Maintenance fluid (Holliday-Segar 4-2-1)

4 mL/kg/hr (first 10 kg) + 2 mL/kg/hr (next 10 kg) + 1 mL/kg/hr (each kg above 20) — works for peds and adults. Modern guidance de-emphasizes aggressive NPO-deficit replacement; clear liquids OK up to 1h pre-op (ASA 2017).

Clinical note:Holliday-Segar (1957) is the foundational pediatric maintenance formula. Adults follow the same rule for routine maintenance. Surgical replacement (insensible + third-space) is layered on top per Miller's. Education only.