Chapter 26 ICU Infections

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SECTION II • Medical and Surgical Crises

have an obvious portal of entry in the foot or lower extremity but have relatively few signs of toxicity and relatively little local pain. Because such infec- tions are usually due to gas-forming organisms, imaging of the lower extremity may be diagnostic. A different picture—“type 2” necrotizing fasci- itis—is usually presented by nondiabetic patients who have high fever, often an inconspicuous portal of entry, and intense local pain out of proportion to the physical findings. Although infection may be polymicrobial, group A Streptococcus (or “GAS”) is the primary pathogen in most such cases. To achieve a successful outcome, a combined medi- cal/surgical treatment approach must be executed rapidly. Cultures of blood should be obtained, in conjunction with biopsy or aspiration culture of the affected tissue. The primary indication for surgical intervention is severe pain in conjunc- tion with a compatible clinical setting, toxic signs, and elevated creatine kinase. Physical examina- tion may be seriously misleading (Fig. 26-11). Disease-consistent imaging studies may be sup- portive but are not required. If there is any sus- picion that vaccination is not up to date, tetanus immunization and toxoid should be administered. Although the choice of antibiotics should be guided by Gram stain and culture, empiric regi- mens usually include an antistaphylococcal peni- cillin and clindamycin or metronidazole. Wider Gram-negative coverage is advisable in patients who have been recently exposed to antibiotics or who have been hospitalized for longer periods. Extensive debridement (or amputation) frequently is required for control of necrotizing fasciitis. As a general rule, dissection and excision of involved tissue is necessary down to the plane of uninvolved fascia (Fig. 26-12). Reexploration of the wound is usually indicated after 24 hours to ensure effective debridement of necrotic debris. A particularly virulent form of lower extremity tissue necrosis follows systemic or local infection with the bacteria Vibrio vulnificus . More commonly occurring in the immunocompromised patients and those with cirrhosis, the infection causes a rapidly progressive syndrome beginning with abdominal pain and blistering dermatitis. Within hours, micro- vascular thrombosis infarcts huge masses of tissue, sometimes whole limbs. Not surprising because of the ferocity of the illness, it is often fatal, despite prompt treatment with ceftriaxone and doxycy- cline—the recommended antibiotics.

Most soft tissue infections at intravenous sites are the result of Streptococcus and Staphylococcus inoculated from the skin. Gram-negative rods may be causative in the colonized ICU patient. Removal of the catheter, application of warm compresses, and administration of analgesics and antibiotics usually resolve such infections rapidly. Treatment with a penicillinase-resistant penicillin usually will suffice. In less serious cases, oral therapy is acceptable. If methicillin-resistant staphylococci are likely, vanco- mycin represents appropriate initial therapy. Toxigenic infections present a unique set of characteristics. “Toxic shock” syndrome, an uncom- mon but lethal disease often mediated by the Staphylococcus toxin TSST-1, was first reported in menstruating women using high-absorbency tampons. It is now recognized, however, that this syndrome occurs in many settings and can result from streptococci as well. Traumatic or postop- erative wound infections may serve as the source for the toxin, even when the surgical wound itself appears uninfected. Toxic shock syndrome should be suspected in any patient with the triad of fever, erythematous (eventually exfoliative) rash, and shock. Therefore, toxic shock can be confused with Rocky Mountain spotted fever, Stevens–Johnson syndrome, leptospirosis, measles, or drug eruption. Because toxic shock syndrome is a toxin-medi- ated disease, local cultures are often positive for Staphylococcu s, whereas blood cultures frequently remain negative. Therapy includes appropriate drainage (surgical drainage of wounds, removal of tampons), antistaphylococcal antibiotics (vancomy- cin is a good initial choice), and general supportive therapy with fluids, oxygen, and vasopressors. FIGURE 26-12. The extent of necrotic infection ( arrow ) can only be determined by surgical exposure and excision down to plane of healthy tissue.