What is Sepsis?  Multi-Organ Failure

     
       

 

         
       

How does sepsis effect the various organs of the body?

Below is a list of organs, and the injuries that they sustain in sepsis and MODS.

Organ ischemia in sepsis (click on thumbnail)

Autoregulated Organs

The brain and kidneys are normally protected from swings in blood pressure by autoregulation:

In early sepsis - autoregulation curve shifts rightwards (due to and increase in sympathetic tone).

In late sepsis - vasoplegia occurs- and autoregulation fails, making these organs susceptible to the swings that occur in systemic blood pressure. In addition, “steal phenomena” may occur (areas of ischemia may have their blood stolen by areas with good perfusion). This is known as “vasomotor neuropathy”.

CNS

Patients become confused, delirious and ultimately stuporose and comatose due to a variety of insults: hypoperfusion injury, septic encephalopathy, metabolic encephalopathy and, of course drugs used for sedation.

Heart

Myocardial O2 supply is dependent on diastolic blood pressure, which falls following vasoplegia, and intravascular volume depletion. This may lead to ischemia. There is reversible biventricular dilatation, decreased ejection fraction, and decreased response to fluid resuscitation and catecholamine stimulation. A circulating myocardial depressant substance is responsible for this phenomenon. This substance has been shown to represent low concentrations of TNF-alpha and IL-1beta acting in synergy on the myocardium through mechanisms that include NO and cGMP generation (8).

Lungs

Ventilation / perfusion mismatches occur, initially due to increased dead space (due to hypotension and fluid shifts), subsequently due to shunt (due to acute lung injury (19)). Up to 70% of patients develop nosocomial pneumonia.

The most dramatic manifestation of sepsis on the lung is acute respiratory distress syndrome.

Kidneys

Acute renal failure is common in sepsis, due to fluid redistribution, hypoperfusion and circulating nephrotoxins, many of which are liberated following cell injury.

Liver

ICU jaundice

Uncontrolled production of inflammatory cytokines by the kuppfer cells (of the liver), primed by ischemia and stimulated by endotoxin (derived from the gut), leads to cholestasis and hyperbilirubinaemia.

Splanchnic Circulation

GUT mucosa is usually protected from injury by autoregulation. Hypotension and hypovolemia leads superficial mucosal injury. This leads to atrophy and translocation of bacteria into the portal circulation and stimulate liver macrophages causing cytokine release and amplification of SIRS.

Metabolic and Endocrine

Metabolic abnormalities in sepsis include hyperglycemia due to sepsis & catecholamines (both cause insulin resistance), lactic acidosis, a generalized catabolic state which leads to muscle breakdown. There is relative hypothyroidism, hypopituitarism and adrenal insufficiency.

References

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THIS TUTORIAL BY PATRICK NELIGAN MD, UNIVERSITY OF PENNSYLVANIA

       
       

 

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