As previously discussed, bacteremia may indicate the presence of a focus of disease, such as intravascular infection, pneumonia, or liver abscess, or it may represent transient release of bacteria into the bloodstream. Septicemia or sepsis indicates a condition in which bacteria or their products (toxins) are causing harm to the host. Unfortunately, clinicians often use the terms bacteremia and septicemia interchangeably. Signs and symptoms of septicemia may include fever or hypothermia (low body temperature), chills, hyperventilation (abnormally increased breathing leading to excess loss of carbon dioxide from the body) and subsequent respiratory alkalosis (a condition caused by the loss of acid leading to an increase in pH), skin lesions, change in mental status, and diarrhea. More serious manifestations include hypo tension or shock, DIC, and major organ system failure. The syndrome known as septic shock, characterized by fever, acute respiratory distress, shock, renal failure, intravascular coagulation, and tissue destruction, can be initiated by either exotoxins or endotoxins. Septic shock is mediated by the production of cytokines from activated mononuclear cells, such as tumor necrosis factor and interleukins.
Shock is the gravest complication of septicemia. In septic shock, the presence of bacterial products and the host’s response act to shut down major host physiologic systems. Clinical manifestations include a drop in blood pressure, increase in heart rate, functional impairment in vital organs (brain, kidney, liver, and lungs), acid- base alterations, and bleeding problems. Gram-negative bacteria contain a substance in their cell walls, called endotoxin, which has a strong effect on several physio logic functions. This substance, a lipopolysaccharide (LPS) comprising part of the cell wall structure, may be released during the normal growth cycles of bacteria or after the destruction of bacteria by host defenses. Endotoxin (or the core of the LPS, lipid A) has been shown to mediate numerous systemic reactions, including a febrile response, and the activation of complement and certain blood-clotting factors. Although gram-positive bacteria do not contain the lipid A endo toxin, many produce exotoxins, and the effects of their presence in the bloodstream may be equally devastating to the patient.
Disseminated intravascular coagulation (DIC) is a disastrous complication of sepsis. DIC is characterized by numerous small blood vessels becoming clogged with blood clots and bleeding as a result of the depletion of coagulation factors. DIC can occur with septicemia involving any circulating pathogen, including parasites, viruses, and fungi, although it is most often a consequence of gram-negative bacterial sepsis.
