Fluid Types (IVF)

Hypertonic:

What is it?

A solution is hypertonic if it has a higher concentration of solutes compared to another solution. When comparing to the inside of a cell, a hypertonic solution has more solutes (of fewer water molecules) than the cells cytoplasm.

Effect on the cell:

When a cell is in a hypertonic solution, water will flow out of the cell (osmosis) to try to equilibrate the solute concentrations inside and outside the cell. The can cause the cell to shrivel or crenate.

Uses:

  • To reduce oedema (swelling).

  • Used in some instances to treat hyponatremia.

Considerations:

It can cause cellular dehydration if used excessively. Over-correction with hypertonic saline in hyponatremia, for instance, can lead to osmotic demyelination syndrome, a serious neurological condition.

Examples:

  • 3% and 5% saline

  • 5% dextrose in 0.9% saline

  • 5% dextrose in 0.45% saline

  • 5% dextrose in lactated ringer’s

  • 10% dextrose in water

Isotonic

What is it?

An isotonic has the same concentration of solutes as another solution. When comparing to the inside of a cell, an isotonic solution has an equivalent solute concentration to the cell’s cytoplasm

Effect on the cell:

Cells remain stable in isotonic solutions, with no net movement of water in or out of the cell.

Uses:

  • To maintain blood volume.

  • As a vehicle for medication delivery.

  • For hydration.

Considerations:

They are generally safe for intravenous administration, but its essential to monitor for potential overhydration in susceptible patients.

Examples:

  • 0.9% sodium chloride

  • Lactated ringer’s and Hartman’s

  • 5% Dextrose in 0.225% saline

  • 5% Dextrose in water

Hypotonic

What is it?

A solution is hypotonic if it has a lower concentration of solutes compared to another solution. When comparing tot he inside of a cell, a hypotonic solution has fewer solutes (or more water molecules) than the cells cytoplasm.

Effect on the cell:

If a cell is placed in a hypotonic solution, water will flow into the cell, potentially causing it to swell and burst (lyse).

Uses:

  • Rehydration

  • Sometimes used to treat cellular dehydration or elevated sodium levels.

Considerations:

Excessive use can cause cellular lysis. Its crucial not to administer hypotonic solutions too rapidly, especially in cases of hypernatremia (high sodium levels). as this can lead to cerebral oedema.

Examples:

  • 0.45% saline

  • 0.225% saline

  • 0.33% saline

  • 5% dextrose in water