Chapter 36. Sepsis and Septic Shock

Epidemiology

(Lancet 2005;365:63; Clin Infect Dis 2010;50:814)

• Yearly incidence: 50–95 cases/100,000; 10% of admissions to ICUs with >750,000 cases/y in U.S. alone; mortality: 25–70%; #1 cause of death in noncoronary ICUs, 13th leading cause of death overall
• Factors leading to ↑ incidence of sepsis: immunocompromised patients, invasive devices, resistant organisms, aging population, comorbid conditions (DM, malignancies, COPD, chemotherapy)

Pathophysiology: infection → endothelial dysfunction & microvascular thrombosis → hypoperfusion & ischemia → acute organ dysfunction → death (N Engl J Med 2006;355:1699)

• Etiology: respiratory tract, intra-abdominal, urinary tract, & bloodstream infections most common (Lancet 2005;365:63)
• Pathogens: gram + > gram − > fungi > anaerobes, viruses, & rickettsiae (Clin Infect Dis 2010;50:814)

Definitions

(Chest 1992;101:1644)

• Systemic inflammatory response syndrome (SIRS): Temp >38°C (100.4°F) or <36°C (96.8°F), HR >90bpm, RR >20 or PaCO2 <32mmHg, WBC > 12,000cell/mm3 or <4000cells/mm3 or >10% bands (left shift)
• SIRS + suspected infection = sepsis
• Sepsis + organ dysfunction or tissue hypoperfusion = severe sepsis
• Severe sepsis + hypotension refractory to fluid resuscitation = septic shock

Signs & symptoms: fever or hypothermia, chills, hyperventilation, tachycardia, altered mental status, skin lesions

Labs

• Serial serum chemistry, CBC with differential, LFTs, INR, lactic acid, & blood gases
• Appropriate cultures (blood: 2 sets for anaerobic & aerobic pathogens, 1 blood culture for each vascular access device in place >48h; urine; sputum; others depending on suspected source of infection) (Crit Care Med 2008;36:296)

Treatment Goals: timely diagnosis & identification of pathogen, rapid elimination of source of infection, early initiation of appropriate antibiotics, interruption of progression to shock, avoidance of organ failure (Crit Care Med 2008;36:296)

• SCCM Recommendations: (Crit Care Med 2008;36:296)
  • Early goal-directed therapy (EGDT): goals w/in first 6h of identification of sepsis→ ↓28d mortality 46.5 vs 30.5% (N Engl J Med 2001;345:1368)
    • Central venous pressure (CVP): 8–12mmHg (12–15mmHg if mechanically ventilated); marker of fluid status; the amount of blood returning to the heart through the thoracic vena cava
    • Mean arterial pressure (MAP): ≥ 65mmHg (MAP = 2/3 DBP + 1/3 SBP); marker of hemodynamic status
    • Urine output ≥0.5mL/kg/h; marker of renal function
    • Central venous oxygen saturation ≥70%; marker of tissue oxygenation & perfusion
  • Fluid therapy
    • Best initial therapeutic intervention for hypotension (↑CVP, ↑MAP)
    • Goal is to maintain adequate tissue perfusion to vital organs
    • Treatment options
      • Crystalloids (500–1000mL boluses or 30mL/kg); options: normal saline (0.9%), lactated Ringer's, Normosol
      • Colloids (300–500mL boluses); 5–25% albumin most common
      • Blood products: give to meet H/H goal or ↑ CV O2Sat ≥70%
  • Vasoactive therapy
    • Consider if SBP <90mmHg or MAP <60–65mmHg after adequate fluid resuscitation; sepsis is ↑CO & ↓SVR state initially
    • Use LOWEST dose possible
    • Preferred initial agents: norepinephrine ...