This is an altered level of consciousness attributed to the effects of an extracranial infection.
An excellent article on the subject earns significant brownie points by quoting Tolstoy in the opening paragraph.
"The doctors said that it was puerperal fever and that it was ninety-nine chances in a hundred it would end in death. The whole day long there was fever, delirium, and unconsciousness. At midnight the patient lay without consciousness, and almost without pulse.
The end was expected every minute."
Septic encephalopathy is present in up to 80% of septic patients. When graded using the Glasgow Coma Scale, it is associated with an increased mortality, ranging from 20% for a GCS of 14-13 to 63% for GCS of 8 and below.
Pathogenesis of septic encephalopathy
In short, nobody knows why this happens. Certainly the bacteria themselves are not to blame - infusing E.coli lipopolysaccharide into healthy volunteers only increased their level of alertness. Several factors are thought to be to blame for the syndrome. A recent review article lists several potential aetiological contributors:
- Oxidative stress
- Cytokine excess
- Cerebral circulatory disturbances
- Increased blood-brain barrier permability
- Altered levels of neurotransmitters
- Changes in amino acid levels
- Entry of bacterial endotoxin through the blood-brain barrier.
One can represent this complex interaction with a big confusing flowchart.
Diagnosis of septic encephalopathy
This is a diagnosis of exclusion. Certainly, arriving at a diagnosis of septic encephalopathy does not steer one any closer to a specific management strategy, because there is none. One manages this sort of delirium in a similar manner to all other sorts of delirium in the ICU. However, it should be mentioned that in contrast to other forms of delirium, this one should resolve as the septic episode concludes, and thus the management of sepsis should be one's priority (as if it weren't already).
Certainly, it seems imaging and EEG findings in septic encephalopathy are non-specific.
In general, supportive management is geared towards the control of organ system dysfunction and prevention of all the other factors in the "multifactorial aetiology" of delirium. If you can prevent the kidneys and liver from shutting down, if you can control your use of sedating drugs, and if the patient remains normoxic normoglycaemic and normotensive, one can say that one has done everything possible to address the non-septic components, and all that remains is to wait for the antibiotics to have their effect.