Classification System

Identical clinical manifestations without bacterial infection are observed in patients suffering from polytrauma, ischemia, hemorrhagic shock, and acute pancreatitis, resulting in intensive care physicians proposing an expanded nomenclature and classification. The classification system that has been amended ever since is important in evaluating the prognosis of a patient suffering from sepsis and assessing of the success of new therapeutic approaches. It is based on the following criteria (Bone et al. 1992; Reinhart et al. 2004):

Criterion I: Definitive evidence of infection (positive hemoculture) or clinically suspected infection. Bacteremia maybe low-grade (< 10 bacteria/ml) and transient. Multiple blood cultures maybe required.

Criterion II: Systemic inflammatory response syndrome (SIRS)

2. Heart rate 90 beats/min

3. Respiratory rate 20 breaths/min

4. Respiratory alkalosis PaCO2 < 32 mmHg

6. Immature neutrophils (bands) > 10%. Criterion III: Multiple organ dysfunction syndrome

1. Cardiovascular: arterial systolic blood pressure < 90 mmHg or >40 mmHg less than patient's normal blood pressure, or the mean arterial blood pressure < 70 mmHg for at least 1 h despite adequate fluid resuscitation, adequate in-travascular volume status, or the use of vaso-pressors in an attempt to maintain a systolic blood pressure > 90 mmHg

2. Renal: urine output <0.5 ml/kg of body weight/h for 1 h, despite adequate fluid resuscitation

3. Respiratory: PaO2 < 75 mmHg while breathing room air, or PaO2/FiO2 < 250 in the presence of

Table 5.1. Classification of sepsis stages and lethality

Lethality

Table 5.2. Clinical stages of urosepsis

Criteria

Sepsis Criterion I + 2 criteria II

Severe Criterion I + >2 criteria II + sepsis > 1 criterion III

Septic Criterion I + >2 criteria II + shock refractory hypotension (criterion III), i.e., arterial blood pressure < 90 mm systolic, or 40 mm less than patient's normal blood pressure, or mean arterial blood pressure < 70 mm Hg, for > 2h, or need for vasopressors to maintain systolic blood pressure 90 mm Hg or mean arterial pressure > 70 mm Hg.

2 Criteria II, 7%

3 Criteria II, 10%

4 Criteria II, 17%

Per afflicted organ (liver, lung, kidney), lethality is increased by 15%-20%

other dysfunctional organs or systems, or <200, if the lung is the only dysfunctional organ (PaO2, partial pressure of arterial oxygen; FiO2, fractional concentration of inspired O2 [~0.21 when breathing room air])

4. Hematologic: platelet count <80x109/l or 50% decrease in platelet count from highest value recorded over previous 3 days

5. Metabolic acidosis: a pH < 7.30, or a base deficit >5 mm/l, a plasma level of lactate >1.5 times the upper limit of normal

6. Brain: somnolence, confusion, agitation, delirium, coma

Following these criteria, sepsis can be clinically categorized into three different stages (Table 5.1). Prognostic criteria concerning lethality are also based on the above-mentioned classification system.

In an intensive care unit (ICU), patient's illness is often categorized into grades of severity following a scoring system, e.g., the Apache II (Acute Physiology and Chronic Health Evaluation II) system, which is based upon age, type of intensive care unit admission, a chronic health problem score, and 12 physiologic variables.

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