Causes and features of sepsis
Sepsis is used to describe the overwhelming systemic disease that results from infection with a microbial pathogen. There is exaggerated stimulation of the normal host responses to the invading pathogen, leading to a widespread release of inflammatory mediators and vasodilation. This is initially compensated for by an increase in cardiac output, which helps to maintain a reasonable blood pressure and adequate organ perfusion. At this stage, the symptoms found in a septic patient are fever, tachypnoea and tachycardia.
As the syndrome progresses, the systemic vascular resistance decreases more profoundly, with a concurrent fall in cardiac output. This is accompanied by an increase in the permeability of capillaries, loss of plasma water, and a relative hypovolaemic state. The end result is a fall in arterial blood pressure, inadequate organ perfusion and oxygenation, and eventually, multiple organ failure. The septic patient may have hypoxia, lactic acidosis and oliguria, with or without local signs of inflammation at the source of the infection. Admission to an intensive care or high dependency facility for appropriate supportive therapy is usually required at this stage.
At a consensus conference held in August 1991, the American College of Chest Physicians (ACCP) and Society of Critical Care Medicine (SCCM) agreed on definitions for the various stages of disease within the sepsis syndrome (see Table 1, p94).1 These were designed to allow standardisation of entry criteria for sepsis trials, and provide some uniformity that had previously been lacking.
The term systemic inflammatory response syndrome (SIRS) was introduced to describe patients who exhibited a sepsis-like syndrome, but who were not infected. Some clinicians dislike the term because they believe that a diagnosis of SIRS would preclude the search for an infective source. However, when patients manifest such severe symptoms, debates about terminology are of much less consequence than the need to take appropriate action. SIRS may be precipitated by insults such as pancreatitis, burns or trauma, in addition to many conditions which are less common. Significant haemodynamic instability may also be present,although this is not included in the standard definition.
Angus et al2 conducted an observational cohort study across 847 hospitals in seven US states. By comparing data from over 6.5 million hospital discharge records with population and hospital records from the last US census, Centers for Disease Control and financing organisations, an estimate of the incidence, cost and outcome of severe sepsis in the US was produced. A projected 750,000 cases occur each year (three cases per 1,000 of the population and 2.25 cases per 100 hospital discharges), at a cost of $22,100 per case, or $16.7bn for all cases.
Severe sepsis is associated with a high mortality rate. The study by Angus et al predicts 215,000 deaths per year, equivalent to a mortality rate of 28.6 per cent.2 In a subgroup analysis, patients with single organ dysfunction had a projected mortality rate of 21.1 per cent. The rate rises to 76.2 per cent for those in whom four or more organs are involved.
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Citation: Hospital Pharmacist URI: 10975342
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