What are the different Iv fluids and their functions?

Normal saline 1.9%, 5% dextrose in water are called crystalloids and are mainly used for fluid replacement. They are not that efficient in volume replacement because most of the water diffuses by osmosis into the extracellular space. You have to give 4 litres of crystalloid to obtain a 1 litre rise in blood volume. However, they are dirt cheap.

Haemecell, human albumin etc are colloids and mimic the "weight" of blood. They are expensive but most of the fluid remains in the blood.