Exudate : An Overview

Introduction

The skin is a magnificent barrier against infection. But accidents happen, and sometimes the skin barrier is broken, either because of a cut or scrape or some other type of injury. After an injury, the body's repair mechanisms spring into action. Soldier cells (a specific type of white blood cell) are sent to the area to fight against any infection that may attempt to enter through the opened tissue. Some of these soldier cells die, as do some of the skin cells that were damaged in the injury. All of these dead cells contribute to forming something called an exudate.

Exudate is the fluid produced by a wound as it heals, and it is a normal part of the healing process. However, sometimes infection sets in, changing the appearance of the exudate.

What Is an Exudate?

Exudate is a fluid comprised mainly of protein and cellular elements that oozes out of blood vessels in nearby tissues and gets deposited there. This happens due to inflammation as the permeability of blood vessels changes which allow the bigger molecules and solid matter to pass through their walls.

The word ‘exudate’ is derived from a Latin word, exsudare, meaning - to sweat out. Hence, exudate denotes vessels that seem to weep or sweat.

An exudate possesses a high specific gravity (>1.020). It has a fluid to serum total protein ratio of less than 0.5, and a fluid to serum LDH ratio greater than 0.6. An exudate may also come out from cuts or from sites of infection or inflammation and is also known as pus. In diabetic retinopathy, exudate gets deposited in the retina of the eye.

Why Does Exudate From Wounds Occur?

• Wound exudate occurs in response to aggression; it comprises various substances that are essential for healing.

• Water and electrolytes like sodium, are the main components of an exudate. In the exudate that comes out from wounds, immune system cells like leukocytes, proteolytic enzymes, and inflammatory mediators are also present.

• These mediators further stimulate the migration of other cells of the immune system to the infected or affected area. The exudate also contains growth factors that cause stimulation of cell proliferation and help in the healing of the wound.

• However, wounds’ exudate can portray other effects also. In chronic wounds, the exudate carries more inflammatory mediators and proteolytic enzymes.

What Is the Difference Between Exudates and Transudates?

• Exudates are made up of fluids, cells, or other cellular substances that slowly seep from blood vessels, particularly from inflamed tissues. Transudates have a more fluid component. They also flow through a membrane or ooze through tissue into the extracellular tissue spaces. They are comparatively thin and watery, carry few cells or proteins, and occur due to the alteration in hydrostatic or colloid osmotic pressure, and not by inflammation.

• In comparison, a transudate is a fluid that permeates a membrane that filters out most of the protein and cellular elements and leaves a watery solution behind. The transudation process occurs due to increased pressure in the veins and capillaries. This pressure forces fluid through the vessel walls and leads to low levels of serum proteins. So the transudate is actually a filtrate of blood.

What Are the Types of Exudates?

Wound drainage is of four types namely serous, sanguineous, serosanguinous, and purulent. The serous drainage production is a usual response of the body during the normal healing stage of inflammation.

Types of exudates are:

1. Fibrinous Exudate - Cloudy and thin with strands of fibrin.

2. Serous Exudate - A clear, amber, thin, and watery plasma. It is normal during the inflammatory stage of wound healing, and smaller amounts are considered normal.

3. Sanguineous Exudate - Occurs as fresh bleeding in deep partial or full-thickness wounds. It is also produced normally in small amounts during the inflammatory stage.

4. Serosanguineous Exudate - It is thin and watery in consistency and pale red to pink in color.

5. Seropurulent Exudate - It is thin and watery in consistency, has a cloudy appearance, and is yellow to tan in color.

6. Purulent Exudate - It is a thick and opaque exudate that is tan, yellow, green, or brown in color. It is not normally seen in a wound bed and is usually associated with infection or high amounts of bacteria.

7. Haemopurulent Exudate - It is reddish, viscous, and milky.

Which Factors Determine the Amount of Exudate?

• The exudate quantity is also influenced by the evaluation. When the wound is in the healing process, the amount of exudate usually gets reduced. However, if it does not heal properly, the amount of exudate may remain the same.

• So, an excessive amount of exudate causes the inflammatory process to be maintained. Moreover, humid conditions also hamper the healing.

• However, there are some more factors that influence the exudate quantity, like the wound extent. The larger the affected or infected area, the more drainage occurs. Exudate amounts also depend on the type of wound. Burns, venous ulcers, and inflammatory ulcers cause abundant oozing of exudates.

• Similarly, in cases of peripheral edema or infection, commonly a profuse exudate is seen. In leg wound cases, if the leg is kept at a low level, the fluid is drained out by gravity.

Conclusion

What we must remember is that exudating wounds are normal. Exudate refers to the draining of liquid from open wounds in the human body; it occurs in response to injury or infection to encourage 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 in diagnosis.