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Chapter 45: Sepsis and Septic Shock

INTRODUCTION

  • The definitions of terms related to sepsis are given in Table 45–1. Physiologically similar systemic inflammatory response syndrome can be seen even in the absence of identifiable infection.

TABLE 45–1Definitions Related to Sepsis
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TABLE 45–1 Definitions Related to Sepsis
Condition Definition
Bacteremia (fungemia) Presence of viable bacteria (fungi) in the bloodstream
Infection Inflammatory response to invasion of normally sterile host tissue by the microorganisms
SIRS Systemic inflammatory response to a variety of clinical insults, which can be infectious or noninfectious. The response is manifested by two or more of the following conditions: temperature >38°C (>100.4°F) or <36°C (<96.8°F); HR >90 beats/min; RR >20 breaths/min or PaCO2<32 mm Hg (<4.3 kPa); WBC >12,000 cells/mm3 (>12 × 109/L), <4,000 cells/mm3 (<4 × 109/L), or >10% (>0.10) immature (band) forms
Sepsis

SIRS secondary to suspected or documented infection

Additional criteria include general variables (altered mental status, positive fluid balance of >20 mL/kg over 24 hours, hyperglycemia >120 mg/dL [>6.7 mmol/L]); inflammatory variables (plasma C-reactive protein/procalcitonin >2 SD above normal value); hemodynamic variables (arterial hypotension <90mm Hg (<12.0 kPa) or MAP <70 mm Hg (<9.3 kPa), elevated mixed venous oxygen saturation of >70% (>0.70); CI >3.5 L/min (>0.058 L/s); organ-dysfunction variables (arterial hypoxemia; acute oliguria of <0.5ml/kg/hr or 45 ml/hr for at least 2 hr, creatinine increase >0.5 mg/dL (>0.44 μmol/L), coagulation abnormalities, paralytic ileus, platelets <100,000 /mm3 (<100 × 109/L), bilirubin >4 mg/dL (>68 μmol/L); tissue-perfusion variable (hyperlactatemia >1 mmol/L, decreased capillary refill)
Severe sepsis Sepsis associated with one or more organ dysfunctions, hypo­perfusion, or hypotension. Hypoperfusion and perfusion abnormalities may include but not limited to arterial hypoxemia (PaO2 /FiO2<300) lactic acidosis, oliguria, increase in creatinine, coagulation abnormalities (INR>1.5), and elevated bilirubin
Septic shock Sepsis with persistent hypotension despite fluid resuscitation (intravenous fluid of 30 mL/kg) or hyperlactatemia >1 mmol/L

(CI, cardiac index; HR, heart rate; INR, international normalized ratio; RR, respiratory rate; SD, standard deviation; SIRS, systemic inflammatory response syndrome; T, temperature; WBC, white blood cell (count).)

Adapted from Levy MM, Fink MP, Marshall JC, et al. 2001 SCCM/ESICM/ACCP/ATS/SIS International Sepsis Definitions Conference. Crit Care Med 2003;31:1250-1256.

ETIOLOGY AND PATHOPHYSIOLOGY

  • The sites of infections that most frequently lead to sepsis are the respiratory tract (39%–50%), urinary tract (5%–37%), and intra-abdominal space (8%–16%). Sepsis may be caused by gram-negative (50%–62% of sepsis) or gram-positive bacteria (37%–47%), as well as by fungi (5%) or other microorganisms.

  • Escherichia coli, Klebsiella species, and Pseudomonas aeruginosa are the most commonly isolated gram-negative pathogens in sepsis. Other common gram-negative pathogens are Serratia spp., Enterobacter spp., and Proteus spp. P. aeruginosa is the most frequent cause of sepsis fatality. Common gram-positive pathogens are Staphylococcus aureus, Streptococcus pneumoniae, coagulase-negative staphylococci, and Enterococcus species.

  • Candida species (particularly Candida albicans) are common ...

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