Skin and Soft Tissue Infections - Incision, Drainage, and Debridement Technique

After proper positioning and anesthesia (see Periprocedural Care), incision and drainage is carried out in the following manner.

A skin incision is made with a No. 11 or 15 surgical blade in the most prominent and fluctuant part of the abscess. The direction of the incision should parallel the natural skin creases as far as possible so as to prevent unsightly scars. If there is no obvious pus pointing or fluctuant area in the abscess, the incision is made at the dependent portion of the abscess; however, a dependent incision should be avoided if a tubercular pathology is suspected.

In areas where no important neural or vascular structures are expected to be present, a bold incision that cuts through the skin, subcutaneous tissue, and deep fascia may be made to achieve entry into the abscess cavity. However, in areas where important neurovascular structures are present, only skin and subcutaneous tissue are incised. The abscess cavity is entered by insinuating a pair of blunt artery forceps or sinus forceps through a small opening in the deep fascia, then gradually opening the blades.

Once the cavity is entered, pus is seen extruding through the opening. At this point, a pus swab may be sent for microbiologic analysis if indicated. The abscess cavity is explored, and an artery forceps with a gauze piece wrapped around its tip is used to break up all the loculi and drain all the pus pockets. The same result may be achieved with the surgeon's gloved finger if the presence of a foreign body in the cavity can be ruled out.

The abscess cavity is irrigated with saline solution to flush out all the pus, debris, and blood, then packed with gauze or surgical sponge to achieve hemostasis. After a few minutes, the packing is taken out, and any active bleeding points are cauterized or ligated.

The use of wound packing is controversial but is not likely necessary. If used, packing should be inserted loosely. It is then covered with a dry absorbent dressing that soaks up exudate and blood. The dressing is changed after 24 hours and again every 24 hours thereafter until the wound is dry. When healthy granulation tissue is seen in the cavity and no fresh exudate or pus is visible, a simple dressing with gauze is sufficient.

Surgery is the most effective method of debridement. Surgical debridement is usually done with the patient under general anesthesia, but local or regional anesthesia may be employed if the lesion is not very extensive. If debridement is being done on a limb, a tourniquet may be used to minimize blood loss.

The lesion is cleaned and draped. The slough over the lesion is then slowly excised off the underlying healthy tissue with a scalpel or scissors (see the images below); smaller areas of dead tissue can be excised using a curette. The slough is excised until the wound starts bleeding, but this must be done without damaging the underlying healthy tissue. The margins of the wound are also freshened. The tourniquet is released, and any active bleeding points are cauterized.

The raw area created by debridement is covered with a nonadherent dressing (eg, tulle gras). The first dressing is changed after 24 hours; regular dressing changes follow at 24-hour intervals. At each dressing, the wound is inspected for any new slough or pus formation. Repeated debridements may be necessary until the wound becomes clean and active infection is controlled by appropriate antibiotics. Once the wound is clean, dressings may be changed at 36-hour intervals.

Other methods of debridement

Debridement methods that may be used as alternatives to surgical debridement include the following ^[11] :

• Mechanical

• Chemical

• Autolytic

• Biological

• Ultrasonic

Mechanical debridement is accomplished by using the wet-to-dry dressing method. The wound is dressed with a wet dressing (usually gauze soaked in saline) covered with a dry dressing. The dressing is then allowed to dry on the wound over the following 24-36 hours. When the dry dressing is taken off, it peels the adherent necrotic tissue away from the healthy tissue. This is a very painful method and is not much favored.

Chemical debridement is performed by using certain enzymatic chemicals on the wound that cause lysis of the necrotic tissue in the wound. Commercially available collagenase enzyme granules are sprinkled onto the wound daily until the wound is clear of necrotic tissue. Regular dressings then follow.

Autolytic debridement is a process in which the body sheds the dead necrotic tissue by the use of moisture. This process is helped by the presence of enzymes called matrix metalloproteinases (MMPs), which are produced by damaged tissue and which disrupt the proteins that bind the dead tissue to the body.

This process can be enhanced by applying dressings that encourage a balanced moist environment in the wound. Heavily exuding wounds benefit from the application of alginates, cellulose dressings, and foams; these dressings absorb the excess exudate and prevent maceration of surrounding healthy tissue while still maintaining a moist environment that promotes desloughing. Dry wounds benefit from the application of hydrogels and hydrocolloids, which donate moisture to the dead tissue to facilitate debridement. ^[12]

Biological debridement (ie, maggot therapy) involves exposing the wound to the maggots of Lucilia sericata (the greenbottle fly). These organisms digest the necrotic tissue and bacteria in the wound but spare the underlying healthy tissue. This method has not gained much favor among patients.

Ultrasonic debridement involves applying ultrasonic vibrations to the wound bed through a liquid medium. This causes cavitation (ie, the creation and destruction of small bubbles within the fluid surrounding the probe). During cavitation, the bubbles oscillate in size and shape. They expand and rapidly collapse, causing shockwave formation, and this implosion leads to erosion of tissues. Ultrasonic debridement causes necrotic tissue disruption, fragmentation and emulsion.

When a limb is being operated on, a tourniquet is used so as to obtain a bloodless field. The 3 zones of necrotizing fasciitis are delineated (see the images below). A bold incision is made that runs through the entire length of the lesion from normal skin (zone 3) proximally to normal skin distally. The incision should extend to the muscle.

The deep fascia is identified, and a finger is passed along it to probe the extent of its involvement. Healthy deep fascia can be identified by its glistening appearance and its firm attachment to the skin and subcutaneous tissue. Unlike necrosed deep fascia, it does not separate easily from the skin and subcutaneous tissue

At this point, tissue specimens are obtained and sent for aerobic and anaerobic culture and antibiotic sensitivity and for histopathologic examination to establish the diagnosis.

Once the extent of deep fascial involvement has been established, radical excision of the deep fascia is carried out with scissors to expose the underlying healthy muscle. The overlying skin and subcutaneous tissue are then inspected for viability.

Tissues in zone 1 are necrosed and are excised. Tissues in zone 2 are inspected carefully for viability and excised when involved. Viability can be checked by looking for dermal bleeding, calcification and liquefaction of subcutaneous fat, and thrombosed blood vessels. ^[13] The involved skin and subcutaneous tissue is excised.

The tourniquet is then deflated, and the tissue is examined for viability. Further debridement is carried out if necessary. Once debridement is complete, hemostasis is achieved by means of electrocauterization, and the wound is washed thoroughly with saline.

The extensive debridement required in cases of necrotizing fasciitis results in a large raw wound. The wound is carefully dressed with a nonadherent dressing and bandaged with absorbent dressing. The dressing is changed after 24 hours.

Bleeding is the most common complication associated with these procedures. Bleeding after debridement (especially debridement for necrotizing fasciitis) may cause rapid deterioration of an already compromised patient. Meticulous hemostasis is hence mandatory. In most cases, pressure dressing is sufficient to control the bleeding; in some cases, the patient may have to be returned to the operating room for control of persistent bleeding.

Drainage of an abscess or debridement of necrotic tissue may result in dissemination of bacteria and bacterial toxins into the bloodstream and thereby cause severe sepsis. Accordingly, it is imperative that these procedures be done under antibiotic coverage.

Injury to underlying nerves and blood vessels is another potential complication. The surgeon must be careful while making the incision and during debridement if the abscess or ulcer is in close proximity to important anatomic structures such as nerves and blood vessels.