Download Ultrasound guided superior laryngeal nerve block

Anaesth Intensive Care 2010; 38: 946-948
Ultrasound-guided bilateral superior laryngeal nerve block to
aid awake endotracheal intubation in a patient with cervical
spine disease for emergency surgery
S. Manikandan*, P. K. Neema†, R. C. Rathod‡
Department of Anaesthesiology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, Kerala, India
Summary
Ultrasound has been widely used to locate nerves for various nerve blocks. The potential advantages of using
ultrasound imaging for nerve blocks include reduction in the amount of local anaesthetic required, improved success
rate, reduced time to perform the block and reduced complication rate. We describe the successful performance
of ultrasound-guided bilateral superior laryngeal nerve block to facilitate awake fibreoptic intubation in a patient
presenting for emergency surgery on the cervical spine.
Key Words: superior laryngeal nerve block, ultrasound, awake intubation
Ultrasound can be useful to identify and assist in
blocking the superior laryngeal nerves in patients
with difficult neck anatomy undergoing awake
fibreoptic bronchoscope (FOB) intubation. In
addition, ultrasound may reduce the likelihood of
accidental injection into blood vessels in this area
which are particularly numerous.
anaesthetise the larynx, bilateral superior laryngeal
nerve (SLN) block at the level of the greater horn
of hyoid (GHH) was undertaken. Due to soft
tissue oedema of the neck caused by previous
surgery, identification of landmarks was considered
difficult. Hence, we decided to use ultrasound for
identification of the laryngeal nerves.
CASE HISTORY
A 50-year-old male patient (weight 66 kg)
underwent posterior fixation for atlantoaxial
dislocation uneventfully under general anaesthesia.
Two days later he developed sudden onset of
weakness of both lower limbs and required
emergency re-exploration. In the operating room,
with appropriate monitoring, intravenous and radial
artery cannulation were performed under local
anaesthesia. Airway assessment showed mouthopening of less than two fingers. Considering the
immobile upper cervical spine by implants and the
onset of new neurological deficits, awake intubation
using a flexible FOB was planned. Glycopyrrolate
0.2 mg was administered intravenously for its
antisialogogue action. Topical lignocaine 10% was
sprayed over the anterior aspect of his tongue. To
*M.D., D.N.B., P.D.C.C., Associate Professor.
†M.D., Additional Professor.
‡ M.D., Professor and Head of Department.
Address for correspondence: Dr S. Manikandan, B-14, NFQ, SCTIMST,
Poonthi Road, Kumarapuram, Trivandrum-695011, Kerala, India. Email:
[email protected]
Accepted for publication on March 28, 2010.
Figure 1: The initial position of the probe insinuating the submandibular gland (1), lingual artery (2) and hypoglossal nerve (3).
Anaesthesia and Intensive Care, Vol. 38, No. 5, September 2010
Case Report
Figure 2: The second position of the probe insinuating the external
carotid artery (1), superior laryngeal artery (2), superior laryngeal
nerve (3), superior thyroid artery (4), greater horn of hyoid (5).
Technique
The neck area was cleaned with antiseptic
solution. The head was kept in the neutral position.
Ultrasound localisation was performed with the SiteRite™ 5 Ultrasound system (Bard Access Systems,
Inc, Salt Lake City, UT, USA). The Site-Rite™ 5
uses a 5 to 10 MHz linear probe for identification
of structures. The probe was initially placed over
the submandibular triangle just below and parallel
to the mandibular border and adjusted to visualise
the submandibular gland. Along the lower pole
of the submandibular gland arterial pulsations
were identified, which is the lingual artery in the
long axis plane. The lingual artery runs below the
sublingual gland parallel with the hypoglossal nerve
(Figure 1). The probe was moved caudally and
laterally approximately 0.5 cm and adjusted to
visualise the external carotid artery that can be
identified as a round structure with pulsations in the
short axis view (Figure 2). Pulsations of a branch
arising from the external carotid artery running
medially and parallel to the probe can be viewed
at this plane, which is the superior thyroid artery
(STA). The probe was moved slightly medially and
the STA could be seen giving rise to the superior
laryngeal artery (SLA) that runs parallel to the probe,
wth the main artery continuing inferiorly (Figure
Anaesthesia and Intensive Care, Vol. 38, No. 5, September 2010
947
Figure 3: The final position for the placement of local anaesthetic
agent. 1) omohyoid, 2) external carotid artery, 3) greater horn of
hyoid, 4) superior laryngeal artery, 5) superior laryngeal nerve,
6) superior thyroid artery.
3). The greater horn of the hyoid bone could also
be seen as a bright structure medial to the SLA.
Additional confirmation was obtained by moving
the probe medially, which showed the curved bright
image of the hyoid bone. The internal branch of
SLN (ibSLN) runs along with the SLA, just below
the level of GHH. A 22 gauge hypodermic needle
was passed perpendicular to the skin at this point
between the GHH and SLA. Lignocaine 2% 0.75 ml
was injected after negative aspiration of blood, and
the solution was seen spreading in the plane. The
procedure was repeated on the other side. After a
few minutes the patient had voice changes indicating
the onset of the block. The FOB was introduced
and the vocal cords appeared paralysed. The
trachea was intubated successfully without any
discomfort to the patient.
DISCUSSION
Techniques employed to anaesthetise the airway
for awake FOB intubation include topical anaesthesia
combined with bilateral SLN block or lignocaine
nebulisation combined with either ‘spray-as-yougo’ topical anaesthesia or cricothyroid puncture and
instillation of a local anaesthetic drug1. In a recent
study, Xue et al found that with topical application
948
S. Manikandan, P. K. Neema, R. C. Rathod
of either 2 or 4% lignocaine in the spray-as-yougo technique, one could successfully intubate the
trachea using awake FOB. However, they noticed
that 61 to 74% patients had grimace or cough
response during intubation and they attributed this
to inadequate anaesthesia of the airway2. They
suggested that this may be due to non-uniform
spread of the lignocaine and variability in the
absorption of the local anaesthetic agents caused by
oropharyngeal secretions. In a volunteer study,
Woodall et al found increases in blood pressure and
heart rate during awake nasal FOB with the
spray-as-you-go technique combined with nebulised
lignocaine without intravenous sedation3. They also
reported a failure rate of 10% and complications
related to local trauma to the nose. Translaryngeal
instillation of local anaesthetic technique is another
method used for airway anaesthesia. However, translaryngeal block predominantly produces anaesthesia
of infraglottic structures and the trachea; it produces
inadequate anaesthesia of the supraglottic area for
FOB intubation. Moreover, it can be associated with
cough, bleeding and airway compromise1. In
contrast, bilateral SLN block combined with topical
anaesthesia has been found to produce better
haemodynamic stability and patient comfort than
the spray-as-you-go technique4.
The SLN arises from the vagus nerve and descends
posteriorly to the carotid arteries towards the larynx.
The SLN divides into external and internal branches.
The external branch has a motor supply to the
cricothyroid muscle. The internal branch provides
sensory innervation to the base of the tongue,
epiglottis and the mucous membrane of the larynx as
far inferiorly as the vocal folds. The internal branch
passes immediately inferior to the greater horn of
the hyoid bone and approaches the thyrohyoid membrane accompanied by the SLA, a branch of the STA.
The approach to blockade of the ibSLN can be
either anterior or lateral5. The anterior approach
involves identifying the thyroid cartilage incisura
and introducing the needle in a cranial and lateral
direction. In the commonly used lateral approach,
the nerve is blocked by inserting the needle below
and slightly anterior to the GHH. In a large study,
the success of bilateral ibSLN blocks using a lateral
approach combined with topical application of
local anaesthetic was found to be 92%6. The failure
rate could be due to variations in the anatomical
position of SLN with respect to hyoid bone. Furlan
found that the distance between the ibSLN and
GHH varied between 0 to 20.1 mm (mean 2.4 mm,
variance 10.9 mm)5. In a cadaveric study of
structures around the GHH, Lemaire et al found
that the hypoglossal nerve and lingual artery lie
approximately 6.3±1.8 mm superior in the submandibular triangle and the ibSLN lies approximately
9.6±1.7 mm below the GHH7.
Wide variation exists in the origin of the superior
thyroid artery. The STA arises from the bifurcation of
the carotid artery (type I 49.3%), but can arise from
either the common carotid artery (type II 26.6%) or
external carotid artery (type III 23.2%). The origin of
the STA lies approximately within 1.5 cm of the carotid
bifurcation in type II and III8. Despite this variable
origin, the arterial pulsation seen immediately below
the lingual artery pulsations is mainly the STA, which
helps its identification. The SLA is usually the first
branch of STA. Infrequently, it can arise directly
from the external carotid artery (78%) or carotid
bifurcation8. Kiray et al in a cadaveric study found
that the ibSLN is the only nerve to traverse between
the GHH and the thyroid cartilage from lateral to
medial side. It is accompanied by the superior
laryngeal artery9. The position of the SLA is
considered to be a useful landmark for identification
of the ibSLN during surgical dissections10. Similarly,
we have used this anatomical landmark to identify
and successfully block the ibSLN.
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Anaesthesia and Intensive Care, Vol. 38, No. 5, September 2010
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