About 25 to 30 ml/kg/day of water with 1 mmol/kg each of sodium and potassium
Expansion
Adult daily maintenance
- Water: 25 to 30 ml/kg
- Sodium, potassium and chloride: about 1 mmol/kg each
- Glucose: 50 to 100 g, to limit ketosis (not for nutrition)
For a 70 kg adult that is roughly 2 litres of water with 70 mmol of sodium. A litre of 0.9 per cent saline contains 154 mmol of sodium, so two litres would supply more than four times the requirement.
Paediatric (Holliday-Segar)
- 100 ml/kg/day for the first 10 kg
- 50 ml/kg/day for the next 10 kg
- 20 ml/kg/day thereafter
Losses to add: fever (about 10 per cent extra per degree above 37), burns, drains, vomiting, diarrhoea, high stoma output, and third space losses.
Two hazards to avoid: hyponatraemia from hypotonic fluid, particularly in children and postoperative patients where antidiuretic hormone is high, which is why isotonic maintenance fluid is now recommended in children; and fluid overload, since prescribing maintenance without reviewing the patient’s actual state is a common source of harm.