AWAKE INTUBATION Techniques and Tips Jennifer Ranieri N 747 Fall 2014

Indication for Awake Intubation Safety! “If they do not inspire, they expire” Thorough preoperative history and physical evaluation Assess difficulty with direct laryngoscopy or difficulty ventilating the patient when ablating reflexes or relaxing tissue

Why Awake Intubation? Maintenance of natural airway structure Optimized gas exchange Maintenance of muscle tone to keep relevant airway structures separated and easier to identify Avoids anterior laryngeal movement that occurs during induction of anesthesia that potentially worsens visualization of airway structures Tongue, vallecula, epiglottis, larynx, esophagus, posterior pharyngeal wall

Conditions Tumors Infections Congenital Abnormalities Foreign Body Trauma Obesity Inadequate Neck Extension Anatomic Variations PATHOLOGIC AND ANATOMIC CONDITIONS Tumors include: cystic hygroma, hemangioma, hematomas(head, neck, upper chest) Infections include: submandibular abscess, peritonsillar abscess, epiglottitis Congenital abnormalities: pierre-robin syndrome, treacher collins syndrome, laryngeal atresia, goldenhar syndrome, craniofacial dystosis, Trauma: laryngeal fracture, mandibular or maxillary fracture, inhalational burn, cervical spine injury Neck issues: RA, ankylosing spondylitis, halo traction Anatomic variations: micrognathia, prognathism, large tongue, arched palate, short neck, prominent upper incisors, RADIATION or burns to the face or neck, severe overbite

Choices and Preparation Preparation is key- awake intubation often more time consuming Inform the patient Oral versus nasal approach Equipment selection Anesthetizing the airway Sedation and anxiolysis Back up plan Difficult airway supplies Additional anesthesia providers Otolaryngology at the ready Surgical airway

Techniques & Equipment Blind nasal intubation Uses breath sounds as a guide Awake direct laryngoscopy Video versus traditional Awake optical stylets Fiberoptic scope Transtracheal jet ventilation

Flexible Bronchoscope Not a requirement for an awake intubation, but a frequent choice Nasal or oral Warm tube to soften, lubricate scope, keep it straight Stepstool may help Insufflation of O2 via the suction port allows for increased FiO2 administration during procedure Prevents fogging, may assist in removing secretions from scope tip Grasping tongue with gauze may assist with visualization as well as jaw thrust forward or cricoid pressure Ovassapian airway is specially designed for FOB intubation Protects scope from damage from biting Patient must be well topicalized to tolerate Disconnect ETT adapter because it will not fit through airway Nasal FOB: nasal airway can connect 15mm adapter to circuit to provide O2 as well

Relevant Airway Innervation Nose Greater and lesser palatine nerves Anterior ethmoidal nerve Mouth and proximal airway structures Glossopharyngeal Branches of facial nerve Larynx and distal airway structures Vagus Superior Laryngeal Nerve Recurrent Laryngeal Nerve trigeminal nerve (lingual branch of the mandibular division) also in mouth 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. Blocks of nasal nerves not really discussed here, according to NYSORA blocks often with basic topicalization (pledgets or reservoirs of local for 10-15 min) Nasal blocks are highly technical and huge risk of vascular injury so they are rarely done in airway management

Topicalization of the Airway Mucosal application of local anesthetic to facilitate local uptake and neural blockade May be sufficient airway anesthesia alone Adequate application time required May be inadequate due to pressure receptors at base of tongue causing gag reflex Submucosal, not blocked topically

Topicalization Continued Viscous lidocaine - swish and spit Lidocaine ointment 4% “lollipop” (blob on stick), onset ~15 minutes Nebulized lidocaine 2-4% Highly variable results, limit inhalation to 15-30mins, well tolerated 10ml syringe with 2-4% lidocaine to atomize oral or nasal passages Safe even if large amount swallowed Local anesthetic soaked cotton swabs and pledgets Cocaine excellent for this methodology but difficult to obtain plus concern about cocaine toxicity Can add epinephrine or phenylephrine to lidocaine to achieve similar vasoconstriction Must vasoconstrict nasal passages Cetacaine spray: contains benzocaine, tetracaine and butamben in pressurized container Consider risk of methemoglobinanemia with benzocaine use, 1 sec spray recommended In summary, the maximum safe dose o lidocaine that can be topically applied to the mucous membrane of the airway is difficult to determine and must take into account the method of topicalization employed as well as the time course of administration. Traditional dosage guidelines may be excessively conservative when some or the entire dose is administered by aerosol, based on the available evidence with respect to serum levels and toxicity occurrences. the smallest amount of anesthetic sufficient to achieve the desired effect should be used, Consider risk of bleeding in liver patients, anticoagulated patients or thrombocytopenia patients

Airway Blockade Unfortunately, no single nerve can be blocked for adequate anesthesia to the airway Glossopharyngeal Block (CN 9) Anesthesia to oropharynx, tonsils, soft palate, posterior portion of the tongue, and the pharyngeal surface of the epiglottis Superior Laryngeal Nerve Block (Branch of CN 10) Anesthesia to base of tongue, posterior surface of epiglottis, aryepiglottic fold, and the arytenoids Recurrent Laryngeal Nerve Block (Branch of CN 10) Anesthesia to glottis and subglottic structures Transtracheal Block

Glossopharyngeal Block Bilateral blockade of the pharyngeal, lingual and tonsillar branches of the CN 9 Eliminates gag reflex and facilitates nasal intubation by blockade of posterior pharynx Not adequate alone Patient opens their mouth, 22-25 gauge needle used to inject 2-4 mL of local anesthetic bilaterally at the base of the palatoglossal arch (also called the anterior tonsillar pillar) High risk intravascular injection: aspirate and/or consider epinephrine as marker of intravascular injection The glossopharyngeal nerve provides 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).  It is most easily blocked where it crosses the palatoglossal arch.  It can be blocked using one of three methods: topical spray application, direct mucosal contact of soaked pledgets, or     direct infiltration by injection.  Glossopharyngeal nerve block is not adequate as a solo technique to facilitate intubation, but in combination with other     techniques it is highly effective.

Glossopharyngeal Block The glossopharyngeal nerve provides sensory innervation to the posterior third of the tongue, the vallecula, the anteriorsurface of the epiglottis (lingual branch), the walls of the pharynx (pharyngeal branch), and the tonsils (tonsillar branch).  It is most easily blocked where it crosses the palatoglossal arch.  It can be blocked using one of three methods: topical spray application, direct mucosal contact of soaked pledgets, or     direct infiltration by injection.  Glossopharyngeal nerve block is not adequate as a solo technique to facilitate intubation, but in combination with other     techniques it is highly effective.

Superior Laryngeal Nerve Block Mucosal application of local anesthetic may anesthetize SLN, but if saturation time not available bilateral SLN regional blockade can be effective The internal branch originates from the superior laryngeal nerve lateral to the greater cornu of the hyoid bone, passes approximately 2-4 mm inferior to the greater cornu of the hyoid bone

SLN Block Continued Palpate outward from the thyroid notch along the upper border of the thyroid cartilage until the greater cornu is encountered just superior to its posterolateral margin Displace the hyoid bone with contralateral pressure by no dominating hand This brings the ipsilateral cornu and the internal branch of the superior laryngeal nerve toward the anesthetist Pulsation of the carotid artery being displaced deep to the palpating finger tip Supine with head extended, identify landmarks and prep skin Can be uncomfortable to push hyoid TOWARDS anesthetist

SLN Block Continued 22-25g needle is inserted until lateral aspect of the greater cornu is contacted Walk needle downward toward the midline (1-2 mm) off the inferior border of the greater cornu If thyrohyoid membrane is pierced then the internal branch alone is blocked If the needle is retracted slightly after contacting the hyoid, both the internal and external branches of the superior laryngeal nerve are blocked May result in cricothyroid muscle weakness due to lack of function as an airway dilator, but motor function of the RLN is spared and therefore does not result in clinically significant change in laryngeal inlet diameters Negative for blood for air aspiration, inject 2ml solution and repeat on other side Noninvasive methodology: pledget placement in pyriform fossa Air= needle in larynx Blood= close proximity to vessels (carotid), take out needle and reassess high likelihood of intravasc injection a less invasive technique for blocking the superior laryngeal nerve can be accomplished by using soaked pledgets. After topicalization, the patient is asked to stick the tongue out. The tongue is then grasped using a gauze pad.With a right-angled forceps (Jackson-Krause forceps) the anesthetic-soaked pledgets are placed in the pyriform fossae located on either side of the root of the tongue. After 5-10 minutes, a sufficient degree of anesthesia should be present for intubation

Recurrent Laryngeal Nerve Block Avoidance of coughing during endotracheal tube manipulation between and below the cords Abolition of hemodynamic responses, may help avoid vagal responses that can occur Accomplished via the transtracheal block Why not direct RLN blockade? Motor innervation for all the muscles of the larynx except the cricothyroid from the RLN Blockade will result in obstruction of airway Sufficient blockade of the recurrent laryngeal nerve can often be accomplished using the inhalational technique previously described. Again, some patients may not achieve a sufficient amount of anesthesia to facilitate intubation.

Transtracheal Block Identify the cricothyroid membrane Midline neck, palpate caudad from thyroid cartilage Prep skin, local wheal 22- 20g needle on a 10-mL syringe with 4mL of 4% lidocaine is advanced perpendicular to the axis of the trachea and pierces the membrane Aspirate for air, positive air identifies you are in trachea, then inject Patient will cough! (You should have warned them of this before hand) Coughing disperses the local anesthetic to sensory nerve endings, motor function remains intact Rapid injection minimizes trauma to airway from needle placement and coughing, larger gauge needle may be preferable

Transtracheal Block

Intravenous Adjuncts Antimuscarinic and antisialagogue Glycopyrrolate Easy Reversibility and titratability Midazolam Fentanyl Maintenance of Spontaneous Ventilation Ketamine Dexmedetomidine Psychological Preparation Do not use medication to compensate for poor airway anesthesia Consider REVERSIBILITY and duration of action Sedative agents that do not ablate spontaneous ventilation is preferable minimize discomfort, produce anxiolysis, and attenuate recall Patient MUST be able to follow commands

Glycopyrrolate Anticholinergic anti-muscarinic Antisialagogue 0.2-0.4mg IV Can be given IM as well Allows better application of topic anesthetic agents Can double the duration of lidocaine Improves visualization Prevents laryngovagal reflexes Atropine would suffice, but increased risk of tachycardia and psychosis

Midazolam and Fentanyl Benzodiazepine; produces anxiolysis and amnesia 0.25-4mg Reversal: Flumazenil, imidazobenzodiazepine competitive antagonist of benzodiazepines 0.2mg over 15 sec, repeat q2min max 1mg (some sources say 3mg) Fentanyl Opioid agonist; sedation, analgesia, antitussive 10-100mcg Reversal- Naloxone, competitive opioid receptor antagonist 0.4 mg/mL vial diluted in 9 mL saline to 40mcg/ml can be titrated in increments of 0.5-1 mcg/kg (1-2ml) every 3-5 min until adequate ventilation and alertness are achieved Increments SMALL! May help to dilute

Ketamine NMDA antagonist, dissociative, provides sedation Upper airway reflexes remain largely intact, ventilatory drive minimally affected Best as an adjunct with other amnestics and sedatives due to hallucinations Consider cardiovascular side effects Directly proportional to dosage Low dose 10-50mg GA induction dose is 1-2mg/kg

Dexmedetomidine Sedative, centrally acting alpha 2 agonist Provides analgesia, anxiolysis, xerostomia, and some degree of amnesia Maintains spontaneous respiratory rate Consider hemodynamics Loading dose: 0.5-1 mcg/kg over 10 min 
 Infusion: 0.2–1 mcg/kg/hr More selective for alpha 2 than clonidine

References Benumof, J. (1991). Management of the Difficult Adult Airway With Special Emphasis on Awake Tracheal Intubation. Anesthesiology, 75(6), 1087-1110. Butterworth, J.F., Mackey, D.C., Wasnick, J.D. (2013). Morgan & Mikhail’s Clinical Anesthesiology. (5th Ed.). New York, NY: McGraw Hill. Hung, O., Murphy, M.F. (2012). Management of the Difficult and Failed Airway (2nd Ed.). New York, NY: McGraw Hill. Marcucci, C., Cohen, N.A, Metro , D.G., Kirsch, J. (2008). Avoiding Common Anesthesia Errors. Philadelphia, PA: Lippincott, Williams and Wilkins. New York School of Regional Anesthesia. (2008). Regional & Topical Anesthesia for Endotracheal Intubation. http://www.nysora.com/techniques/nerve-stimulator-and-surface-based-ra-techniques/head-and-neck-blocka/3022-regional-topical-anesthesia-for-endotracheal-intubation.html