Sepsis classification

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Classification

Sepsis

Sepsis is considered present if infection is highly suspected or proven and two or more of the following systemic inflammatory response syndrome (SIRS) criteria are met:

• Heart rate > 90 beats per minute
• Temperature < 36 (96.8 °F) or > 38 °C (100.4 °F)
• Tachypnea > 20 breaths per minute or, on blood gas, a P_aCO₂ < 32 mm Hg
• White blood cell count < 4000 cells/mm³ or > 12000 cells/mm³ (< 4 x 10⁹ or > 12 x 10⁹ cells/L), or > 10% band forms (immature white blood cells / bandemia).

Consensus definitions however continue to evolve with the latest expanding the list of signs and symptoms of sepsis to reflect clinical bedside experience.

Severe Sepsis

Patients are defined as having "severe sepsis" if they have sepsis plus:

Sepsis-induced hypotension

• "systolic blood pressure (SBP) < 90 mm Hg or mean arterial pressure (MAP) < 70 mm Hg or a SBP decrease > 40 mm Hg or less than two standard deviations below normal for age in the absence of other causes of hypotension"

or:

• Serum lactate > upper limits of laboratory normal

or:

• End organ dysfunction
  • Urine output < 0.5 mL/kg/hr for more than 2 hrs despite adequate fluid resuscitation
  • Acute lung injury with PaO2/FiO2 < 250 in the absence of pneumonia as an infection source
  • Acute lung injury with PaO2/FiO2 < 200 in the presence of pneumonia as an infection source
  • Creatinine > 2.0 mg/dl
  • Bilirubin > 2 mg/dl
  • Platelet count < 100,000 per µl
  • Coagulopathy (International normalized ratio > 1.5)

Septic Shock

Septic shock is defined as sepsis with refractory arterial hypotension. Refractory arterial hypotension is further defined as:

• Mean systemic blood pressure (SBP) of < 60 mm Hg or < 80 mm Hg (in hypertensives) despite adequate fluid resuscitation.
  • Adequate fluid resuscitation is defined as infusion of following at the said rates:
    • 20 to 30 mL/kg of starch
    • 40 to 60 mL/kg of saline solution
    • Measured pulmonary capillary wedge pressure - 12 to 20 mmHg
    • Central venous pressure of 8 to 12 mmHg
• Maintenance of the systemic mean blood pressure of > 60 mmHg or > 80 mmHg (in hypertensives) despite adequate fluid resuscitation requires:
  • Dopamine > 5 mcg/kg/min
  • Norepinephrine < 0.25 mcg/kg/min
  • Epinephrine < 0.25 mcg/kg/min

Refractory Septic Shock

Refractory Septic shock is defined as sepsis with refractory arterial hypotension and maintenance of the systemic mean blood pressure of > 60 mmHg or > 80 mmHg (in hypertensives) despite adequate fluid resuscitation requires:

• Dopamine > 15 mcg/kg/min
• Norepinephrine > 0.25 mcg/kg/min
• Epinephrine > 0.25 mcg/kg/min
• Adequate fluid resuscitation is defined as infusion of the following at the said rates:
  • 20 to 30 mL/kg of starch,
  • 40 to 60 mL/kg of saline solution
  • Measured pulmonary capillary wedge pressure - 12 to 20 mmHg
  • Central venous pressure of 8 to 12 mmHg

Multiple Organ Dysfunction Syndrome

• It is defined as a progressive organ dysfunction that require interventions for maintenance of homeostasis.
• It is the most severe manifestation of either SIRS or sepsis continuum.
• Primary MODS can be directly connected to the source of infection. However, secondary MODS occurs as a result of host response to the primary insult.
• Parameters used to judge MODS are:
  • Liver - Serum bilirubin
  • Nervous system - Glasgow coma scale
  • Hematology - Platelet count
  • Renal - Serum creatinine
  • Respiratory - PO2/FiO2 ratio
  • Cardiovascular - Pressure-adjusted heart rate = Heart rate multiplied by the ratio of central venous pressure and mean arterial pressure

Neonatal Sepsis

The criteria for diagnosing an adult with sepsis does not apply to infants under one month of age (neonatal sepsis). In infants, only the presence of infection plus a "constellation" of signs and symptoms consistent with the systemic response to infection are required for diagnosis.

Systemic Inflammatory Response Syndrome

Criteria for SIRS were agreed upon in 1992. SIRS can be diagnosed when two or more of the following are present:

• Heart rate > 90 beats per minute
• Temperature < 36 (96.8 °F) or > 38 °C (100.4 °F)
• Tachypnea > 20 breaths per minute or, on blood gas, a P_aCO₂ < 32 mm Hg
• White blood cell count < 4000 cells/mm³ or > 12000 cells/mm³ (< 4 x 10⁹ or > 12 x 10⁹ cells/L), or > 10% band forms (immature white blood cells / bandemia).

Severe SIRS

• When two or more of the systemic inflammatory response syndrome criteria are met without evidence of infection, patients may be diagnosed simply with "SIRS."
• Patients with SIRS and acute organ dysfunction may be termed "severe SIRS."

Difference between SIRS and Sepsis

SIRS with a suspected or proven infection is called sepsis.