Wound exudate is a set of substances and elements that are extravasated in a lesion or inflammatory process. Commonly, people refer to it as what comes out of the wound, the fluid from the wound, or the drain.
Wound exudate can appear unsightly and even be worrisome in some cases. The reason is that it has a variable appearance, depending on how the injury is. Therefore, its characteristics can give a lot of clinical information.
In addition, this set of substances play a very important role in healing. Therefore, in this article we explain what exudate from wounds consists of, what it is composed of and what types exist.
What is wound exudate?
Wound exudate is a fluid of different colors and viscosities that is made up of different substances. The word exudate as such, refers to the fluid that leaks from the blood vessels. It is similar to plasma. That is, the liquid part of the blood, with a high concentration of proteins.
This fluid leaks from the blood capillaries. The filtering depends on the permeability and the pressure difference between the intracellular and the extracellular fluid. Typically, the filtrate is reabsorbed by the capillaries themselves.
In addition, the small amount that is not reabsorbed by the circulatory system passes into the lymphatic system. So, it returns back to the blood. In this way, a balanced situation between the fluids of the whole body is maintained.
The exudate of the wounds is produced by the inflammatory process that is triggered when an injury occurs. When there is an attack on the body, a series of substances are released that increase the permeability of the capillaries.
With more permeability, cells of the immune system and pro-inflammatory substances can move to the site of injury. This is why excess fluid is produced that seep through the wound.
Why does exudate from wounds occur?
Wound exudate occurs in response to aggression. According to a publication of the Wound Essentials, it contains various substances that play important roles in healing.
First of all, water and electrolytes, such as sodium, are fundamental components. In the exudate of the wounds there are also cells of the immune system (leukocytes), proteolytic enzymes and inflammatory mediators.
These mediators are substances that are responsible for further stimulating the migration of cells of the immune system to that area. The exudate contains growth factors that are responsible for stimulating cell proliferation to heal the wound.
However, exudate from wounds can have other effects. In those wounds that do not heal and become chronic, this compound has more inflammatory mediators and proteolytic enzymes.
Main types of exudate
Wound exudate can be of different types. According explains one publication of Wound Source, there are 5 main types: serous, blood, serosanguinous, purulent and hemorrhagic. Each occurs more typically at different times in healing.
1. Serosanguinous exudate
The serosanguinous exudate is the most frequent. It has a fine, pinkish appearance and a watery consistency. The reason is that it contains small amounts of blood cells interspersed with serous fluid.
2. Serous exudate
The exudate from serous wounds is a clear fluid. It is considered to be the body’s normal response to injury. In other words, the healing process is taking place properly. This exudate does not smell or is too slimy.
The fluid is produced because the skin, as it regenerates, generates waste. For example, dead cells and proteins. The problem is that if it becomes very abundant, it can indicate a problem in healing.
3. Bloody discharge
The bloody exudate is a reddish liquid, more intense in color than the serosanguinous one. It usually occurs when cleaning the wound or when it moves too much, especially soon after it occurs.
It is normal for it to appear during the inflammatory stage. At this time, it is common for some blood to leak into the wound. However, if it appears later, when the tissue had already begun to regenerate, it is usually due to trauma to the injury itself.
4. Purulent exudate
Exudate from purulent-type wounds appears thicker and more viscous. It can have a grayish, green or yellowish color. The reason for this is that it has a higher number of white blood cells and bacteria. That is why it is indicative of an infection.
5. Hemorrhagic exudate
Hemorrhagic exudate can be confused with exudate from bloody wounds. However, this indicates injury to a blood vessel due to infection or trauma. In this case, the color is redder and has a thicker consistency.
Other aspects of wound exudate
There are a number of important issues to consider when assessing wound exudate. As explained in a publication by Nursing Times, color is one of the parameters to be fixed. Light or slightly yellowish color is considered normal.
However, if the fluid looks cloudy, it may indicate an infection. Especially if it has a greenish or brown color. It can even be associated with the appearance of necrotic tissue. The reddish color, as we pointed out before, is indicative of the presence of blood.
The viscosity of the wound exudate is also decisive. When it is too viscous or thick it signals an infection and high protein content. However, if it is an aqueous liquid, the protein content is low.
What does the amount of exudate depend on?
The amount of exudate also influences your evaluation. When the wound is in the process of healing, it is normal for the exudate to be progressively reduced. However, if it does not heal properly, production may persist.
In this way, there is an excessive amount that causes the inflammatory process to be maintained. Also, humid conditions interfere with healing.
On the other hand, there are more factors that can influence the amount of exudate. The first is the extent of the wound. The larger the surface, the more drainage will occur. The same happens with the type of wound. Burns, venous ulcers, and inflammatory ulcers often have abundant exudates.
Similarly, if there is peripheral edema or infection, it is more common for it to be a profuse exudate. If the wound is on the leg and the leg is kept low, the fluid tends to drain out by gravity.
There are wounds that have little exudate by their nature. For example, ischemic ulcers. They are those that are produced by lack of blood supply.
The exudate from the wounds is indicative
What we must remember is that exudate from wounds is normal. It occurs in response to injury, to promote the healing and healing process. However, if it is a chronic wound, the exudate can interfere negatively.
In addition, we must bear in mind that the characteristics of the exudate, such as color or viscosity, are decisive. They can help find out if there is an infection or bleeding.