15.24A: Sepsis and Septic Shock

Septic shock occurs when a body’s response to an infection (sepsis) leads to life-threatening low blood pressure.

Learning Objectives

• Compare and contrast the symptoms of: sepsis, severe sepsis, septic shock

Key Points

• Sepsis results from certain bacterial infections, often acquired in a hospital. Having certain conditions, such as a weakened immune system, certain chronic disorders, an artificial joint, or heart valve increases the risk.
• Symptoms of sepsis include either fever or low body temperature, rapid breathing, chills and shaking, rapid heartbeat, decreased urine output, and confusion or delirium.
• Severe sepsis often causes extremely low blood pressure, which limits blood flow to the body and can result in organ failure and death. This is known as septic shock.
• Sepsis is treated with antibiotics, fluids, and medicines to support blood pressure and prevent organ damage.

Key Terms

• septic shock: A life-threatening condition caused by infection and sepsis, often after surgery or trauma.
• sepsis: A life-threatening medical condition caused by a severe inflammatory response of the human body triggered by the presence of an infectious agent.
• mortality rate: the number of deaths per given unit of population over a given period of time

Sepsis is a potentially deadly medical condition characterized by a whole-body inflammatory state (called a systemic inflammatory response syndrome or SIRS) that is triggered by an infection. Septic shock is a medical condition as a result of severe infection and sepsis, though the microbe may be systemic or localized to a particular site. Its most common victims are children, immuno-compromised individuals, and the elderly, as their immune systems cannot deal with the infection as effectively as those of healthy adults. Frequently, patients suffering from septic shock are cared for in intensive care units. The mortality rate from septic shock is approximately 25–50%.

Sepsis

Sepsis is an illness in which the body has a severe response to bacteria or other germs. The body may develop this inflammatory response by the immune system to microbes in the blood, urine, lungs, skin, or other tissues. A popular term for sepsis is blood poisoning. Severe sepsis is the systemic inflammatory response, infection, and the presence of organ dysfunction.

A bacterial infection anywhere in the body may set off the response that leads to sepsis. Common places where an infection might start include:

• the bloodstream
• bones (common in children)
• the bowel (usually seen with peritonitis)
• the kidneys (upper urinary tract infection or pyelonephritis )
• the lining of the brain ( meningitis )
• the liver or gallbladder
• the lungs (bacterial pneumonia )
• the skin (cellulitis)

For patients in the hospital, common sites of infection include intravenous lines, surgical wounds, surgical drains, and sites of skin breakdown known as bedsores (decubitus ulcers).

The therapy of sepsis rests on intravenous fluids, antibiotics, surgical drainage of infected fluid collections, and appropriate support for organ dysfunction. This may include hemodialysis in kidney failure, mechanical ventilation in pulmonary dysfunction, transfusion of blood products, and drug and fluid therapy for circulatory failure. Ensuring adequate nutrition—preferably by enteral feeding, but if necessary by parenteral nutrition—is important during prolonged illness.

Septic Shock

In sepsis, blood pressure drops, resulting in septic shock. Major organs and body systems, including the kidneys, liver, lungs, and central nervous system, stop working properly because of poor blood flow.

Most cases of septic shock are caused by Gram-positive bacteria, followed by endotoxin-producing Gram-negative bacteria. Endotoxins are bacterial membrane lipopolysaccharides (LPS) consisting of a toxic fatty acid (lipid A) core common to all Gram-negative bacteria, and a complex polysaccharide coat (including O antigen) unique for each species. Analogous molecules in the walls of Gram-positive bacteria and fungi can also elicit septic shock. In Gram-negative sepsis, free LPS attaches to a circulating LPS-binding protein, and the complex then binds to a specific receptor (CD14) on monocytes, macrophages, and neutrophils.

If sepsis worsens to the point of end-organ dysfunction (renal failure, liver dysfunction, altered mental status, or heart damage) then the condition is called severe sepsis. Once severe sepsis worsens to the point where blood pressure can no longer be maintained with intravenous fluids alone, then the criteria have been met for septic shock. The precipitating infections which may lead to septic shock if severe enough include appendicitis, pneumonia, bacteremia, diverticulitis, pyelonephritis, meningitis, pancreatitis, and necrotizing fasciitis.

Figure: Sepsis: Sepsis due to meningococcal disease.

Treatment primarily consists of the following:

1. Volume resuscitation
2. Early antibiotic administration
3. Early goal directed thearpy
4. Rapid source identification and control.
5. Support of major organ dysfunction.

There are new drugs that act against the extreme inflammatory response seen in septic shock. These may help limit organ damage.

The mortality rate from sepsis is approximately 40% in adults, and 25% in children, and is significantly greater when left untreated for more than seven days.