It provides approximately 20% of the normal caloric needs of the patient enough to prevent ketoacidosis from starvation and protein degradation
It does not provide adequate calories, protein, fat, minerals ( calcium, phosphorus, magnesium or bicarbonate) and vitamins.
Calculation of maintenance fluid
Body Weight Method for calculating Maintenance Fluid Volume
The maximum total fluid per day is normally 2,400 ml Eg. 25kg child (1000+500+100) = 1600ml/day 100ml/kg/day, plus 50ml/kg/day, plus 20ml/kg/day 1st 10kg BW 2nd 10kg BW BW > 20kg Total Fluid Requirement BW (kg)
GI tract is potentially a source of considerable water loss;
GI losses are often associated with loss of potassium, leading to hypokalemi a and bicarbonate, causing metabolic acidosis which maybe aggravated when there is hypoperfusion causing a concurrent lactic acidosis;
emesis or losses from NG tube cause a metabolic alkalosis .