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- Review the epidemiology and pathophysiology of sepsis
- Discuss implications of clinical exam findings
- Review emerging trends in patient treatment and management strategies
Sepsis is a clinical syndrome that results from the human body’s response to infection. While bacteria probably account for most cases, sepsis can also be the result of infection by fungi, viruses and parasites.
Traditionally there was considerable confusion regarding specific definitions of the various sequelae associated with sepsis. In 1992, the American College of Chest Physicians and Society of Critical Care Medicine issued a consensus statement establishing uniform criteria defining the sepsis syndromes. New definitions were offered for some terms, while others were discarded completely. Broad definitions of sepsis and the systemic inflammatory response syndrome were determined, as were specific physiologic parameters by which patients may be categorized.1 These definitions are useful in that they help delineate a clinically observable spectrum of disease.
An infection is the invasion by and multiplication of pathogenic organisms in a body tissue, which may result in cellular injury and an immune response. Bacteremia is the presence of culturable bacteria in the bloodstream. Fungemia, parasitemia and viremia can occur as a result of fungal, parasitic and viral infections, respectively. Systemic inflammatory response syndrome (SIRS) is defined as an “abnormal, generalized inflammatory reaction remote from the initial insult.”2 Clinically, it is the presence of two or more of the following:
• Temperature less than 96.8°F or greater than 100.4°F;
• Heart rate greater than 90 bpm;
• Respiratory rate greater 20 or a PaCO2 less than 32 mmHg;
• White blood cell count less than 4,500 or greater than 10,000 l/mm.3
The identification of SIRS does not confirm a diagnosis of sepsis, or even an infection; other etiologies of SIRS exist, including trauma, burns and pancreatitis.3 Sepsis is said to occur when there is an identifiable infection plus clinical criteria for SIRS. For instance, a 64-year-old female with tachycardia, tachypnea and a fever with no identifiable infection site would be suspected of having SIRS, while that same patient with a known history of urinary tract infection would have sepsis high up on her differential diagnosis.
Contrary to common belief, microbial invasion of the bloodstream is not an essential component of sepsis, since a local inflammatory response can also elicit the characteristic organ dysfunction and hypotension. For example, bacteremia is often present in patients with sepsis, but does not have to be present for patients to receive a diagnosis of sepsis. Severe sepsis is sepsis with organ dysfunction, which may be evidenced by findings such as acute lung injury, oliguria (low urine output), altered mental status or lactic acidosis. A lactate greater than 4.0 mmol/L when an infection is suspected is considered indicative of severe sepsis. Septic shock is severe sepsis plus hypotension that is unresponsive to fluid therapy, with hypotension defined as a systolic blood pressure below 90 mmHg. To continue our example from earlier, a 64-year-old female with tachycardia, tachypnea, fever, oliguria and altered mental status would be considered to have severe sepsis, and the same patient with hypotension refractory to a fluid bolus would be considered in septic shock.