A hypertonic solution is a solution that contains higher concentration of a solute compared to a standard reference solution. One of the major balances that a human body maintains on a daily basis is that of water and electrolyte levels in the body. We know that water (fluid) makes up most of a body’s weight. This water is equally distributed amongst blood vessels, between cells, tissues and organs and helps in stability of the body parts. Osmosis is a process of regulating the water and electrolyte distribution in the body. In simple words osmosis is defined as the movement of water from an area of lower concentration of solute to an area of higher concentration of solute, through a semi-permeable membrane. This ensures that there are equal solute ions on both ends of the semi-permeable membrane. With respect to the human body, the semi-permeable membrane refers to all the veins, the capillary vessels and cell membranes.
When water or fluid levels in the body increase well beyond normal levels, it causes conditions such as over hydration and edema and causes the body to swell and bloat. In such cases, hypertonic solutions are used to absorb all the extra fluids in the body. This is because hypertonic solutions typically have a tonicity exceeding 350mEq/L and are used in repairing electrolyte and acid imbalances in the body. A hypertonic solution contains an impermeable solute on one side of the semi-permeable membrane and when a cell’s cytoplasm is submerged in a hypertonic solution, it actively starts extracting extra fluid from the cell to the external side thereby resulting in uniform fluid levels on either side. This excess water is then ideally forced through the kidneys to enable it to pass out of the body as urine. If the balance is not constantly monitored, this may result in hypertonic dehydration which means that the body part which is in contact with the hypertonic solution shrinks and water levels fall to below normal limits.
Common combinations of hypertonic solutions are 0.9% sodium chloride (salt) with 5% dextrose or even higher, 3% normal saline and 10% dextrose. This solution is usually given intravenously. Hypertonic solution should not be administered in some cases when the patient is suffering from heart or kidney disorders, patients who have a tendency of cellular dehydration and hypertension.