Evidence Based Medicine “Practical Guidelines for Management of the Difficult Airway”
Practical GuidelinesPractice guidelines are systematically developed recommendations that assist practitioner and patient in making decisions about health care.American Society of AnesthesiologistsAnesthesiology 2013 (February); 118:251-70
DefinitionsDifficult Airway:The clinical situation in which a conventionally trained anesthesiologist experiences difficulty with facemask ventilation of the upper airway, difficulty with tracheal intubation or both
Sub Definitions1. Difficult facemask or supraglottic airway (SGA): Difficulty in providing ventilation because of one or more problems. Inadequate mask or SGA seal Excessive gas leak Excessive resistance to ingress or egress of air
Sub Definitions2. Difficult SGA placement: Requires multiple attempts, in presence or absence of tracheal pathology3. Difficult Laryngoscopy: Not possible to visualise any portion of the vocal cords after multiple attempts at conventional laryngoscopy
Sub Definitions4. Difficult Tracheal intubation: Requiring multiple attempts in the presence or absence of tracheal pathology5. Failed intubation: Placement of ETT fails after multiple attempts.
1. Evalution of the AirwayHistory:• Association between several characters (age, obesity, OSA, H/O snoring) and difficult laryngoscopy (B2—H)• Difficult intubation or extubation in patients with mediastinal masses (B3—H)• Difficult laryngoscopy or intubation in variety of disease states e.g; ankylosis, tonsillar hypertrophy, osteoarthritis, pierre robin. (B4—H)
1. Evalution of the AirwayPhysical Examination:• Association between anatomical features like features of head and neck and likelihood of difficult airway (B2—H)• Radiography, CT scans, fluroscopy can identify variety of acquired and congenital features in patients with difficult airways (B3—B)
1. Evalution of the AirwayRecommendations:1. An airway history should be conducted with the intent to detect medical, surgical and anesthetic factors that may indicate presence of a difficult airway.2. An airway physical examination should be conducted with the intent to detect physical characteristics leading to difficult airway.
2. Basic Preparation• Preanesthetic preoxygenation by mask maintains higher O2 saturation values compared with room air controls (A3—B)• 3mins preoxygenation maintains higher oxygen saturation values compared to 1min preoxygenation (A2—B)
2. Basic Preparation• Oxygen saturation levels after preoxygenation are equivocal in preoxygenation for 3mins and fast track preoxygenation of 4 VC breaths in 30mins (A1—E)• Lower frequencies of arterial desaturation during transport with supplemental oxygen to PACU than without oxygen (A1—B)
2. Basic PreparationRecommendations:1. Inform the patient of special risks and procedures pertaining management of difficult airway.2. Atleast one additional assistant should immediately be available to serve.3. Always administer facemask preoxygenation.4. Actively pursueopprtunities to deliver supplemental oxygen throughout the process.5. Atleast one portable specialised unit for difficult airway management should be readily available.
3. Strategy for Intubation• A preplanned preinduction strategy should always be planned for every anesthetic. “Non invasive interventions”a. Awake intubationb. Video assisted laryngoscopyc. Intubating stylets or tube changersd. SGA for ventilation (LMA, Laryngeal tube)e. SGA for intubation (ILMA)f. Rigid larynogscopesg. Fiberoptic guided intubationsh. Light wands
3. Strategy for Intubation• Awake fiberoptic intubation is successful in 88-100% difficult airway cases (B3—B)• Higher frequency of first attempt intubations with video assisted laryngoscope (A1—B)• No time differences between VAL and conventional laryngoscopes (A1—E)• No differences in degree of cervical spine deviation between VAL and conventional laryngoscopes (A3—B)
3. Strategy for Intubation• LMA providing rescue ventilation in 94.1% who cannot be mask ventilated or intubated (B3—B)• Laryngeal tubes provide adequate ventilation for 95% of patients with pharyngeal and laryngeal tumors (B4—B)• When ILMA was used with semirigid collar, 3 of 10 patients were successfully intubated (B3—B)• Higher first attempt intubation for fibreoptic ILMA than standard fibreoptic intubation (A2—B)
3. Strategy for Intubation• Laryngoscopes of alternate design may improve glottis visualisation (B3—B)• Equivocal findings with rigid fiberscopes and rigid direct laryngoscopy for successful intubation and time to intubate (A2—E)• ETCO2 confirms tracheal intubation in 88.5-100% patients (B3—B)
3. Strategy for IntubationRecommendations:1. Assessment of the likelihood and anticipated clinical impact of six basic problems. a. Difficulty with uncooperative patient b. Difficult mask ventilation c. Difficult SGA placement d. Difficult laryngoscopy e. Difficult Intubation f. Difficult surgical airway access
3. Strategy for Intubation2. Consideration of the relative clinical merits and feasibility of four basic choices: a. Awake vs Intubation after GA b. Noninvasive vs Invasive techniques c. VAL as initial approach to intubation d. Preservation vs Ablation of spontaneous ventilation3. Confirmation of tracheal intubation using capnography is mandatory requirement.
4. Strategy for ExtubationRecommendations:1. Consider merits of awake extubation vs extubation before return of consciousness.2. An airway management plan should be implemented if the patient is unable to maintain ventilation.3. Short term use of intubating bougie can serve as a guide for expedited reintubation
4. Strategy for Extubation Criteria for Awake ExtubationSubjective:1. Following commands2. No blood/secretions in hypopharynx3. Intact gag reflex4. Headlift/tongue blade for 5sec5. Adequate pain relief6. Minimal end tidal conc. of inhaled anesthetics
4. Strategy for Extubation Criteria for Awake ExtubationObjective:1. Vital Capacity >10ml/kg2. Tidal volume > 6ml/kg3. Inspiratory intrathoracic pressure > -20cm H2O4. Train of four T1/T4 > 0.75. Sustained tetanic contraction for 5sec6. Alveolar to arterial PaO2 difference < 350mm Hg
5. Follow-up CareRecommendations:1. A detailed description of the airway difficulties encountered.2. A detailed description of the various airway management techniques used and indicate whether they played beneficial and detrimental role.