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Anatomy for the Anesthetist

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Title: Anatomy for the Anesthetist


1
Anatomy for the Anesthetist
  • Marianne Cosgrove,
  • CRNA, DNAP, APRN

2
Components of the Respiratory System
  • The nose
  • The pharynx
  • The larynx
  • The trachea
  • The bronchi
  • The lungs

3
Conducting Portion of the Respiratory System
  • nasal cavities
  • oral cavity
  • pharynx
  • larynx
  • trachea
  • bronchial tree

A.K.A. dead space
4
Lining of the Respiratory Tract
  • Nonciliated stratified squamous epithelium
  • anterior nose, oropharynx, laryngopharynx
  • Ciliated pseudostratified squamous epithelium
  • posterior nose, nasopharynx, laryngeal mucosa
    above cords
  • Ciliated pseudostratified columnar epithelium
  • larynx below cords, trachea, bronchiolar tree
  • Nonciliated cuboidal epithelium
  • terminals and respiratory bronchioles

5
The Nose and Sinuses
  • The external nose
  • The internal nose
  • bony septum
  • nasal turbinates
  • posterior nares
  • The paranasal sinuses
  • maxillary
  • frontal
  • sphenoid
  • ethmoid

6
Functions of the Nose
  • Warms inspired air
  • Humidifies air
  • Cleans inhaled air
  • Organ of olfaction
  • Resonator for speech

7
The Pharynx
  • a musculomembranous tube extending from the
    undersurface of the skull to the level of C6 and
    lower border of the cricoid cartilage where it is
    continuous with the esophagus.

8
The Pharynx
  • Divisions
  • nasopharynx
  • oropharynx
  • laryngopharynx
  • Innervation
  • sensory
  • via glossopharyngeal (cranial nerve IX)
  • motor
  • via vagus (cranial nerve X)
  • Primary motor function
  • swallowing

9
Divisions of the Pharynx
  • nasopharynx
  • Behind posterior nares and above soft palate
  • oropharynx
  • Extends from the soft palate to the base of the
    tongue

10
Divisions of the Pharynx contd
  • laryngopharynx
  • Extends from the base of the tongue to the
    opening of the esophagus
  • Contains the landmarks for endotracheal
    intubation epiglottis, aryepiglottic folds,
    arytenoid cartilages

11
Landmarks for Intubation
12
Esophagus
  • upper 1/3 striated muscle
  • voluntary
  • airway protection against regurgitation via the
    cricopharyngeus muscle (A.K.A. upper esophageal
    sphincter (UES))
  • motor innervation via the RLN
  • lower 2/3rds
  • involuntary tone/contraction under ANS control
  • distal 3-5 cm ? lower esophageal sphincter (LES)
  • A functional structure may be manually opened
    with 18 cm H2O pressure

13
Classifications of the Airway
Mallampati
Cormack-Lehane
14
The Larynx consists structurally of a
framework of articulating cartilages linked
together by ligaments which move in relation to
each other by the action of laryngeal muscles.
15
The Larynx
  • Location
  • adult
  • anterior neck at the level of C4-6
  • child
  • anterior neck at the level of C3-5

16
The Larynx
  • Blood supply
  • Arterial
  • subclavian artery to inferior thyroid artery to
    inferior laryngeal artery
  • Venous
  • inferior laryngeal vein to brachiocephalic vein
    to SVC

17
The Laryngeal Cartilages
  • Singular cartilages
  • thyroid
  • cricoid
  • epiglottis
  • Paired cartilages
  • arytenoids
  • corniculates
  • cuneiforms

18
Thyroid Cartilage
  • Largest cartilage
  • Two broad sheets of cartilage which unite in a V
    shape anteriorly to form the Adams Apple
  • Attached to the hyoid bone by the thyrohyoid
    membrane
  • Attached to the cricoid cartilage by the
    cricothyroid membrane
  • Provides the anterior attachment for the vocal
    cords

19
Cricoid Cartilage
  • Consists of the only complete ring in the larynx
    which broadens into a plate like structure on the
    posterior aspect A.K.A. The Signet Ring
    Cartilage
  • forms the inferior and posterior borders of the
    larynx
  • Is the narrowest portion of the pediatric airway

20
Epiglottis
  • Leaf like, elastic
  • Projects obliquely upward behind the tongue and
    in front of the entrance to the larynx
  • Functions to cover the glottic opening to prevent
    entrance of solids and liquids into the airway
    during swallowing
  • Attached to the posterior surface of the thyroid
    cartilage above the vocal cords
  • First cartilage encountered during laryngoscopy

21
Arytenoid Cartilages
  • Pyramidal in shape sit on cricoid cartilage
  • Each has a muscular process which is the
    insertion of the posterior and lateral
    cricoarytenoids
  • Each has a vocal process which is the posterior
    attachment of the vocal cords

22
Corniculate Cartilages
  • Cone shaped structures situated in posterior part
    of the aryepiglottic folds
  • Each is attached to the apex of an arytenoid
    cartilage

23
Cuneiform Cartilages
  • Elongated structures located slightly posterior
    to the corniculates at the base of the epiglottis

24
C3
C4
C6
The Laryngeal Cartilages
Netter, Plate 71
25
Other Laryngeal Structures
  • Aryepiglottic folds
  • Ventricular folds (false vocal cords)
  • Vocal folds (true vocal cords)
  • The glottis
  • The rima glottis is the narrowest portion of the
    adult airway
  • cricothyroid membrane
  • palpated between the lower border of the thyroid
    cartilage and the cricoid ring
  • allows for easy surgical access to the airway via
    cricothyrotomy in cant ventilate, cant
    intubate scenario

26
Muscles of the Larynx muscle
action effect
Posterior cricoarytenoids (2) Rotate arytenoids outward ABduction (widens rima)
Lateral cricoarytenoids (2) Rotate arytenoids inward ADduction (approximates vocal cords)
Transverse arytenoid (1) Approximate arytenoids ADduction (approximates vocal cords)
Thyroarytenoids (2) Draw arytenoids forward Relaxes and shortens cords
Cricothyroids (2) Draw up arch of cricoid and tilt lamina back Tenses and elongates cords
27
Posterior, Lateral Views of Laryngeal Muscles
Netter, Plate 72
28
Lateral Dissection of Laryngeal Muscles
Netter, Plate 72
29
Superior View of Laryngeal Muscles
Netter, Plate 73
30
Action of Posterior and Lateral Cricoarytenoids
Netter, Plate 73
31
Action of Cricothyroid Muscles
Netter, Plate 73
32
Action of Transverse Arytenoid, Thyroarytenoid
Muscles
Netter, Plate 73
33
Innervation of the Larynx
  • Superior laryngeal nerve
  • A branch of the vagus nerve contains internal
    and external branches
  • Internal branch supplies sensory innervation
    above the vocal cords
  • stimulation may precipitate
  • laryngospasm
  • External branch supplies motor innervation to the
    cricothyroid muscles

34
Innervation of the Larynx
  • Recurrent laryngeal nerve
  • A branch of the vagus nerve
  • Supplies motor innervation to all muscles of the
    larynx except the cricothyroid muscles
  • Supplies sensory innervation to the larynx below
    the vocal cords
  • May be damaged during thyroid/parathyroid surgery

35
Damage to the Recurrent Laryngeal Nerve
  • Unilateral transection hoarseness
  • Bilateral damage from ischemia complete airway
    obstruction from laryngospastic cords
  • Bilateral transection flaccid vocal cords
  • May have some passage of air

36
Laryngeal Nerves
Netter, Plate 74
37
The Trachea
  • Cartilaginous and membranous tube extending from
    the vocal cords to the carina to form the right
    and the left mainstem bronchi
  • Lies anterior to the esophagus and is protected
    anteriorly with cartilaginous rings
  • Posterior wall is membranous
  • The carina lies at the level of T5

38
Airway Measurements
female
male
Incisors to vocal cords 10-14 cm 12-16 cm
Incisors to carina 24-26 cm 26-28 cm
39
The Bronchi
  • Mainstem (A.K.A primary bronchus)
  • Right
  • Shorter, wider, and less acute angle off trachea
  • In adults, forms a 25 degree angle
  • In children less than 3 years old, forms a 50
    degree angle
  • Divides into 3 lobar branches
  • Inhaled foreign bodies are more likely to enter
    the R mainstem bronchus

40
The Bronchi
  • Mainstem (A.K.A primary bronchus)
  • Left
  • Longer, narrower, more horizontal than right
  • In adults and children, forms a 40-60 degree
    angle off trachea
  • Divides into two lobar branches

41
The Tracheobronchial Tree, Respiratory
Bronchioles, and Alveoli
  • Continued branching produces
  • Segmental bronchi
  • Small bronchi
  • Bronchioles
  • Terminal bronchioles
  • Respiratory lobules

42
The Terminal Bronchioles
  • The tracheobronchial tree ends at the 16th level
    from the trachea at the level of the terminal
    bronchioles
  • Diameter is lt1 mm, cilia disappears, cartilage is
    absent
  • This marks the end of anatomic dead space

43
Anatomic Dead Space
  • Equal to approximately 1cc/lb in both adults and
    children
  • Examples
  • 70 Kg pt 155 lbs
  • Approximate anatomic dead space 155 cc
  • 4 kg infant 9 lbs
  • Approximate anatomic dead space 9 cc

44
The Respiratory Lobule
  • Comprised of
  • respiratory bronchiole
  • alveolar duct
  • alveolus (air sac)

45
The Respiratory Bronchiole
  • Where actual respiratory exchange begins
  • Muscle layer of bronchial tree is thickest here
    (relatively speaking)
  • Forms a thin band around the openings of the
    alveolar ducts
  • No muscle is found beyond this point

46
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47
Classification of airways by order of
branchingCommon name
Generation of airway
Trachea 0
Main bronchi 1
Lobar bronchi 2-3
Segmental bronchi 4
Small bronchi 5-11
Bronchioles, terminal bronchioles 12-16
Respiratory bronchioles 17-19
Alveolar ducts 20-22
Alveolar sacs 23
48
Trachea and Major Bronchi
49
The Lungs
  • Lie free in the pleural cavity attached only at
    the hilum
  • The bronchi, major vessels, and lymphatics enter
    and leave here
  • Each lung has a concave base
  • Rests upon the diaphragm
  • Each lung has an apex

50
The Right Lung
  • Three lobes
  • Right
  • Middle
  • Lower
  • Broader, shorter than the left lung due to
    elevation of the diaphragm from the liver
  • The right apex extends further above the clavicle
    than the left

51
The Left Lung
  • Two lobes
  • Upper
  • Lower
  • Smaller than the right due to the position of the
    heart

52
The Thoracic Cavity
  • Three divisions separated from each other by
    partitions of pleura
  • Pleural space
  • Contains the lungs
  • Pericardial space
  • Contains the heart, pericardium
  • Mediastinal space
  • Contains the major vessels, lymphatics

53
The Bronchial Circulation
  • Feeds the parenchyma of lung
  • Venous return to the pulmonic vein
  • Accounts for a normal 1-3 shunt (deoxygenated
    blood mixing with arterial blood)
  • Not to be confused with pulmonary circulation
  • Where respiration occurs

54
Shunt vs. Dead Space
  • Shunt
  • perfusion without aeration
  • Dead space
  • aeration without perfusion
  • A.K.A. an area of bi-directional air flow

55
The Pleura
  • A double layered serous membrane
  • Parietal
  • Lines the entire thoracic cavity, inner surface
    of ribs, superior surface of diaphragm
  • Visceral
  • Adheres to the surface of each lung
  • The pleural space is a potential space between
    the pleura
  • A small amount of serous fluid is present

56
Muscles of respiration
  • diaphragm
  • responsible for 70 of tidal volume
  • accessory muscles of respiration

inspiration expiration
sternocleidomastoid scalenes pectoralis major pectoralis minor serratus anterior serratus posterior superior upper iliocostalis external oblique internal oblique rectus abdominus lower iliocostalis lower longissimus serratus posterior inferior
57
Cardiac Anatomy
58
Coronary Arteries
Thebesian veins drain directly into cardiac
chambers, adding to physiologic SHUNT
59
Other Zones of Anesthetic Interest
60
Major Nerve Plexuses
  • A nerve plexus is a network of intersecting
    nerves which combine sets of spinal nerves that
    serve the same area of the body into one large
    grouped nerve

61
Cervical plexus (C1-C5)
  • A plexus of the ventral rami of the first four
    cervical nerves
  • Branches
  • Lesser occipital nerve (C2)
  • Greater auricular nerve(C2,3)
  • Transverse cervical nerve (C2,3)
  • Supraclavicular nerves (C3-4)

Supplies the skin behind the ear, at the angle of
the jaw, in the anterior and lateral triangles of
the neck to shoulder and below the clavicle
62
Cervical Plexus, contd
  • Branches, contd
  • Muscular
  • Ansa cervicalis
  • Hypoglosssal
  • Thyrohyoid, genohyoid

Innervate the rhomboids, serratus anterior, SCM,
trapezius, levator scapulae, and scalenus medius
63
Cervical Plexus, contd
  • Communicating
  • From the SNS (superior cervical sympathetic
    ganglion)
  • C1 communicates with hypoglossal
  • supplies geniohyoid and thyrohyoid
  • C2 and C3 form ansa hypoglossi
  • supplies sternohyoid, sternothyroid, and omohyoid
    muscles

64
Cervical Plexus, contd
  • Mixed (sensory, motor, and sympathetic)
  • Phrenic nerve (C5) ? diaphragm

65
Cervical plexus
contributes to brachial plexus
66
The Brachial Plexus
  • Supplies the upper limb with sensory and motor
    innervation
  • A branching network of nerves derived from the
    anterior (ventral) rami (roots) of spinal nerves
    C5, 6, 7, 8, and T1

67
Brachial Plexus Divisions
  • Roots (Randy)
  • C5-T1
  • Trunks (Travis)
  • Upper, middle, lower
  • Divisions (Drinks)
  • Anterior, posterior
  • Cords (Coffee)
  • Lateral, medial, posterior
  • Branches (Black)

68
The Brachial Plexus
clavicle
69
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70
Distribution of terminal nerves
cords branches innervation to
lateral musculocutaneous median UE flexors (m) lateral aspect forearm from elbow to wrist (s) most difficult to block medial aspect forearm (s) see below
posterior axillary radial shoulder (m,s) UE extensors (m) thumb, 2nd finger, inner medial 3rd finger (s)
medial median ulnar dorsal-distal half 2nd, 3rd fingers medial ½ 4th finger (s) ventral-thumb, 2nd, 3rd, and ½ of 4th finger (s) 4th, 5th fingers, lateral hand (s)
71
Brachial Plexus Block
  • Four approaches
  • 1) Interscalene
  • - Trunks emerge between anterior and middle
  • scalenes proximity of RLN, stellate
    ganglion, phrenic nerve, and vertebral artery
    predisposes to high rates of incidental blockade
    or intravascular injection
  • 2) Supraclavicular (AKA subclavian)
  • - Plexus is compacted here provides excellent
    blockade high incidence of pneumothorax (1-6)
  • 3) Infraclavicular
  • - Risk for pneumo, hemo, chylo (L sided) thorax
  • 4) Axillary
  • - Remember the musculocutaneous nerve!
  • Visit www.nysora.com

72
Celiac (solar) Plexus
  • Formed (in part) by the greater and lesser
    splanchnic nerves of both sides, and also parts
    of the right vagus nerve
  • includes a number of smaller plexuses which
    supply viscera
  • hepatic
  • splenic
  • gastric
  • pancreatic
  • suprarenal
  • renal
  • testicular/ovarian
  • superior mesenteric plexus
  • inferior mesenteric plexus

73
Lumbosacral plexus
  • Lumbar plexus (T12-L4)
  • Main branches
  • iliohypogastric
  • ilioinguinal nerve
  • genitofemoral nerve
  • Dorsal divisions
  • lateral femoral cutaneous
  • femoral nerve ? adductors of hip, extensors of
    knee, and skin over medial surfaces of thigh and
    leg
  • saphenous is main branch
  • Ventral divisions.
  • obturator nerve ? adductors of hip and skin over
    medial surface of thigh
  • accessory obturator nerve

74
Lumbar plexus, contd
75
Sacral plexus (L4-S4)
  • gluteal nerves ? adductors and extensors of hip
    and skin over posterior surface of thigh
  • sciatic nerve ? (L4-S3) 2 nerves contained within
    a sheath
  • common peroneal
  • tibial
  • flexors of knee and ankle, flexors and extensors
    of toes, and skin over anterior and posterior
    surfaces of leg and foot
  • posterior and medial cutaneous nerve ? skin over
    medial surface of leg
  • pudendal nerve (S2-4)

76
Sacral Plexus
77
The Great Veins of the Neck
  • Internal jugular
  • Right IJ best for cannulation and passage of a PA
    catheter
  • External jugular
  • Beware of the large valve at the junction of the
    EJ and the subclavian
  • Anterior jugular
  • Subclavian

78
The Great Veins of the Neck
79
The Thoracic Duct
80
Aortic Arch
81
BrachiocephalicInnominate
82
The Antecubital Fossa
83
The Circle of Willis
  • an anastomosis of the internal carotids and the
    vertebral arteries which is found at the base of
    the brain. All cerebral arteries are derived
    from this anastomosis.
  • This circle is directly responsible for cerebral
    perfusion.
  • During carotid X-clamping, collateral flow to the
    circle is via the contralateral carotid and the
    vertebro-basilar system.

84
Cerebral Perfusion Pressure
  • CPP MAP - ICP

or CVP, whichever is higher
85
The Circle of Willis
86
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87
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88
CSF circulation
CSF secreted by choroid plexus to Lateral
ventricles 1 2 to Foramen of Munro to 3rd
ventricle to Aqueduct of Sylvius to 4th
ventricle to Foramina of Luschka and
Magendie to Subarachnoid space to Reabsorption
by arachnoid villi
Total volume 150 ml
Adults form 400-500 ml/day (approximately 20
ml/hr)
89
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90
The Cranial Nerves
  • with regard to their regions of innervation, are
    nerves of the head. They spread through the
    head-neck region, except for the parasympathetic
    portions of the vagus nerve which pass to the
    abdominal organs.

91
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92
Cranial Nerves I-VI Cranial nerves
Type Function
I. Olfactory S smell
II. Optic S sight
III. Oculomotor M eye movement, pupil constriction
IV. Trochlear M eye movement
V. Trigeminal (three branches) ophthalmic (S), maxillary (S), mandibular (M S) B chewing, great sensory of face
VI. Abducens M eye movement
93
Cranial nerves VII-XIICranial nerves
Type Function
VII. Facial (five branches) temporal, zygomatic, buccal, mandibular, cervical B taste, great motor of the face
VIII. Acoustic (A.K.A. vestibulocochlear) S hearing, balance
IX. Glossopharyngeal B swallowing, afferent carotid body and sinus
X. Vagus (branches superior laryngeal and recurrent laryngeal nerves may be injured during intubation) B Great Wanderer afferent and efferent
XI. Accessory (A.K.A. spinal accessory) M larynx and pharynx
XII. Hypoglossal (may be injured during intubation) M tongue
94
The Spine
Largest interspace is L5-S1 (A.K.A. Taylors
space)
95
Spinal cord
  • Extends from the foramen magnum to the level of
    L1 (adults), L3 (children)
  • Terminates to conus medullaris and filum
    terminale
  • lower spinal nerves form the cauda equina
  • Tuffiers line the plane which crosses the
    iliac crests bilaterally
  • Approximately the L4 level in most individuals
  • Cord may extend below the L1 level in obese pts
  • Conus is at approximately L3 in children

96
Tuffiers Line
( T7)
97
Spinal Cord termination
98
Blood supply
  • Derived from a single anterior and paired
    posterior spinal arteries
  • Anterior spinal artery
  • formed from the vertebral artery
  • supplies anterior 2/3rds of the cord
  • Posterior spinal arteries
  • Arise from cerebellar artery

99
Additional blood supply to the cord
  • Intercostals (thorax)
  • Lumbar arteries (abdomen)
  • Artery of Adamkiewicz (great ventral radicular
    artery, arteria radicularis magna)
  • arises from the aorta
  • unilateralusually from the L side
  • provides the major blood supply to the anterior,
    lower 2/3rds of the spinal cord

100
Cross section of spinal cord
101
Substantia gelatinosa
  • Found in the dorsal horn of the spinal cord
  • Plays a major role in processing and modulating
    nociceptive input from cutaneous nociceptors
  • Major site of action for intrathecal opioids
  • AKA Rexeds Lamina II

102
Vertebrasuperior view
103
Vertebra--lateral view
104
Vertebra and disc
105
Spinal Ligaments
106
Spinal anesthesia
107
Epidural Anesthesia
108
Epidural Anesthesia
109
Epidural Anesthesia
epidural space venous plexus ligamentum flavum
Epidural space widens as it descends the cord
widest at L2-3
110
Schematic of Spinal vs. Epidural Anesthesia
111
Miscellaneous
112
Diaphragmatic Innervation
  • Phrenic nerve (R L branches)
  • Arises from C3, 4, 5
  • This is the source of motor innervation
  • (C3,4,5 keeps a man alive)
  • Sensory innervation
  • Lower 6 intercostal nerves

113
Cardioaccelerator nerves
  • Arise from T1-4
  • Bradycardia usually noted in quadriplegia or high
    level of spinal anesthesia

114
Landmarks for Sensory Levels
T4 Nipple
T6 Xiphoid
T7 Lower border of scapula
T8 Lower border of rib cage
T10 Umbilicus
L4 Iliac crest
115
Dermatome Man
116
Peripheral Nerve Stimulation
  • Most common site of placement of PNS is along the
    groove of the ulnar nerve
  • Elicits a response from the
  • adductor pollicis brevis
  • May use the facial nerve distribution for
    placement if arms are not accessible
  • Elicits a response from the
  • orbicularis oculi
  • corrugator supercilii

117
Arterial Supply of the Hand
118
Sites for arterial cannulation
  • Radial artery
  • Most commonly selected site
  • Ulnar artery
  • Major blood supply of the hand
  • Difficult to cannulate deep, tortuous
  • Brachial artery
  • Large, easy to cannulate
  • Risk of median nerve damage
  • Axillary artery
  • Femoral artery
  • Good to use in low flow states
  • Dorsalis pedis artery
  • May have distortion of waveform falsely high SBP
    2º distance from aorta

119
Positioning
  • neuropathies following surgery are from
  • stretching of nerves for sustained periods of
    time
  • pressure on nerves for sustained periods of time
  • leads to ischemia of the nerve ? neuropathy
  • alopecia of occipital area particularly in
    low-flow states
  • anesthetized pts are unable to compensate for
    awkward/painful positions
  • muscle relaxation allows for positioning that
    would otherwise not be tolerated by the pt
  • proper positioning considered a shared
    responsibility among OR team (however)

120
Positioning
  • upper extremity
  • ulnar nerve is the most frequently damaged in
    pts in the supine position
  • neuropathy may manifest as sensory and/or motor
    deficit
  • usually transient
  • 70-90 of injured pts are male
  • other predisposing factors to development of
    injury
  • extremes of weight (particularly obese pts)
  • extended bedrest (before and/or after surgery)
  • long surgery
  • preexisting neuropathy in the contralateral limb

121
Brachial plexus injury
  • most associated with median sternotomy
  • particularly with dissection of IMA
  • probably 2º uneven retraction of chest wall
  • increased risk with
  • arm abduction gt 90º from side
  • compounded if head is turned contralaterally
  • prone position with arms on rests beside head
  • may occur with arms at sides if shoulders allowed
    to prolapse forward with no support

122
Positioning
  • lower extremity
  • lithotomy position carries a high risk of
    perioperative nerve injury
  • usually mild/self limiting
  • severe ? footdrop
  • common peroneal nerve
  • most commonly injured nerve in the lower
    extremities
  • relatively superficial
  • wraps around the head of the fibula on the
    lateral aspect of the knee

123
Lower extremity nerves, contd
  • sciatic nerve
  • adjacent to the hamstrings
  • stretch from hyper flexion of the hip, especially
    when coupled with an extended leg/flexed foot
  • femoral nerve
  • more commonly injured with deep, lower abdominal
    retraction
  • sustained compression of the iliac or femoral
    arteries leads to ischemia
  • pronounced abduction of thigh (frog leg)

124
Lower extremity nerves, contd
  • obturator
  • injured with pronounced abduction of the thigh
  • neuropathies are usually sensory (numbness inner
    aspect of thigh)
  • lithotomy position caveats
  • padding of bony prominences is essential
  • position changes of the LEs must be made
    simultaneously
  • 1º risk factor for the development of neuropathy
    following lithotomy is obesity

125
Supine position
  • minimal circulatory and ventilatory changes noted
  • FRC may be slightly ? due to cephalad
    displacement of diaphragm/abdominal contents
  • stress on lower back
  • may be attenuated with mild knee flexion
  • pressure on heels
  • legs crossed sural (upper leg) and peroneal
    (lower leg) pressure
  • upper extremities should be neutral
  • if supinated, abduction from body not to exceed
    90º
  • pronation may cause undue pressure on the ulnar
    groove
  • individualize to each pt

126
Trendelenburg
  • head down associated with many physiologic
    changes
  • ? pulmonary compliance, FRC from diaphragmatic
    displacement
  • ? myocardial O2 demand
  • from ? preload, slight impedance of forward LVSV
  • may ultimately ? CO
  • ?ICP, IOP
  • leads to facial, scleral edema possible retinal
    detachment, POVL
  • ? R mainstem intubation vs. extubation
  • ? risk of passive regurgitation possible
    aspiration
  • arms should be secured if abducted
  • shoulder braces should be placed on
    acromio-clavicular processes with padding

127
Prone
  • face down head and neck should remain in a
    neutral position
  • turned head may obstruct vertebral artery flow
    and jugular drainage
  • upper extremities are best placed at sides
  • should not be abducted gt 90º if extended
    alongside the head
  • physiologic changes include
  • ? FRC with ? intraabdominal pressure
  • FRC may actually be unchanged or facilitated
    in absence of increased IAP
  • ? intraabdominal pressure
  • may impede venous return via IVC thereby
    reducing preload/CO
  • collaterals via epidural vessels may see ?
    intraoperative blood loss from congestion
  • ? pulmonary compliance
  • pooling of blood in lower extremities
  • facial/ocular edema
  • retinal artery occlusion may lead to blindness
  • risk compounded by overhydration with
    crystalloid, prolonged periods of hypotension,
    direct pressure on the orbits, EBL gt 2.5 l,
    prolonged surgery
  • pressure on breasts, genitalia
  • ? risk for airway compromise during position
    changes or intraoperatively
  • pt should be log rolled after induction with neck
    maintained in a neutral position

128
Sitting
  • venous air embolism (VAE) is the 1º complication
    associated with this position
  • occurs when the operative site is above the level
    of the heart
  • treatment
  • have the surgeon flood the operative site with
    saline
  • discontinue N2O
  • aspirate air through a central venous catheter
  • resuscitate with fluids, ionotropic support, ()
    pressure ventilation
  • other effects of sitting include
  • ?BP, preload, CO from pooling
  • ?CPP (brachial reading underestimates pressure at
    the Circle of Willis!)
  • ?intrathoracic blood volume V/Q mismatching

129
Lateral decubitus
  • side lying physiologic changes generally
    pulmonary overall V/Q mismatch from
  • ? pulmonary compliance with ? perfusion to the
    upper lung ? ? dead space
  • ? pulmonary compliance and FRC with ? perfusion
    to the dependent lung ? ? shunt
  • compression of IVC
  • pressure on axilla on dependent side
  • brachial plexus injury common
  • pulse oximetry on dependent hand recommended to
    assess perfusion
  • Axillary roll a misnomer!
  • pressure on medial aspects of knees
  • potential injury to dependent eye/ear
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