Airway Management

Airway Anatomy Airway Assessment Airway Devices Difficult Airway Surgical Airway Complications

Airway Anatomy Fig. 1.11 The Larynx

Airway Assessment

Risk factors for Difficult airway Mouth opening less than 4cm Thyromental distance less than 6cm Mallampati Class III or IV Neck movements less than 80% Limited jaw protrusion Body Weight > 110kg History of difficult intubation

Structured Airway Evaluation

Airway Devices

Bag Mask Ventilation (BMV)

Difficulties with BMV Lack of proper seal Facial trauma Limited chest wall movement e.g. distended abdomen Poor neck stability Obesity Airway obstruction

Laryngeal Mask Airway (LMA)

Indications Alternative to face mask for maintaining airway Suitable in elective procedures where tracheal intubation is not necessary Known or unexpected difficult airway Establishing airway in unconscious patient with absent glossopharyngeal and laryngeal reflexes when intubation not possible

Contraindications Patients with aspiration risk e.g. Not fasted, obese, pregnant Patients with decreased pulmonary compliance e.g. Pulmonary fibrosis

Endotracheal Intubation

The Decision to Tube... Is there failure of airway maintenance or protection? Is there failure of ventilation? Is there failure of oxygenation? Is there an anticipated need for intubation (ie, what is the expected clinical course)?

Indications Surgery on head, face, neck, shoulder or thorax Patients at risk of aspiration/regurgitation Muscle paralysis Lengthy surgery Major abdominal surgery Failure of mask anaesthesia Abnormal positions Limited airway access Morbid obesity

Positioning

Verifying Placement ET CO2 Auscultation Chest movement Direct vision Vital signs Condensation in tube Tube markings Movement of reservoir bag Pulse oximetry Fiberoptic bronchoscopy

The Difficult Airway “One that requires multiple attempts, multiple operators, multiple devices, excessive lifting force, external laryngeal manipulation, or is performed with an inadequate glottic view”

The LEMON Law Look externally: body habitus, obesity, facial trauma Evaluate (3-3-2 rule): 3:mouth opening > 3 fingers 3: Thyromental distance > 3 fingers 2: Superior laryngeal notch >2 fingers

Mallampati score Obstruction/Obesity Neck mobility e.g can be placed in “sniffing” position

Difficult BMV Mask seal e.g. anatomy, facial hair, vomitus Obstruction/Obesity Age No teeth Stiffness e.g. poor lung compliance

Fig. 9.5 Cannot intubate, cannot ventilate algorithm Transtracheal jet ventilation (TTJV) or low pressure ventilation Fig. 9.5 Cannot intubate, cannot ventilate algorithm

Anatomical Considerations in Children The position of the larynx is higher and more anterior than in adults, hyperextension of the neck may worsen obstruction of the upper airway. Airways more susceptible to obstruction from edema, mucous plugs, or foreign body Larger occiput causes passive flexion of the cervical spine, a rolled towel under the child's upper shoulders keeps the chin tilted up Tongue is relatively larger compared to the oral cavity in the child than in the adult and can fall back against the hypopharynx in a child with a decreased level of consciousness

Anatomy of Cricothyroid space

Surgical Airway Needle/catheter cricothyroidotomy

Minitracheostomy

Complications Barotrauma (subcutaneous emphysema, pneumothorax, pneumomediastinum, pneumopericardium) Breakage or bending of the needle Kinking, dislodgement, or breakage of the catheter Perforation of the esophagus or other structures in the neck or thorax Bleeding at the insertion site or into the trachea, causing obstruction Expiratory obstruction Hypoventilation with hypercapnia and acidosis Sore throat Infection

Emergency Cricothyroidectomy

Extubation Criteria CNS criteria Ventilation and oxygenation criteria The patient should be awake and cooperative Protective reflexes are present (cough, gag, and swallow) Ventilation and oxygenation criteria The patient is breathing spontaneously The respiratory rate is less than 25/min The tidal volume is at least 5 ml/kg The vital capacity is at least 15 ml/kg The arterial pH is greater than 7.35 The arterial PaCO2 is less than or equal to 50 mmHg The oxyhemaglobin saturation is greater than or equal to 90% when the FiO2 is less than or equal to 0.4 Neuromuscular criteria The patient has unassisted head lift greater than 5 s Full reversal from neuromuscular relaxant drug blockade has been documented by testing with a nerve stimulator

Airway Emergencies Pharyngeal Muscle Weakness Loss of pharyngeal tone → obstruction Due to residual neuromuscular blocks, anesthetic effect or opoids Managed with jaw thrust + CPAP Consider reversals if persistent

Laryngospasm More common in paeds Risk factors Inadequate anaesthesia Premature extubation Semicomatose state Aspiration NGT Positive pressure ventilation ± succinylcholine (0.1 mg/kg IV)

Aspiration Risk factors Emergency Abdominal surgery Pregnancy Obesity/recent meal Delayed gastric emptying e.g. Hx reflux Preventative measures include: antacids, RSI, ET Managed with 100% O2, suction, PPV/PEEP

Hypoxia Inadequate O2 supply