Supplements such as calcium, magnesium, and phosphorus are not routinely added to maintenance fluid therapy. However, maintenance intravenous fluids for neonates may represent one instance in which some practitioners may consider adding calcium

The main components of mentainance fluids are Sodium, Potassium and Glucose.

After about 2 days, you should add calcium, magnesium and phosphorus as mentainance, if still NPO

After about 3 to 5 days if still NPO, you should add proteins and lipids.

After that if still NPO, you should add trace elements and vitamins. At this point the patient is recovering TPN.

If the patient is expected to be NPO for longer duration, you can start TPN from day one.

Cardiac patient, can start calcium and magnesium from day one.

When sepsis and/or critically ill and unstable ICU patients, you can delay the start of proteins and lipids untill the patient is stable.