Chapter 135. Gas Gangrene and Other Clostridial Infections (Part 4)

Gas Gangrene (Clostridial Myonecrosis) Gas gangrene is characterized by rapid and extensive necrosis of muscle accompanied by gas formation and systemic toxicity and occurs when bacteria invade healthy muscle from adjacent traumatized muscle or soft tissue. The infection originates in a wound contaminated with clostridia. Although 30% of deep wounds are infected with clostridia, the incidence of clostridial myonecrosis is quite low. These infections occur in both military and civilian settings. An essential factor in the genesis of gas gangrene appears to be trauma, particularly involving deep muscle laceration. The entity of clostridial myonecrosis is relatively uncommon after simple,...
Nội dung trích xuất từ tài liệu:
Chapter 135. Gas Gangrene and Other Clostridial Infections (Part 4) Chapter 135. Gas Gangrene and Other Clostridial Infections (Part 4) Gas Gangrene (Clostridial Myonecrosis) Gas gangrene is characterized by rapid and extensive necrosis of muscleaccompanied by gas formation and systemic toxicity and occurs when bacteriainvade healthy muscle from adjacent traumatized muscle or soft tissue. Theinfection originates in a wound contaminated with clostridia. Although >30% ofdeep wounds are infected with clostridia, the incidence of clostridial myonecrosisis quite low. These infections occur in both military and civilian settings. Anessential factor in the genesis of gas gangrene appears to be trauma, particularlyinvolving deep muscle laceration. The entity of clostridial myonecrosis isrelatively uncommon after simple, through-and-through bullet wounds withoutshattering of bone and is relatively common after shrapnel fragmentation wounds,particularly when deep muscle is involved. In civilian cases, gas gangrene canfollow trauma, surgery, or IM injection. The trauma need not be severe; however,the wound must be deep, necrotic, and without communication to the surface.Indeed, seeding of muscle tissue by C. septicum from a gastrointestinal source—often a malignancy—may lead to spontaneous nontraumatic clostridialmyonecrosis (Fig. 135-1). The incubation period of gas gangrene is usually short: almost always At surgery, muscle may appear pale because of the intensity of edema, butit does not contract when probed with a scalpel. When dissected, the muscle isbeefy red and nonviable and can progress to become black, friable, andgangrenous. It is important to establish a diagnosis early, preferably by frozen-section biopsy of muscle. Despite hypotension, renal failure, and (often) body crepitation, patientswith myonecrosis frequently have a heightened awareness of their surroundingsuntil just before death, when they lapse into toxic delirium and coma. In untreatedcases, as the local wounds progress, the skin becomes bronzed; bullae appear,become filled with dark red fluid, and are accompanied by dark patches ofcutaneous gangrene. Gas appears in later phases but may not be as obvious as inanaerobic cellulitis. Jaundice is rare in wound gas gangrene (in contrast to uterineinfections) and, when it does appear, is almost invariably associated withhemoglobinuria, hemoglobinemia, and septicemia. Cases of clostridialmyonecrosis without a history of trauma have been reported. These patients havebullous lesions and crepitation of the skin; they present with a rapidly worseningcourse that includes myonecrosis, especially of the extremities. Bacteremia and Clostridial Sepsis The relatively common entity of transient clostridial bacteremia can arise inany hospitalized patient but is most common with a predisposing focus in thegastrointestinal tract, biliary tract, or uterus. Fever frequently resolves within 24–48 h without therapy. Despite the finding of clostridial bacteremia following septicabortions and the frequent isolation of clostridia from the lochia, most of thepatients involved do not have evidence of sepsis. In one series of 60 patients withclostridial bacteremia, half had an infected site that could be associated with thebacteremia, while the other half had a totally unrelated illness, such as tuberculouspneumonia, meningitis, or benign gastroenteritis. By the time blood culture reportsare returned, patients frequently are completely well and sometimes have beendischarged. Therefore, when a blood culture is positive for clostridia, the patientmust be assessed clinically rather than simply treated on the basis of the cultureresult. Clostridial sepsis is an uncommon but almost invariably fatal illnessfollowing clostridial infection—primarily that of the uterus, colon, or biliary tract.This entity must be differentiated from transient clostridial bacteremia, which ismuch more common. C. perfringens causes the majority of cases of both sepsisand transient bacteremia. C. septicum, C. sordellii, and C. novyi account for mostof the remainder of cases. C. sordellii sepsis with toxic shock syndrome has beenassociated with pregnancy and more recently with medically induced abortion.Clostridia account for 1–2.5% of all positive blood cultures in major hospitalcenters. The majority of cases of clostridial sepsis originate from the female genitaltract and follow septic abortion. Introduction of a foreign body is a commonantecedent event. In the uterus, residual necrotic fetal and placental tissues andtraumatized endometrium may allow the growth of clostridia. Only a smallfraction of cases of septic abortion (1%) are followed ...