Septic Shock

Septic shock is a serious medical condition in repsonse to infection and sepsis, causing such effects as multiple organ failure and death. Its most common victims are children, the elderly, and immunocompromised individuals, as their immune systems cannot cope with the infection as well as the immune systems of full-grown adults. The mortality rate from septic shock is approximately 50%.

Definition of septic shock

To diagnose septic shock, the following two criteria must be met:

1. A proven source of infection, such as a positive blood culture.
2. Refractive hypotension—hypotension despite adequate fluid resuscitation.
   • In adults, it is defined as a systolic blood pressure < 90 mmHg, or a mean arterial pressure (MAP) < 60 mmHg, or a reduction of 40 mmHg in the systolic blood pressure from baseline.
   • In children, it is BP < 2 standard deviations of the normal blood pressure.

In addition to the two criteria above, two or more of the following must be present:

• Heart rate > 90 beats per minute.
• Body temperature < 36 or > 38°C.
• Hyperventilation (high respiratory rate) > 20 breaths per minute or, on blood gas, a P_aCO₂ less than 32 mmHg.
• White blood cell count < 4000 cells/mm³ or > 12000 cells/mm³ (< 4 x 10⁹ or > 12 x 10⁹ cells/L).

Types

A subclass of distributive shock, septic shock refers specifically to decreased tissue perfusion resulting in end-organ dysfunction. Cytokines TNFα, IL-1β, IL-6 released in a large scale inflammatory response results in massive vasodilation, increased capillary permeability, decreased systemic vascular resistance, and hypotension. The decreased intravascular volume (plasma volume) results in the above tissue hypoxia. Finally, in an attempt to offset decreased blood pressure, ventricular dilatation and myocardial dysfunction will occur.

The various shock conditions include: septic shock, systemic inflammatory response syndrome, toxic shock syndrome, adrenal insufficiency, and anaphylaxis.

Causes

The process of infection by bacteria or fungi can result in systemic signs and symptoms that are variously described. In rough order of severity, these are bacteremia or fungemia; septicemia; systemic inflammatory response syndrome (SIRS), sepsis, severe sepsis or sepsis syndrome; septic shock; refractory septic shock; multiple-organ dysfunction syndrome, and death.

The condition develops as a response to certain microbial molecules which trigger the production and release of cellular mediators, which act to stimulate immune response.

Treatment consists primarily of antimicrobial chemotherapy, removal of the source of infection, and haemodynamic, respiratory, and metabolic support. Antimediator agents may be of some limited use in certain clinical situations.

See Also

• Sepsis
• Inflammation