Before any anaesthetic, classify physical status with the ASA scale and ensure appropriate fasting to minimise the risk of aspiration.
How it's asked: ASA classes I–VI and fasting times for clear fluids, breast milk, formula and solids.
Why this is true
General anaesthesia abolishes protective airway reflexes and relaxes the lower oesophageal sphincter, so gastric contents can be regurgitated and aspirated into the lungs (Mendelson's syndrome). Fasting times reflect how quickly each substance leaves the stomach: clear fluids empty within an hour or two, breast milk faster than formula, and fat- or protein-rich meals slowest. ASA grading summarises the patient's systemic disease burden, which correlates with perioperative risk.
Key points
Fasting guidelines (ASA)
| Intake | Minimum fast |
|---|---|
| Clear fluids | 2 hours |
| Breast milk | 4 hours |
| Infant formula / non-human milk | 6 hours |
| Light meal | 6 hours |
| Fried / fatty meal | 8 hours |
Common traps
- Breast milk (4 h) and formula (6 h) have different fasting times.
- A well-controlled hypertensive is ASA II; ASA III requires severe disease with functional limitation.
Clinical case
A 60-year-old with poorly controlled diabetes, stable angina limiting activity, and morbid obesity is posted for elective hernia repair.
High-yield
ASA I healthy → VI brain-dead donor; 'E' for emergency. Fasting: clear 2 h, breast milk 4 h, formula 6 h, light meal 6 h, fatty 8 h.
Quick check
Q1.Minimum fasting time for breast milk before anaesthesia:
Q2.A brain-dead patient for organ harvest is ASA class: