assessed during the passage of fibrescope to assess the efficacy of airway blocks

Table 2.

Patients comfort score intraoperatively and satisfaction score postoperatively were assessed using the following scores

Statistical analysis

All data were tabulated and analyzed statistically using software SPSS 17.0 (It was acquired by IBM in 2009 and is one of the brands under IBM Software Group's Business Analytics Portfolio). Patient's characteristics (nonparametric data) were analyzed using the Descriptive analysis. The intra group comparison of the parametric data was done using the “Paired t-test.” P < 0.05 was taken as significant and P < 0.001 as highly significant. Results were analyzed and compared with previous done studies. Power of study was calculated to be above 90%.

RESULTS

There was a gradual increase in HR, systolic BP (SBP), and diastolic BP (DBP) at each minute during FOB [Graph 1]. Maximum changes were seen at the time of intubation from the basal value, which was significant [Table 3] and gradually normalized toward the basal levels after 3^rd–4^th min of intubation and even lesser until 10^th min of monitoring [Table 4].

Graph 1.

Overall there was a gradual increase in the percentage of patients having increases over 15% of basal values in heart rate, systolic blood pressure, diastolic blood pressure, mean arterial pressure at each minute from the time of introduction of fiberoptic bronchoscope until the 4^th-5^th min of bronchoscopy

Table 3.

Hemodynamic changes seen at the time of intubation

Table 4.

Hemodynamic parameters changes seen at 4^th and 10^th min after the intubation

The SpO₂ was well-maintained throughout the procedure of FOB and intubation with insignificant falls seen during intubation.

The mean time taken for endotracheal intubation was 2.12 ± 0.12 min [Graph 2].

Graph 2.

The mean time taken for endotracheal intubation was 2.12 ± 0.12 min. Majority of the patients (n = 32, 64%) were intubated within 2 min

In our study, the efficiency and adequacy of the blocks given were assessed by using Intubation scores which included (a) Vocal cord movements (b) Cough score (c) Limb movements.

In our study of 50 patients 43 (86%) patients had open vocal cords reflecting complete bilateral blockade of the superior laryngeal block with only 5 (10%) patients had open but moving cords reflecting partial block, whereas in 2 (4%), the block was not effective. 40 (80%) patients had no coughing episodes, whereas only two patients out of all had severe coughing due to retained sensitivity of laryngeal surface. 29 (58%) patients did not move their limbs while the procedure was being carried out; 15 (20%) patients moved their arms and legs slightly to moderately. Patients in whom the blocks were not effective were intubated under propofol (2 mg/kg) using FOB.

Further comfort of the patient was assessed using 5-point patient comfort score during the procedure [Graph 3], 3-point comfort score after awake orotracheal intubation [Graph 4] and patient satisfaction score was seen postoperatively also [Graph 5].

Graph 3.

Patient comfort score during the passage of fibrescope showed that 45 patients (90%) were quite comfortable where as 5 patients (10%) showed uncomfortable behavior during the fiberscope procedure

Graph 4.

After the procedure 48 patients (96%) were cooperative and tolerated the tube well, with only 2 patients showing high resistance and intolerance to the endotracheal tube

Graph 5.

Patient satisfaction score showed 45 patients (90%) were satisfied with the procedure whereas only 5 patients (5%) were highly dissatisfied by it

DISCUSSION

The use of fiberoptic tracheal intubation is well-established since its very first description by Murphy in 1967 and has been extensively supported in the literature for managing the difficult airway.[10,11,12,13]

These include, but are not limited, to the following: Compromised airway, restricted or limited neck movement,[14,15] anatomic deformities, and in general anesthesia where intubation may become highly difficult and challenging in the face of the difficult airway. The difficult airway algorithm which includes a call for help in such a scenario may not be applicable in this case as we do not have much time left after paralyzing the patient.[16] An awake fiberoptic intubation allows the patient to maintain the tonicity of the airway muscles providing a degree of safety that may be lost in the anesthetized, paralyzed patient.[17,18] However, this can be highly stressful for these patients and will result in a fighting patient, which may raise the BP to such an extent that it may lead to intracranial hemorrhage in old age patients and risk for pulmonary aspiration.

To lose the patients cooperation can significantly increase the danger of respiratory deterioration and make fiberoptic intubation more challenging. Keys to successful intubation include control of secretions by the use of an antisialagogue, adequate sedation to alleviate anxiety,[19,20] and adequate anesthesia to ensure patient comfort.[21]

Anesthesia for awake fiberoptic intubation can be accomplished by a variety of techniques, which include topical anesthesia with nebulized LA, gargles, lozenges, sprays, airway blocks, and LA through the working channel of FOB. Although the above-mentioned techniques can be combined in various ways, we chose the combined regional nerve block technique exclusively to see its efficacy, hemodynamic effects, and patient comfort.

Through this technique, we blocked the three major reflexes of the patients including gag reflex, cough reflex, and glottis closure reflex by blocking bilateral glossopharyngeal, bilateral superior laryngeal, and recurrent laryngeal nerve, respectively. In our study, we observed an increase in HR, SBP, DBP and mean arterial pressure during the procedure of fiberoptic intubation (maximum seen at the time of tracheal intubation) which later on settled until the 3^rd to 4^th min after intubation was done, which was similar to that observed by Ovassapian et al.[22] while performing nasotracheal intubation in awake patients under LA. In a study conducted by Trivedi and Patil[8] in 2009 in which they evaluated airway blocks versus general anesthesia concluded that hemodynamic changes were less in airway block patients.

The mean time taken for endotracheal intubation was 2.12 ± 0.12 min. A study conducted by Gupta et al.[9] also showed average time of 123.0 ± 46.7 s taken for awake intubation under regional nerve blocks. In our study, the efficiency and adequacy of the blocks given were assessed by using Intubation scores which included (a) Vocal cord movements (b) Cough score (c) Limb movements which showed successful application of block in around 80% of patients. The further comfort of the patient was assessed by using 5-point patient comfort score during the procedure and 3-point comfort score after awake orotracheal intubation.

Kundra et al.[23] in 2000 conducted a study which compared two methods of anesthetizing the airway for awake fiberoptic nasotracheal intubation which included nebulization with 4 ml of 4% lidocaine and the other received airway block (translaryngeal, bilateral superior laryngeal, and lidocaine-soaked cotton swabs in the nose). It was seen that patients who received lidocaine nebulization for airway anesthesia had to undergo significantly higher stress during the insertion of an endotracheal tube through the glottis. The grimace scores, as well as the mean HR and BP in the nebulization group, were significantly higher during endotracheal tube insertion. Gupta et al.[9] conducted a study in 2014 which also showed that patient comfort was better in the nerve blocks group as compared with the nebulization group and also vocal cord visibility and ease of intubation as assessed by the bronchoscopist were better in the nerve block group as compared with the nebulization group. Trivedi and Patil[8] also showed that postoperative analgesia was better, patients were more calm and required less postoperative nebulization who were given airway block as compared to general anesthesia for taking a laryngeal biopsy.

In our study also it was seen that 90% patients were quite comfortable during and even after awake fiberoptic intubation. Graham et al.[24] also reported that the bronchoscopist preferred transtracheal instillation of LA as compared to LA nebulization or LA instillation through the working port of FOB. Postoperatively also patients were asked about their experience with the procedure, using Patient satisfaction score - 45 patients were satisfied with the procedure. Our findings are consistent with the study of Ovassapian et al.,[22] in which 82% of patients had good comfort during awake nasotracheal fiberoptic intubation.

Such airway blocks may be highly useful in the era of fiberoptic intubation for better-operating conditions and postoperative analgesia for the patients in elective, emergency as well as in intensive care settings. Our limitation of the study is like any other regional technique; practice will improve the success rate as well as the ability of the practitioner to provide the blocks. Thus, our clinical study concludes that awake fiberoptic orotracheal intubation done under adequate LA given by combined regional nerve blocks is associated with good intubating conditions and patient comfort with minimal effect on in hemodynamics.

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Conflicts of interest

There are no conflicts of interest