|Table 1: Types of Wound Exudate |
Serous: clear, amber, thin and watery
Fibrinous: cloudy and thin, with strands of fibrin
Serosanguineous: clear, pink, thin and watery
Sanguineous: reddish, thin and watery
Seropurulent: yellow or tan, cloudy and thick
Purulent: opaque, milky; sometimes green
Hemopurulent: reddish, milky and viscous
Hemorrhagic: red, thick |
Assessment of Exudate
Wound exudate should be assessed for color, consistency, quantity and odor. Wound exudate is described using the terms serous, fibrinous, serosanguineous, sanguineous, seropurulent, purulent, hemopurulent or hemorrhagic (Table 1). The consistency of exudate may vary from thick and viscous to thin and watery. Thick exudate may result from liquefying necrotic material and bacteria. Infected wounds often exhibit increased viscous exudate. Exudate may be clear or cloudy and may range in color from amber to red, pink, yellow or brown, depending on its constituents. 6
Serous exudate is a clear liquid that is typically amber in color and thin and watery in consistency. Fibrinous exudate is thin and cloudy and contains protein strands of fibrin. Serosanguineous exudate is clear and pink and is also thin and watery. Sanguineous exudate is red and has a thin, watery consistency. Seropurulent exudate is cloudy and yellow or tan in appearance. It has a thicker consistency than the types mentioned previously, and infection usually coexists with it.
Purulent exudate is opaque and has been described as "milky" in appearance. Infection is usually present with this form of exudate. Purulent exudate produced by Pseudomonas aeruginosa is green. Hemopurulent exudate is also milky in appearance, but it contains red blood cells and is viscous in consistency. The appearance of hemopurulent exudate is a sign of infection and capillary damage. This gives it a blood-stained appearance. Red blood cells are the major component of hemorrhagic exudate, and this substance is thick in consistency. Hemopurulent exudate is a sign of infection and trauma and reflects the bleeding that has occurred. 3,4
The quantity of exudate may be determined in part by wound type. Arterial wounds are associated with minimal exudate, and venous ulcers are highly exudative. Other factors that may determine the quantity of exudate are as follows:
- the size of the wound
- the stage of wound healing
- the presence of infection
- underlying cardiac disease
- peripheral edema.
Generally, larger wounds produce more exudate than smaller wounds. For example, large stage IV pressure ulcers often have high amounts of exudate. Wounds in the inflammatory stage of healing produce more exudate than those in later stages of healing. A sudden increase in exudate amount may be a sign of wound infection or osteomyelitis.
Comorbid conditions such as heart disease decrease the ability of the body to recirculate fluid and cause wound exudate to increase. Dehydration may cause wound exudate to decrease.
Exudate quantity or volume has traditionally been described as light, moderate or heavy. The Pressure Ulcer Scale for Healing (PUSH) tool includes wound exudate quantity as one of its criteria for monitoring healing. The tool defines exudate as none, light, moderate or heavy. Exudate is considered light when it covers less than 25% of the wound surface, moderate when it covers 50% to 75% of the wound surface, and heavy when it covers 75% to 100% of the wound surface.
Researchers have proposed a rating scale (Bates-Jensen classification) to quantify the amount of exudate as follows: 7,8
- scant with no measurable exudate
- small with wet wound tissue
- moderate with saturated wound tissue
- large with wound tissue bathed in wound fluid.
Another researcher developed the following four categories to quantify wound exudate (Mulder classification): 9
- minimal (less than 5 cc of exudate per 24 hours)
- moderate (5 cc to 10 cc every 24 hours)
- high (more than 10 cc every 24 hours).
Whichever method is chosen, remember that measuring wound exudate is subjective, and accuracy is dependent on the skill of the provider. Dressings are the primary option for managing exudate. Determining the volume of exudate helps in dressing selection because dressings are marketed based on exudate volumes. Another reason to measure wound exudate is that a sudden increase in wound exudate volume may reflect wound infection. And for home care agencies, the documented amount of exudate is one of the main requirements for coverage of surgical dressings.
All wound exudate has some type of odor. Exudate from necrotic ulcers may have a more offensive odor than exudate from clean wounds. Exudate from infected wounds may have a distinct putrid odor. Dressings used in the management of the wound may also be a source of odor.
Methods to measure odor are subjective. Odor descriptions should include a description of the odor (e.g., "like rotten eggs") and the amount or power of the odor (e.g., "filled the room").