Evidence Based Medicine

“Practical Guidelines for Management of the Difficult Airway”

“Practical Guidelines for Management of the Difficult Airway”

Practical Guidelines

Practice guidelines are systematically developed recommendations that assist practitioner and patient in making decisions about health care.

American Society of Anesthesiologists

Anesthesiology 2013 (February); 118:251-70

Definitions

Difficult 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 Definitions

1. 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 Definitions

2. Difficult SGA placement:

Requires multiple attempts, in presence or absence of tracheal pathology

3. Difficult Laryngoscopy:

Not possible to visualise any portion of the vocal cords after multiple attempts at conventional laryngoscopy

Sub Definitions

4. Difficult Tracheal intubation:

Requiring multiple attempts in the presence or absence of tracheal pathology

5. Failed intubation:

Placement of ETT fails after multiple attempts.

Availability & Strength of Evidence

CATEGORY ‘A’

Level ‘1’ : Sufficient number of RCTs to conduct meta-analysis and meta-analytic findings

Level ‘2’ : Number of RCTs is insufficient to conduct viable meta-analysis

Level ‘3’ : Single RCT

CATEGORY ‘B’

Level ‘1’ : Observational comparisons between clinical interventions for a specified outcome

Level ‘2’ : Observational studies with associative statistics (relative risk, correlations)

Level ‘3’ : Noncomparative observational studies with descriptive statistics (frequencies, percentages)

Level ‘4’ : Case reports

Inferred findings are given a directional designation of:

Beneficial (B)

Harmful (H)

Equivocal (E)

GUIDELINES

STEP 1: Evalution of the Airway

1. Evalution of the Airway

History:• 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 Airway

Physical 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 Airway

Recommendations: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.

1. Evalution of the Airway

STEP 2: The Basic Preparation

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 Preparation

Recommendations: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.

2. Basic Preparation

STEP 3: Strategy for Intubation

3. Strategy for Intubation

• A preplanned preinduction strategy should always be planned for every anesthetic.

“Non invasive interventions”a. Awake intubation

b. Video assisted laryngoscopy

c. Intubating stylets or tube changers

d. SGA for ventilation (LMA, Laryngeal tube)

e. SGA for intubation (ILMA)

f. Rigid larynogscopes

g. Fiberoptic guided intubations

h. 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 Intubation

Recommendations: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 Intubation

2. 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 ventilation

3. Confirmation of tracheal intubation using capnography is mandatory requirement.

3. Strategy for Intubation

STEP 4:Strategy for Extubation

4. Strategy for Extubation

Recommendations: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 Extubation

Subjective:1. Following commands

2. No blood/secretions in hypopharynx

3. Intact gag reflex

4. Headlift/tongue blade for 5sec

5. Adequate pain relief

6. Minimal end tidal conc. of inhaled anesthetics

4. Strategy for Extubation

Criteria for Awake Extubation

Objective:1. Vital Capacity >10ml/kg

2. Tidal volume > 6ml/kg

3. Inspiratory intrathoracic pressure > -20cm H2O

4. Train of four T1/T4 > 0.7

5. Sustained tetanic contraction for 5sec

6. Alveolar to arterial PaO2 difference < 350mm Hg

STEP 5:Follow-up Care

5. Follow-up Care

Recommendations: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.

THE ALGORITHM

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