Septic shock is a serious medical condition caused by decreased tissue perfusion and oxygen delivery as a result of infection and sepsis, though the microbe may be systemic or localized to a particular site.^[1] It can cause multiple organ dysfunction syndrome (formerly known as multiple organ failure) and death.^[1] Its most common victims are children, immunocompromised individuals, and the elderly, as their immune systems cannot deal with the infection as effectively as those of healthy adults. The mortality rate from septic shock is approximately 50%.^[1]

[edit] Definition of septic shock

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

1. Evidence of infection, through a positive blood culture.
2. Refractory hypotension - hypotension despite adequate fluid resuscitation and cardiac output.
   • In adults it is defined as a systolic blood pressure < 90 mmHg, or a mean arterial pressure < 60 mmHg, without the requirement for inotropic support, or a reduction of 40 mmHg in the systolic blood pressure from baseline.
   • In children it is BP < 2 standard deviation of the normal blood pressure.

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

• Tachypnea (high respiratory rate) > 20 breaths per minute or, on blood gas, a less than 32 mmHg.
• White blood cell count < 4000 cells/mm³ or > 12000 cells/mm³

[edit] Types

A subclass of distributive shock, shock refers specifically to decreased tissue perfusion resulting in end-organ dysfunction. Cytokines 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 causing tissue Hypoxia. Finally, in an attempt to offset decreased blood pressure, ventricular dilatation and myocardial dysfunction will occur.

[edit] Causes

When organisms get into the blood stream, it produces a condition known as bacteremia. If the organisms are particularly virulent, or the host is immunocompromised, then the host organism may develop a condition known as Systemic Inflammatory Response Syndrome (or SIRS). Sepsis is bacteremia, combined with SIRS.

[edit] Epidemiology

According to the US CDC, septic shock is the 13th leading cause of death in the United States, and the #1 cause of deaths in intensive care units. There has been an increase in the rate of septic shock deaths in recent decades, which is attributed to an increases in invasive medical devices and procedures, increases in immunocompromised patients, and an overall increase in elderly patients. Tertiary care centers (such as hospice care facilities) have 2-4 times the rate of bacteremia than primary care centers, 75% of which are nosocomial infections.

The process of infection by bacteria or fungi can result in systemic signs and symptoms that are variously described. Approximately 70% of septic shock cases were once traceable to Gram staining gram-negative bacilli that produce endotoxins; however, with the emergence of MRSA and the increased use of arterial and venous catheters, Gram-positive cocci are implicated approximately as commonly as bacilli. In rough order of increasing severity, these are bacteremia or fungemic; septicemia; sepsis, severe sepsis or sepsis syndrome; septic shock; refractory septic shock; multiple organ dysfunction syndrome, and death.

35% of septic shock cases derive from urinary tract infections, 15% from the respiratory tract, 15% from skin catheters (such as IVs); over 30% of all cases are idiopathic in origin.

The mortality rate from sepsis is approximately 40% in adults, and 25% in children.^[2]

[edit] Treatment

Treatment primarily consists of the following.

1. Oxygen administration and airway support.
2. Volume resuscitation.
3. Early antibiotic administration.
4. Rapid source identification and control.
5. Support of major organ dysfunction.

Among the choices for pressors, a randomized controlled trial concluded that there was no difference between norepinephrine (plus dobutamine as needed for cardiac output) versus epinephrine.^[3]

However, dopamine has more beta adrenergic activity, and therefore is more likely to cause arrhythmia or myocardial infarction.

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

• Low dose steroids (hydrocortisone) for 5 – 7 days lead to improved outcomes.^[4][5]
• Recombinant activated protein C (drotrecogin alpha) has been shown in large randomized clinical trials to be associated with reduced mortality (Number needed to treat (NNT) of 16) in patients with multi-organ failure.^[6] If this is given, heparin should probably be discontinued.^[7]

[edit] See also

• Anaphylactic shock
• Cardiogenic shock
• Neurogenic shock
• Sepsis
• Shock
• Systemic inflammatory response syndrome (SIRS)

[edit] References