Septic shock

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

Definition of septic shock

To diagnose septic shock^[1] the following two criteria must be met:

Evidence of infection, through a positive blood culture.
Refractive hypotension - hypotension despite adequate fluid resuscitation.
- In adults it is defined as a systolic blood pressure < 90 mmHg, or a MAP < 60 mmHg, or a reduction of 40 mmHg in the systolic blood pressure from baseline.
- In children it is BP < 2 SD 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, 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. Hypotension reduces tissue perfusion pressure and thus tissue hypoxia ensues. Finally, in an attempt to offset decreased blood pressure, ventricular dilatation and myocardial dysfunction will occur.

The various conditions resulting in distributive shock include: septic shock, toxic shock syndrome, adrenal insufficiency, neurogenic shock 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; 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, such as tumor necrosis factor (TNF); these act to stimulate immune response. Besides TNFα, other cytokines involved in the development of septic shock include interleukin-1β, and interferon γ.

The condition can also come about as a result of certain poisons, such as ricin. For example, Georgi Markov, the Bulgarian dissident who was assassinated in London, died of septic shock after being injected with ricin.

Treatment

Treatment primarily consists of antimicrobial chemotherapy, removal of the source of infection, and haemodynamic, respiratory, and metabolic support.

Antimediator agents may be of some limited use in severe clinical situations:

Corticosteroids, especially if combined with a mineralocorticoid, can reduce mortality among patients who have relative adrenal insuffuciency^[2]
Activated protein C can reduce mortality in patients with organ failure^[3]

References

↑ Tslotou AG, Sakorafas GH, Anagnostopoulos G, Bramis J. Septic shock; current pathogenetic concepts from a clinical perspective. Med Sci Monit. 2005 Mar;11(3):RA76-85. PMID 15735579 Full Text.
↑ Annane D, Sebille V, Charpentier C, Bollaert PE, Francois B, Korach JM, Capellier G, Cohen Y, Azoulay E, Troche G, Chaumet-Riffaut P, Bellissant E. Effect of treatment with low doses of hydrocortisone and fludrocortisone on mortality in patients with septic shock. JAMA. 2002 Aug 21;288(7):862-71. PMID 12186604
↑ Bernard GR, Vincent JL, Laterre PF, LaRosa SP, Dhainaut JF, Lopez-Rodriguez A, Steingrub JS, Garber GE, Helterbrand JD, Ely EW, Fisher CJ Jr; Recombinant human protein C Worldwide Evaluation in Severe Sepsis (PROWESS) study group. Efficacy and safety of recombinant human activated protein C for severe sepsis. N Engl J Med. 2001 Mar 8;344(10):699-709. PMID 11236773