FRCA Notes

Preoperative Fasting in Children

Curriculum

The curriculum asks for knowledge on "Pre-operative fasting in children".

There are no paediatric-specific questions on this, although the March 2026 CRQ was on fasting in adults.

Resources


  • Fasting aims to reduce the risk of pulmonary aspiration of gastric contents
  • However, fasting must balance aspiration risk against the harms of a prolonged fast, which children tolerate poorly

Mechanism of aspiration

  • For aspiration to occur, gastric contents must overcome three protective barriers:
    • Lower oesophageal sphincter barrier pressure
    • Upper oesophageal sphincter
    • Protective airway reflexes e.g. cough, laryngospasm

  • Risk factors therefore fall into three groups:
    • Increased regurgitation due to GORD, strictures or reduced lower oesophageal sphincter tone
    • Loss of airway reflexes owing to neuromuscular disorders, general anaesthetics or analgesics
    • Increased gastric volume from inadequate fasting or delayed gastric emptying

  • Of these, gastric volume is the most modifiable risk factor prior to surgery

Paediatric considerations

  • Regurgitation is very common in the first 6 months of life because of higher resting intragastric pressure (small stomach crowded by abdominal organs) and a relaxed gastro-oesophageal sphincter
  • During inhalational induction, any upper airway obstruction generates negative intrapleural pressure
    • This negative pressure is transmitted to the oesophagus
    • This increases the gastro-oesophageal pressure gradient and the risk of regurgitation
    • A meta-analysis from premature neonates to adults found age is not a significant determinant of gastric emptying

    Residual gastric volume

    • Residual gastric volume (RGV) is still used as a surrogate for aspiration risk, but no causal link or critical volume threshold has been demonstrated
    • The often quoted 'at risk' values of 0.4 ml/kg (25 ml) with pH <2.5 originate from a single unpublished Rhesus monkey experiment; 40-80% of fasted healthy adults exceed these values
    • Aspiration can still occur with an empty stomach due to regurgitation of fluid from the small and large intestine


ESA 2011 (6-4-2) ESAIC 2022 (6-4-3-1) CPOC
Solids 6 h 6 h 6 h
Formula
Cow's milk
Light meal		 6 h 4 h –
Breast milk 4 h 3 h 3 h
Clear fluids 2 h 1 h Sips ≤3 ml/kg/h (max 170 ml/h) from 2 h

Notes

  • Water, pulp-free fruit juice, and squash are clear liquids
  • Cow's milk and powdered milk are treated as solid food
  • Most local policies (including SipTilSend) count sweets, lollipops and chewing gum as solid food
  • Clear fluids follow first order emptying kinetics in neonates, infants and older children
    • The volume drunk does not appear to affect gastric volume or pH, including in overweight and obese children
  • Children should be enouraged to drink until the cut-off, rather than just permitted to do so
  • Evidence for carbohydrate loading drinks in children is limited although there may be some benefits

Cardiovascular

  • Dehydration
  • Post-induction hypotension; optimised fasting in children <36 months improves MAP at induction

Neurological

  • Thirst, hunger, anxiety, irritability and crying
  • Less smooth induction
  • Possible risk factor for emergence delirium

Gastrointestinal

  • Possible increase in PONV
  • Children allowed clear fluids 2hrs preoperatively do not have higher gastric volumes or lower gastric pH than those fasted longer

Nutritional and metabolic

  • Metabolism shifts from hepatic glycogenolysis to gluconeogenesis, lipolysis and ketogenesis as glycogen stores deplete
  • Ketoacidosis has been demonstrated in children <3 years fasted >7 h
  • Hypoglycaemia
  • Surgical stress response adds further catabolism and insulin resistance, which is proportional to the degree of surgical trauma and associated with complications and longer length of stay

Practical

  • More attempts at venous cannulation
  • Lower patient and parental satisfaction

Incidence

  • Perioperative aspiration in children is rare; more common in emergency than elective surgery
  • Older series quote 0.02–0.1%; contemporary data suggest approximately 1–2 per 10,000 anaesthetics
  • The consequences of clear fluid aspiration are not catastrophic; no deaths were reported in any of the large paediatric series
  • Fasting status may not be an independent predictor of aspiration; most aspirations occur in children who have fasted for longer than 2 h

EUROFAST (2025)

  • Prospective international cohort; 31 centres; 306,900 anaesthetics in children <16 years
  • Compared centres using sip til send, ≥1 h and ≥2 h clear fluid fasting

Clear fluid regimen Anaesthetics Confirmed aspiration (per 10,000)
Sip til send 34,028 1.2
≥1 h 251,021 0.96
≥2 h 21,851 1.8

  • Both sip til send and 1 h fasting were noninferior to 2 h for confirmed aspiration, transient regurgitation and escalation of care
  • No deaths, cardiac arrests or brain injury
  • Gastrointestinal pathology was the commonest risk factor in children who aspirated
  • Conclusion: reducing clear fluid fasting from 2 h to 1 h is safe in children

Complications of regurgitation events

  • Hypoxaemia (commonest; ~1/3)
  • Laryngospasm
  • Pneumonitis or pneumonia
  • Bronchospasm
  • Bradycardia

Trauma

  • The injured child should be treated as having a full stomach
  • Gastric volume relates to the interval between the last meal and the injury rather than the length of fasting since

Sedation

  • There is insufficient evidence that fasting before procedural sedation reduces adverse outcomes in children
  • In a large prospective analysis of children sedated or anaesthetised outside theatres, fasting status was not an independent predictor of aspiration or major adverse events

Delayed gastric emptying

  • Obesity, GORD and diabetes do not require longer fasts, although they may alter overall anaesthetic management
  • These conditions are, however, listed as contraindications to the more liberal 1hr clear fluid regimen

  • Children should be allowed to eat and drink as they wish after elective surgery
  • Oral intake should not be insisted upon before discharge from day surgery
  • Withholding fluids postoperatively does not reliably reduce vomiting