Anesthesia for Otolaryngologic Surgery Edited by Basem Abdelmalak and D

Cambridge University Press 978-1-107-01867-9 - Anesthesia for Otolaryngologic Surgery Edited by Basem Abdelmalak and D. John Doyle Excerpt More information

Section 1 Introduction Chapter Clinical head and neck anatomy 1 for the ENT anesthesiologist Nicole M. Fowler and Joseph Scharpf

Introduction plan including the use or avoidance of long-acting muscle relaxants for the case. The huddle process also An understanding of anatomy is paramount to the ensures that both the anesthesiologist and surgeon are ability to safely anesthetize the head and neck sur- present and ready to handle any potential periopera- gery patient. In contrast to other patient populations, ' tive complications. The head and neck surgeon the head and neck surgery patient s pathology may should be considered an airway specialist and partner obfuscate normal anatomy and impede or even pre- with the anesthesiologist. vent the anesthesiologist from being able to intubate the patient. Furthermore, recognized anatomic vari- ations may complicate the anesthesiologist's man- Face anatomy agement of the patient. Cooperation among the The basic underlying structure of the face is formed entire operating team is the key to a successful oper- by the skull, facial bones and mandible (Figure 1.1). ation. The surgeon and anesthesiologist must discuss The skull is formed by a series of eight bones: the particular patient's anatomy and specific proced- paired parietal and temporal bones and single frontal, ural needs prior to each case. Potential airway man- occipital, sphenoid and ethmoid bones [1]. The facial agement options such as routine oral intubation, skeleton creates the anterior portion of the skull and nasotracheal intubation, awake fiberoptic intubation includes the orbits, nares, maxilla and mandible. The and even awake tracheotomy must be considered. face is formed by 12 uniquely shaped bones: paired Contemporary technological advances can enhance lacrimal bones, nasal bones, maxillae, zygomatic and this discussion by including photography and video- palatine bones and a single vomer and mandible. The graphy. For example, computerized imaging systems maxillae and mandible support the teeth (Figure 1.1). in use in modern operating rooms can be synchron- The teeth are numbered from superior right to left ized to a server in the otolaryngology clinic to allow and inferior left to right from 1 to 32 for adults and the review of both photographs and videos of lettered A–T in the same order for pediatric primary patients' airways and the extent that they have been dentition. Normal occlusion, also termed class altered through disease progression. While the added I occlusion, is defined by the mesiobuccal cusp of dimension of visual review integrated into the dis- the first maxillary molar impacting the mesiobuccal cussion can be an invaluable adjunct to this team groove of the first mandibular molar [2]. Class II approach, always bear in mind that conditions could occlusion, commonly referred to as retrognathic, have worsened significantly since the imaging was occurs when the mesiobuccal cusp of the first maxil- performed. lary molar impacts mesial to the groove (overbite). Patient safety concerns continue to be increasingly Class III occlusion, commonly referred to as prog- recognized as a vital component of modern health nathic, occurs when the mesiobuccal cusp of the first care. At the authors' institution we perform both an maxillary molar impacts distal to the groove operative “huddle” with the patient awake and a sur- (underbite). gical “time-out” prior to performing any procedure. Trauma resulting in facial fractures can compli- The huddle is an ideal time to review the intubation cate intubation. Mandibular fractures are usually

Anesthesia for Otolaryngologic Surgery, ed. Basem Abdelmalak and D. John Doyle. Published by Cambridge University Press. 1 © Cambridge University Press 2013.

© in this web service Cambridge University Press www.cambridge.org Cambridge University Press 978-1-107-01867-9 - Anesthesia for Otolaryngologic Surgery Edited by Basem Abdelmalak and D. John Doyle Excerpt More information

Section 1: Introduction

(A)

Frontal bone

Parietal bone

Glabella Supraorbital notch Greater wing of sphenoid bone Orbital surface of frontal bone Nasal bone Temporal fossa Lacrimal bone Greater wing of sphenoid bone Inferior orbital fissure Perpendicular plate of ethmoid bone Zygomatic bone Infraorbital foramen Maxilla Vomer Mastoid process Temporal bone Ramus Anterior nasal spine

Alveolar processes Mandible Angle of mandible Mental foramen Mental protuberance

Figure 1.1. Anterior cranium and overlying facial topography. Artwork created by Emily Evans.

paired and occur on opposite sides of the mandible. preparing to intubate a patient with a mandibular Fractures of the maxillae are commonly categorized fracture carefully evaluate the teeth as the tooth based on the Le Fort classification [3]. Le Fort roots are areas of bony weakness and may be I fracture is a horizontal fracture of the maxilla involved in the fracture. Orbital fractures com- superior to the alveolar process and the pterygoid monly of the inferior orbital rim may result in plates of the sphenoid. Le Fort II fractures involve entrapment of the extraocular muscles; particularly an oblique fracture of the maxillary sinus and hori- theinferiorrectuscanresultinactivationofthe zontal fractures of the lacrimal and ethmoid bones oculocardiac reflex [4]. This reflex between the acrossthenoseresultinginanunstablemidface trigeminal and vagus nerve can result in bradycar- where the hard palate is separated from the skull. dia, a junctional rhythm, asystole or even death. Le Fort III fractures involve a horizontal fracture Treatment includes surgical release of the muscle, through the superior orbital fissure, the ethmoid atropine or glycopyrrolate. and nasal bones through the greater wing of the Face shape is determined by the bones, muscles sphenoid bone and frontozygomatic sutures. This and subcutaneous tissue (Figure 1.2). The muscles of may occur in conjunction with fractures of the facial expression lie within the subcutaneous tissue. zygomatic arches resulting in an unstable midface The muscles of facial expression are innervated by where the maxilla and zygomatic bones are no the facial nerve. They generally attach to bone or longer attached to the skull. If significant facial fascia and act by pulling the skin to create facial trauma has occurred the patient may have resulting expression. When performing surgery around the skull and brain injuries which may supersede treat- facial nerve or its branches, including otologic pro- ment of the facial injuries. Depending on the sever- cedures, parotidectomy, submandibular gland exci- ity of the trauma, the airway may have been triaged sion and neck dissections, neuromuscular blockage is in the field and an emergency cricothyroidotomy contraindicated and all or part of the ipsilateral face 2 or tracheotomy may have already been performed may need to be included in the surgical field for if an oral intubation was not possible. When monitoring.

Chapter 1: Clinical head and neck anatomy for the ENT anesthesiologist

(B) Incisors

8 9 7 10 6 11 Canine Incisors 5 12 Bicuspids E F 4 13 D G Maxilla Canine C H 3 14

B I 2 15 Molars Maxilla Molars A J 1 16

T K 32 17 Molars Mandible S L 31 18 Molars Mandible Canine R M 30 19 Q N P O 29 20 Bicuspids Incisors 28 21 27 22 Canine 26 23 25 24

Incisors Figure 1.1. (cont.)

Ear anatomy containing the saccule and utricle, which along with the semicircular canals control balance. The labyrin- The ear is divided into three parts: the external, thine and tympanic portions of the facial nerve lie in middle and internal. The external ear (Figure 1.3) close proximity to these structures and may be dehis- includes the external auditory canal to the tympanic cent, necessitating lack of neuromuscular blockade membrane. This is approximately 2–3 cm in length. and close monitoring of facial movements during The lateral one-third is cartilaginous and the inner certain otologic procedures. two-thirds is composed of skin directly on the periosteum of the tympanic portion of the temporal bone. The middle ear is an air-filled cavity containing the Nose anatomy three auricular ossicles – the malleus, incus, and The nose projects from the face largely based on the stapes. The middle ear pressure is regulated by the amount of cartilage. Extending from the nasal bone eustachian tube, which opens into the nasopharynx. are the upper and lower lateral cartilages. Stability is The inner ear is contained within the petrous portion provided from the underlying nasal septum which is of the temporal bone and includes the cochlea, vesti- also composed of both bone and cartilage. The pos- bule and semicircular canals. The cochlear hair cells terior bony septum is formed from the perpendicular activate the cochlear nerve, resulting in hearing trans- plate of the ethmoid and vomer but the majority of 3 mission. The vestibule is a small oval chamber the septum, the anterior septum, is the quadrangular

Section 1: Introduction

Frontalis

Temporalis

Procerus Orbital part Orbicularis oculi Palpebral part

Levator labii superioris Nasalis aleque nasii Zygomaticus minor Levator labii superioris Zygomaticus major

Orbicularis oris Risorius

Masseter Depressor anguli oris Depressor labii inferioris

Sternocleidomastoid Mentalis

Platysma

Figure 1.2. Muscles of facial expression. Artwork created by Emily Evans.

cartilage. The nasal ala are supported by U-shaped supply. The anterior nasal septal area is referred to alar cartilage which is free and mobile, allowing the as Kiesselbach's plexus and is the site of a capillary dilatation or constriction of each nostril. In prepar- anastomosis from the sphenopalatine artery, anterior ation for a nasotracheal intubation or a fiberoptic and posterior ethmoid arteries, greater palatine artery intubation the nares should be examined for any and the superior labial artery. Any object placed into septal deviation. The degree and site of deviation the nose should be directed along the floor of the may help decide which nostril to use for the intub- nose, which is wider than the roof. In preparation 4 ation. Care must be taken when placing any foreign for any nasal manipulation the nasal mucosa should object into the nose because of its robust blood be treated with a vasoconstrictor and anesthetic.

Chapter 1: Clinical head and neck anatomy for the ENT anesthesiologist

Figure 1.3. External ear structure. Artwork created by Emily Evans. Helix Scaphoid fossa Triangular fossa Crura of antihelix

Antihelix Concha Entrance to external Tragus auditory meatus Intertragic incisure Antitragus

Lobule of ear

A vasoconstrictor such as phenylephrine or oxyme- process of the maxilla and the horizontal plate of the tazoline will act on the erectile tissues of the nasal palatine bone. Figure 1.5 shows a rare primary palatal mucosa and result in decongestion and opening tumor. Tumors are very friable and will bleed easily of the nasal passages. If profuse bleeding occurs so in this patient great care was taken to avoid any pressure should be applied, and medications such manipulation of the palate. The retromolar trigone is as oxymetazoline (Afrin), phenylephrine or an epi- a triangular area just anterior to the ascending ramus nephrine-soaked pledget can be placed into the of the mandible. A triangle is drawn with its medial nares. Following successful nasotracheal intubation aspect coinciding with the anterior tonsillar pillar, the extreme care must be taken to position the nasotra- base being across the mandibular alveolus posterior to cheal tube such that it is not applying pressure to the the last molar and its apex being the coronoid process. nasal alar skin. Even slight pressure can result in In this area the mucosa is tightly adherent to the necrosis of the alar skin. Within each nostril are the ascending ramus of the mandible. Carcinomas origin- three turbinates, inferior, middle and superior, ating in this region tend to invade the mandibular which increase the surface area for humidification periosteum and medial pterygoid muscle causing sig- and warming of the inspired air. The paranasal nificant trimus. Referred otalgia is also a common sinuses are air-filled spaces extending into the symptom due to innervation by the mandibular frontal, ethmoid, sphenoid and maxillary bones. branch of the trigeminal nerve, the lesser palatine Since the advent of the endoscope much of rhinology nerve and the glossopharyngeal nerve. The has become endoscopic. circumvallate papillae and terminal sulcus divide the tongue into an anterior two-thirds and posterior one- third. The anterior two-thirds of the tongue can Mouth anatomy largely be easily visualized by the patient and The mouth is subdivided into the oral cavity and the clinician. Patients will routinely present with a small oropharynx. The oral cavity begins at the skin– non-healing ulcer or sore lesion. The oral tongue is vermilion junction of the lips and extends posteriorly composed of three extrinsic tongue muscles: the to the junction of the hard and soft palate superiorly genioglossus, hyoglossus and styloglossus muscles and to the line of the circumvallate papillae on the (Figure 1.6; Table 1.1a). In combination with the tongue inferiorly. The oral cavity therefore includes intrinsic tongue musculature these muscles assist with the lips, buccal mucosa, maxillary and mandibular speech articulation and deglutition. The tongue mus- alveolar ridges/teeth/gingival, floor of the mouth, culature is innervated by the hypoglossal nerve hard palate, the retromolar trigone and the anterior (CNXII). Taste to the anterior oral tongue is supplied oral tongue (Figure 1.4). The hard palate forms the by the lingual nerve (CNV3) having received fibers roof of the mouth and separates the oral cavity from from the chorda typani nerve. As these nerve fibers 5 the anterior nasal vault. It is composed of the palatine travel with those to the external ear, external auditory

Section 1: Introduction

Vallecula

Epiglottis Foramen cecum Median glossoepiglottic fold Palatopharyngeal arch Palatopharyngeal muscle Lateral glossoepiglottic fold Palatine tonsil Palatoglossus muscle Root of tongue Palatoglossal arch Lingual tonsil and lingual follicles Terminal sulcus

Vallate (circumvallate) papillae

Foliate papillae Filiform papillae

Body of tongue Median sulcus

Fungiform papillae

Apex of tongue

Figure 1.4. Dorsal tongue anatomy. Artwork created by Emily Evans.

pierced by the submandibular gland duct (Wharton's duct) bilaterally on either side of the lingual frenulum. The length and site of attachment of the lingual frenulum on the ventral surface of the tongue can affect tongue protrusion. Tethering of the tongue is termed ankyloglossus and can be surgically cut if it affects speech articulation or feeding as an infant. Odontogenic infections can become life-threatening if they spread into the submental or submandibular spaces. Ludwig's angina is a severe infection involving the floor of mouth. As the infection and swelling worsens the tongue is pushed posteriorly and superiorly, causing respiratory obstruction. The patient may have marked trismus in addition to odynophagia Figure 1.5. Photo of primary palatal tumor. Photo courtesy of and may have dysphagia to the extent that they Dr. Joseph Scharpf. cannot tolerate their own secretions. Infections in this space are considered an airway emergency and may canal and tympanic membrane referred otalgia is a require an awake tracheotomy for management. common presenting symptom with tongue cancers. Complete airway obstruction is the most frequent Lateral tongue cancers drain to the ipsilateral level IB cause of death from this disease [2]. The oropharynx or II nodes. The medial tongue may drain directly to extends from an imaginary line extending back from level III. The tip of the tongue drains to level IA. The the hard palate superiorly to the level of the hyoid 6 floor of the mouth is the mucosa lying between the bone inferiorly and includes the soft palate, tonsils, mandibular alveolus and the oral tongue. This area is base of tongue and posterior pharyngeal wall. This

Chapter 1: Clinical head and neck anatomy for the ENT anesthesiologist

Table 1.1a. Muscles of the soft palate. Reproduced with permission from Olson TR, Pawlina W. ADAM Student Atlas of Anatomy. Cambridge University Press, 2008

Muscle Superior attachment Inferior Innervation Main actions attachment Levator veli Cartilage of auditory tube Palatine Pharyngeal br. Of Elevates soft palate during palatini and petrous part of aponeurosis vagus n. via pharyngeal swallowing and yawning temporal bone plexus (CN X) Tensor veli Scaphoid fossa of medial Medial pterygoid n. Tenses soft palate and palatini pterygoid plate, spine of (a br. Of the opens cartilagenous part of sphenoid bone & cartilage mandibular n.) via auditory tube during of auditory tube otic ganglion (CN V3) swallowing and yawning Palatoglossus Palatine aponeurosis Side of Pharyngeal br. Of Elevates posterior part of tongue vagus n. (CN X) via tongue and draws soft pharyngeal plexus palate onto tongue Palatopharyngeus Hard palate and palatine Lateral wall Tenses soft palate and pulls aponeurosis of pharynx walls of pharynx superiorly, anteriorly, and medially during swallowing Musculus uvulae Posterior nasal spine and Mucosa of Shortens uvula and pulls it palatine aponeurosis uvula superiorly

Cartilaginous part of auditory tube (eustachian tube)

Levator veli palatini Salpingopharyngeus Soft palate Tensor veli palatini Palatoglossus Superior pharangeal constrictor Longitudinal muscle of tongue Stylopharyngeus Stylohyoid ligament Styloglossus Palatopharyngeus Hyoglossus Middle pharangeal constrictor Genioglossus Hyoid bone Geniohyoid Mylohyoid Thyrohyoid membrane Inferior pharangeal constrictor Thyroid cartilage

Cricothyroid

Tracheal cartilage Esophagus

Figure 1.6. Sagittal view of the pharyngeal musculature. Artwork created by Emily Evans.

area is much more difficult to visualize for both the 1.1b and Table 1.2). Posterior to the buccopharyngeal patient and the clinician. The pharyngeal walls are fascia is the retropharyngeal space. This potential composed of mucosa, submucosa, pharyngobasilar space exists between the buccopharyngeal fascia and fascia, the superior and upper middle constrictor the alar layer of the prevertebral fascia (Figure 1.7). 7 muscle, and buccopharyngeal fascia (Figure 1.7; Table This space extends from the skull base to the superior

Section 1: Introduction

Table 1.1b. Extrinsic muscles of the tongue. Reproduced with permission from Olson TR, Pawlina W. ADAM Student Atlas of Anatomy. Cambridge University Press, 2008

Muscle Stable Mobile attachment Innervation Actions attachment Genioglossus Sup. part of Dorsum of tongue Hypoglossal Protrudes, retracts and depresses mental spine of and body of hyoid n. CN XII tongue; its post. part protrudes mandible bone tongue Hyoglossus Body and greater Side of tongue Depresses and retracts tongue horn of hyoid bone Styloglossus Styloid process Side and inf. aspect Retracts tongue and draws it up and stylohyoid lig. of tongue to create a trough for swallowing Palatoglossus Palatine Side of tongue Pharyngeal br. CN Elevates post. part of tongue aponeurosis of X and pharyngeal soft palate plexus

Thyroid cartilage Anterior jugular vein Vocal folds Sternothyroid Cricoid cartilage Sternohyoid Esophagus Omohyoid Internal jugular vein

Sternocleidomastoid Internal carotid artery Vagus nerve Longus colli Lymph nodes Anterior scalene Vertebral artery and vein Middle scalene Annulus fibrosus Posterior scalene Nucleus pulposus Levator scapulae Spinal cord Splenius capitis C5 vertebra

Superficial cervical fascia Trapezius

Fascial layers;

Superficial (investing) layer Fascia of infrahyoid muscles Pretracheal layer of deep cervical fascia

Carotid sheath Prevertebral layer

Figure 1.7. Divisions of the cervical fascia. Artwork created by Emily Evans.

Chapter 1: Clinical head and neck anatomy for the ENT anesthesiologist

Table 1.2. Pharyngeal muscles Reproduced with permission from Olson TR, Pawlina W. ADAM Student Atlas of Anatomy. Cambridge University Press, 2008

Muscle Lateral attachments Medial Innervation Main actions attachments Circular pharyngeal muscles Superior constrictor Pterygoid hamulus, Median raphe of Pharyngeal and sup. Constrict wall pterygomandibular raphe, pharynx and laryngeal brr. of of pharynx post. end of mylohyoid line pharyngeal tubercle vagus n. [CN X] during of mandible and side of through pharyngeal swallowing tongue plexus Middle constrictor Stylohyoid lig. and greater and lesser horns of hyoid bone Inferior constrictor Oblique line of thyroid Median raphe of Elevate cartilage and side of cricoid pharynx pharynx and cartilage larynx during Longitudinal pharyngeal muscles swallowing, Palatopharyngeus Hard palate and palatine Post. border of speakinga aponeurosis lamina of thyroid cartilage and side of pharynx and esophagus Salpingopharyngeus Cartilaginous part of Blends with auditory tube palatopharynegeus Stylopharyngeus Styloid process of temporal Post. and sup. Glossopharyngeal bone Borders of thyroid n. [CN IX] cartilage with palatopharynegus m. a The salpingopharyngeus muscle also opens the auditory tube.

mediastinum. Contingent upon the patient, his or her superficial plane creating an irregularity to the clinical history, and the location of a retropharyngeal surface. Alternatively, base of tongue tumors may space abscess in relation to the great vessels (carotid grow to very large sizes with minimal symptoms. artery, internal jugular vein), the abscess may be Patients with a large base of tongue tumor may be amenable to transoral drainage versus a more trad- able to maintain their airway but extreme caution itional transcervical drainage. The tonsils are housed should be taken prior to induction. An awake trache- within a fossa created by two muscles, the anterior otomy should be considered based on the anesthesiol- tonsillar pillar formed from the palatoglossus muscle gist's experience and comfort with awake fiberoptic and the posterior tonsillar pillar by the palatopharyn- intubation. geal muscle. A small primary tonsillar or base of The throat or pharynx is subdivided into the tongue tumor may be asymptomatic and present with larynx and the hypopharynx. The larynx is further metastatic cervical lymphadenopathy. Careful exam- subdivided into three spaces: the supraglottis, ination of the oral excursion is advised in any patient glottis and subglottis. Furthermore the larynx is com- with a tonsillar tumor as invasion into the lateral posed of nine cartilages joined by ligaments and pterygoid muscle may result in trismus, which will membranes: three single cartilages: thyroid, cricoid not improve with muscular relaxation. The soft palate and epiglottic; and three paried cartilages: arytenoid, is composed of the levator veli palatini, tensor veli corniculate and cuneiform (Figure 1.8). The largest of palatini, musculus uvulae and tonsillar pillars muscles the cartilages, the thyroid cartilage, was so named as above. The base of the tongue extends from from the Greek word thyreos, or shield, due to its the circumvallate papillae to the glossoepiglottic fold. shield-like appearance and its main function being 9 The lingual tonsils are found laterally and lie in a that of protection of the vocal cords. It is composed

Section 1: Introduction

Epiglottis Thyroid cartilage Vestibular folds Vocal folds Rima glottidis Corniculate and cuneiform tubercles Cricoid cartilage Superior

Lesser horn of hyoid bone Hyoid bone Greater horn of hyoid bone Epiglottis Superior horn of thyroid cartilage

Aryepiglottic muscle Laryngeal prominence Arytenoid cartilage Thyroid cartilage Oblique arytenoid Transverse arytenoid Inferior horn of thyroid cartilage Posterior arytenoid Cricoid cartilage Lamina of cricoid cartilage Cricothyroid

Tracheal cartilage

Posterior Anterior Figure 1.8. Laryngeal skeleton and musculature. Artwork created by Emily Evans.

of two large plate-like laminae which fuse in the to move medially and laterally, as well as tilt anteri- midline forming a prominent V, which in men is orly and posteriorally. The vocal ligament is the skel- termed the “Adam's apple”. Inferior to the thyroid eton on which the vocal cords form and extends from is the cricoid cartilage, which is shaped as a signet ring the thyroid cartilage to the arytenoid cartilages. The and is the only complete cartilaginous ring in the supraglottis begins at the top of the epiglottis to the airway. In women the cricoid cartilage is the most ventricles. This includes the epiglottis (both lingual prominent cartilaginous landmark. The cricothyroid and laryngeal surfaces), arytenoids, aryepiglottic folds membrane bridges the gap between the thyroid and (AE folds) and false vocal cords. The epiglottis is a cricoid cartilages. This cricothyroid space is easily heart-shaped elastic cartilage which is pedicled off palpable as a soft spot either inferior to the thyroid the thyroid cartilage extending superiorly. The epi- cartilage (in men) or immediately superior to glottis may be omega-shaped, retroflexed or floppy the prominent cricoid cartilage (in women). This is and may decrease the ability to visualize the vocal the site of the most superficial aspect of the cords on intubation (depending on intubation tech- larynx that is externally accessible. An emergency nique). Sensation of the supraglottis is supplied by the cricothyroidotomy utilizes these critical features in internal branch of the superior laryngeal nerve. Figure an airway emergency. The two cartilages articulate 1.9A is a drawing of the laryngeal complex with a at the cricothyroid joint. This joint allows rotation supraglottic mass centered in the epiglottis. Safe of the thyroid cartilage, resulting in changes in the intubation techniques include an awake fiberoptic vocal cord length and tension and ultimately intubation. Figure 1.9B is a picture of an actual laryn- changes in vocal pitch. Posteriorly the cricoid cartil- geal complex having been removed as a total laryn- 10 age articulates with the arytenoid cartilage, forming gectomy specimen for a patient with an extensive the cricoarytenoid joint, which allows the arytenoids supraglottic tumor. The glottis includes each true