Bacteremia & Sepsis, Gram-Negative

Key Features

• Most common sites for gram-negative bacteremia

  • Genitourinary system

  • Hepatobiliary tract

  • Gastrointestinal tract

  • Lungs

• Less common sources include

  • Intravenous lines

  • Infusion fluids

  • Surgical wounds

  • Drains

  • Pressure injuries

• Mortality rates

  • 40–60% in patients with potentially fatal underlying conditions in the short term, such as

    • Neutropenia

    • Immunoparesis

  • 15–20% in patients with serious underlying diseases likely to be fatal in 5 years, such as

    • Solid tumors

    • Cirrhosis

    • Aplastic anemia

  • ≤ 5% in patients with no underlying diseases

Clinical Findings

• Fevers and chills, often with abrupt onset

• However, some patients are hypothermic (temperature ≤ 36.4 °C) at presentation

• Hyperventilation with respiratory alkalosis and changes in mental status are important early manifestations

• Hypotension and shock are unfavorable prognostic signs

Diagnosis

• Neutropenia or neutrophilia, often with increased numbers of immature forms of polymorphonuclear leukocytes

• Thrombocytopenia occurs in 50% of patients, laboratory evidence of coagulation abnormalities in 10%, and overt disseminated intravascular coagulation in 2–3%

• If possible, three sets of blood cultures from separate sites should be obtained in rapid succession before starting antimicrobial therapy

Treatment

• Antibiotics

  • In general, bactericidal antibiotics should be used and given intravenously to ensure therapeutic serum levels

  • Penetration of antibiotics into the site of primary infection is critical for successful therapy

  • Sepsis caused by gram-positive organisms cannot be differentiated on clinical grounds from that due to gram-negative bacteria. Therefore, initial therapy should include antibiotics active against both types of organisms

  • Table 30–4 provides a guide for empiric therapy

• Remove predisposing factors

  • Decrease or stop immunosuppressive medications

  • Give granulocyte colony-stimulating factor (filgrastim; G-CSF) to the neutropenic patient with positive blood cultures

• Identify source of bacteremia and remove it (central venous catheter) or drain it (abscess)

• Supportive measures include

  • Maintaining blood pressure with vasopressor medications

  • Managing disseminated intravascular coagulation with

    • Antimicrobials for underlying infection

    • Platelet transfusions and fresh frozen plasma for significant bleeding

    • Cryoprecipitate for bleeding and fibrinogen levels < 80–100 mg/dL

    • Low-dose heparin infusion for refractory bleeding