11.10 Cutaneous Abscess or Pustule

agk’s Library of Common Simple Emergencies

Presentation

With or without a history of minor trauma (such as an embedded foreign body) the patient has localized pain, swelling and redness of the skin. The area is warm, firm, and, usually fluctuant to palpation. There is sometimes surrounding cellulitis or lymphangitis and, in the more serious case, fever. There may be an spot where the abscess is close to the skin, the skin is thinned, and pus may break through to drain spontaneously (“pointing”). A pustule will appear only as a cloudy tender vesicle surrounded by some redness and induration, and occasionally will be the source of an ascending lymphangitis.

What to do:

• A pustule may not require any anesthesia for drainage. Simply snip open the cutaneous roof with fine scissors or an inverted #11 blade, grasp an edge with pickups and excise the entire overlying surface. Cleanse the open surface with normal saline and cover it with povidone- iodine ointment and a dressing.
• When the location of an abscess cavity is uncertain, attempt to aspirate it with a # 18 gauge needle after prepping the area with povidone-iodine. If an abscess cavity cannot be located, send the patient out on antibiotics and intermittent warm moist compresses and have him seen again in 24 hours.
• When the abscess is pointing or has been located by needle aspiration, prepare the overlying skin for incision and drainage with povidone-iodine solution. Anesthetize the area with regional field block, accomplished by injecting a ring of subcutaneous 1% lidocaine solution approximately l cm away from the erythematous border of the abscess. In addition, inject lidocaine into the roof of the abscess along the line of the projected incision.
• The incision should be made with a #11 or #15 blade at the most dependent area of fluctuance. It should be large and directed along the relaxed skin tension lines to reduce future scarring
• In larger abscesses insert a hemostat into the cavity to break up any loculated collections of pus. The cavity may then be irrigated with normal saline and loosely packed with Iodoform or plain gauze. Leave a small wick of this gauze protruding through the incision to allow for continued drainage and easy removal after 48 hours.
• The patient should be instructed to use intermittent warm water soaks or compresses for a few days when there is no packing used or after packing is removed.
• A dressing should be provided to collect continued drainage.

What not to do:

• Do not incise an abscess that lies in close proximity to a major vessel, such as in the axilla, groin or antecubital space, without first confirming its location and nature by needle aspiration.
• Do not treat deep infections of the hands as simple cutaneous abscesses. When significant pain and swelling exists, or there is pain or range of motion of a finger, seek surgical consultation.

Discussion

Either trauma or obstruction of glands in the skin can lead to cutaneous abscesses. Incision and drainage is the definitive therapy for these lesions and, therefore, routine cultures and antibiotics are generally not indicated. Exceptions exist in the immunologically suppressed patient, the toxic, febrile patient, or where there is a large area of cellulitis or lymphangitis, in which cases an antibiotic can be selected on the basis of a Gram stain or presumptively based on body location.

It is sometimes not possible to achieve total regional anesthesia for incision and drainage of an abscess, perhaps because local tissue acidosis neutralizes local anesthetics. In such cases, additional analgesia may be obtained by premedication with narcotics or brief inhalation of nitrous oxide.

References:

Llera JL, Levy RC: Treatment of cutaneous abscess: a double-blind clinical study. Ann Emerg Med 1985;14:15-19.

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