Unit 1: Ophthalmology & Otorhinolaryngology June 4th – June 25thRequired Readings for Opthalmology & Otorhinolaryngology

Barash, Cullens, & Stoelting 7th ed. Chapters 47 & 48Nagelhout & Plaus 5th ed. Chapters 38, 39, & 42

Recommended Readings for Opthalmology & OtorhinolaryngologyMiller 7th ed.Chapter 75 & &77 (online Dykes library)

Morgan, Mikhail, & Murray 5th ed. 36 & 37

Objectives: 

1.      List potential drug interactions between ophthalmic and anesthetic agentsa.  Anesthesia that increases IOP

i. 30-40mmHg; coughing, straining, vomiting, intubation ii. 50mmHg; forceful lid squeeze ex is biting down on the tube and

squeezing your eyes shut .(normal blinking is 10mmHg)iii. Hypoventilation ( due to vasodilation)iv. Arterial hypoxemiav. Succinylcholine (6-12mmHg); succ peaks at 1-4 min and IOP elevation

resolves around 7 min, etomidate (due to myoclonus)vi. Ketamine (modest increase); typically avoided for eye cases

b. Anesthesia that decreases IOPi. Volatile anesthetics dose related response

ii. Opioids little to no decreaseiii. Hyperventilation ( due to vasoconstriction) iv. Hypothermia ( due to vasoconstriction and decreased aqueous humor

production)v. NDMB

Acetazolamide- carbonic anhydrase inhibitor. It is used in the treatment of glaucoma to decrease chronically elevated IOP. It induces an alkaline diuresis that may result in potassium depletion. May inc. perioperative hyperglycemia-increase insulin requirements. Inc loss of NA, K and water- may cause electrolyte imbalances and cardiac dysrhythmias. Given 500mg dissolves in 10 ml of sterile water.

Echothiophate- If used with Succs -use neuromuscular blockade monitoring d/t possibility of prolonged paralysis caused from the anticholinesterase effect of

echothiophate. 1 month or more of tx will result in plasma pseudocholinsterase activity that is <5% of normal. Echothiophate is very long-acting. Returns 4-6 weeks after d/c of echo. used to maintain miosis in the treatment of glaucoma. Systemic absorption leads to total body inhibition of plasma cholinesterase. Inhibition of the metabolism of ester-type local anesthetics may predispose a patient to local anesthetic toxicity.

Mannitol-lg doses may cause renal failure, CHF, electrolyte imbalance hypo/hypertension MI and allergic reaction. Need foley with administration. osmotic diuretic. It causes a decrease in IOP lasting 5 to 6 hours. Patients who receive the drug during surgery may need a urinary catheter to avoid overdistention of the bladder. Mannitol causes an increase in the circulating blood volume, which may lead to

congestive heart failure in patients with poor ventricular function.

Phenylephrine- used to dilate pupil. Abdorption of the 10% solution may cause-hypertension, headache, tachycardia, tremulousness. 2.5% is safer. If pt has CAD- may cause MI, dysrhythmias and ischemia. If pt has aneurysm- may cause hemorrhage.

Pilocarpine/ acetylcholine- inc. cholinergic toxicity, bradycardia, hypotension. Reverse with atropine. Halothate increases effects of aceylcholine. Bradycardia and acute bronchospasm have been reported.

Timolol- inc. hypotension, bradycardia. May exacerbate myasthenia gravis. Cause post op apnea in neonates and infants. Systemic absorption causes β-blockade, with possible bradycardia, bronchospasm, or exacerbation of congestive heart failure.[106] Care should be taken especially in a patient with severe chronic obstructive pulmonary disease.

Tamsulosin hydrocholoride-has selective α-adrenoreceptor antagonistic properties and binds for a long period to nerves to the iris dilator muscle, affecting iris dilation and leading to complications in cataract surgery. The iris remains floppy even after 7- to 28-day interruption of the tamsulosin regimen

Sulfur hexafluoride- suggested to not use with nitrous oxide d/t the bubble increasing in size. Avoid for 10 days after administration. Perfluoropropane (longer acting agent for detached retina) is in the eye for 30 days. Avoid nitrous. ( If using nitrous oxide, d/c 15 min prior to admin of gas bubble)

2.      Determine ocular effects of phospholine iodine (Echothiophate) and beta blockers,a.  Beta blockers (Timolol and Betaxolol), given topically, may decrease aqueous

humor production or facilate drainage. Used as an antiglaucoma drug. Since considerable conjunctival absorption may occur, use caution with patients with COPD, CHF, or 1st AVB, and asthma.

b.  Echothiophate- is a long acting antichlinesterase miotic that lowers IOP by decreasing reisitenace to the outflow of aqueous humor.

3.      Explain the ocular effects of neosynephrine, ephedrine, and epinephrine

 Neosynepherine causes pupillary dilation and capillary decongestion.

b. Epinepherine/ephedrine, is used for open angle glaucoma, increases outflow and decreases aqueous production

4.      Identify competitive muscarinic cholinergic antagonists and their actions

Competitive muscarinic cholinergic antagonists:o Direct muscarinic antagonist (competitive with Ach)

MOA: selective for muscarinic receptors (not nicotinic therefore no action at ganglia or NMJ)

Parasympatholytic

Positive chronotrope Drugs (aka cycloplegics or mydriatics)

o Atropine - An anticholinergic that produces mydriasis to aid with ocular examination and surgery. It also can precipitate central anticholinergic syndrome. (Sx range from dry mouth, tachycardia , agitation, delirium, and hallucinations to unconsciousness.) Physostigmine 0.01-0.03 mg/kg will ↑ central acetylcholine and reverse the symptoms. (It may be repeated after 15-30 min).

o Homoatropineo Cyclopentolate - A commonly used mydriatic with the potential for CNS toxicity,

including Sz, psychotic reactions, and dysarthria.

Actionso Pupillary dilators

Cause temporary paralysis of ciliary muscle and muscles of accommodation

o ↓ lacrimal secretionso ↑ intraocular pressure

Nagelhout Box 39-2 p. 983

5.      Describe the adverse effects of  succinylcholine and open globe injuries

 Open globe injuries run the risk of expulsion of intraocular contents from IOP Any ↑ in venous pressure (coughing, straining, head-down position, DL) can ↑ IOP Mydriatic drugs can ↑ IOP Common scenario for anesthesia is open globe injury + full stomach Sux ↑ IOP – sustained contracture of extraocular muscles can cause intraocular expulsion RSI??? Choosing or avoiding sux is a matter of balance of risk Ask 2 questions:

1. Is it a difficult airway?2. Is eye viable?

Answer:1. Easy airway avoid sux - regardless of aspiration risk and eye viability – use

roc 2. Difficult airway but surgeon feels eye is viable use sux

Time meds to decrease stimulation from DL Can pretreat with NDMB + lidocaine (1.5 – 2mg/kg given 1.5-2 min before

DL) Rule is: difficult airway + viable eye = sux Nagelhout pg 993-994

6.      Formulate proper positioning to alleviate possibility of intraocular pressure.

 Normal lOP ranges from 10-22 mmHg, depending on the rate of formation and drainage of aqueous humor, choroidal blood volume, scleral rigidity, ex traocular muscle tone, as well as extrinsic pressure on the eye (e.g. , a poorly fitting mask or retrobulbar hematoma). Patient movement, coughing, straining, vomiting, hypercarbia, HTN, and ET

intubation also may ↑ IOP to 40 mmHg or more.o > 22mmHg abnormalo Diurnal variation 2-5mmHg with higher value observed on awakening

Head down position (trendelenburg) ↑ IOP Propofol and etomidate ↓ IOP Inhalation induction in infants and children ↓ IOP NMBD ↓ IOP Lidocaine can attenuate the ↑ IOP from DL (see question 5) Procdures performed supine with bed rotated 90-180° away from anesthetist Jaffe p. 158, Nagelhout p. 993, Barash p. 1376

7.      Cite etiology of the oculocardiac reflex and its prevention and/or treatment.•  First described in 1908 by Bernard Aschner and Guiseppe Dagnini

• Most common manifestation is sinus bradycardia• Occurrence 16-82%, large variance• Trigeminovagal response triggered by by pressure on the globe and by traction on the

extraocular mm, conjunctiva, or orbital structures• Afferent limb – orbital contents to ciliary ganglion to ophthalmic division of the

trigeminal nerve to the sensory nucleus of the trigeminal near the fourth ventricle• Efferent limb - vagal nerve to the heart

Treatments• Ask the surgeon to STOP manipulation of the eye!!

– Don’t be shy to ask them to stop what they are doing• IV atropine 7mcg/kg increments• May consider pretreatment IV atropine or glycopyrrolate (pt. history of conduction

block, vasovagal responses, b-blocker therapy, & also CAD!)

BOOK:

Oculocardiac Reflex

Bernard Aschner and Giuseppe Dagnini first described the oculocardiac reflex in 1908. This reflex is triggered by pressure on the globe and by traction on the extraocular muscles, as well as on the conjunctiva or the orbital structures. Moreover, the reflex may also be elicited by performance of a retrobulbar block,30 by ocular trauma, and by direct pressure on tissue remaining in the orbital apex after enucleation. The afferent limb is trigeminal and the efferent limb is vagal. Although the most common manifestation of the oculocardiac reflex is sinus bradycardia, a wide spectrum of cardiac dysrhythmias may occur, including junctional rhythm, ectopic atrial rhythm, atrioventricular blockade, ventricular bigeminy, multifocal premature ventricular contractions, wandering pacemaker, idioventricular rhythm, asystole, and ventricular tachycardia.31 This reflex may appear during either local or general anesthesia; however, hypercarbia and hypoxemia are believed to augment the incidence and severity of the problem, as may inappropriate anesthetic depth.

Reports on the alleged incidence of the oculocardiac reflex are remarkable in their striking variability. Berler30 reported an incidence of 50%, but other sources quote rates ranging from 16% to 82%. Commonly, those articles disclosing a higher incidence included children in the study population, and children tend to have more vagal tone.

A variety of maneuvers to abolish or obtund the oculocardiac reflex have been promulgated. None of these methods have been consistently effective, safe, and reliable. Inclusion of intramuscular anticholinergic drugs such as atropine or glycopyrrolate in the usual premedication regimen for oculocardiac reflex prophylaxis is ineffective.32

Atropine given intravenously within 30 minutes of surgery is believed to reduce incidence of the reflex. However, reports differ concerning dosage and timing. Moreover, some anesthesiologists claim that prior intravenous administration of atropine may yield more serious and refractory cardiac dysrhythmias than the reflex itself. Clearly, atropine may be considered a potential myocardial irritant. A variety of cardiac dysrhythmias33 and several conduction abnormalities,34 including ventricular fibrillation, ventricular tachycardia, and left bundle-branch block, have been attributed to intravenous atropine.

Although administration of retrobulbar anesthesia may provide some cardiac antidysrhythmic value by blocking the afferent limb of the reflex arc, such a regional technique is not devoid of potential complications, which include, but are not limited to, optic nerve damage, retrobulbar hemorrhage, and stimulation of the oculocardiac reflex arc by the retrobulbar block itself.

It is generally believed that the aforementioned prophylactic measures, fraught with inherent hazards, are usually not indicated in adults. If a cardiac dysrhythmia appears, initially the surgeon should be asked to cease operative manipulation. Next, the patient’s anesthetic depth and ventilatory status are evaluated. Commonly, heart rate and rhythm return to baseline within 20 seconds after institution of these measures. Moreover, Moonie et al.35 noted that, with repeated manipulation, bradycardia is less likely to recur, probably secondary to fatigue of the reflex arc at the level of the cardioinhibitory center. However, if the initial cardiac dysrhythmia is especially serious or if the reflex tenaciously recurs, atropine should be administered intravenously, but only after the surgeon stops ocular manipulation.

For pediatric strabismus surgery; however, some anesthesiologists administer intravenous atropine, 0.02 mg/kg, before commencing surgery.36 Alternatively, glycopyrrolate, 0.01 mg/kg administered intravenously, may be associated with less tachycardia than atropine in this setting.

8.      Communicate anesthetic procedures to overcome hazards of penetrating ocular injury.•  Injury from:

– Anesthetic mask/Induction– Surgical drapes– Spillage of solutions– Emergence/Pt hands– Ablation of corneal reflexes

Induction: anesthetist watch or id badge can cause corneal abrasionPrevention > treatment--- decrease/proper control IOP; Prevention: maintain adequate MAP (keep within 20% of baseline)

Decreases In IOP• Volatile anesthetics

– Dose related response• Opioids (little or no decrease)*• Hyperventilation• Hypothermia• NDMB**

BOOK

The anesthesiologist involved in caring for a patient with a penetrating eye injury and a full stomach confronts special challenges. He or she must weigh the risk of aspiration against the risk of blindness in the injured eye that could result from elevated IOP and extrusion of ocular contents.

Although regional anesthesia is often a valuable alternative for the management of trauma patients who have recently eaten, this option had traditionally been considered contraindicated in patients with penetrating eye injuries because of the potential to extrude intraocular contents via pressure generated by injection of local anesthetics. Nonetheless, some anecdotal case reports of successful use of ophthalmic blocks in this setting have been published.114 Recognizing that there are several distinct permutations of eye injuries, Scott et al.115 developed techniques to safely block patients with select open-globe injuries. In a 4-year period, 220 disrupted eyes were repaired via regional anesthesia at Bascom Palmer Eye Institute. A significant number of injuries were caused by intraocular foreign bodies and dehiscence of cataract or corneal transplant incisions. Blocked eyes tended to have more anterior, smaller wounds than those repaired via general anesthesia. There was no outcome difference—that is, change of visual acuity from initial evaluation until final examination—between the eyes repaired via regional versus general anesthesia. Moreover, combined topical anesthesia and sedation for selected patients with open-globe injuries has also been reported.116

Nonetheless, it is not always possible to determine the extent of disruption preoperatively, and general anesthesia is typically considered prudent in this setting. Preoperative prophylaxis against aspiration may involve administering H2 receptor antagonists to elevate gastric fluid pH and to reduce gastric acid production. Metoclopramide may be given to induce peristalsis and enhance gastric emptying.

Traditionally, an induction agent and nondepolarizing neuromuscular blocking drug technique was described as the method of choice for the emergency repair of an open eye injury; the nondepolarizing drug pancuronium in a dose of 0.15 mg/kg has been shown to lower IOP.

However, this method has its disadvantages, including risk of aspiration and death during the relatively lengthy period—ranging from 75 to 150 seconds—during which the airway is unprotected. Performance of the Sellick maneuver during this interval may afford some protection. Furthermore, a premature attempt at intubation of the trachea produces coughing, straining, and a dramatic rise in IOP, emphasizing the need to confirm the onset of drug effect with a peripheral nerve stimulator while appreciating, nonetheless, that muscle groups vary in their response to muscle relaxants. Moreover, the cardiovascular side effects of tachycardia and hypertension may prove worrisome in patients with coronary artery disease. Also, the long duration of action of intubating doses of pancuronium may mandate postoperative mechanical ventilation of the lungs. Intermediate-acting nondepolarizing drugs such as vecuronium have briefer durations of action, and less dramatic, if any, circulatory effects, but nevertheless have an onset of action similar to that of pancuronium.

Several studies have explored the use of extremely large doses of nondepolarizing muscle relaxants to accelerate the onset of adequate relaxation for endotracheal intubation. Using vecuronium doses of 0.2 and 0.4 mg/kg, Casson and Jones117 found mean onset times of 95 and 87 seconds, respectively. Ginsberg et al.118 found that by increasing the vecuronium dose from 100 to 400 μg/kg the corresponding times to endotracheal intubation decreased from 183 to 96 seconds.

Succinylcholine offers the distinct advantages of swift onset, superb intubating conditions, and brief duration of action. If administered after careful pretreatment with a nondepolarizing drug and an induction dose of thiopental (4 to 6 mg/kg), succinylcholine produces only small increases in IOP.119 Although the advisability of this technique has been debated vociferously, there are no published reports of loss of intraocular contents from a pretreatment barbiturate–succinylcholine sequence when used in this setting.120 Moreover, in 1993, McGoldrick121 pointed out that the 1957 watershed article of Lincoff et al.18 states: “Various communications have been received from ophthalmologists who have used succinylcholine in surgery. This includes several reports of cases in which succinylcholine was given to forestall impending vitreous prolapse only to have a prompt expulsion of vitreous occur.” Under such desperate circumstances, it is extremely difficult to attribute the expulsion of vitreous directly to succinylcholine.121

Rocuronium, with its purportedly rapid onset, may prove to be a useful drug in these circumstances, provided adequate doses (1.2 mg/kg intravenously) are administered. Unfortunately, it has an intermediate duration of action that could be disadvantageous, compared with succinylcholine, in a patient with an unrecognized difficult airway. Sugammadex may provide a solution. It is an oligosaccharide chelating agent that rapidly reverses the effects of aminosteroid neuromuscular blocking agents, particularly rocuronium. Recovery of >90% train-of-four responses may be accomplished in <120 seconds.122 Thus, in the future, a new paradigm for the “open-globe, full-stomach” scenario may entail rapid-sequence induction with high-dose rocuronium to achieve swift onset of superb intubating conditions, followed by quick termination of neuromuscular blocking effect by sugammadex if the situation is encountered in which one cannot intubate or cannot ventilate.123 As of this writing, however, sugammadex has not been approved for use in the United States.

9.      Discuss how acid base imbalance affects ophthalmologic physiological parameters

IOP determined by rate of aqueous production and humor outflow

Production = Main determinate of IOP = Sodium is actively transported into aqueous humor in posterior chamber. Bicarbonate and chloride ions passively follow the sodium ions – this results in osmotic pressure of aqueous humor being many times that of plasma

o Hypertonic solutions (mannitol) – lower IOP because small change in solute concentration of plasma markedly influences formation(Barash 1376)

In Respiratory acidosis –> papilledema, constricted pupils (helps lower IOP)

Dilated pupils -> Fontana spaces narrow -> resistance to outflow -> IOP rises (undesirable in glaucoma use miotics and minor dehydration)

Dilated blood vessels -> venous fluctuations -> increases in blood volume or pressure -> decrease aqueous outflow -> Increases IOP

Metabolic acidosis -> nausea/vomiting -> increased IOP by 40 mm Hg or more 

10.  Relate  techniques to  prevent coughing and vomiting postoperatively – Ch 36 Nagelhout pg 992-993

Cough

o Sedation meds like Propofol– small dose

o Lidocaine 2% 1.5-2mg/kg before extubation

o Suction of airway while deep or awake only

o If patient is awake have them clear there throat, which decreases force of cough

o Apply phenylephrine nose drops – if have a postnasal drip

o Dry throat – give patient a sip of water if awake enough – prevents coughing

o Quick shallow breaths – prevent coughing

Vomiting:

o Anti-nausea meds

5HT3 antagonists

Histamine 2 antagonists

Reglan

Propofol or etomidate

o For Ear/nose/throat/facial surgies - Decrease accumulation of blood in posterior oropharynx, which drains to stomach (OG suction or pack throat with surgical pack)

o Low dose narcotics 11.  Describe how  providers coordinate care when intraocular gas expansion is used

During retinal detachment surgery – sometimes injecting an expandable gas is preferred, in that case, cessation of N20 is necessary about 15 min prior to injection

If patient requires anesthesia after that, do NOT use N20 for 5 days after air injection or 10 days after sulfur hexafluoride

Medical alert bracelets are available now for providers to give to patients after ocular surgery as a communication tool to other providers

Barash 1391-1392 

12.  List the hazards and complications associated  with  laser surgery (Nagelhout, Ch 42, p.1041- ) two most common CO2 and Nd:YAG. Nd:YAG

waveleght is shorter and there for less less absorption and subsequently less tissue penetration. (ex, CO2 laser would burn the cornea, but the Nd:YAG laser would just go right through it)

Laser (light amplification by stimulated emission of radiation). Lasers are associated with rapid and precise vaporization or coagulation of tissues and are commonly used in a variety of unrelated diagnostic and therapeutic procedures. The CO2 laser is the most widely used in medical practice, having particular application in the treatment of laryngeal or vocal cord papillomas. The energy emitted by a CO2 laser is absorbed by water contained in blood and tissues. Human tissue is approximately 80% water, and laser energy absorbed by tissue water rapidly increases the temperature, denaturing protein and vaporizing the target tissue. The thermal energy of the laser beam cauterizes capillaries as it vaporizes tissues; thus, bleeding and postoperative edema are minimized.

Four classification of Lasers I-IV p. 1043 Any facility that has a Laser with Class IIIb or IV must have a Laser Safety Officer

(LSO) Warning signs should be posted outside the room with the type of Laser in use and

the specific type of eye ware needed.

All windows should be covered

Most common hazards of medical laser include thermal trauma, eye injury, perforation of organs or vessels, gas embolization, electrical shock, air contamination, and fire

Thermal trauma is the most common cause of laser-induced tissue damage. To prevent, restric assess to Laser area. To avoid cutaneous burns from deflected beams, wet towels should be applied to exposed skin of the face and neck when the laser is being used in the airway

The human eye is extremely vulnerable to Laser radiation b/c it is coherent, and all the energy gets focused on the retina and cornea. It is all depended on the power and wavelength of the laser beam and duration. Rods make up 95% of the retina and are for detecting light, Cones make up 5% and are for detecting colors. Laser eye wear must be worn by everyone in the room with eh right optical density.

Operator error while using the Lase can cause perforation of vessel of cause a pneumothorax

Venous Air Embolism is a rare but life threatening potential complication Laser smoke plumes may cause damage to the lungs. The amount of smoke produced

1 gm of tissue = 3-6 cigarettes. A local exhaust ventilation system with a HEPA filter should be used.

Want Patient paralyzed, both O2 and N2o support combustion so use a combination of blended air and oxygen or helium and oxygen /c less the 30% O2, ET Tube is flammable, may want laser resistant tube, Eyes are exspecially vulnerable to laser damage so you will want protective eye wear specific to the type of laser being used. Want high filtration mask, and signs on the door to warn anyone entering the OR room and cover windows with window shades.

Fire requires three things to be present- Oxidizer, fuel sources, and an ignition source.

Box 42-1 Laser Safety Precuations p. 1045 Box 42-2 Prevention of Surgical Fires p. 1046 Box 42-3 Management of Airway fires p. 1048

13.  Describe the technique for  translaryngeal block anesthesia, A translaryngeal block is simple to perform and results in anesthesia of the trachea below the vocal cords. However, injection of local anesthetic usually stimulates the cough reflex, and this block should be avoided in patients in whom coughing is undesirable.

With the patient in the supine position, the cricothyroid membrane is located, and a 20-gauge or smaller, 3- to 5-cm plastic catheter over a needle is introduced in the midline (Fig. 52-30). The inner steel cannula is withdrawn with the plastic catheter held firmly in place; aspiration of air confirms correct catheter placement. Between 3 and 5 mL of a 4% lidocaine solution is injected rapidly and usually results in a vigorous cough, which aids in spread of the solution within the trachea.

Another sources…

Inform the patient about the procedure, what is expected of him, and likelihood of coughing. Anesthetist should be in position to place index and third fingers of the non-dominant hand in the space between the thyroid and cricoid cartilages (identifying the cricothyroid membrane). The trachea can be held in place by placing the thumb and third finger on either side of the thyroid cartilage. The midline should then be identified and injected lightly to create a local skin wheal (using a 22-guage or smaller needle). A 10 ml syringe containing 4% lidocaine (or other desired concentration), is mounted on a 22-guage, 35 mm plastic catheter over a needle, and is introduced into the trachea. The catheter is advanced into the lumen, midline thru the cricothyroid membrane, at an angle of 45 degrees, in a caudal direction. *Immediately after the introduction of the catheter into the trachea, a loss of airway resistance and aspiration of air confirms placement, and the needle is removed from the catheter. The patient is then asked to take a deep breath and then asked to exhale forcefully. At the end of the expiratory effort, 3-4 ml of local anesthetic solution is rapidly injected into and over the back of the trachea. This will usually cause patient to first inhale to catch his or her breath and then forcefully cough, spreading the lidocaine over the trachea, making distal airway anesthesia more predictable This area is nearly devoid of major vascular structures.

14.  Outline superior laryngeal nerve  and glossopharyngeal  block procedures. Barash page 790-791Glossopharyngeal BlockThe oropharynx is innervated by branches of the vagus, facial, and glossopharyngeal nerves. The glossopharyngeal nerve travels anteriorly along the later surface of the pharynx, its three branches supplying sensory innervation to the posterior third of the tongue, the vallecula, the anterior surface of the epiglottis (lingual branch), the walls of the pharynx (pharyngeal branch) and the tonsils (tonsillar branch). A wide variety of techniques may be used to anesthetize this part of the airway. The simplest techniques involves aerosolized local anesthetic solution, or a voluntary “swish and swallow.” Some patients may require a glossopharyngeal nerve block, especially when topical techniques do not adequately block the gag reflex. The branches of this nerve are most easily accessed as they transverse the palatoglossal folds. These folds are seen as soft tissue ridges that extend from the posterior aspect of the soft palate to the base of the tongue, bilaterally. A noninvasive technique employs anesthetic-soaked cotton-tipped applicators that are positioned against the inferior most aspect of the folds and left in place for 5-10 minutes. When the noninvasive technique proves inadequate, local anesthetic can be injected. Standing on the side contralateral to the nerve to be blocked, the operator displaces the extended tongue to the contralateral side and a 25-gague spinal needle is inserted into the fold near the floor of the mouth. An aspiration test is performed. If air is aspirated, the needle has passed through and through the membrane. If blood is aspirated, the needle tip is redirected more medially. The lingual branch is most readily blocked in this manner, but retrograde tracking of the injectate has also been demonstrated.

FROM POWERPOINT• Indication:

▫ abolition of the gag reflex or hemodynamic response to laryngoscopy. • Drugs:

▫ Cetacaine spray (mix of 14% Benzocaine and 2% Tetracaine)▫ Lidocaine spray 10%▫ Lidocaine gel 2-5%▫ Viscous lidocaine 2%▫ Tetracaine .5% soln▫ Lidocaine 4% soln

 Barash page 790-791Superior laryngeal nerve   An external block is performed with the patient supine with the head extended and the clinician standing on the side ipsilateral to the nerve to be blocked. The clinician identifies the superior cornu of the hyoid bone beneath the angle of the mandible. Using one hand, medially directed pressure is applied to the contralateral hyoid cornu, displacing the ipsilateral hyoid cornu toward the clinician. Caution must be taken to locate the carotid artery and displace it if necessary. The needle can be inserted directed of the hyoid cornu and then “walked” off the cartilage in an anterior-caudad direction until it can be passed through the ligament to a depth of 1-2 cm. Before injection of the local anesthetic, an aspiration test should be performed to ensure that one has not entered the pyriform sinus or a vascular structure. Local anesthetic (1.5-2mL) is injected in the space between the thyrohyoid membrane and the pharyngeal mucosa. The superior laryngeal nerve can also be blocked with a noninvasive internal technique. The patient is asked to open the mouth widely, and the tongues is grasped using a gauze pad or tongue blade. A right angled forceps (e.g. Jackson Krasue forceps) with anesthetic soaked cotton swabs is slid over the lateral tongue and into the pyriform sinuses bilaterally. The cottons swabs or sponge are held in place for 5 minutes.

FROM POWERPOINT• Indications:

▫ To block the internal (sensory) branch of the SLN, resulting in abolition of the gag reflex or hemodynamic responses to laryngoscopy or bronchoscopy

▫ The internal branch is the nerve of interest in this block; it is blocked where it enters the thyrohyoid membrane just inferior to the caudal aspect of the hyoid bone.

• Drugs:

▫ 2-4 ml of Lidocaine 1% or 2% lidocaine, with or without epinephrine.

15.  Identify the advantages and disadvantages Miller and Macintosh laryngoscope blades  (From Miller’s. There’s no powerpoint up yet, so I just put in all the information from Miller’s until she specifically tells us what she wants us to know, then I’ll edit it…sorry so long, just wanted to be thorough)

Macintosh Laryngoscope and Technique of Orotracheal Intubation

The Macintosh curved laryngoscope is radically different from the preexisting straight laryngoscopes. In particular, the long axis of the blade is curved, the cross section is a right-angled “Z” section, the web and flange are bulky, the tip is atraumatic, and the light bulb is shielded by the web. However, Macintosh's key innovation was his novel technique of indirect elevation of the epiglottis, achieved by tensioning the hyoepiglottic ligament after the tip of the laryngoscope was positioned in the vallecula. This technique is the key to success of the Macintosh laryngoscope—and its fundamental flaw. When it works well, the epiglottis is elevated completely and lies behind and along the posterior surface of the laryngoscope blade. However, it is not possible to position the Macintosh laryngoscope correctly in some patients. Minor difficulty results in partial elevation of the epiglottis, erroneously described as a “floppy epiglottis,” and major difficulty leads to complete failure to elevate the epiglottis with the consequence that the vocal cords cannot be seen.

Full mouth opening facilitates insertion of the laryngoscope. It is inserted from the right side of mouth and to the right of the tongue while taking care to not trap the lips between the laryngoscope blade and the teeth. The laryngoscope is advanced and simultaneously moved into the midline to displace the tongue to the left. Progressive visualization of anatomic structures minimizes the risk of trauma. The epiglottis is the first key anatomic landmark. The tip of the laryngoscope is advanced into the vallecula, and the epiglottis is elevated indirectly by applying a force that tensions the hyoepiglottic ligament. Elevation of the epiglottis is optimized and a further lifting force is applied to the laryngoscope to achieve the best view of the larynx (Fig. 50-7). It is very important not to lever on the

maxillary teeth because this may cause dental damage[58] and reduce the view of the larynx. If visualization of the larynx cannot be achieved without pressure on the teeth, use of this laryngoscope should be abandoned and another technique of tracheal intubation used.

When a good view of the larynx is achieved, the vocal cords, aryepiglottic folds, posterior cartilage, and interarytenoid notch can be identified (Fig. 50-8). The view should be optimized to facilitate passage of the tracheal tube. If the view of the larynx is poor, it is important to check that the basic technique has been performed optimally and other maneuvers used (Box 50-6). External laryngeal manipulation (better described as “bimanual laryngoscopy,” which implies internal movement of the laryngoscope with external manipulation of the larynx), performed by the anesthesiologist who guides an assistant (Fig. 50-9), consistently improves the laryngeal view. It is a key maneuver.

Tracheal Tube Passage with Successful Macintosh Laryngoscopy

Not all of the factors that contribute to difficulty with direct laryngoscopy have been identified. Factors that impair insertion of the laryngoscope, lateral displacement of the tongue, or elevation of the epiglottis will impair the efficacy of direct laryngoscopy. Anatomic causes include limited mouth opening, awkward dentition, hypoplastic mandible, impaired TMJ function, and limited head extension. A final common pathway of difficulty with the Macintosh laryngoscope was suggested by a soft tissue radiology study of laryngoscopy.[62] In patients with known difficult laryngoscopy the tongue could not be completely displaced and part was trapped between the tip of the laryngoscope and the hyoid bone. The tip of the laryngoscope could not enter the vallecula and advancement of the laryngoscope displaced the epiglottis further into the line of sight. Thus, indirect elevation of the epiglottis, the novel feature of the Macintosh technique, is also its fundamental flaw.

Blind Endotracheal Intubation with the Macintosh Laryngoscope

If the larynx cannot be seen, it is not possible to intubate the patient under vision with the Macintosh laryngoscope, and failure and soft tissue trauma are potential risks. The anesthesiologist must decide whether to use a blind technique with the Macintosh laryngoscope, abandon further attempts at tracheal intubation and awaken the patient, or use an alternative visual technique of laryngoscopy—provided that skills have been developed. Use of an SAD for elective surgery in these patients when tracheal intubation had been the first choice places them at risk if the airway becomes obstructed.

Modifications of the Macintosh laryngoscopeMany variations have been described, most without data about their efficacy. A Macintosh-type laryngoscope with a hinged tip that flexes when a lever on the handle is depressed was introduced by McCoy. It works well in simulated difficult laryngoscopy, and there have been many clinical reports of success when the glottis could not be visualized with the Macintosh laryngoscope. However, an angulated straight laryngoscope performed much

better than the McCoy in clinical unanticipated difficult intubation, and there have been many reports of failure of the McCoy laryngoscope to achieve a view of the glottis.

Straight LaryngoscopeLaryngoscopy for tracheal intubation was first performed with the straight laryngoscope, which remains the diagnostic and therapeutic laryngoscope used by ENT surgeons. Many studies[45] have reported successful tracheal intubation under vision with the straight laryngoscope in patients in whom intubation proved impossible with the Macintosh laryngoscope. Corroborative evidence of the value of this technique comes from many reports of successful use of the ENT straight laryngoscope and the rigid bronchoscope in such patients.The mechanism of the greater efficacy of the straight laryngoscope is probably both improved control of the tongue and more reliable elevation of the epiglottis and is consistent with the reduced force and head extension needed with the straight laryngoscope.[55] The straight laryngoscope is of particular value with laryngeal lesions (including lingual tonsil hypertrophy) and in patients with a hypoplastic mandible. It is useful in some patients with awkward dentition, particularly the presence of a gap in the right upper dentition. Mastery of the straight laryngoscope is an asset to any anesthesiologist.The technique described here, the paraglossal technique, affords optimum control of the tongue. Initial preparation for tracheal intubation is identical to that used with the Macintosh laryngoscope. Head extension is as important as in the Macintosh technique. It is essential to displace the entire tongue to the left of the laryngoscope. The laryngoscope is inserted lateral to the tongue and advanced carefully along the paraglossal gutter between the tongue and tonsil. Application of continued moderate lifting force to the laryngoscope handle helps maintain lateral displacement of the tongue and reduces contact with the maxillary teeth. As the laryngoscope is advanced, the epiglottis comes into view and the tip of the laryngoscope is passed posterior to it. The optimal position of the tip of the straight laryngoscope is in the midline of the posterior surface of the epiglottis, close to the anterior commissure of the vocal cords (Fig. 50-11). This position achieves good control of the epiglottis and facilitates passage of the tracheal tube. The direction of force applied to the handle of the straight laryngoscope is at right angles to the straight laryngoscope blade (and in line of sight of the larynx). Under no circumstances should levering action be applied to the teeth. Not only does this risk dental damage, but it also degrades the view. If a good view cannot be achieved, a different technique of laryngoscope or tracheal intubation should be used.

The Miller laryngoscope is popular because its low profile facilitates insertion and positioning, but there are some problems. The tip has a small point of contact with the posterior surface of the epiglottis, so there is a risk of trauma and unstable elevation of the epiglottis. Precise positioning is difficult because the tip is not visible. The major problem with the Miller laryngoscope is that its cross section impedes passage of the tracheal tube. Straight laryngoscopes have been designed to overcome problems with the Miller laryngoscope. The Belscope is a narrow angulated straight laryngoscope with a low profile and an atraumatic tip that was designed to reduce contact with the maxillary teeth. The efficacy of the Belscope when the larynx cannot be seen with the Macintosh laryngoscope has been confirmed. The C-shaped cross section of the Henderson laryngoscope facilitates the passage of tracheal tubes.

16.  Relate steps used in performing fiberoptic, retrograde block, and blind intubations.FIBEROPTIC:

The fiberoptic bronchoscope can be used to evaluate the airway, facilitate intubation of the patient with a difficult

airway, check ETT placement, change an existing ETT, and perform post-extubation evaluations. The flexible fiber optic laryngoscope consists of multiple strands of tiny glass fibers that transmit light.

Indications for fiber optic intubation are an anticipated difficult airway, cervical spine immobilization, anatomic abnormalities of the upper airway, anatomic abnormalities of the upper airway, failed intubation attempt but ventilation that is possible with a mask or SGA.

Steps: The patient’s airway should be anesthetized with either topical anesthesia, nerve blocks, or a combination of the two. Glyco. can be given 5-20 minutes prior to the procedure. Light sedation may help reduce the patient’s stress and provide for a more relaxed environment for the provider. Remifentanil can be used. A yaunker must be accessible whenever the fiberoptic bronchoscope is used. Medications for airway management should be readily available. Local anesthetic, resuscitation bag, induction drugs, and muscle relaxants. An ETT is first loaded onto the fiberoptic scope and is then inserted through either the mouth or the nose and advanced to the posterior pharynx. If at any time the provider is not sure of the location of the tube it should be retracted back. The tip of the scope is inserted into the glottic opening until the tracheal rings are present. The ETT is then slipped downward and the scope is used like a stylet and then through the cords into the trachea. After the ETT is advanced into the trachea, the operator can verify placement by visualization of the carina.

Retrograde block:

The oropharynx is innervated by branches of the vagus, facial and glossopharyngeal nerves (Figure 1). These nerves travel anterior along the lateral surface of the pharynx, and the three branches provide sensory innervation to the posterior third of the tongue,[8] the vallecula, the anterior surface of the epiglottis (lingual branch), the walls of the pharynx (pharyngeal branch), and the tonsils (tonsillar branch). The sensory innervation of the anterior two thirds of the tongue is provided by the trigeminal nerve (lingual branch of the mandibular division).8 Given that it is not a part of the reflex arcs controlling gag or cough, its blockade is not essential for comfort during fiberoptic intubation.

The internal branch of the superior laryngeal nerve is a branch of CN X (vagus nerve) (Figure 2). The superior laryngeal nerve provides sensory innervation to the base of the tongue, posterior epiglottis, aryepiglottic folds, and arytenoids.7 This branch originates from the superior laryngeal nerve lateral to the greater cornu of the hyoid bone. The recurrent laryngeal nerve provides sensory innervation of the vocal folds and trachea and motor function of all intrinsic laryngeal muscles except the cricothyroid supplied by the external branch of the superior laryngeal nerve.7

The internal branch of the superior laryngeal nerve is a branch of CN X (vagus nerve) (Figure 2). The superior laryngeal nerve provides sensory innervation to the base of the tongue, posterior epiglottis, aryepiglottic folds, and arytenoids.7 This branch originates from the superior laryngeal nerve lateral to the greater cornu of the hyoid bone. The recurrent laryngeal nerve provides sensory innervation of the vocal folds and trachea and motor function of all intrinsic laryngeal muscles except the cricothyroid supplied by the external branch of the superior laryngeal nerve.7

Clinical Pearls

Three major neural pathways supply sensation to airway structures (see Figure 1).

Terminal branches of the ophthalmic and maxillary divisions of

the trigeminal nerve supply the nasal cavity and turbinates. The oropharynx and posterior third of the tongue are supplied by

the glossopharyngeal nerve. Branches of the vagus nerve innervate the epiglottis and more

distal airway structures.

 

Techniques for Anesthetizing the Airway

Preparation for Awake Intubation

The process of intubating an awake patient requires careful preparation. The anesthesiologist must evaluate each patient’s needs on an individual basis. Nearly every patient experiences some degree of anxiety associated with the surgery, anesthesia, and perhaps outcome. For this reason, most patients require some degree of sedation and analgesia. For this purpose, it is best to use short-acting or reversible agents for sedation or agents that do not cause a considerable degree of respiratory depression. Some examples of commonly used medication for awake intubation include midazolam, alfentanil, and fentanyl. These sedatives/analgesics are particularly useful in this setting because of their easy titratability to effect easy reversal with flumazenil or naloxone. Similarly, dexmedetomidine does not cause respiratory depression and is suitable in this setting.9

Antisialogogues should be used before any airway instrumentation. Oral secretions may make visualization via the fiberoptic equipment difficult and may serve as a barrier to effective penetration of local anesthetic into the mucosa. Glycopyrrolate 0.4 mg given intramuscularly or intravenously helps to diminish secretions.10 Alternatively, atropine 0.5–1 mg may be used intramuscularly or intravenously to similar effect. Intramuscular administration is favored over intravenous administration to avoid undesired side effects such as tachycardia and, less commonly, psychosis (with atropine) (Table 1).

Table 1: Commonly Used Medications and DosagesWith Their Reversal Agents

Medication Dosage and Route Effect Reversal Agent

Atropine 0.5–1 mg IV, IM AntisialogogueN/A

Glycopyrrolate 0.2–0.4 mg IV, IM AntisialogogueN/A

DexmedetomidineLoading dose: 1 mcg/kg/min over 10 min

Sedative N/A

Infusion: 0.2–0.7 mcg/kg/min

Midazolam 0.5–4 mg IV Sedative Flumazenil

Fentanyl 10–100 mcg IV Opioid Naloxone

Alfentanil 100–1000 mcg IV Opioid Naloxone

Topical Anesthesia of the Nose, Mouth, Tongue, & Pharynx

One way to achieve anesthesia for oral or nasal fiberoptic intubation is to topicalize the structures involved with a local anesthetic. Topicalization of the airway is the spreading of local anesthetic over a region of mucosa to achieve local uptake and neural blockade of that region.

By far, the simplest of these techniques involves the spraying or swishing of local anesthetic directly onto themucosa of the mouth, pharynx, tongue, and/or nose. This can be accomplished with any of the many commercially available local anesthetics, particularly viscous lidocaine preparations and mixtures of benzocaine and tetracaine. The popular benzocaine (Cetacaine), a pressurized solution of benzocaine,

tetracaine, and butamben in a small canister, delivers a spray via a long spray nozzle that is pointed in the desired direction (Figure 3). The anesthetic is delivered in an oily foam, which is absorbed rapidly into the mucosa and provides excellent topical anesthesia of the mucosa.

Alternatively, a 10-mL syringe can be filled with lidocaine 2–4% and sprayed via a small-bore single or multiperforated catheter or the working channel of the fiberoptic bronchoscope.11 This arrangement produces a fine stream of local anesthetic liquid, whichwith sufficient aliquots directed at the target mucosa achieves an adequate topical anesthetic effect. The safety and efficacy of both techniques are well established. Even with large amounts of swallowed anesthetic, plasma levels of local anesthetic should not reach toxic levels.12,13

Topicalization by Use of Local Anesthetic Reservoirs

Topicalization can also be accomplished by the use of local anesthetic-soaked cotton pledgets or swabs. These are soaked in either viscous or aqueous solutions of local anesthetic and then left for 5–15 minutes on the region of mucosa that requires anesthesia. The cotton acts as a reservoir for the anesthetic agent, producing a dense block. This technique is especially effective in the nasal passages. In the past, cocaine-soaked pledgets were used because they resulted both in a

Figure 3: Topicalization of the mouth mucosa using a benzocaine spray.

superb local anesthetic effect and in localized vasoconstriction. This practice has fallen out of favor, however, as concerns about cocaine toxicity grew. In addition, because of cocaine’s high profile as an illicit drug, there are significant regulatory hurdles associated with stocking it in a hospital formulary (eg, DEA paperwork, theft, accurate accounting of usage). As a method of achieving similar results, most clinicians have used the technique of adding small concentrations of epinephrine (1:200,000 or less) or phenylephrine (0.05%) to lidocaine. Alternatively, a vasoconstricting nasal spray can be applied before application of the local anesthetic. This approach results in dry mucosa, which then can be more easily anesthetized with local anesthetic because the local anesthetic does not get diluted with nasal secretions or saliva. The resulting vasoconstriction is nearly as effective as that of cocaine and offsets lidocaine’s powerful vasodilatation.

The applicationof highly concentrated local anesthetic-soaked cotton pledget reservoirs can be exploited to achieve highly specific nerve blocks as well. These methods are detailed later with the description of individual nerve blocks.

Inhalation of Aerosolized (Atomized) Local Anesthetic

Inhalation of aerosolized local anesthetic is another simple technique to achieve oropharyngeal anesthesia. To perform this technique, local anesthetic is added to a standard nebulizer with a mouthpiece or face mask attached. The patient is then asked to inhale the local anesthetic vapor deeply. After a period of approximately 15–30 minutes, the patient should have inhaled a sufficient quantity of local anesthetic to achieve a reasonably good level of topical anesthesia throughout the oropharynx and trachea. Focused aerosolized local anesthetic from an atomizer is ideal for nasal intubation. A number of disposable commercially available syringe-powered atomizers are available but are deficient in achieving small particle size unless outfitted with a side-stream air/oxygen flow to enhance dispersion by virtue of the Venturi principle (Figure 4).

For these techniques, lidocaine in concentrations of 0.5%–4% has been suggested; however, quicker and denser blockade is achieved by using concentrations in the range of 2–4%. This technique has a proven clinical track record of safety; however, little data are available regarding the blood levels of local anesthetic that are achieved using these techniques or regarding metabolism of swallowed local anesthetics. Parkes et al.[14] showed plasma concentrations of 0.29–0.45 mg/L in healthy volunteers after inhalation of 10% lidocaine solution. Because these levels were well below the generally accepted 5 mg/L safe level, it can be inferred that inhaling a

Figure 4: Anesthetizing airway using inhalation of aerosolized lidocaine.

2–4% lidocaine for 15–30 minutes should be safe in most patients, particularly as a stand-alone technique.14

The major advantage of this technique lies in its simplicity and lack of discomfort. In addition, very little working knowledge of the anatomy of the region is required for its successful implementation.

Although this technique may seem ideal, it does have some drawbacks that limit its usefulness. The main disadvantage is that the density of the anesthesia achieved throughout the airway is highly variable. Many patients still experience an intact cough reflex, which can make intubation technically challenging. The rate of onset of this technique is highly dependent on patient compliance. Many patients who need an awake intubation are incapable or unwilling to take deep breaths. Also, inhalation of local anesthetic vapors can lead to central nervous system depression in patients whose mental status may already be depressed owing to other disease processes.

Clinical Pearls

Topicalization is the simplest method for anesthetizing the airway.

Local anesthetic can be sprayed directly onto the desired mucosa. Nebulization of lidocaine 2–4% via face mask or oral nebulizer

for 15–30 minutes can achieve highly effective anesthesia of the oral cavity and trachea for intubation.

Atomization is ideal for airway topicalization during nasotracheal intubations.

Density of anesthesia is variable and often requires supplementation to facilitate intubation.

Anesthetic-soaked cotton can be applied to targetedmucosal surfaces for 5–15 minutes to effect selective blockade of underlying nerves.

Vasoconstrictors such as epinephrine (1:200,000) or phenylephrine (0.05%) can be added to the solution to reduce mucosal bleeding.

Adequate time allocation is needed to achieve optimal conditions.

 17.  Outline procedures to maintain a patent airway with maxillary/mandibular fractures

 Le Fort determined the common fracture lines of the maxilla and face by experimentation on cadavers in 1901. The Le Fort classification is based on his finding that blunt trauma tends to cause fractures along three particular lines of the face. There are three types of Le Fort fractures I, II, and III.

A Le Fort I fracture causes little difficulty for the anesthesia provider. Patients may be intubated orally or nasally and the airway secured without a problem. The Le Fort II and Le Fort III fractures are of a particular concern when contemplating nasal intubations. In both of these fractures the cribriform plate is disrupted and placement of an endotracheal tube can inadvertently go intracranial. An attempted naso-tracheal tube in a patient with a basal skull fracture involves the very serious risk of introducing the tube into the skull. This can ultimately lead to meningitis. The tube can also cause damage to the brain. It causes a great deal of force to cause these fractures so you need to rule out cervical neck fractures, pneumo, and etc. If in doubt perform a tracheostomy or awake oral intubation with topical anesthesia. These patients are treated as a full stomach. Always perform an assessment of the ABC’s. The repair of a facial fracture is not an emergency and can be fixed at a later time. Then after the ABC’s the patient’s mouth needs to be assessed. It may be difficult to open the jaw but the provider needs to see if it is due to pain or an obstruction. Versed or a short acting narcotic can assist with this. This will make the decision of what route to intubate someone. With mandibular and maxillary fractures, nasal intubation is the best because the teeth are brought together and the jaw is often wired shut. The patient’s blood should be cross matched, because patient’s blood loss is usually extensive with facial fractures. Blood needs to be immediately ready. The patient should awake on emergence and be able to protect airway. Wire cutters need to be available. The naso-tracheal

tube should be secured away from the surgical site and make sure it is not causing a necrotic injury to the nares. The patient may remain intubated after fixing these fractures for days due to the risk of airway swelling.

18.  Calculate allowable dosages of epinephrine added to local anesthetic solutions.Epinephrine in Varying concentrations of 5micrograms/mL (1:200,000), (1:100,000) or 10mcg/ml, and (1:50,000) or 20 mcg/ml may be added to local anesthetic solutions to produce vasoconstriction. Nagelhout p.958 

19.  Compose potential complications with various ophthalmic regional techniquesMost complications of regional ocular anesthetics can be attributed to direct traumatization of the orbital vessels, the globe, and the optic nerve.

Retrobulbar hemorrhage results from trauma to an orbital vessel. The retrobulbar bleeding moves the eyeball forward (proptosis), and a subconjunctival hemorrhage is usually present.

Intravascular Injection grand mal seisures have been reported to occur after retrobullar injections with lidociane-bupivicaine combinations. Seizures may result from a less-than-toxic dose of local anesthesia by direct intraarterial injection, resulting in retrograde flow to the cerebral circulation.

Globe puncture patients may or may not exhibit signs and symptoms of a puncture immediately, and the diagnosis has been made from 1-14 days after event. The most devastating globe injury reported, is an ocular explosion. The globe can literally burst apart from the intraocular pressure exerted by the local anesthesia injection.

Optic Nerve Sheath Trauma anesthetic agents injected into the subdural or subarachnoid space may track back to the optic chiasm. The anesthetic can affect the contralateral eye by blocking cranial nerves II and III as they proceed through the subdural or subarachnoid space, this block can result in contralateral amaurosis. The condition can be a precursor to the continued migration of the anesthetic to the respiratory centers of the midbrain, resulting in respiratory arrest.

Ocular Ischemia studies have reported, a decrease in the pulsatile ocular blood flow after ocular blocks, secondary to the pressure exerted by the volume of local anesthesia injected into the orbit.

Retinal ischemia; occurs from several sources, all which puts pressure on optic nerve. Positioning of pt. is key. Prone/jackknife

Central retinal arterial occlusion, signs of eye injury are apparent. Proptosise, lid brusing, chemosis, hyphema. Prevention>treatment

Extraocular muscle palsy and ptosis

Inferior muscle palsy has been reported after retrobulbar anesthesia. The initial signs and symptoms of this problem manifest after surgery as persistent vertical diplopia. Surgical intervention is indicated for correction of this procedure.

Typically after the injection of local anesthesia, the surface muscle fibers degenerate, then regenerate. However, direct injections of local anesthesia into the rectus muscle resulted in massive internal muscle lesions that were large enough to produce noticeable functional deficit. The myotoxicity of local anesthestics also may play a role in postoperative ptosis, especially in the elderly, because regeneration of their muscle fibers may not be as complete as that in younger patients.

Facial nerve blocks patients commonly experience discomfort as a result of blocks of cranial nerve VII. Patients have also complained of jaw ache with movement for several weeks after a cranial nerve. VII block.

Oculocardiac reflex the oculocardiac reflex is a trigeminal-vagal reflex that was first described in 1908. The stimulus for this reflex is generated by pressure on the globe, the orbital structures (e.g., the optic nerve), or the conjunctiva, or by traction on the extraocular muscles (particularly the medial rectus muscle)

Afferent=trigeminal

Efferent=vagus

Corneal abrasion corneal abrasion is the most common injury occurring after general anesthesia. It is believed to result from the drying of the exposed cornea or from direct trauma, such an anesthesia-mask injury. Need ophthalmic consult right away. Usually healing occurs 24hrs.

Central retinal artery occlusion may result from prolonged pressure on the eye.

Chemical injury typically due to skin preparations into the eye. Hibiclens has shown serious corneal damage. Wash out with a salt based solutions.

Hemorrhagic Retinopathy, happens in healthy patients 2/2 hemodynamic changes with wild emergence. Venous, resolves 48-72 hours. Post injections due to rapid increase in csf with increased in retinal venous pressure. Arterial hem. After trauma; Purtscher retinopathy needs to be ruled out in trauma patients with post-anesthesia vision loss. Poor prognosis for vision.

Ischemic optic Neuropathy; most common cause of SUDDEN visual loss in pt >50 yo, nonsurgical setting, Anterior injury temporary, hypoperfusion of vessels supplying anterior portion of optic nerve

CV and Endocrine dz more at risk, male>female, increased IOP with large fluid amts intraop, painless vision loss, prognosis varies but grim.

Posterior injury has less blood supply than anterior. Produced by reduced O2 delivery to the retrolaminar part of the optic nerve. Symptoms present later and may be delayed several days *Afferent pupillary dilation or nonreactive pupil* Less related to CV history, Male>Female, seen after neck, nose, sinus or spine surgeries

Cortical Blindness brain injury rostral to optic nerve, damage to visual path beyond the lateral geniculate nucleus. More common in pts undergoing CABG with systemic dz. Causes: emboli and sustained, profound hypotension. Will have loss of optokinetic nystagmus with normal eye motility. Recovery: previously healthy patients could have good outcomes but may take longer to recover. Prevention: maintain adequate MAP (Keep within 20% of baseline)

 20.  Communicate the types of  tracheal tubes used for laser airway surgery

 The most frequent laser related complication is airway fire. Laser Resistant ETTs are used to prevent airway fires during laser surgery of the airway. Initially, fires are located on surface of ETT and cause thermal injury to tissues. If the fire burns through to interior of ETT, O2 and positive pressure ventilation create a blow torch effect, blowing heat and toxic products down into lung. Cuff puncture allowing O2 enriched atmosphere can also increase chance of fire after laser burst.

All standard polyvinyl chloride (PVC) endotracheal tubes are flammable and can

ignite and vaporize producing hydrochloric acid when in contact with the laser beam.

Red rubber endotracheal tubes wrapped with reflective metallic tape do not vaporize

but deflect the laser beam instead; however, the introduction of commercially

available laser-specific endotracheal tubes has essentially replaced the use of these

endotracheal tubes.

Cuffed endotracheal tubes should be inflated with sterile saline to which methylene

blue has been added so that a cuff rupture from a misdirected laser spark is readily

detected by the blue dye and extinguished by the saline. 

Some have a double cuff to ensure protection of the airway in the event of a cuff

rupture, and some have a special matte finish that effectively prevents reflected laser

beam scattering; some have both.

Nonreflective flexible metal endotracheal tubes are also specifically manufactured for

use during laser surgery.

The outer diameter of each size of metal laser tube is considerably greater than the

PVC counterpart, especially in the small sizes used for pediatric anesthesia.

An apneic technique is preferred by some surgeons, especially when working on the airway

of small infants and children. The advantage of this technique is an unobstructed surgical field to

the absence of an endotracheal tube, which may obscure the surgical field. In this circumstance, a

child is anesthetized and rendered immobile by the use of a muscle relaxant or deep inhalation of

a volatile anesthetic. The patient’s trachea is not intubated, and the airway is given over to the

surgeon, who uses the laser for brief periods. Between laser applications, the patient’s lungs are

ventilated by mask. Because apnea is a component of this technique, it is prudent to ventilate the

lungs with oxygen. Although this technique has been widely used with safety, there is a greater

potential for debris and resected material to enter the trachea as well as the potential for airway

trauma as a result of repeated endotracheal intubation.

The use of a jet ventilator is a modification of the apneic technique that does not require

tracheal intubation but does provide for oxygenation; ventilation during laser surgery uses a jet

ventilator. The operating laryngoscope is fitted with a catheter through which oxygen is

delivered under pressure through a variable reducing valve. Additional room air is entrained, and

the patient’s lungs are ventilated with this combination of gases. This technique produces a quiet

surgical field because large chest excursions of the diaphragm are eliminated and ventilation is

uninterrupted. In morbidly obese patients and those with severe small airway disease, effective

ventilation is difficult to impossible with this technique, and an alternate technique should be

used.

The final technique that may be used is spontaneous ventilation without the aid of an

endotracheal tube. In this technique, a surgical laryngoscope fitted with an oxygen insufflation

port is inserted into the larynx. Anesthesia may be induced with a volatile agent by mask but is

maintained with total intravenous agents without muscle relaxant in the spontaneously breathing

patient. Propofol may be infused with or without a short-acting narcotic, and the vocal cords may

be sprayed with 4% lidocaine to decrease reactivity. This technique is advantageous in that

longer periods of uninterrupted laser application may be provided. Disadvantages include the

absence of complete control of the airway, limited protection from laryngospasm, limited

protection from debris entering the airway, vocal cords’ motion, and difficult scavenging.

21.  Describe the advantages /disadvantages of N20  with inner ear procedures

 The middle ear and sinuses are air-filled, nondistensible cavities.

An increase in the volume of gas in these structures results in an increase in pressure.

N2O diffuses along a concentration gradient into the air-filled middle ear spaces more

rapidly than nitrogen moves out.

Passive venting occurs at 20 to 30 cm H2O pressure, and it has been shown that the use of

N2O results in pressures that exceed the ability of the eustachian tube to vent the middle

ear within 5 minutes, leading to pressure buildup.

During procedures in which the eardrum is replaced or a perforation is patched, N2O

should be discontinued or, if this is not possible, limited to a maximum of 50% during the

application of the tympanic membrane graft to avoid pressure-related displacement.

Another source reports: Accumulation of N2O in the middle ear can diminish hearing

postoperatively and is contraindicated for tympanoplasty because the increased pressure

can dislodge a tympanic graft.

After N2O is discontinued, it is quickly reabsorbed, creating a void in the middle ear with

resulting negative pressure. This negative pressure may result in serous otitis,

disarticulation of the ossicles in the middle ear (especially the stapes), and hearing

impairment, which may last up to 6 weeks after surgery. The use of N2O is related to a

high incidence of postoperative nausea and vomiting, which is a direct result of negative

middle ear pressure during recovery. The vestibular system is stimulated by traction

placed on the round window by the negative pressure that is created. Although all

patients have the potential for nausea and vomiting after surgery, children younger than 8

years of age seem to be most affected. If the use of N2O cannot be avoided, vigorous use

of antiemetics is warranted.

Nitrous oxide is a sweet-smelling, nonflammable gas of low potency (MAC = 104%),

and is relatively insoluble in blood. It is most commonly administered as an anesthetic

adjuvant in combination with opioids or volatile anesthetics during the conduct of general

anesthesia. At room temperature it is a gas; its boiling point is –88.48°C It is stored in

cylinders and condensed to 50 atmospheres, leading to a pressure of 745 psi. This

pressure is maintained in the cylinders until no liquid remains. Only cylinder weight is a

reliable indicator of the volume of N2O in storage tanks. Although not flammable, N2O

will support combustion. Unlike the potent volatile anesthetics in clinical use, N2O does

not produce significant skeletal muscle relaxation, but it does have analgesic effects.

Despite a long track record of use, controversy has surrounded N2O in four areas: Its role

in postoperative nausea and vomiting; its potential toxic effects on cell function via

inactivation of vitamin B12; its adverse effects related to absorption and expansion into

air-filled structures and bubbles; and lastly, its effect on embryonic development.

The one concern that seems most valid and most clinically relevant is the ability of N2O

to expand air-filled spaces because of its greater solubility in blood compared to nitrogen.

This might explain the increased post-operative nausea and vomiting (PONV) associated

with N2O use since closed gas spaces reside in the middle ear and bowel. Other closed

spaces may occur as a result of disease or surgery, such as a pneumothorax. Since

nitrogen in air-filled spaces cannot be removed readily via the bloodstream, N2O

delivered to a patient diffuses from the blood into these closed gas spaces quite easily

until the partial pressure equals that of the blood and alveoli. Compliant spaces will

continue to expand until sufficient pressure is generated to oppose further N2O flow into

the space. The higher the inspired concentration of N2O, the higher the partial pressure

required for equilibration. Seventy-five percent N2O can expand a pneumothorax to

double or triple its size in 10 and 30 minutes, respectively.

Air-filled cuffs of pulmonary artery catheters and endotracheal tubes also expand with the

use of N2O, possibly causing tissue damage via increased pressure in the pulmonary

artery or trachea, respectively. 

22.  Relate how anesthesia accommodates the surgeon to sustain facial identification Nerves being monitored during ENT surgeries:

CN VII: facial nerve which is located at the tragus of the ear and has 6 branches: temporal, zygomatic, buccal, mandibular, cervical, and posterior auricular

o Provides motor and sensory supply to the muscles for facial expression (familiarize yourself with the muscles that are innervated by this nerve)

CN V: trigeminal nerve divides into 3 branches: ophthalmic (V1), maxillary (V2), and mandibular (V3).

o All theses branches provide sensory and motor innervation to the nose, sinuses, palate, and tongue.

o They help in motor control of the face and in mastication (familiarize yourself with muscles innervated by this nerve)

CN IX: glossopharyngeal nerveo Provides sensory and motor innervation for the base of the tongue, nasopharynx,

and oropharynxo Responsible for eliciting a gag reflex during instrumentation of the posterior

pharynx and vallecula. CN X: Vagus nerve, which divides into superior laryngeal (internal and external

branches) and recurrent laryngeal nerves.o Please review slide notes for their importance and muscles that are

innervated with these branches!!!!

Accommodating the surgeon during ENT procedures:

All theses procedures are a shared airway concept between the surgeon and the anesthesia provider!!

o Plan ahead, communicate with the surgical personnel and the OR staff and if possible ask the surgeon which way they prefer the table turned.

o Consider types of airway instruments needed: smaller ETT tube, nasal or oral raes, NIM tube, etc and what side you would want your ETT tube taped to

o Most of the times, the table is rotated 90 or 180 degrees away from the anesthetists

ONLY use muscle relaxants for induction and intubation Avoid patient’s neck and head movement

Avoid use of local anesthetics: they have a suppressive effect on muscle action potential amplitudes and muscle movement

PONV risk is higher in these patients so plan accordingly Avoid wild wakeups If performing laser surgery on vocal cords, REMEMBER to decrease your O2

concentration to about 30% unless contraindicated in your patient (NOTIFY the surgeon if you can’t get to 30% without dropping your patient’s saturation.)

23.  Discuss the hazards of mastoid surgery Mastoid surgery: to perform mastoid surgeries, the head is positioned on a headrest, which may be lower than the rest of the table, and extreme degrees of lateral rotation may be required. Also a bloodless field is essential

Hazards of mastoid surgery:

Risk of the sternocleidomastoid muscle injury 2nd to tension on the heado In children, this can result in C1 to C2 subluxation due to laxity of the ligaments

of the cervical spine and the immaturity of odontoid process. Use of epinephrine solutions (1:1000) to produce vasoconstriction can cause

dysrhythmias and wide swings in BPs Do not use N2O: causes the pressure buildup in the inner ear that can result in hearing

loss lasting up to 6 weeks. Also N2O increases chances of PONV A bloodless field required a tight control on BPs, This can be risky for patients with

essential HTN This procedure increases the chances of PONV

24.  Name causes of diabetes insipidus and anesthesia interventionsDiabetes insipidus is characterized by marked impairment in renal concentrating ability that is

due either to decreased ADH secretion (central diabetes insipidus) or failure of the renal tubules to respond normally to circulating ADH (nephrogenic DI)

Central (neurogenic) DI – frequently develops with brain death and transient DI is also commonly seen following neurosurgical procedures and head trauma which often resolves in 5-7 days.

Nephrogenic DI - may occur in association with genetic mutations, hypercalcemia, hypokalemia, and medication-induced nephrotoxicity. Ethanol, demeclocycline, phenytoin, chlorpromazine, and lithium all inhibit the action of ADH or its release.

Hallmark sign of DI is polyuria. The inability to produce concentrated urine results in dehydration and hypernatremia. Treatment protocols for DI depend on the degree of ADH deficiency. Desmospressin (DDAVP) is often preferred agent because it has less vasopressor

activity, a prolonged duration of action, and enhanced antidiuretic properties. DDAVP can be administered nasally, IV, SQ, and orally.

***Perioperative administration of vasopressin is usually NOT NECESSARY in the pt with PARTIAL DI, because the stress of surgery causes enhanced ADH release. The surgical pt with a total lack of ADH may be managed with desmopressin (1 mcg SQ) or aqueous vasopressin (IV bolus of 0.1 unit, followed by a continuous IV infusion of vasopressin at 0.1-0.2 units/hr). caution is advised when administering these drugs to pts with CAD or HTN because of the arterial constrictive action of ADH.

Plasma osmolarity, Urine output, and serum sodium concentration should be measured hourly during surgery and in the immediate post-op period

Isotonic fluids can generally be administered safely during the intra-op period.

If the plasma osmolarity rises above 290 mOsm/L, hypotonic fluids should be considered and the vasopressin infusion increased above 0.2 units/hr

Pre-op assessment of the pt includes careful appraisal of plasma electrolytes (especially serum Na), renal function, and plasma osmolarity

Dehydration will make these pts especially sensitive to the hypotensive effects of anesthesia agents.

IV volume should slowly be restored preoperatively over a period of at least 24-48 hours.

Hypernatremia may manifest as seizures and hyperreflexia

25.  Construct safety approaches for handling LeForte fractures 

 

Le Fort I – (In purple - below the nose) Horizontal fracture above the teeth and palate, separating the teeth and lower maxillary components from the upper facial structures. Generally causes little difficulty for the anesthesia provider. Pts may be intubated orally or nasally and the airway secured without a problem.

Le Fort II – (In Orange - across the nose and descends down) is a triangular fracture with a fracture line across the nose, below the infraorbital rims, and extending through the entire lower maxillary structures. It is of particular concern when contemplating nasal intubation. In this fracture, disruption of the cribriform plate may occur, opening the underside of the cranial cavity. The presence of CSF in the nose, blood behind a tympanic membrane, periorbital edema, or “raccoon-eyes” hematoma are indications that attempts to pass an ET tube or NG tube through the nares could lead to inadvertent intracranial placement. Although the insertion of a nasal tube may aid the surgeon, an attempted nasotracheal intubation of

Le Fort III – (In green - is essentially a disassociation of the cranium and face) Same as Le Fort II - It is of particular concern when contemplating nasal intubation. In this fracture, disruption of the cribriform plate may occur, opening the underside of the cranial cavity. The presence of CSF in the nose, blood behind a tympanic membrane, periorbital edema, or “raccoon-eyes” hematoma are indications that attempts to pass an ET tube or NG tube through the nares could lead to inadvertent intracranial placement. Although the insertion of a nasal tube may aid the surgeon, an attempted nasotracheal intubation of a pt with a basal skull fracture involves the very serious risk of introducing the tube into the skull.

For all Le Fort fractures:

****the forces required to produce facial fractures are considerable and may be associated with other trauma. Soft-tissue injury to the airway and blood or debris in the oropharynx may make visualization impossible. If in doubt while in the ER, a tracheostomy under local anesthesia or an awake oral intubation with topical anesthesia should be considered. These patients should be treated with full stomach precautions.

It may be challenging to open the pt’s mouth for intubation because of edema, pain, or trismus (spasms of the muscles of mastication).

Intubation may pose difficulty if the patient also has a c-spine injury

Blood loss from facial fractures can be extensive – be sure to type and crossmatch

Fixation process closes the teeth in proper occlusion and prevents access to the oropharynx – masking the pt at emergence requires that the pt be awake with intact reflexes at extubation

Deliberate hypotensive anesthetic techniques are often used if the pt remains stable

Proper cutting tools should be at the pt’s bedside for emergency airway issues

Edema will often be extensive and progress over the first 24 hours after surgery

Pt is to remain intubated for several days post-operatively to avoid respiratory problems

If extubation is necessary, it should be done only when the pt is awake, in full command of protective reflexes, and can be carefully monitored in the post-op period

Antiemetics is beneficial in pts who have their jaws wired or banded together

Invasive monitoring may be required in pts with intracranial or other trauma, or for controlled hypotension. Muscle relaxants will interfere with facial nerve monitoring

Potential complications during surgery include ETT damage and oculocardiac reflex