1. Hypotonic Solution: Normal saline has a concentration of 0.9% NaCl, making it a slightly hypotonic solution compared to the blood plasma, which has a normal saline concentration of approximately 0.9%. When infused intravenously, the hypotonic saline can cause the influx of water into red blood cells, leading to a condition called hemolysis. Hemolysis occurs when red blood cells rupture due to the osmotic pressure difference between the cells and the surrounding fluid.
2. Electrolyte Imbalance: Normal saline contains only sodium and chloride ions, and lacks other essential electrolytes such as potassium, magnesium, and calcium. These electrolytes play crucial roles in various physiological processes, and their absence can disrupt cellular functions. For instance, low potassium levels can affect nerve and muscle function, while low calcium levels can impair cardiac contractility.
3. Fluid Overload: Since normal saline is a hypotonic solution, it can lead to fluid overload if infused intravenously. The hypotonic nature of the solution causes water to move from the extracellular space into the intracellular space, increasing the total fluid volume in the body. This can result in edema, pulmonary edema, and other complications associated with fluid overload.
4. Acid-Base Imbalance: Normal saline has a pH of around 5.5, which is slightly acidic. Repeated or excessive use of normal saline for intravenous purposes can cause metabolic acidosis due to the accumulation of chloride ions. This can disrupt the acid-base balance and affect various physiological processes.
Therefore, it is essential to use isotonic solutions such as 0.9% NaCl with dextrose (D5W) or balanced electrolyte solutions (such as Ringer's lactate) for intravenous infusions to avoid the risks associated with using normal saline.