Chapter 26 ICU Infections

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SECTION II • Medical and Surgical Crises

Necrotizing fasciitis

Contact dermatitis

Cellulitis

Erysipelas

Erythema multiforme

Ecthyma

Deep vein thrombosis

Folliculitis

Impetigo

FIGURE 26-8. External appearances of common inflammatory skin conditions.

the setting of tissue ischemia or gross contamina- tion (Fig. 26-9). Risk factors for gas-forming infec- tion include diabetes, penetrating foot lesions, peripheral vascular disease, and open trauma. Gas- producing infections may be classic gas gangrene with myonecrosis or a mixed organism (synergistic) necrotizing fasciitis. Both may spread with alarming speed. A mixture of aerobic and anaerobic organ- isms (Gram-positive cocci and Gram-negative rods) causes most gas-producing soft tissue infections. Classic clostridial gangrene occurs less commonly. Aggressive soft tissue infections spread along fascial planes where blood supply is tenuous. Because observable cutaneous changes may be few, a high clinical suspicion is essential. Some of these life-threatening infections resemble a relatively uncomplicated cellulitis (Fig. 26-10). A number of general principles apply to the recognition of nec- rotizing infections: (1) soft tissue imaging, which is positive for gas, is more sensitive than physical examination; (2) CT and MRI improve detection

of soft tissue gas; (3) identification of fluid and edema in tissue is neither sensitive nor specific for aggressive soft tissue infection; and (4) among important clinical features are pain disproportion- ate to findings on physical examination, particularly if joint or muscle group use is compromised. Skin changes such as necrosis, cutaneous anesthesia, and formation of bullae may be helpful. Laboratory data are nonspecific and of limited diagnostic aid. Nonetheless, leukocytosis, hyponatremia, and ele- vated blood urea nitrogen (BUN) increase the likeli- hood of aggressive soft tissue infection. Where soft tissue infection is suspected, early surgical consulta- tion is essential. Appropriate surgical treatment may include wide opening of tissue planes at the level of the fascia and excision of nonviable tissue. In some cases, effective debridement requires amputation of the infected extremity or distal portions thereof. Necrotizing fasciitis is a pernicious infection that may easily elude detection until it is far advanced (Fig. 26-11). Diabetic patients usually