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

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

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

Treatment

• See Table 30–4

• Antibiotics should be given as soon as the diagnosis is suspected, since delays in therapy have been associated with increased mortality rates, particularly once hypotension develops

• 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—ie, if the infection originates in the CNS, antibiotics that penetrate the blood-brain barrier should be used—eg, third- or fourth-generation cephalosporin—but not first-generation cephalosporins or aminoglycosides, which penetrate poorly

• Initial therapy for sepsis should include antibiotics active against both gram-positive and gram-negative organisms

• Combination therapy has not been shown to be superior to a single-drug regimen with any of several broad-spectrum antibiotics (eg, a third-generation cephalosporin, piperacillin-tazobactam, carbapenem)

• If multiple drugs are used initially, the regimen should be modified and coverage narrowed based on the results of culture and sensitivity testing

• 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 and managing disseminated intravascular coagulation with antimicrobials for underlying infection and blood products for significant bleeding (Table 14–6)

• Corticosteroids are not helpful