Topical airway anesthesia for awake fiberoptic
intubation: Comparison between airway nerve
blocks and nebulized lignocaine by ultrasonic
nebulizer
Babita Gupta, Santvana Kohli,
Kamran Farooque1,
Gopal Jalwal, Deepak Gupta2,
Sumit Sinha2, Chandralekha
Departments of Anesthesiology
and Intensive Care, 1Orthopedics,
and 2Neurosurgery, All India
Institute of Medical Sciences,
New Delhi, India
A B S T R A C T
Overview: Awake fiberoptic bronchoscope (FOB) guided intubation is the gold standard
of airway management in patients with cervical spine injury. It is essential to sufficiently
anesthetize the upper airway before the performance of awake FOB guided intubation
in order to ensure patient comfort and cooperation. This randomized controlled study
was performed to compare two methods of airway anesthesia, namely ultrasonic
nebulization of local anesthetic and performance of airway blocks. Materials and
Methods: A total of 50 adult patients with cervical spine injury were randomly allocated
into two groups. Group L received airway anesthesia through ultrasonic nebulization
of 10 ml of 4% lignocaine and Group NB received airway blocks (bilateral superior
laryngeal and transtracheal recurrent laryngeal) each with 2 ml of 2% lignocaine and
viscous lignocaine gargles. FOB guided orotracheal intubation was then performed.
Hemodynamic variables at baseline and during the procedure, patient recall, vocal
cord visibility, ease of intubation, coughing/gagging episodes, and signs of lignocaine
toxicity were noted. Results: The observations did not reveal any significant differences
in demographics or hemodynamic parameters at any time during the study. However,
the time taken for intubation was significantly lower in Group NB as compared with the
Group L. Group L had an increased number of coughing/gagging episodes as compared
with Group NB. Vocal cord visibility and ease of intubation were better in patients who
received airway blocks and hence the amount of supplemental lignocaine used was less
in this group. Overall patient comfort was better in Group NB with fewer incidences of
unpleasant recalls as compared with Group L. Conclusion: Upper airway blocks provide
better quality of anesthesia than lignocaine nebulization as assessed by patient recall
of procedure, coughing/gagging episodes, ease of intubation, vocal cord visibility, and
time taken to intubate.
Key words: Airway management, bronchoscopy, laryngeal nerves, lidocaine, nebulizers
Address for correspondence:
Dr. Santvana Kohli,
Department of Anesthesiology and
Intensive Care, All India Institute of
Medical Sciences, New Delhi, India.
E-mail: dr.santvana.kohli@gmail.com
to airway management in most cases of difficult airway,
especially in patients with cervical spine injury. This
technique reduces the risk of neurologic injury before the
onset of surgical procedure.[3] It is essential to sufficiently
anesthetize the upper airway and suppress the gag, swallow
and cough reflexes prior to awake FOB guided intubation
and thus ensure patient comfort.[1,2] This can be achieved
in multiple ways, which can broadly be divided into two
groups: (a) Topical administration of local anesthetic (LA),
or (b) blockade of neural supply to oropharynx and larynx.
Topical administration of LA in the form of sprays, gargles,
lozenges, or impregnated swabs causes fewer trauma to the
oropharyngeal and laryngeal tissues as compared to nerve
blocks. The risk of inadvertent injection into a blood vessel
is also avoided by using this technique. In contrast, nerve
INTRODUCTION
Securing the airway during general anesthesia in patients
with difficult airway poses a risk to the patient and presents
challenges for the anesthesiologists.[1,2] Awake fiberoptic
bronchoscope (FOB) guided intubation is a safe approach
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DOI:
10.4103/1658-354X.144056
O R I G I N A L A R T I C L E
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Gupta, et al.: Comparison between airway blocks and nebulized lignocaine for fiberoptic intubation
Vol. 8 (Supplement 1), November 2014 Saudi Journal of Anesthesia
Page | S16
block techniques typically require a smaller dose of LA
as compared with topical administration of LA, possibly
decreasing the risk of systemic toxicity.
Topical application of LA by nebulization technique is one
of the techniques used to anesthetize the airway. Customary
compressed air driven jet nebulizers atomize only highly
concentrated anesthetics, so that the maximum dose of LA
can be exceeded within a short period of time. Ultrasonic
nebulizer has been designed to deliver liquid medication in
the form of droplets with an average diameter of just 3.5 μm
to the airway. Ultrasonic nebulizers are often used in the
treatment of pulmonary hypertension. Due to the fine mist of
vaporized anesthetics, a remarkably lower dose of lignocaine is
required and hence the probability of toxicity due to overdose
is avoided.[4] It also anesthetizes the trachea beyond glottis.
This randomized controlled study was conducted to assess
and compare the efficacy of ultrasonic nebulization with
nerve block technique to achieve upper airway anesthesia
for awake FOB guided intubation. The findings may
influence clinical practice in the management of the
difficult airway during anesthesia.
MATERIALS AND METHODS
After approval of the protocol by the Institutional
Review Board, 50 adult patients with traumatic cervical
spine injury undergoing cervical spine fixation surgery
were recruited for the study over a period of 12 months.
A written informed consent was obtained from each
patient. Uncooperative patients, those allergic to LA,
asthmatics, epileptics and those with deranged coagulation,
hemodynamic instability, bradyarrhythmias, or infection at
the local site were excluded from the study.
A thorough preoperative evaluation including a complete
airway evaluation (mouth opening, mallampati grading,
thyromental distance, and evaluation of dentition) was
performed. Standard fasting guidelines and anti-aspiration
prophylaxis with tablet ranitidine 150 mg were prescribed.
The patients were explained about the awake FOB guided
intubation during preoperative assessment. Injection
glycopyrrolate 5 μg/kg was given intramuscularly half
an hour before shifting the patient to the operating room
(OR). Inside the OR, standard monitoring, including
electrocardiography (ECG), noninvasive blood pressure
(BP), and pulse oximetry (SpO2) were applied in all patients.
An intravenous (IV) line was secured and ringer lactate
was started. An arterial line was established under local
anesthesia. After recording the baseline heart rate (HR),
BP and SpO2, injection midazolam 20 μg/kg and injection
fentanyl 1 μg/kg were given IV.
The patients were randomly allocated into two groups.
Randomization was done using computer generated tables
of random numbers. Group L (n = 25) received 10 ml of
4% lignocaine by ultrasonic nebulizer (LD 10185, Honsun,
Shanghai, China) for 15 min, and Group NB (n = 25)
received bilateral superior laryngeal nerve and transtracheal
instillation of 2 ml of 2% lignocaine, along with viscous
xylocaine gargles twice. Adequate effect of local anesthesia
was confirmed by heaviness of tongue in Group L patients
and by hoarseness of voice in Group NB patients.
While giving supplemental oxygen through nasal prongs,
FOB guided intubation was performed. Size 8.0 mm
internal diameter endotracheal tube was used for male
patients and 7.5 mm for female patients. Vital parameters
(HR, BP, and SpO2) were also recorded during intubation
and at 1 min and 3 min postintubation. Supplemental LA
was given as 1 ml aliquots of 2% lignocaine through the
working channel of FOB (next aliquot given only after
waiting for 30-60 s). Other parameters such as gag/cough
reflex, cord visibility (relaxed, partially relaxed or adducted
on endoscopic view), and ease of intubation [Table 1]
were also recorded. Any signs of lignocaine toxicity such
as ECG changes, seizures, and bronchoconstriction were
also noted. After the airway was secured, general anesthesia
was administered with propofol 2 mg/kg, and rocuronium
0.6 mg/kg. Postoperatively, patient comfort was assessed
for complete amnesia, partial recall, and unpleasant
memories during awake FOB guided intubation.
All data were tabulated and analyzed statistically. Parametric
values were reported as mean ± standard deviation.
Hemodynamic variables were compared using the unpaired
Student’s t-test. Intubation grades and patient comfort
scores were compared using the Mann — Whitney U test.
Statistical significant value was considered if P < 0.05.
RESULTS
The demographic data [Table 2] showed no significant
differences between the two groups. There was no
statistically significant difference between both groups
at any interval for HR or BP [Figure 1]. Patients in both
Table 1: Grades of intubating condition
Grade of intubating
conditions
Description
Optimal No collision (hold-up) encountered
Suboptimal Hold-up, relieved by rotation of the tube once
Difficult Hold-up, requiring more than one rotation of the tube
or alteration in the patient’s head or neck position
Failure Failure of the attempt at FOB guided tracheal
intubation
FOB: Fiberoptic bronchoscope
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Gupta, et al.: Comparison between airway blocks and nebulized lignocaine for fiberoptic intubation
Saudi Journal of Anesthesia Vol. 8 (Supplement 1), November 2014
Page | S17
Group NB [Figure 2]. It was due to this reason that
supplemental lignocaine had to be used in significantly
more number of patients in Group L as compared with
Group NB (n = 16 in Group L as compared to n = 5 in
Group NB, P = 0.009). The mean supplemental lignocaine
volume used was 1.06 ± 0.87 ml and 0.6 ± 0.64 ml in
Group L and Group NB, respectively. This difference was
statistically significant (P = 0.004). The highest quantity of
supplemental lignocaine used in a single patient was 4 ml
in Group L (n = 1) and 2 ml in Group NB (n = 3).
The vocal cord visibility [Figure 3] was better in Group NB
as compared to Group L (P = 0.006). Only three patients
in Group L had completely relaxed vocal cords as opposed
to 12 patients in Group NB. Partially relaxed vocal cords
were observed in seven patients in Group L and 11
patients in Group NB. Completely adducted vocal cords
were seen in 12 patients in Group L. However, this did not
have much impact on the ease of intubation [Figure 4],
probably because of supplemental LA instillation. There
groups exhibited a slight decrease in SpO2 during the
procedure, but the lowest SpO2 recorded was 92%. All the
patients remained sufficiently awake to cooperate with the
procedure and none of the patients showed any evidence
of lignocaine toxicity.
Awake FOB guided intubation was accomplished in
all patients in both groups and in no patient was the
procedure abandoned due to discomfort. The time taken
to perform FOB guided intubation was less in Group NB
(123.0 ± 46.7 s) as compared with Group L (200.4 ± 72.4 s)
and this was statistically significant [Table 2]. Significantly
more number of patients experienced gag and coughing
during the procedure in Group L as compared with
Figure 1: Comparison of hemodynamic variables between the two
groups at baseline, 1 min and 3 min after intubation
Figure 2: Comparison between the number of patients experiencing
coughing/gagging in each group
Figure 3: Comparison of vocal cord visibility between the two groups
Figure 4: Comparison of the intubating conditions between the two
groups (no failure was encountered)
Table 2: Demographic data and time taken for
FOB guided intubation
Group A Group B P value
Age (years) 39.9±10.4 39.8±8.0 0.964
Sex (male/female) 23/1 21/4 0.171
Weight (kg) 61.4±3.8 57.0±10.0 0.480
Time for FOB (s) 200.4±72.4 123.0±46.7 0.047
FOB: Fiberoptic bronchoscope
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Gupta, et al.: Comparison between airway blocks and nebulized lignocaine for fiberoptic intubation
Vol. 8 (Supplement 1), November 2014 Saudi Journal of Anesthesia
Page | S18
Administration of lignocaine through nebulization for
anesthesia of upper airway and larynx has also been
previously studied. In their study Cullen et al.[6] found
that lignocaine nebulization decreased the discomfort of
nasogastric tube insertion. In 2007, Techanivate et al.[7]
found adequate upper airway anesthesia with 2% lignocaine
nebulization and topical cocaine application to the nose for
fiberoptic nasotracheal application.
In our study, the time taken to perform FOB guided
intubation was significantly more in the nebulization group
as compared to the nerve blocks group. Our results are
contradictory to the randomized double-blinded study
conducted in 1995 by Reasoner et al.,[3] which compared
nebulized lignocaine with airway blocks to aid in FOB guided
intubation in patients with cervical spine instability. The
topical anesthesia group received 20 ml of 4% lignocaine
via nebulization followed by a 3 ml transtracheal injection.
On the other hand, the nerve block group received bilateral
glossopharyngeal and superior laryngeal nerve blocks along
with the transtracheal injection. They found no significant
difference in the time taken to intubate between the groups.
This was probably because nebulization was supplemented
by transtracheal injection of 3 ml lignocaine, which further
improved the quality of anesthesia.
Kundra et al.[8] also compared two methods of anesthetizing
the airway for awake fiberoptic nasotracheal intubation.
One of the groups received 4 ml of 4% lignocaine
through nebulization and the other received airway blocks
(translaryngeal, bilateral superior laryngeal and lignocaine
soaked cotton swabs in the nose). Although the time
taken to intubate was similar in both groups, patients who
received lignocaine nebulization for airway anesthesia had
to undergo significantly higher stress during the insertion of
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.
Patient comfort was better in the nerve blocks group as
compared with the nebulization group in our study, as
deduced by the coughing/gagging episodes as well as the
patient assessment of procedure recall. These findings
are similar to those reported by Graham et al.[9] in 1992.
They compared three different methods to provide airway
anesthesia during FOB. All patients received benzocaine
lozenges, lignocaine sprays for posterior pharynx and
lignocaine jelly for nasal passages along with either 4 ml
of 2.5% cocaine injection through FOB working channel,
transtracheal injection of the same amount of cocaine or
nebulized 4 ml of 4% lignocaine. They reported that the
transtracheal injection of cocaine provided significantly
superior patient comfort and less coughing episodes as
compared with the rest of the techniques. The findings
was no statistical difference in between the two groups
regarding the intubating conditions (P = 0.315). Patient
comfort was also significantly different between the
two groups [Figure 5]. Only six patients in Group L
reported complete amnesia as compared to 13 patients
in Group NB. No patient in Group NB reported recall
of unpleasant memories as compared with six patients
in Group L (P = 0.007).
DISCUSSION
Awake tracheal intubation with the aid of a fiberoptic
device was first described by Murphy in 1967,[5] who used
a choledochoscope to facilitate nasotracheal intubation
in patients with difficult airway. Since then, numerous
subsequent authors have described the anesthetic
techniques and experiences with awake FOB guided
intubation. It offers several advantages over use of FOB
after induction of general anesthesia in patients with
cervical spine instability:
a. Patient remains in a neutral position, minimizing the
risk of neurological deterioration;
b. patient’s neurological status can be assessed after
intubation, and
c. spontaneous ventilation is preserved.[3]
There are multiple ways of anesthetizing the airway
to facilitate the performance of awake FOB guided
intubation. Among them, topical anesthesia with
nebulized LA, gargles, lozenges, sprays, airway blocks and
LA through the working channel of FOB is commonly
used. Although the above-mentioned techniques can
be combined in various ways, we chose two mutually
exclusive techniques to compare their efficacy and patient
comfort. There is a paucity of literature comparing the
efficacy and safety for such methods in a population with
cervical spine fixation surgery.
Figure 5: Comparison between the patient comfort and degree of recall
of events during fiberoptic bronchoscope guided intubation
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Gupta, et al.: Comparison between airway blocks and nebulized lignocaine for fiberoptic intubation
Saudi Journal of Anesthesia Vol. 8 (Supplement 1), November 2014
Page | S19
reported by Reasoner et al.[3] were also similar. Although,
there was no difference in the number of coughing/
gagging episodes between the two study groups, patient
recall of the procedure was more in the nebulization
group. Kundra et al.[8] also reported higher grimace scores,
mean HR and BP during insertion of endotracheal tube
in patients who received lignocaine via nebulization as
compared to nerve blocks. However, the patient comfort
and recall of the procedure were comparable between the
two groups.
In our study, 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. This finding is similar to that observed by Graham
et al.[9] They reported that the bronchoscopist preferred
transtracheal instillation of LA as compared to LA
nebulization or LA instillation through the working port
of FOB. However, Reasoner et al.[3] did not find any
difference in the quality of airway anesthesia between
nebulized LA and nerve blocks as assessed by a blind
observer/bronchoscopist.
Gal[10] reported that lignocaine mist produced as an
aerosol during ultrasonic nebulization causes airway
irritation in subjects as evidenced by coughing. Later
however, it results in bronchodilatation due to its
membrane stabilizing action. No such adverse effects
caused by lignocaine mist were noted in our study.
The maximum total dose of lignocaine used in our study was
400 mg through nebulization. Such a dose of lignocaine has
been safely used and reported for FOB in many previous
studies. In 1997, Parkes et al.[11] used 6 mg/kg of 10%
lignocaine solution through nebulization mask for fiberoptic
intubation. The serum lignocaine levels measured remained
below the accepted threshold of 5 mg/l at all times (highest
levels obtained were 0.45 mg/l). Similarly, Langmack et al.[12]
measured the serum lignocaine levels in 51 asthmatic
volunteers undergoing FOB with topical lignocaine. The
average total dose used was 600 mg (8.2 mg/kg), which
was found to be safe in all patients as assessed by serum
lignocaine concentrations. However, in 1993, Wu et al.[13]
have reported seizures in a patient after administration of
a total dose of 300 mg of topical lignocaine during FOB.
The serum lignocaine concentrations were found to be well
above the acceptable toxic limits. Hence, a constant lookout
for signs and symptoms of lignocaine toxicity is mandatory
while using large doses.
The limitations of our study are that it is an unblinded
study allowing some amount of bias. Furthermore, serum
lignocaine levels were not measured due to nonavailability
of this facility at our center.
Given the results of the study and the above discussion,
the following conclusions may be drawn. The performance
of bilateral superior laryngeal and transtracheal recurrent
laryngeal nerve blocks provides adequate airway anesthesia
to aid in awake FOB guided intubation. Furthermore,
10 ml of 4% lignocaine through ultrasonic nebulizer may
not provide acceptable conditions for bronchoscopy, but
a higher dose might be able to adequately anesthetize
the airway. However, a lower dose of lignocaine through
nebulization along with supplemental lignocaine instillation
through the working channel of FOB might provide
adequate airway anesthesia. More studies need to be
performed to determine the amount of lignocaine, which
can be used for nebulization with serum lignocaine levels.
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How to cite this article: Gupta B, Kohli S, Farooque K, Jalwal G,
Gupta D, Sinha S, C. Topical airway anesthesia for awake fiberoptic
intubation: Comparison between airway nerve blocks and nebulized
lignocaine by ultrasonic nebulizer. Saudi J Anaesth 2014;8:15-9.
Source of Support: Nil, Conflict of Interest: None declared.
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