NPO 2-4-6-8 — ASA fasting guidelines
Pre-op fasting time by intake type
Mnemonic device
2-4-6-8 hours
Mapping
2 hours
Clear liquids (water, black coffee/tea, clear juice, sports drinks; NO pulp/milk)
4 hours
Breast milk (infants)
6 hours
Light meal (toast + clear liquid) OR infant formula OR non-human milk
8 hours
Full meal (fatty/fried/meat)
Clinical note: ASA 2017 update — clear liquids encouraged up to 2h pre-op (better hydration, less induction hypotension, more comfortable). Diabetics: continue clear liquids; metformin held morning of surgery; long-acting insulin half-dose. Full stomach (trauma, opioids, severe GERD, pregnancy >18 weeks) → RSI regardless of NPO time.