Fasting

Fasting:

• Aims to ↓ the risk of perioperative regurgitation and aspiration of gastric contents
  May lead to:
  • Chemical pneumonitis
  • Bacterial pneumonia
  • Airway obstruction
• Should be of duration to minimise aspiration
• May be detrimental when prolonged Fasting >6 hours may:
  • Prevent optimal gastric emptying
  • Lead to deleterious metabolic effects
  • Annoy patients

Physiology

• Gastric residual volume often used as a surrogate for risk
  • No known volume which indicates a particular threshold of risk or eliminates all risk
• Fluids empty by first-order kinetics
• Solids empty by zero-order kinetics
• Gastric emptying time is ↑ following trauma, and standard fasting times may not be adequate

Fasting for Adults

For elective surgery:

• Solid food up to 6 hours prior
• Clear fluid of 200ml per hour up to 2 hours prior
  Clear fluids are defined as:
  • Water
  • Pulp-free juice
  • Clear cordial
  • Black tea
    Note milk is excluded.
  • Black coffee
• Medications may be taken up to 2 hours prior with water
• Chewing gum should be discarded
  Due to risk of aspiration/foreign body rather than due to ↑ gastric contents.

Exceptions

These guidelines may not apply. Important considerations:

• High-risk patients
  • Delayed gastric emptying
  • Previous bariatric surgery
    
    • Lap bands
    • Gastric bypass
  • Previous oesophagectomy
  • Oesophageal dysmotility
  • Pregnancy
• Use of risk-reduction techniques
  • Pharmacological
    • PPI
    • H₂-antagonists
    • Antacids
      • Sodium citrate
      • Aluminium hydroxide
  • Rapid-Sequence Induction

Fasting for Children

For elective surgery in children > 6 months old:

• Breast milk, formula, and limited solid food up to 6 hours prior
  Includes milk drinks, food, lollies, and chewing gum.
• Clear fluids up to 1 hour prior
  Clear fluids should be encouraged up to this point.
  • Timing varies depending on guideline
    Check you local institutional practice.

For elective surgery in children < 6 months old:

• Formula up to 4 hours prior
• Breast milk up to 3 hours prior
• Clear fluid up to 1 hour prior

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References

1. PS07: Guidelines on Pre-Anaesthesia Consultation and Patient Preparation. ANZCA. 2016.
2. Royal Children’s Hospital Melbourne. Fasting. Accessed 6/19.
3. Splinter WM, Schreiner MS. Preoperative fasting in children. Anesthesia and analgesia. 1999;89(1):80–9.