Anesthesiology

• Perform an airway assessment
• Identify a potentially difficult airway
• List the indications for Endotracheal intubation
• List the indications and contraindications for the use of the LMA
• Have an approach to the management of a difficult airway
• Prior anaesthetic records should be reviewed for previous problems with airway management
• Relevant pathologies that may indicate a potentially difficult airway include:

  • Certain syndromes with craniofacial abnormalities e.g. Downs Syndrome
  • Trauma to the head and neck
  • Facial burns
  • Infective causes e.g. submandibular/retropharyngeal abscesses
  • Tumours e.g. thyroid tumours/mediastinal masses
• Performing an airway assessment of all patients prior to an anaesthetic is mandatory, including patients in whom a regional technique is planned
• A comprehensive assessment of an airway requires the evaluation of 11 features as outlined by the ASA algorithm:

  1. Teeth

  • Large/missing upper incisors
  • Anterior protrusion of upper incisors
  • Upper lip bite test

  2. Mouth

  • Mouth opening
  • Mallampati score
  • High arched palate

  3. Jaw

  • Thyromental distance
  • Mandibular compliance

  4. Neck

  • Short thick neck
  • Sternomental distance
  • Increased neck circumference
  • Reduced mobility of the neck
  • Cervical spine instability
• Another practical approach to doing an airway assessment is to evaluate the airway in three parts:

  • Mask Ventilation
  • Laryngoscopy and intubation
  • Rescue airway
• Predictors of difficult mask ventilation can be defined by the mnemonic "BONES":

  • Beard
  • Obesity
  • No teeth
  • Extremes of Age
  • Snores
• Predictors of difficult laryngeal visualisation:

  • Dysmobility
  • Disproportion
  • Distortion
  • Dentition
• If the patient is assessed to have a potentially difficult airway, mark the cricothyroid membrane prior to any airway intervention for ease of identification
• Mallampati Grading
• Options for securing the Airway:

  • Awake intubation
  • "Quick look"
  • Induce and paralyse
• Investigations that may be useful include a chest x-ray/CT scan of the head/neck/chest which may reveal a displaced/distorted larynx/trachea
• Bag Mask Ventilation:

  • Induction of anaesthesia is accompanied by loss of muscle tone
  • Repositioning the head or doing a jaw thrust can help maintain a secure seal with the face mask
• Indications for endotracheal intubation:

  • Airway protection
  • Maintenance of a patent airway
  • Pulmonary toilet
  • Application of positive pressure ventilation
  • Maintenance of adequate oxygenation
• Airway Devices may be divided into supra and infraglottic devices:

  Infraglottic Devices:

  1. Endotracheal Tubes (ETT)

  2. Double lumen tubes

  3. Bronchial blockers
• Essential Equipment for Intubation (as per the SASA regulations):

  1. Facemasks - size 0-3 for paeds and 3-5 for adults

  2. Guedel airways - size 0-2
• Essential equipment for intubation (as per SASA regulations):

  • Facemasks: size 0-3 for paeds and 3-5 for adults
  • Guedel airways: size 0-2 for paeds and 3-5 for adults
  • Two laryngoscope handles: Mackintosh (curved) and Miller (straight)
  • Laryngoscope blades
  • Endotracheal tubes: sizes 5.5-8 cuffed for adults, sizes 2.5-5 cuffed and uncuffed for paeds
  • Suction nozzles and tubing
  • Suction catheters to fit available ETTs
  • Magill’s forceps including a smaller size for paediatrics
  • Bag valve mask with oxygen
• Additional devices:

  • Malleable stylet, including a smaller size for paeds
  • Malleable bougies
• Endotracheal tube size selection:

  • Males: usually 7.5-8.0 mm
  • Females: usually 7.0-7.5 mm
  • Paeds: (age/4 + 4)
• Endotracheal tube depth of insertion:

  • Males: 22+2 cm at the teeth
  • Females: 20+2 cm at the teeth
  • Paeds: (age/2) + 12 cm
• Laryngeal Mask Airway (LMA) indications:

  • Alternative to tracheal intubation for starved patients and most elective surgery
  • Difficult airway scenarios
  • Pre-hospital care setting
  • Emergency cart or ambulance tool for intubation
  • Cardiopulmonary resuscitation
• Supraglottic devices commonly used:

  • Laryngeal Mask Airway (LMA)
  • Guedels Airway
  • Nasopharyngeal Airway
• Laryngeal Mask Airway (LMA) contraindications:

  • Mouth opening less than 1.5 cm
  • Non-fasting patients and patients at increased risk of aspiration
  • Patients with poor lung compliance requiring airway pressures of more than 20 cm H2O
• Laryngeal Mask Airway (LMA) size selection based on weight and sex:

  • <5kg: size 1
  • 5-10kg: size 1.5
  • 10-20kg: size 2
  • 20-30kg: size 2.5
  • 30-50kg: size 3
  • Adult female: size 2-4
  • Adult male: size 4-5
• Difficult airway defined by ASA:

  • Difficulty with mask ventilation, tracheal intubation, or both
  • More than 2 attempts at intubation with the same laryngoscopic blade
  • Change in blade or use of intubation stylet required
  • Alternative intubation or rescue technique required
• Difficult bag-mask ventilation:

  • Critical skill for the anaesthetist
  • First line rescue in failed intubation attempt
  • Overcome by better positioning, use of oral and nasal airways, and two-person technique
• Difficult laryngoscopy:

  • Inability to visualize vocal cords despite multiple attempts
  • Reasons for failed intubation: inadequate equipment preparation and poor patient positioning
  • Improve view by changing laryngoscope blade/handle size, releasing cricoid pressure, applying BURP technique, and considering bimanual laryngoscopy
• Ultimate aim in airway management:

  • Maintain oxygenation of the patient
  • Follow ASA Difficult Airway Algorithm for non-emergency and emergency pathways