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2014-04-26 14:13:58

ENT anesthesia
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  1. Describe the anatomy of the larynx.  Where does it lie?  How many cartilages?  Where does the blood supply come from?
    The larynx extends vertically from the tip of the epiglottis to the inferior border of the cricoid cartilage. It lies in the anterior neck, at the level of C3-C6 vertebrae, in the adult, C4-6 and child is C3-5. The laryngeal skeleton consists of 9 cartilages joined by ligaments and membranes. The blood supply the larynx: arterial supply comes from the subclavianartery to the inferior thyroid artery to the inferior laryngeal artery & then venous drainage to the inferior laryngeal vein from there to the brachial cephalic vein and from there to the SVC.
  2. what are the cartilages of the larynx?
    3 single cartilages: thyroid, cricoid& epiglottic

    3 paired: arytenoids, corniculate, andthe cuneiform.

    Hyoid bone is connected to but not partof the larynx.
  3. What shields the cartilages of the larynx and the epiglottis?
    the thyroid cartilage shields the smallercartilages of the larynx just as the hyoid bone shields the superior part ofthe epiglottis.
  4. What is the largest of the laryngeal cartilages?  What attaches the thyroid cartilage to the hyoid bone?
    The thyroid cartilage is the largest of the laryngeal cartilages and the inferior 2/3 of the thyroid cartilage is that plate like laminae that fuse anteriorly and this is what forms the laryngeal prominence (aka Adams apple)The V shaped superior thyroid notch(thyroid notch) is above the laryngeal prominence. The thyrohyoidmembrane will attach to the superior horn of the posterior border of thethyroid cartilage. It attaches the thyroid cartilage to the hyoid bone.
  5. Tell me about the cricoid cartilage?  how does it articulate with the thyroid cartilage?
    The inferior horns of the thyroidcartilage then articulate w/the lateral surfaces of the cricoid cartilages.

    Cricoid cartilage is shaped like a signet ring, band facing anteriorly and is much smaller than thyroid cartilage but it is also thicker and stronger and only complete ring of cartilage to encircle any part of the airway,

    narrowest part of airway in pediatric patients.
  6. How is The cricoid is attached to the thyroid cartilage?
    The cricoid is attached to the thyroidcartilage inferiorly by the median cricothyroidligament.

    Attached to the 1st tracheal ring by the cricotrachealligament.

    The cricothyroid ligament can be felt as the soft spot on the neck inferior to the thyroidcartilage, this is where the larynx is closest to skin and most accessible.
  7. Epigottic cartilage
    The epiglottic cartilage gives flexibility to the epiglottis which is a heart shaped cartilage covered w/mucus membrane, posterior to the root of tongue and hyoid bone andanterior to laryngeal inlet. The epiglottis functions to cover the glottis when swallowing to prevent food and liquids from getting into lungs when we’re eating. Epiglottis is the first cartilage seen on direct laryngoscopy.
  8. arytenoid cartilages
    The arytenoid cartilages arepairs of 3 sided pyramid like structures. They sit on the cricoid, each one hasan apex superiorly, a vocal cord process anteriorly, and a large muscularprocess that projects laterally from it’s base. The apex will bear the corniculate cartilage
  9. what cartiage is on top of the arytenoids?
    The corniculate cartilages have been described as looking like party hats sitting on top of the arytenoids
  10. where are the cuneiform cartilages?
    The cuneiforms are elongated sitting a bit behind the corniculates on the base of the epiglottis.
  11. The cricoarytenoid joints.  What do they do?
    The cricoarytenoid joints are between the bases of the arytenoids and the superior lateral surfaces of the laminar of the cricoid cartilage. These permit the arytenoids to slide toward or away from one another to tilt anteriorly, posteriorly, and also to rotate. These movements are important to proximate, tensing, and relaxing the vocal cords.
  12. he 3 single cartilages of the larynx?The three paired?Then from top to bottom, there’s the..........
    The 3 single cartilages of the larynx arethyroid, cricoid, and the epiglottis. The three paired are the arytenoid, the cuneiform, and the corniculate. Then from top to bottom, there’s the hyoid bone, the thyrohyoid membrane, the thyroid cartilage, the cricothryomembrane, thecricoid cartilage, the cricotrachealligament and the 1st tracheal ring.
  13. where is a trach usually done?
    A trach is usually done midway between the thyroid notch and the suprasternal notch, through a vertical incision through the 2nd and 3rd tracheal rings with the thyroid isthmus divided and retracted
  14. The Rima glottis?
    • The Rima glottis is the opening between the vocal cords and this slide will show the variations in this opening that is associated with the normal physiology of the larynx. So the shape of the rima varies according to the position of the cords.
    • •During ordinary breathing as you can seein A, the opening is narrow and wedge shaped.
    • •With forced respiration in B, it’s wideand kite shaped,
    • • during phonation (c) the vocal cords areclosely approximated so the rima is slit like.
    • •The voice will change in pitch accordingto the tension and length of the vocal cords, the width of the rimaglottis and the intensity of the expiratory effort.
  15. 3 Functions of the larynx
    The 3 functions of the larynx are protection of the airway, respiration, and vocalization.

    The protective function is by both reflex and involuntary processes primarily. The glottis closes by a reflex that gets activated when we swallow and it’s a basic primitive reflex that gets elicited by many different sensory stimuli that effect the superior laryngeal nerve.
  16. extrinsic muscles of the larynx
    •the Extrinsic Laryngeal muscles moves the larynx as a whole

    • there are 8 extrinsic muscles that get divided into 2 groups:
    • •Infrahyoid:  depress hyoid and larynx
    • •Suprahyoid and Stylopharyngeal muscles: elevate hyoid and  and larynx
  17. Intrinsic laryngeal muscles
    • Intrinsic muscles: move laryngeal parts, makes changes in length and tension of vocal chords. 
    • Essentially the opening of the glottis. 

    • They essentially have 3 functions:
    • 1.)open vocal chords during inspiration,
    • 2.)close vocal chords during swallowing,
    • 3.)change tensions of vocal chords during speech.

    •the intrinsic can be grouped according to their actions:

    • •1.the adductors and abductors ( adductions toward midline, abduction away frommidline)
    • •2.the shpinctors
    • •3. the tensors
    • •4. the relaxors

    •want to star this, all but one of the intrinsic muscles is supplied by the recurrentlaryngeal nerve.
  18. Intrinsic and extrinsic muscles of the larynx?
    • the muscles of the larynx are divided into the intrinsic and extrinsic routes.
    • •the Extrinsic Laryngeal muscles moves the larynx as a whole, there are 8 extrinsic muscles that get divided into 2 groups:

    •Infrahyoid:  depress hyoid and larynx•Suprahyoid and Stylopharyngeal muscles: elevate hyoid and  and larynx 

    • •Intrinsic muscles: move laryngeal parts, makes changes in length and tension of vocal chords.  Essentially the opening of the glottis.  They essentially have 3 functions: open vocal chores during inspiration, close vocal chords during swallowing, and changestensions of vocal chords during speech.
    • •the intrinsic can be grouped according to their actions:
    • •1.the adductors and abductors ( adductions toward midline, abduction away frommidline)
    • •2.the shpinctors
    • •3. the tensors
    • •4. the relaxors•want to star this, all but one of the intrinsic muscles is supplied by the recurrentlaryngeal nerve.
  19. which cartilage is innervated by the external laryngeal nerve?
    only the cricoid thyroid is innervated by external laryngeal nerve
  20. T or F all but one of the intrinsic musclesof larynx are supplied by the recurrent laryngeal nerve?

    • -all but one of the intrinsic muscles
    • of larynx are supplied by the recurrent laryngeal nerve.

    • -( see under innervation that ) only
    • the cricoid thyroid is innervated by external laryngeal nerve.  all the other intrinsic muscles are supplied
    • by the recurrent laryngeal nerve which is a branch of the 10th
    • cranial nerve of the vagus.

    -the external laryngeal nerve is one of the two terminal branches of the superior laryngeal nerve.
  21. What is the job of the Cricothyroid muscles?
    • -Cricothyroid muscles: are the  principle tensors, they will tilt or pull angle of thyroid cartilage anteriorly & inferiorly toward the arch of the the cricoid cartilage.  Tense and
    • elongate the vocal chords. As vocal chords lengthen and tighten that rises the
    • pitch of the voice.
  22. Posterior Cricothyroids Arytenoid muscles, what do they do?
    • -Posterior Cricothyroids Arytenoid muscles
    • are the only abductors, what happens when they contract they widen the rima
    • glottis, opening vocal chords, move arytenoids outward
  23. What do the Lateral Cricoarytenoid muscles do?
    • -Lateral Cricoarytenoid:   principle adductors, pull muscular process in opposite direction,  close vocal chords.  When they work in combo w/transverse arytenoid muscles, that pull the arytenoid together, this is where air gets pushed through rima glottidis causing vibration of vocal ligaments and
    • causing phonation.
  24. Transverse arytenoids
    • -Transverse arytenoids
    • are also adductors, (you can think of transverse arytenoid and lateral
    • cricoarytenoid muscles as working together)
  25. thyroarytenoids muscles job?
    • -thyroarytenoids muscles : are
    • the principle relaxers,  pull the
    • arytenoid cartilage  anteriorly towards
    • the  thyroid prominence, relaxing vocal
    • chords, lowering the voice.


    • -the combined actions of the most of the
    • muscles of laryngeal inlet will result in sphincter type action that will
    • closes inlet to  protect glottis during
    • swallowing
  26. oblique arytenoid job?
    • -oblique arytenoid these
    • along with lateral cricoarytenoid, 
    • transverse arytenoids, and aryepiglottic muscles  will bring the aryepiglottic folds
    • together,  pull arytenoid towards
    • epiglottis, they will fall in to the category of sphincters
  27. What nerves supply the larynx?
    •the vagus nerve, CN 10, supplies the larynx; does so both through Superior laryngeal nerve and Recurrent laryngeal nerve

    • •the Superior laryngeal nerve is divided
    • into: the internal branch & external branch
  28. what does the Superior Layngeal Nerve provide innervation to?  how is it divided?
    •Superior Layngeal Nerve provides sensory innervation of larynx down to the vocal chords

    •Internal branch : mainly sensory with a few motor fibers leading to the arytenoid muscles

    •External branch of superior laryngeal nerve : motor, innervates cricothyroid muscles & inferior pharyngeal muscle

    •(again the cricothyroid is the only intrinsic laryngeal muscle not innervated by recurrent laryngeal nerve)

    •the Recurrent Laryngeal Nerve will innervate all other intrinsic muscles (other than the cricothryroid ); it provides sensory innervation of larynx below vocal chords

    •RLN is something that can be damaged during thyroid or parathyroid surgery

    •Extrinsic Muscles are innervated by cervical plexus C1-C3
  29. Extrinsic Muscles are innervated by
    •Extrinsic Muscles are innervated by cervical plexus C1-C3
  30. What does the Recurrent Laryngeal Nerve innervate?
    •the Recurrent Laryngeal Nerve will innervate all other intrinsic muscles (other than the cricothryroid ); it provides sensory innervation of larynx below vocal chords

    •RLN is something that can be damaged during thyroid or parathyroid surgery

    •Extrinsic Muscles are innervated by cervical plexus C1-C3
  31. Unilateral RLN
    Unilateral RLN injury will cause chord ofinjured side to assume a paramedian position.•the voice then is weak and horse, thereis an increased risk of aspiration
  32. RLN can be injured by ?
    • •RLN can be injured by endotracheal
    • intubation, neck surgery, or even stretching of the neck during surgery

    • •resulting tone & position of vocal
    • chords will depend on whether the external branch of the superior laryngeal
    • nerve ( again motor innervation of cricothyroid muscles, leading shortened of vocal chords is also involved)

    • •Unilateral RLN injury will cause chord of
    • injured side to assume a paramedian position.

    • •the voice then is weak and horse, there
    • is an increased risk of aspiration

    • •Bilateral damage from ischemia, there is
    • complete airway obstruction b/c of laryngeal spasm. 

    • •If however the nerve is transected
    • bilaterally, vocal chords will be flaccid but there may be some air passage

    • •laryngeal spasm is due to spasm of glottic
    • muscle, and is mediated superior larygneal nerve
  33. Where do the vocal chords lie on the neck?
    • the vocal chords are at the level of the
    • middle of the laryngeal prominance, the cricoid is an important land mark. Its felt inferior to the laryngeal prominance as the level of the C6 vertebra
  34. Where is cricoid cartilage felt?
    • Cricoid thyroid ligament felt with neck extended and passes inferiorly from thyroid
    • prominence 

    • Cricoid cartilage is key landmark-
    • level C6, site where carotid artery can be compressed against the transverse
    • process at C6, junction of larynx and trachea, where the pharynx and esophagus
    • join,  point where recurrent laryngeal
    • nerve enters larynx, site of cricoid is approx 3cm superior to isthmus of thyroid
    • gland, narrowest part of pediatric airway
  35. Tracheal rings are palpable where?  How do the structures lie from top to bottom?
    Tracheal rings palpable in the inferior part of the neck but 2nd-4th can’t be felt b/c of isthmus of thyroid gland-first ring can be felt just above it

    • Orientation
    • from top to bottom- hyoid, thyroid-hyoid membrane, thyroid, crico-thyroid
    • membrane, cricoid, crico-tracheal ligament then trachea
  36. Where is the pharynx?  It's divides into how many parts?
    Pharynx divided into 3 parts-

    nasopharynx-posterior to nose and superior to soft palate,

    oropharynx-posterior to mouth,

    laryngopharynx-posterior to larynx

    Pharynx extends from base of the skull to below the level of body of C6 where it becomes continuous with the esophagus
  37. Microlaryngoscopy, managing the shared airway
    • Only 5% of micro surgery involving larynx
    • does patho involve lower 1/3rd of VC or posterior commissure – small ETT per Miller 5.5-6 is adequate for oxygenation and ventilation if need be can do 4.5-5 so surgeon can still see surgical field without ETT in the way-balance surgeon goals with ours- they want smallest tube possible but will let the decision be ours

    • Our goals- concerned with safety so want
    • to protect trachea with cuffed ETT, provide adeq oxygenation and ventilation, decrease
    • reflex response to any secretions so minimize laryngospasm and coughing, want patient to wake up quickly with return of reflexes at end of surgeon
  38. Apneic technique of microlaryngoscopy
    • Apneic technique- not often, alternating
    • ventilation with surgical incision-no ETT with removal of incision

    • We maintain anesthesia with TIVA, allow
    • surgeon to have airway and resect lesion while we watch O2 sat-when drops to
    • point where we need to ventilation we mask
    • until sat comes up and then let surgeon resume incision-essentially mask airway
  39. suspending laryngoscopy- 
    • suspending laryngoscope is pretty
    • stimulating- can cause tachycardia. HTN, arrhythmias  incidence of MI or ischemia after suspended laryngoscopy reported to be 1.5-4%

    • patients may have been heaviers
    • smokers- already risk CAD
  40. Barash discusses technique similar to apneic (no secure airway
    • In general muscle relaxation important
    • for microlaryngoscopy

    Barash discusses technique similar to apneic (no secure airway) but pt is spontaneously breathing –anesthesia still pretty deep, tricky-advantage is maintaining some level of ventilation while surgeon is doing incision- Sue has never done this

    Another technique-jet ventilation
    • Another technique-jet ventilation- uses venturi
    • effect-

    • laryngoscope aligned with access of trachea by surgeon- VC must be completely relaxed and path must not be so large that it obstructs flow to trachea, jet gas must   be allowed to exit freely-monitor by watching
    • chest wall excursion

    • ventilation with jet begins with pressures of about 30 PSI-inspiration lasts 1.5sec and passive expiration 6 sec so RR approx 6-7
    • breaths/min

    • contraindicated in peds, obesity and pts with
    • emphysematous bull

    •  Venturi effect-entrainment of ambient gas a tatio of 2 to 3:1 of TV greater than jet vol but
    • naturally variable has composition typically have 100% O2 but RA is being entrained so don’t know FiO2

      Need to be able to see chest excursion- no EtCO2, and follow O2 sat

      Barotrauma is risk re using high pressures
  42. LASER
    One of the techniques that is used in these procedures is LASER

    It stands for light amplification by simulated emission of radiation

    There are various types depending on the emission medium used

    • Lasers can be used in short pulses,
    • long pulses, or in a continuous mode
  43. CO2 laser
    The CO2 laser is suitable for removing lesions of the vocal cords and larynx

     It’s the most widely used laser

    •  It produces radiation w/ a wavelength  of
    • 0.01 mm

    •   What happens is, the laser energy is absorbed by the water in the tissue that
    • increases the temperature which denatures the protein, vaporizing the target tissue
  44. YAG laser
    The YAG and ARGON laser are absorbed by Hgb and pigmented tissue, and they both have deep penetrating affects

     Both get used w/ detached retinas

    We need to be aware of the hazards of using lasers and eye protection is one of the basic things

    • The CO2 will react to the surface of the
    • eye and will cause corneal abrasion

    The YAG has a shorter wavelength and can pass through and damage the retina

      Pts’ eyes need to be protected and everyone else in the room has to have eye protection

    Non-target tissues have to be protected by moist gauze covering
  45. How do airway fires usually occur?
    • The CO2 laser can penetrate an ETT and can
    • ignite a fire which would then be supported by the oxygen and nitrous oxide
    • within the tube

      It’s the subglottic, epiglottic, and oropharyngeal areas that are usually involved

    •   Also, the inhalation of smoke from an airway fire can cause chemical injury,
    • bronchospasm, edema, and respiratory failure
  46. How can we prevent airway fires?
    • Polyvinyl chloride tubes will burn
    • vigorously and produce HCl which is a pulmonary toxin

    • Now, there are commercially available ETT
    • which makes this situation a whole lot better

    Some of the strategies we employ:

    •   We fill the cuffs with NS and methylene blue à if cuff breaks, know that from methylene blue and the NS would hopefully put out
    • the fire

      We want to not use any more than 30% oxygen and nitrogen or air

      Typically, we want to give as close to room air as we can

      Nitrous oxide does supported combustion, don’t want to use that
  47. The treatment of an airway fire:
    The treatment of an airway fire:

      D/C oxygen

      Remove ETT

      Re-intubate trachea

      Flush pharynx w/ cold saline

      A rigid bronchoscope should be used to check for damage, presence of foreign bodies (removal of remnants of ETT)

      Humidified gas, steroids, abx
  48. Nasal polyps
    Pts that need nasal or sinus surgery may have a considerable degree of pre-op nasal obstruction from polyps or deviated septum or congestion from an infection

    Nasal polyps are associated w/ allergic disorders like asthma and they’re a feature of cystic fibrosis

    The nasal mucosa has a rich blood supply
  49. What are some considerations when doing nasal sinus surgery?
    We want to verify pre-op that anti-coagulants have been d/c’d

    • The surgeon will likely utilize techniques intraop that will minimize blood loss intraop:
    • cocaine packing, LA solutions w/ epi for injection into the operative area

    •   When using cocaine, want to remember the max dose is 3 mg/kg, and it’s rapidly absorbed, it peaks in 30 min and may have
    • adverse CV effects b/c cocaine inhibits reuptake of NE and it will potentiate
    • the affects of adrenergic stimulation

    •   The CV responses seen will be HTN and
    • ventricular  ectopic activity

    • Another strategy is to maintain a 15 degree head up position – can help w/ controlled
    • hypotension to cut down on bleeding
  50. Anesthetic techniques for nasal sinus surgery?
    • For these procedures, the choice of anesthetic technique varies from local w/
    • sedation or GA w/ LMA or ETT

    • Want to remember if you’re inducing GA that you will want to have an oral airway
    • available b/c during mask ventilation the effects of nasal obstruction may be
    • such that an oral airway is necessary

    Corneal abrasions are always a risk in surgery involving the head/neck

      The eyes must be taped closed – except during FESS (functional endoscopic sinus surgery) b/c the surgeon may want to periodically check for eye movement during dissection b/c of the close proximity of the sinuses and the orbit

    •   Muscle relaxation may be desired b/c of the
    • potential for neurological or ophthalmologic complications if the pt does move during instrumentation of the sinuses

    Barash talks about the different b/t TIVA and volatile technique

    •   A TIVA w/ Remi and propofol in general yields better visualization and less EBL b/c the pt is less likely to cough on emergence and
    • have PONV

    • On emergence, we need to balance the desire for minimal coughing and bucking w/
    • the risk of pulmonary aspiration of blood in the setting of depressed airway reflexes
  51. Complications of FESS
    FESS: functional endoscopic sinussurgery:

    1% MAJOR  incidence diplopia, csfleak, orbital hematoma, blindness, CNS infection, stroke, carotid injury and death

    5% incidence of MINOR: peri-orbitalemphysema, ecchymosis, lip pain or numbness, bronchospasm, and epistasis

    MAJOR due to: result of perforation ofroof of ethmoid sinus, injury to optic nerve or carotid artery during a sphenoidectomy:palpate orbit to prevent injury from an osteom seeker in the sinus
  52. Location of the sinuses in regard to the orbit
    what are the paranasal sinuses?  what bones are sinus located at?
    Para-nasal sinus’ are air filled extensions of the respiratory part of nasal cavity

    Into the frontal, ethmoid, sphenoid, maxillary cranial bones’

    • Sinus named according to bones where they
    • are located

    • Ethmoid comprise several cavities that are
    • located in the lateral mass of the ethmoid bone between nasal cavity and the orbit

    • Only thin plates of bone separating some
    • of the structures

    • Thin area separating the sphenoid from
    • the optic nerve, pituitary gland, internal carotid arteries, and cavernous sinus’
  53. positioning for ear surgery
    • Positioning: head turned to one side, not too much of extension or torsion or stretch injury
    • to brachial plexus or cervical spine, limited carotid artery flow r/t stenosis particularly vulnerable to lower flow from neck position
  54. Can you use nitrous for ear procedures?
    N2O: 34 x more soluble in blood than nitrogen

    Middle ear and para-nasal sinus’ are normal air filled cavities that consist of open non ventilated spaces the middle ear is vented intermittently when the Eustachian tube opens

    • These air spaces will expand when N2O is
    • used because of the difference in the blood gas partition coefficients: N2O in high concentrations will enter the air cavities faster than nitrogen can leave, fixed cavity like middle ear = increase in pressure

    • Normally the Eustachian tube will
    • passively vent at a pressure of 200-300 mmH2O, but middle ear pressures can
    • reach 375mmH2o within 5-30 minutes of the start of N2o and exceeds the ability
    • of the Eustachian tubes to vent

    • N2O hazardous to patients with previous
    • reconstructive ear surgery and should be avoided up to 6 weeks post op

    • Use of N2O contribute to serous otitis,
    • disarticulating of the stapes, and impaired hearing

    • N2O can cause an increase in PONV; can
    • lead to rupture of the tympanic membrane from elevated middle ear pressure and
    • Eustachian tube malfunction

    Tympanoplasty N2O limited to 50% and/or discontinued 15 minutes prior to closure of the middle ear and tympanic membrane
  55. What are some major considerations during ear surgery?
    • Increase risk of PONV with ear surgery
    • alone

    PONV can undo ear surgery

    Prophylaxis is key

    Preserve the facial nerve
  56. The thyroid gland anatomy and innervation
    Anatomically thyroid two lobes connected by tissues of thyroid isthmus

    Very vascular, innervated by autonomic nervous systems; consists of multiple follicles filled with colloid primarily thyroglobulin, in the thyroid hormones stored in combo with thyroglobulin
  57. thyroidectomy anesthesia considersations

    Medullary thyroid cancer associated with multiple endocrine neoplasia (MEN) meaning patient could have undiagnosed pheochromocytoma: catecholamine storm could mimic thyroid storm


    Epi and thyroxine are derivatives of AA TYROSINE: same SNS from hyperthyroidism

    • Hyperthyroidism: make sure euthyroid
    • accomplished sometimes with lugals iodine therapy

    • Goiter: AIRWAY AIRWAY AIRWAY; may be
    • difficult, surgeon best source, trachea may be compressed or deviated with tracheal ring involvement

    If a patient has a goiter the trachea may be compressed and there may be tracheal ring involvement
  58. preop assessment for throidectomy
    Preoperative assessment

    Is the patient euthyroid?


    Resting heart rate < 85

    Will ↓ risk of thyroid storm by >90%

    Airway, airway, airway

    Tracheal deviation

    Tracheal ring involvement

    Inflammation due to thyroiditis
  59. Thyroid surgery positioning
    Thyroid surgery is in the beach chair position

    HOB 15-20*

    Increased risk of VAE

    Arms tucked at side Towel or positioning device is placed under patients back

    • HOB is put back
    • Be careful that surgeons don’t lean on the airway or the eyes
  60. Periop complications of thyroid surgery
    Periop complcations

    Recurrent laryngeal nerve paralysis, can result in vocal cord paralysis Permanaent nerve injury 1%

    Nerve monitoring is used Usually no NDMR usedNIM (NERVE INTEGRITY MONITOR)- ETT based electrode system. Passive evoked EMG monitors
  61. nerve monitoring during thyroid surgery
    • Left and right thyroarytenoids
    • In the normal position, the cuff in the lower subglottic upper trachea

    The exposed segment of the electrode is in contact with the luminar surface of the bilateral vocal cords

    The recording ground and nerve stimulator electrode are placed by the surgeon on the patient’s shoulder

    The ett and the grounds are then interfaced by the NIM monitor connector with the correct placement of the tube and the connections intact the surgeon can hear and see the EMG activity and the thyroarytenoid muscle innervated by the laryngeal

    nerve is continually monitored

    On this slide you see a cut away view of the larynx and trachea with the tube in

    Also connector of the tube and the monitor
  62. What agents do we need to avoid during thyroid surgery?  Why are they at increased risk of eye injury?
    Eye protection- risk of damage

    Exopthalmus puts the patient at increased risk

    Choice of agent- no ketamine

    • No indirect acting adrenergic agonist
    • These patients may be chronically
    • hypovolemic and vasodilated

    There may be swings in hemodynamic

    Mild hypothyroidism isn’t contraindicated

    • Hyperthyroid- increased risk of hepatic
    • injury due to excelerated biotransformation
    • Neuromuscular blockers- wouldn’t use but
    • if for some reason you needed to, use them cautiously!

    • There is an increased incidence of
    • myasthenia gravis and myopathies

    • Hyperthyroidism doesn’t increase MAC or
    • anesthesia requirements

    • Post op- Airway issues remain
    • Periop laryngeal nerve monitoring

    • Laryngeal muscles should function
    • properly

    • Bleeding can cause tracheal compression
    • post op

    Need to preserve parathyroid to avoid tetany post op
  63. bleeding tonsils
    • Bleeding tonsils- ½% require reoperation,
    • usually within 6 hours of surgery

    Can be until 6th day post op Blood loss may be underestimated

    • Patient may be more hypovolemic than
    • appreciated

    • Blood going into the stomach- full
    • stomach

    • Airway- can be visual issues or obstruction Need to question why they might be
    • bleeding- coagulopathy

    Management for a bleeding tonsil

    Type and cross

    Good venous access/ volume replacement

    • No premedication, need airway reflexes
    • intact

    • RSI slight head down position, need an
    • additional person available to suction blood
    • and a fully awake extubation
  64. epiglottitis
    • Epiglottitis- bacterial infection,
    • progresses rapidly from a sore throat to dysphagia to complete airway obstruction

    All supraglottic structures

    •Can occur in children and adults


    •Age 2-6


    • •Sore throat,
    • dysphagia, hot potato voice, resp distress

    • •Croup(compared
    • to epiglottiitis)

    • •Obstruction
    • of airway, characterized by barking cough

    • •Follows
    • viral infection

    • •Kids
    • 3mo-3years

    •Below the glottis, laryngotracheal bronchitis

    •Progresses slowly and rarely requires intubation


    •Endotracheal intubation and antibiotics can be life saving

    • •In impending airway obstruction Pt will
    • be brought directly to OR for direct laryngoscopy and intubation

    •Preop lateral neck X-ray may show a characteristic thumblike epilottic shadow

    •If present is very specific but is ften absent

    •can also be helpful to rule out foreign body




    •Rapid progression


    •Chest retractions

    •Trach set should be set up prior to induction

    •If cant intubate have to perform trach or rigid bronchoscope

    •ENT surgeon must be present in the OR


    •Careful inhalation induction

    •Keep pt spontaneously breathing but deep

    •May only see air bubbles leaving the trachea may be the only way you know where to place the tube
  65. foreign body in airway
    •Foreign body

    •Can cause sudden airway obstruction don't want to turn a partial into a total

    •Surgeon should be ready to perform trach if needed

    •Gently mask induction without cricoid pressure or postive pressure is preferred

    •Laryngeal edema can last for 24hrs

    •Use humidified O2 after removal
  66. Peritonsillar abcess
    Peritonsillar abcess- resp obstruction

     post op day

    Risks include further obstruction

    Difficult intubation

    Spontaneous rupture of the abcess

    Management includes

    Careful intubation to avoid abcess

    Awake intubation

    • Spontaneous resp with
    • mask induction

    Elective trach

    • Ludwig’s angina- cellulitis of the submandible
    • and Sublingual space

    • May include floor muscles and anterior
    • neck

    • Often impossible to visualize the glottic
    • opening due to stysmus edema distortion

    • GA is contraindicated if there’s stridor
    • at rest

    • A tracheotomy is not ideal but may be the
    • best choice
  67. Nasal airway anesthesia
    • •Applicator gets
    • soak in 4% cocaine, or mixure of lidocaine with phenylephrine

    •First applicator

    • •Directly posterior along inferior
    • turbinate to the posterior laryngeal wall

    •Second applicator

    • •Cephalad angle to follow middle turbinate
    • and advance to its full depth

    • •Apply bilaterally to provide anesthesia
    • to sphenopalatine
    • ganglion as well as the mucosa itself

    •2-3min of contact time is required

    •Mucous membranes of the nose are innnervated

    • •Opthalmic divisions of the trigeminal nerve
    • anteriorly and by the maximally division posteriorly
    • •Superior laryngeal nerve is a branch of the vagus that terminates into two branches the
    • external and internal laryngeal nerves

    • •Lower branch of the superior laryngeal
    • nerve passes close under the surface of the mucosa or the pyriformform fossa supplying the sensory innervation aryepiglottic fold
  69. Superior laryngeal nerve block
    •Superior laryngeal nerve block

    •Either topical or external approach


    • •Apply local anesthetic for 3-5min onto
    • the pyriform fossa mucosa



    •Hyoid bone, thyroid cartilage and thyrohyoid membrane

    •Appropirate if there is no tumor or infection


    •Head is extended

    •Thyroid cartilage and cricoid are indentfied

    •Index finger retracts the skin

    •23-25g needle attached with 1-2% lidocaine

    • •Needle is inserted onto the tip of the
    • cartilage

    •Release index finger

    •Needle is walked off the cartilage superiorly and is inserted just through the firm thyrohyoid membrane

    •Aspirate to verify not intravascular

    •Inject 2.5ml and repeat on opposite side through the firm thyrohyoid membrane.

    • The tip of the needle is now in the loose
    • areolar tissue plane beneath the membrane which is you see in the figure. First aspirate to verify that it is not intravascular. Then inject 2.5 mL into the plane beneath the membrane and repeat on the opposite site.

    • The block of the superior laryngeal nerve
    • will anesthetize all laryngeal mucus membranes above the ??? including the epiglottic and the arytenoeppiglottic folds. This block should be used with caution in those that are full stomach precautions because it will remove some protective reflexes.
  70. Describe the infiltration technique for the glossopharyngeal block?
    With infiltration the direct submucosal injection into the base of the anterior tonsillar pillar will produce a denser anesthesia and gag suppression. So initially there will be some topical anesthesia and then the tongue is retracted medially with a tongue depressor. That will show the inferior curve of the anterior tonsillar pillar.

    A 25-gauge spinal needle is used to inject 2 mL of 1% lidocaine 0.5 cm below the mucosa at a point 0.5 cm lateral to the base of the tongue itself. The use of a longer spinal needle is to make it easier to allow the syringe to remain outside of the mouth à better control.

    • Aspirate first to check for intravascular
    • placement. Bilateral injection is needed to block both lingual branches of the
    • glossopharyngeal nerve to block gag reflex. The risks of intravascular injection and greater discomfort make simple topical anesthesia the best choice for most patients.
    Transtracheal injection will topically anesthetize the trachea.

    First a wheal is created. Then a 20-gauge Angiocath is introduced through the cricothyroid membrane. Aspiration of air confirms tracheal placement. Stylet is removed, then a syringe of 4% lidocaine is attached to the angiocath is injected as the patient takes a deep breath. The spray will cause the patient to cough and will cause the spread of the solution up the trachea to the level of the vocal cords.
  72. Anesthesia implications for radical neck dissection
    Patients are often heavy cigarette smokers and often have heavy ETOH consumption, so we must consider the associated co-morbidities: COPD, malnutrition, electrolyte imbalances, CV disease, anemia, and dehydration. These patients need to be evaluated and treated as difficult intubations. Always check with the surgeon.

    • A tracheostomy is often performed as part
    • of the surgical procedure. It may be done at any time during the resection
    • (beginning, middle, or end).

    • NMDRs are contraindicated because the
    • surgeon will need to identify nerves.

    Carotid sinus stimulation can cause bradycardia, HoTN, and cardiac arrest.

    • VAE may occur as head will be elevated
    • 10-15 degrees.

    Volatiles will dilate bronchi, depress airway reflexes, and cause HoTN (which may help limit blood loss). Usually an A-line is advisable. A phenylephrine drip may be necessary to support the BP so that adequate anesthetic depth and immobility can be achieved.
  73. Radical neck dissection
    In radical neck dissection, the deep cervical lymph nodes and the tissues around them are removed as much as possible. The major arteries, brachial plexus, 10th CN and phrenic nerve are preserved. But most cutaneous branches of the cervical plexus are removed. Naturally, the extent of the procedure will depend on the pathology.

    • The surgery for CA of the head and neck
    • can include: laryngectomy, radical neck dissection, hemimandibulectomy, and radical sinus surgery.
  74. Common doses used for airway anesthesia of cocaine tetracaine and lidocaine
  75. What are the three methods the glossopharyngeal nerve can be blocked?
    • The glossopharyngeal nerve can be blocked
    • by one of three methods:
    • (1) topical spray,
    • (2) direct application of soaked pledgets,
    • (3) infiltration. This is not adequate as a solo technique for an awake
    • intubation.
  76. which block needs to be performed first the glossopharyngeal nerve block or the superior laryngeal nerve block?
    If the glossopharyngeal nerve block is used with the superior laryngeal nerve block, then the superior laryngeal nerve block is performed before to avoid airway obstruction.
  77. The glossopharyngeal nerve
    The glossopharyngeal nerve is the 9th cranial nerve and supplies innervation to the posterior 1/3 of the tongue oropharynx, the tonsils, gag reflex, and block can cause paralysis of the pharyngeal muscles. Relaxation of the tongue will cause some airway obstruction.
  78. Nasal airway anesthesia
    •Applicator gets soak in 4% cocaine, or mixure of lidocaine with phenylephrine

    •First applicator

    • •Directly posterior along inferior
    • turbinate to the posterior laryngeal wall

    •Second applicator

    • •Cephalad angle to follow middle turbinate
    • and advance to its full depth

    • •Apply bilaterally to provide anesthesia
    • to sphenopalatine
    • ganglion as well as the mucosa itself

    •2-3min of contact time is required

    •Mucous membranes of the nose are innnervated

    • •Opthalmic divisions of the trigeminal nerve
    • anteriorly and by the maximally division posteriorly
  79. Epiglottitis
    • Epiglottitis- bacterial infection,
    • progresses rapidly from a sore throat to dysphagia

    to complete airway obstruction

    All supraglottic structures
  80. Lafort classifications
    Trauma often involves other injuries: the eye the brain and c-spine.

    Leftort 1- simple horizontal fracture of the lower maxilla.

    •Separates the maxilla from the palate=mobile palate

    • Lefort 2- crosses the nasal bone on the ascending processes of the maxilla and the
    • lacrimal bone the crosses the medial and inferior orbital rims.

    •Called a triangular or extension of the Lefort 1, sometimes called paramydal.

    •Separates the maxilla from the face.

    • Lefort 3- High level transverse fracture that crosses the front of the maxilla and the
    • lacrimal bone and through the orbits.
  81. Lefort 3
    • Lefort 3- High level transverse fracture that crosses the front of the maxilla and the
    • lacrimal bone and through the orbits.

    •The cribriform plate of the ethmoid may be fractured as well

    •Complete separation of the maxilla from the craino-facial skeleton

    •Often epistaxis and a flat dish face deformity

    •massive force applied to mid-face.

    • Dural tears occur in 25% of 2 and 3
    • fractures

    •Noted by a leakage of CSF

    • Avoid nasal intubation-Avoided in pts that
    • have nasal, orbital or zygomatic fractures

    •Lefort 2-3-b/c ET-tube or NG tube an migrate into the orbit, the base of the skull, or the cranium

    Preoperative evaluation of the airway-critical

    •Special attention to jaw opening, mask fit, neck mobility, or congenital deformities -micrognathia retrognathia, maxillary protrusion or overbite.


    •Dental pathology

    •Nasal patency

    •Intraoral lesions

    •Awake intubation may be considered

    •A right angle ET –tube may be considered

    •Make sure that connections are tight- we are far from the airway.

    •be careful when relieving a case

    •throat packs are often used, need to have wire cutters, antiemetics
  82. Anatomy of the eye
    Like a hollow sphere with a rigid wall.

    •As the contents increase the pressure will also increase

    •Normal IOP 12-20 mmHg

    •>25 mmHg-pathologic

    Most important influences of IOP

    •Movement of aqueous humor

    •Changes in blood volume

    •CVP-When increased, IOP increases b/c decreased aqueous drainage

    •Extra ocular muscle tone

    •Then volume of the blood within the globe

    •Changes in arterial BP and ventilation

    • The aqueous humor in the anterior an posterior chambers is produced by the cilliary
    • process
  83. Glaucoma
    • Glaucoma- cause by and obstruction of
    • outflow of aqueous humor
  84. aqueous humor
    • The aqueous humor in the anterior an posterior chambers is produced by the cilliary
    • process

    • Glaucoma- cause by and obstruction of
    • outflow of aqueous 
    • •Clear provides nutrients for the avascular cornea and the lens

    •Produced at rate of 2-3 mcltrs/min in the posterior chamber

    •Total of .3 mls in the posterior chamber and the anterior chambers

    2/3 of humor is active secretary product of the carbonic anhydrase enzyme system within the ciliarry body of the posterior chamber

    •May be giving Diamox-carbonic anhydrase inhibitor to decrease the IOP

    • Aqueous humor (AH) passes through the
    • pupil into the anterior chamber the AH drains into the scleral venous sinus at
    • the aryto-corneal
    • angle.

    • Main physiologic determinant of IOP is
    • the balance between production of aqueous humor and elimination via the spaces
    • of Fontana in the canal of schlemm
  85. Poiseuille law applied to aqueous humor
    • Poiseulle’s equation-the out flow of aqueous humor from schlemms canal follows poiseulles
    • law of fluid flow. 

    • •Anything that narrows these spaces (glaucoma, infection or debris) will cause
    • resistance  to flow and thereby an
    • increase in IOP.

    •Delta P-intraoccular pressure and venous pressure

    •R is the radius of the Fontana spaces

    •L is the length of Fontana spaces

    •N the viscosity of aqueous humor

    • The size of the pupil effects the size of
    • the spaces of Fontana

    •Dilated-spaces are narrow=increased IOP

    •Constricted-has the opposite effect
    Arterial BP and ventilation

    •During certain times of anesthesia these parameters might change altering IOP


    •Intubation-Increases IOP > than succinylcholine alone

    •Adequate depth of anesthesia is important

    •Airway obstruction

    •Coughing-increase IOP to30-40 mmHg


    •Hypercarbia-causes vasodilation-will cause an increase in IOP

    Pressure of the eye from:-Increases IOP

    •The mask


    •Prone position

    •Eye block

    • Endotracheal intubation alone will increase IOP to a greater extent than succ, so adequate depth of anesthesia
    • is important

    • Pressure on eye from mask, circuit, prone
    • position, and giving an eye block can increase IOP as well

    • Blinking alone increases IOP by 5 mmHg,
    • squinting increases IOP by 26 mmHg
    Most cause no increase or a decrease in IOP

    • Succ, we see on slide, it has 2 up arrows,
    • increases IOP by 5-10 mmHg for 5-10 minutes after administration

      mechanism = prolonged contraction of the extraoccular muscles

      unlike other skeletal muscle the cells of the extraoccular muscles have multiple NMJ

      so repeated depolarization of these cells by succ causes prolonged contracture,

      increase in IOP can have various effects, including spurious measurement of IOP on exam under GA in its with glaucoma

    • Sue posted an article from AANA journal
    • course  about effects of succ on extraoccular
    • muscles and IOP on the website
  88. common opthalmic drugs
    Acetazolamide (Diamox)= carbonic anhydrase inhibitor, will decrease IOP and will diurese

    Echothipate= cholinesterase inhibitor, will cause prolongation of succ

    • Also
    • some eye ggts, like timolol, which is a beta adrenergic blocking agent will decrease IOP, also has other SE including bradycardia
  89. eye surgery
    Eye surgery pts tend to be at the extremes of age, < 10 yo or > 55 yo

    Surgeries include cataract extraction, glaucoma surgery, and retinal surgery typically in adults, all fall under the category of open eye surgery

    • Strabismus repair is the most
    • common pedi eye surgery in the US
  90. anesthesia considerations for eye surgery
    • Most eye surgeries require profound
    • analgesia but not skeletal muscle relaxation

    • As always, we’re concerned about
    • the airway, it can be challenging because we’re usually at a distance from the pt’s
    • airway because the surgeon needs to be close

    Pt needs to be prepared by everyone involved, because sudden movement during block or procedure can be problematic

      Because surgeon is operating under a microscope, even talking can be an issue, but its very surgeon dept

    Sedation given for infiltration of regional block or cataract, glaucoma, or retinal surgery

    •   Be careful not to oversedate
    • so pt falls asleep then wakes up startled and moves suddenly

    • Block itself is often performed in
    • holding area or in PACU- gives time for block to be set up and for room to turn
    • around

      Ensure you have all usual emergency equipment- pt fully monitored, O2 via NC, ambu bag, sx, emergency drugs (specifically anti-muscarinics), also ready access to ETT and laryngoscope
  91. eye trauma
    Occasionally may see a pt with a penetrating eye injury due to trauma

      when the globe is open during surgery following trauma, IOP will approach atm P, any factor that typically increases IOP will   decrease intraoccular volume per Boyle’s law by drainage of aqueous or extrusion of the vitreous through the wound

    •   This can be a serious complication that can worsen the vision and again, this is an
    • example of a conflicting agenda in our practice; we need to consider the risk
    • of aspiration (trauma situation= full stomach pt)
    • against risk of blindness from increased IOP and extrusion of ocular contents

      Its been debated for years if succ if safe in this situation, it does increase IOP but only to the same extent as blinking

      Securing the airway with a high dose of a NDMR might be the better option according to most, but if airway if questionable, succ maybe better choice after consultation with surgeon
  92. Retinal surgery
    Retinal surgery usually done to repair detachment of the retina and to either preserve or recover vision by restoring normal anatomy

    In doing so, it often involves change in intra-occular volume

      The retina is transparent tissue that allows us to see the images that are focused on it by the cornea and the lens, when the retina detaches, the light sensitive lining in the back of the eye peels loose and then floats freely within the eye’s interior, when this happens, sight can be lost

    Causes of retinal detachment= trauma, DM, inflammation, or spontaneously due to changes in consistency of volume of vitreous fluid
  93. detached retina
    A detached retina is associated with a tear or a hole in the retina and so eye fluids can leak thru this hole;

    • because a detached retina lacks oxygen leading to cell death, its an urgent
    • procedure in order to prevent blindness

    •   Because of BG partition coefficient N20 should be discontinued 15-30 minutes before
    • injection of the gas, probably best avoided

    •   Avoid N20 for 5 days after receiving an air injection, and 10 days (some say 1 mo)
    • within receipt of a sulfur hexochloride
    • injection

    • Retinal detachment operations= extraoccular,
    • but may become intra-occular if surgeon decides to perforate and drain some fluid; occasionally mannitol or diamox is requested to decrease IOP
  94. procedures for retinal detachment
    1 procedure for a large detachmentis something called a scleral buckle, this involves suturing a piece of rubberto the sclera of the eye, it bends the wall of the eye inward so that it mendsthe hole in the retinaAnother strategy= internal tamponadeof the retinal detachment, done with an expandable gas like sulfur hexochloride,the gas is injected into the vitreous by the surgeon
  95. strabismus surgery
    • strabismus surgery is done to
    • correct misalignment of the visual axis, this will manifest as diploplia reduction or dimness of vision, loss of depth perception, as I said it’s the most common pedi eye procedure and it involves moving or strengthening an extra ocular muscle, patients may be healthy but the incidence of strabismus of increasing
    • in patients with CNS issues like cerebral palsy, meningomyelocele, and hydrocephalus. It can also be the result of trauma to the ocular motor nerve or from sensory abnormalities .

    Vomiting after eye (eye muscle surgery) surgery is common, and Barash refers to the presence of an oculo-gastric reflex, this may be due to the oculo-cardiac reflex which has produced increased vagal tone
  96. key points in strabismus surgery
    ey points about strabismus surgery: It’s associated with an increased risk of oculo- cardiac reflex and an increased incidence of MH; the association with MH is due to the fact that it may be due to a myopathy and patients susceptible to MH may have localized areas of skeletal muscle weakness. So succ is best avoided dt the risk of MH triggering, and it can interfere with some of the tests the surgeonmay want to perform
  97. In addition to the optic nerve, the nerves
    of the orbit include
    In addition to the optic nerve, the nerves of the orbit include those that supply the ocular muscles.
  98. Sensation in the eye is transmitted through
    Sensation in the eye is transmitted through the afferent fibers from the cornea and conjunctiva to the first branch (ophthalmic division) of the fifth cranial nerve (5th: trigeminal) motor innervation of the extra ocular muscles is by way of the motor fibers of the third of the oculo-motorcranial nerve to all of the muscles of the eye except the lateral rectus.
  99. The lateral rectus is innervated by
    The lateral rectus is innervated by the sixth cranial nerve (6th: abducens) and the superior oblique which is innervated by the 4th cranial nerve of the trochlea.
  100. The motor fibers of the 7th cranial nerve (facial) control
    The motor fibers of the 7th cranial nerve (facial) control contraction of the oblicularis oculi muscles (think: peripheral nerve stimulators).  So just want you to pay attention to these diagrams and some of the nerves and muscles because again it’s easy to pass over these, but you never know what could lend itself to a diagram question on the cert exam: hang on to these for studying later as well
  101. What is the usual anesthetic technique for eye surgery?
    • The usual technique is a regional approach with a peribulbar block. There are other possibilities including a retrobulbar block, topical anesthesia, and even GA. The specific choice depends on the specific patient but also on the nature of the surgery. Cataract surgery is most often done with either a peribulbar block or topical anesthetic, same
    • thing with glaucoma surgery. Retinal surgery usually requires either a peribulbar or a
    • retrobulbar approach. IN most circumstances and locations, it’s the opthamologist that
    • performs the block. In some centers the anesthesiologist performs the block. In
    • some places, CRNA students perform these blocks.
  102. How is Regional anesthesia for eye surgery  achieved?
    • Regional anesthesia for eye surgery can be achieved with a combination of local infiltration of the facial nerve, and blockade of the motor and sensory branches of the posterior orbit through either a retro bulbar or peribulbar approach. Blockade of the facial
    • nerve will produce sensory anesthesia of the periorbital area and also motor block of the lid. The peribulbar or retrobulbar part of the block will create akinesia needed for cataract extraction and other opthalmalic procedures.
  103. What local anesthetics are used for eye surgery?
    • For facial nerve blockade 1% lidocaine is
    • usually what to use. For retrobulbar and peri bulbar blocks either 2% lidocaine or
    • .75% bupivicane may be used. The potential advantages of the dense motor block has to be weighed against the risk of an intravascular injection. The other thing that gets added to retrobulbar injections is Hyaluronidase, it’s an enzyme which will promote the spread of the anesthetic through the muscle column. If Lidocaine is used epi
    • 1:200,000 can be added, but it really has no advantages with bupivicaine. The adjusting of the pH with NaHCO3 has been shown to speed the onset of bupivicaine and will also reduce the need for supplmetnal block with a peribulbar tehcnique.
  104. Blockade of facial nerve (CN 7) produces
    Blockade of facial nerve (CN 7) produces sensory anesthesia of periorbital area & motor lid block

    1% lidocaine
  105. facial nerve block
    This can be blocked from any point from the terminal fibers near the eye to its exit from the cranium near the base of the skull. There are 2 approaches.

    This is the modified atkinson approach:

    • A 1 ½ in. needle is inserted through a
    • skin wheal 2 cm lateral to the lateral border of the orbit. The needle is advanced first superiorly towards the upper orbital rim (B) and 3-4 mL of anesthetic is injected as it’s withdrawn to the insertion point and then it gets redirected to the inferior lateral rim and a repeat injection is made. Sensory block of the lid is achieved by a subcutaneous injection of 1% lidocaine through this single skin puncture.
  106. van lint approach- facial nerve blockade
    It’s slightly more medial at a point 2 cm to the lateral canthus of the eye.  3 mL of local anesthesia (1% lidocaine) is injected as the needle is withdrawn to the entry point and again the needle is left in the skin redirected inferiorly and anteriorly with a similar injection of 3 mL on withdrawal. The two injections should produce a “V” bordering the eye. An additional 2 mL can be injected deeper at the apex of the “V” to provide anesthesia to deeper fibers.
  107. retro bulbar block 3 goals
    • the goal with this block is to immobilize the eye and block the ciliaryganglion. So the three goals of the block can be summarized with 3 A’s:
    • 1. Akinesia of the eye
    • 2. Anesthesia of the eye 
    • 3. Abolishment of the oculo-cardiac reflex.
  108. retrobulbar block
    • Prior to beginning the eye block, topical anesthesia usually 1% tetracaine is applied to the conjunctiva and the patient is sedated, again what’s used for sedation varies (use anything from: midaz, midaz&fent, propofol, remifentanyl) idea being that will sedate the patient, make them comfortable for the block, and then awake during the procedure so they don’t fall asleep and startle. When
    • we worked at the eye center, they used midazolam exclusively in small doses (varied). They preferred this because it was less likely to cause NV

    • So
    • after the little bit sedation and some tetracaine, the inferior border of the
    • orbital rim is located at a point approximately 1/3 of the distance from the
    • lateral to the medial canthus, at this point it’s usually directed inferior to
    • the lateral border of the dilated pupil. The eye is held in neutral forward
    • gaze, so it’s helpful if the patient is a little bit sedated but able to
    • cooperate (look where you want them to look) because upward medial deviation
    • can rotate the optic nerve and then the vessel is in the path that the needle
    • is about to go, so it’s important they can cooperate. A 1 ½ 23 G inch blunt tip
    • needle is introduced perpendicularly into the skin and advanced directly
    • posterior parallel to the floor of the orbit. The tip will usually lie opposite
    • the equator of the globe, just below the skin. 
    • After the needle is advanced past the equator of the globe its angled surpranasally at
    • approximately a 45 degree angle to pass the muscle cone.
  109. resistance of the needle in a retrobulbar block
    • Once the needle passes the muscle body
    • into the cone there is an abrupt release of traction and the globe springs back to a neutral position. After aspiration 3-4mL of anesthetic is injected slowly.  There shouldn’t be any resistance to injection if the needle is in the cone. Resistance might be intramuscular placement and the needle should be repositioned. Sclero perforation should be suspected if the patient complains of pain on injection and again it’s important to remember that sedation may mask this. These special blunt tip needles are designed to hopefully reduce the chance of globe perforation. Then gentle pressure is applied to the globe for 5 mins to facilitate the spread of the solution but again this is released every 30 secs to preserve retinal blood flow.
  110. The peribulbar block
    • this was developed due to concerns of retrobulbar hemorrhage and globe perforation from the classic retrobulbar approach. The peribulbar needle does not enter the muscle cone so theoretically the risk of complications is reduced. The disadvantage to this approach is that there is a slower onset and a need for reinjection 25-35% of the time compared to 10% of the time with retrobulbar injection. The technique is sedation with topical anesthesia with etrocaine, 1 ½” inch 25g needle inserted
    • through the conductive at the inferior temporal area above the inferior orbital rim as shown here. Theneedle is advanced in a slight upward direction parallel to the rising orbital floor without any attempt to enter into the muscle cone and 4-5mL of local anesthetic is injected. The needle is reinserted in the superior nasal area,
    • just below and medial to the supratrochlear
    • notch and an additional 4-5mL is injected. Again the insertion is tangential to the globe without any attempt to enter the cone. With both injections the needle is only advanced 1” into the orbit and this is generally enough to reach behind the equator of the globe. So here again the onset is slower, the block
    • has to be assessed at 10 mins for potential supplementation of the injection. With this approach in particular, loss of vision doesn’t always occur. But 7th cranial nerve anesthesia is often obtained by diffusion of the anesthetic into the subcutaneous tissues of the upper lid without the need for the separateinjection for the facial nerve.