Second only to cardiogenic shock as the leading cause of shock death, septic shock (usually a result of bacterial infection) causes inadequate blood perfusion and circulatory collapse. It occurs most often among hospitalized patients, especially men over age 40 and women ages 25 to 45.
About 25% of patients who develop gram-negative bacteremia go into shock. Unless vigorous treatment begins promptly, preferably before symptoms fully develop, septic shock rapidly progresses to death (often within a few hours) in up to 80% of these patients.
In two-thirds of patients, septic shock results from infection with gramnegative bacteria: Escherichia coli, Klebsiella, Enterobacter, Proteus, Pseudomonas, and Bacteroides; in others, from gram-positive bacteria: Streptococcus pneumoniae, Streptococcus pyogenes, and Actinomyces. Infections with viruses, rickettsiae, chlamydiae, and protozoa may be complicated by shock.
These organisms produce septicemia in persons whose resistance is already compromised by an existing condition. Infection also results from transplantation of bacteria from other areas of the body through surgery, I.V. therapy, and catheters.
Septic shock often occurs in patients hospitalized for primary infection of the genitourinary, biliary, GI, and gynecologic tracts. Other predisposing factors include immunodeficiency, advanced age, trauma, burns, diabetes mellitus, cirrhosis, and disseminated cancer.
Signs and symptoms
Indications of septic shock vary according to the stage of the shock, the organism causing it, and the age of the patient.
Hypothermia and anuria are common late signs. Complications of septic shock include disseminated intravascular coagulation (DIC), renal failure, heart failure, GI ulcers, and abnormal hepatic function.
Diagnosis of septic shock is made by measuring blood pressure, heart rate, and respiration rate, as well as by a consideration of possible sources of infection. Blood pressure may be monitored with a catheter device inserted into the pulmonary artery supplying the lungs (Swan-Ganz catheter). Blood cultures are done to determine the type of bacteria responsible. The levels of oxygen, carbon dioxide, and acidity in the blood are also monitored to assess changes in respiratory function.
The first goal of treatment is to monitor and reverse shock through volume expansion.
I.V. fluids are administered, and a pulmonary artery catheter is inserted to check pulmonary circulation and PAWP. Administration of whole blood or plasma can then raise the PAWP to a satisfactory level of l4 to 18 mm Hg.
A respirator may be necessary for proper ventilation to overcome hypoxia. A urinary catheter allows accurate measurement of hourly urine output.
Treatment also requires immediate administration of I.V antibiotics to control the infection. Depending on the organism, the antibiotic combination usually includes an aminoglycoside, such as gentamicin or tobramycin for gramnegative bacteria, combined with a penicillin, such as carbenicillin or ticarcillin.
Sometimes treatment includes a cephalosporin, such as cefazolin, and nafcillin for suspected staphylococcal infection instead of carbenicillin or ticarcillin. Therapy may also include chloramphenicol for nonsporulating anaerobes (Bacteroides), although it may cause bone marrow depression, and clindamycin, which may produce pseudomembranous enterocolitis.
Appropriate anti-infectives for other causes of septic shock depend on the suspected organism. Other measures to cumbat infections include surgery to drain and excise abscesses and debridement.
Other drug therapy
If shock persists after fluid infusion, treatment with vasopressors, such as dopamine, maintains adequate blood perfusion in the brain, liver, GI tract, kidneys, and skin. Other treatment includes I.V. bicarbonate to correct acidosis and I.V. corticosteroids, which may improve blood perfusion and increase cardiac output.
The risk of developing septic shock can be minimized through treatment of underlying bacterial infections, and prompt attention to signs of bacteremia. In the hospital, scrupulous aseptic technique on the part of medical professionals lowers the risk of introducing bacteria into the bloodstream.
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