The key difference between crystalloids and colloids is that the colloids contain much larger molecules than that of crystalloids.
Crystalloid and colloid solutions are largely useful for medical purposes. Hence, it is vital to know the difference between crystalloids and colloids so as to decide when to use these solutions. When considering their chemistry, based on the size of the molecules they have, there is some difference between crystalloids and colloids.
CONTENTS
1. Overview and Key Difference
2. What are Crystalloids
3. What are Colloids
4. Side by Side Comparison – Crystalloids vs Colloids in Tabular Form
5. Summary
What are Crystalloids?
Crystalloid is a substance that we can crystallize. 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 pass through all the cell membranes and go into cells. When we inject the solutions to blood, they come out of the vascular system and distribute rapidly all over. We can store them at room temperature and also they can contain electrolytes or non-electrolytes. Because of these reasons, crystalloid solutions are useful in medicine.
Figure 01: Saline Water or Salt Water
They are important 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 lifetime, 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 are Colloids?
Colloidal solution is 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) when compared to particles in solutions and suspensions or crystalloids. But like the particles in solutions, they are invisible to the naked eye, and we cannot filter using a filter paper. We name the particles in a colloid as the dispersed material, and the dispersing medium is analogous to the solvent in a solution.
Figure 02: Milk is a Colloid
According to the dispersed material and the medium, there are different types of colloids. For instance, if a gas disperses in a liquid medium, the resulting colloid is ‘foam’ (e.g., whipped cream). If two liquids combine, a colloid is an emulsion(e.g., milk). Blood is also a colloid. The particles distribute within the colloidal medium do not settle down if it is left still. Colloidal solutions are translucent or opaque. Sometimes we can separate out particles in a colloid by centrifugation or coagulation. For example, the proteins in milk coagulate when we supply heat or if we add an acid.
Most commonly, we use colloid solutions such as hetastarch, dextran, plasma protein solutions, etc. in medical science. 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 Crystalloids and Colloids?
Crystalloids refer to a substance that we can crystallize while colloids refer to a solution that has a dispersing material and a dispersing medium. As the key difference between crystalloids and colloids, we can say that they differ from each other according to the particles size; colloids contain much larger molecules than crystalloids do. Apart from that, there is another significant difference between crystalloids and colloids. That is, we can store crystalloids at room temperature whereas we cannot store colloids at room temperature.
Summary – Crystalloids vs Colloids
Crystalloids and colloids are two terms that we use to name two types of substances containing particles. The difference between crystalloids and colloids is that the colloids contain much larger molecules than that of crystalloids.
Reference:
1. “Volume Expander.” Wikipedia, Wikimedia Foundation, 10 Sept. 2018. Available here
2. “Colloid.” Wikipedia, Wikimedia Foundation, 16 Sept. 2018. Available here
Image Courtesy:
1.”3404233″ by lbokel (CC0) via pixabay
2.”Glass of milk on tablecloth”By I, Chedid, (CC BY-SA 3.0) via Commons Wikimedia