Difficult Airways

1. Difficult Airways Presented by Ri龔律至 Ri李又文

2. Brief history • 59 y/o male • Oropharyngeal ca.(SCC) s/p CCRT in 2000 • Local recurrent oropharyngeal ca. s/p Nd-YAG laser tonsillectomy in 2001 • Denied any other systemic disease • Alcohol, betelnut, or cigarette consumption: denied

3. Present Illness • Dysphagia was noted since 2002 Sep. • PES with biopsy showed middle and lower esophageal squamous cell carcinoma. • CCRT (4000cGy / 20 Fractions) was performed and he was referred for subtotal esophagectomy.

4. Pre-op evaluation • ASA class II • Previous intubation hx: No difficult airway was noted. • Mouth opening < 2 cm

6. Awake Fiberoptic Intubation • RobinulFentanyl lidocaine +Neo-Synesin for nasopharynx topical use transtracheal injection of lidocaine successful ETT intubation Pentothal Tracrium

8. Post op evaluation • Sore throat : (-) • Vomiting, headache : (-) • Pain control : Epidural • Pain score : 4 / 10 • The patient was satisfied with the quality of the anesthetic process.

9. Difficult Airways • Difficult airway is defined when trained anesthesiologist experiences difficulty with mask ventilation (unable to maintain SpO2>90% using 100% O2) and/or inability to place ETT with conventional laryngoscopy (>3 attempts or > 10 mins)

10. Difficult Airways • Include both difficult intubations and compromised airways. • Compromised airways implies partial obstruction to air flow and the risk of total obstruction if tumor, infection, or disease further narrows the airway. • All compromised airways are difficult intubations!

11. Difficult Intubation • During routine anesthesia the incidence of difficult tracheal intubation has been estimated 3~18%.

12. Cormack classification Class I: the vocal cords are visibleClass II: the vocals cords are only partly visibleClass III: only the epiglottis is seenClass IV: the epiglottis cannot be seen Difficult IntubationThe best view of the larynx seen at laryngoscopy

13. Predicting Difficult Intubation History A.Previous intubation history B.Facial/maxillary trauma C.Small mandibles or intra-oral pathology such as infections or tumors D.Rheumatoid disease of the neck or degenerative spinal diseases E.Spinal cord injury F.Poor teeth and the inability to open the mouth

14. View obtained during Mallampati test:1.Faucial pillars, soft palate and uvula visualised 2.Faucial pillars and soft palate visualised, but uvula masked by the base of the tongue 3.Only soft palate visualised 4.Soft palate not seen. Specific Screening Tests to Predict Difficult Intubation

15. Specific Screening Tests to Predict Difficult Intubation 1. Thyromental distance 2. Sternomental distance 3. Protrusion of the mandible 4. Mouth opening 5. Ability to flex and extend the neck maximally 6. X-ray studies 7. Preoperative assessment

16. Thyromental distance • Frerk showed that patients who fulfilled the criteria of Gr 3 or 4 Mallampati who also had a thyromental distance of less 7 cm were likely to present difficulty with intubation

17. Sternomental distance • Measured from the sternum to the tip of the mandible with the head extended and is influenced by a number of factors including neck extension. • A Sternomental distance of 12.5 cm or less predicted difficult intubation.

18. Mouth Opening • Mouth opening, which is largely a function of the temporomandibular, is a prime importance to allow the insertion of a blade and subsequent glottic visualization. • Adults should be able to open their mouth >3~4 cm (between upper and lower incisors).

19. Protrusion of the mandible • An indication of the mobility of the mandible. • If the patient is able to protrude the lower teeth beyond the upper incisors, intubation is usually straightforward

20. Limitation • Wilson et al studied a combination of these factors in a surgical population assigning scores. Although their method can predict many difficult intubations, it also produces a high incidence of false positives (someone who is assessed as a likely difficult intubation, but who proves easy to intubate when anesthetised) which limits its usefulness.

21. Special techniques for intubation:Awake Intubation • =Conscious intubation • After appropriate sedation, topical anethesia, and nerve blocks, such intubations can be performed with minimal discomfort in the conscious patient. • Nasal intubation is the best method of awake intubation using a fiberoptic bronchoscope.

22. Awake Intubation • Sedation: fentanyl is recommended. • Anticholinergic agent, such as Robinul is strongly advised. • Anethesia of the nares and nasopharynx should be accompanied by vasoconstriction to widen the passage and decrease bleeding.

23. Awake Intubation • Nasopharygeal anesthesia: (1) Cocaine (4%) up to 1.5 mg/kg (2) Lidocaine (4%) + Neo-Synesin (1%) in a 3:1 combination • Transtracheal (translaryngeal) anesthesia with 2~3 ml 2% lidocaine injection. • Glossopharyngeal block

26. Special techniques for intubation • The Laryngeal Mask Airway • The McCoy laryngoscope • Light wand • The Combi-tube • Retrograde endotracheal intubation • Surgical airway

27. The Laryngeal Mask Airway

29. The McCoy laryngoscope is designed with a movable tip which allows the epiglottis to be lifted and intubation often made easier. The McCoy laryngoscope

30. The Combi-tube is a tube which may be inserted blindly and used to ventilate the patient in an emergency. It is designed in such a way that the tube can be used for ventilation whether it enters the esophagus or the trachea. The Combi-tube

32. Retrograde endotracheal intubation

33. Transtracheal Jet Ventilation(TTJV) • Benumof noted that the incidence of “ cannot ventilate-cannot intubate” situation may be as high as 1/ 5000 anesthesics. • TTJV is a quick, easy, safe solution to the problem of “ cannot ventilate-cannot intubate”.