Sepsis

Description

• Presence of an infection with an associated systemic inflammatory response
• The systemic inflammatory response syndrome (SIRS) is composed of 4 criteria:
  • Temperature >38°C or <36°C
  • Heart rate >90 bpm
  • Respiratory rate >20/min or PaCO₂ <32 mm Hg
  • WBC >12,000/mm³, <4,000/mm³, or >10% bands
• Sepsis = suspected infection with ≥2 SIRS criteria:
  • Release of chemical messengers by the inflammatory response
  • Macrocirculatory failure through decreased cardiac output or decreased perfusion pressure
  • Microcirculatory failure through impaired vascular autoregulatory mechanisms and functional shunting of oxygen
  • Cytopathic hypoxia and mitochondrial dysfunction
• Hemodynamic changes result from the inflammatory response:
  • Elevated cardiac output in response to vasodilatation
  • Later myocardial depression
• Multiple organ dysfunction syndrome (MODS):
  • Acute respiratory distress syndrome (ARDS)
  • Acute tubular necrosis and kidney failure
  • Hepatic injury and failure
  • Disseminated intravascular coagulation
• Sepsis should be viewed as a continuum of severity from a proinflammatory response to organ dysfunction and tissue hypoperfusion:
  • Severe sepsis: Sepsis with at least 1 of the following organ dysfunctions:
    • Acidosis
    • Renal dysfunction
    • Acute change in mental status
    • Pulmonary dysfunction
    • Hypotension
    • Thrombocytopenia or coagulopathy
    • Liver dysfunction
  • Septic shock: Sepsis-induced hypotension despite fluid resuscitation:
    • Systolic BP <90 mm Hg or reduction of >40 mm Hg from baseline
• Sepsis is the tenth leading cause of death in the U.S.:
  • In-hospital mortality for septic shock is ∼20%

Etiology

• Gram-negative bacteria most common:
  • Escherichia coli
  • Pseudomonas aeruginosa
  • Rickettsiae
  • Legionella spp.
• Gram-positive bacteria:
  • Enterococcus spp.
  • Staphylococcus aureus
  • Streptococcus pneumoniae
• Fungi (Candida species)
• Viruses

• Children with a minor infection may have many of the findings of SIRS
• Major causes of pediatric bacterial sepsis:
  • Neisseria meningitidis
  • Streptococcal pneumonia
  • Haemophilus influenzae