Crystalloids vs Colloids
Crystalloid and colloid solutions are largely used for medical purposes. So it is vital to know their differences so that doctors can decide when to use these solutions.
What is Crystalloids?
This is a substance that can be crystallized. These are aqueous solutions of salts, minerals or any other water soluble substances. Saline, which is an aqueous solution of sodium chloride, is a crystalloid. Since they contain small molecules, they can be passed through all the cell membranes and go into cells. When the solutions are injected to blood, they come out of the vascular system and distribute rapidly all over. They can be stored in room temperature and can contain electrolytes or non electrolytes. Because of these reasons, crystalloid solutions are useful in medicine. They are used as volume expanders, as a medium to supply deficient electrolytes to the body, etc. The advantages of crystalloid solutions are that they are inexpensive, easy to store, have a long life time, effective for use, low side effects, easy to prepare and readily available; also, a variety of formulations are available. However, excessive usage of crystalloid fluid for therapies can cause peripheral and pulmonary oedema.
What is Colloids?
Colloidal solution is seen as a homogeneous mixture, but it can be heterogeneous as well (e.g.: milk, fog). The particles in colloidal solutions are of intermediate size (larger than molecules) compared to particles in solutions and suspensions or crystalloids. But like the particles in solutions, they are invisible to the naked eye and cannot be filtered using a filter paper. The particles in a colloid are termed as dispersed material, and the dispersing medium is analogous to the solvent in a solution. According to the dispersed material and the medium, there are different types of colloids. For instance, if a gas is dispersed in a liquid medium, the resulted colloid is ‘foam’ (e.g.: whipped cream). If two liquids are combined, a colloid known as emulsion can be resulted (e.g.: milk). Blood is also considered as a colloid. The particles are distributed within the colloidal medium do not settle down if it is left still. Colloidal solutions are translucent or opaque. Sometimes particles in a colloid can be separated out by centrifugation or coagulation. For example, the proteins in milk are coagulated when supplied heat or added an acid. Most commonly used colloid solutions in medical science are hetastarch, dextran, plasma protein solutions, etc. Since they are remaining in the vascular system, colloids are much more effective to use for expanding the circulatory volume than crystalloids. However, excessive use of colloids can cause side effects such as peripheral and pulmonary oedema and cardiac failure.
What is the difference between Crystalloid and Colloid?
• Colloids contain much larger molecules than crystalloids do.
• Crystalloid solutions can be stored in room temperature, but colloidal solutions cannot be stored in room temperature. They need to be stored in the refrigerator, and there is a limited time period for it too.
• The crystalloid solutions can escape the vascular system and distribute throughout the body, but colloids can’t. They are restricted to the vascular system.
• Crystalloids are much cheaper than colloids, and they are readily available.