Optic Nerve Sheath Diameter for Prediction of Sepsis Associated Encephalopathy

Sepsis is the most common complication in adult critically ill patients, and it has been become the leading cause of morbidity and mortality worldwide. The essential component of sepsis is the presence of an acute organ dysfunction. The brain is highly vulnerable to the inflammatory storm associated with infection and it may be the first organ to show signs of life-threatening organ dysfunction caused by infection. This brain dysfunction is known as "sepsis-associated encephalopathy (SAE)".

Sepsis-associated brain dysfunction is considered the commonest type of encephalopathy seen in intensive care unit (ICU). it is defined as a life- threatening acute diffuse brain dysfunction due to infection outside the central nervous system (CNS) and is mostly caused by the inflammatory storm. It varies from delirium or confusion, seizure or focal neurological sign, and diffuse or multifocal neurological deficits, to stupor or coma with no other diagnoses describing the patient neurological status. SAE may occur in up to 70% of septic patients and it significantly increases mortality. It is a complex syndrome with unclear pathophysiology. The possible causes could include neuro-inflammation, excitotoxicity, impaired cerebral autoregulation, and cerebral ischemia. These Pathophysiological changes may lead to increase in the intracranial pressure (ICP) which may in turn decrease cerebral perfusion and lead to brain edema, brain damage and compromised the outcome of these patients. Therefore, early detection of increased ICP is of paramount importance for timely intervention and improved prognosis. However, direct invasive ICP monitoring is not routinely recommended in non-traumatic coma patients as well as septic patients either due to absence of intracranial infection or coagulopathy; so, a reliable non-invasive ICP monitoring method is highly recommended. Bedside ultrasonographic assessment of the optic nerve sheath diameter (ONSD) offers a satisfactory non-invasive ICP monitoring test and is documented as a sensitive and specific predictor of cerebral edema and is strongly correlated with both invasive ICP measurements and radiographic cerebral edema as diagnosed by CT scan or MRI.

Considering that SAE is a diagnosis of exclusion as well as screening method for SAE is necessary for early diagnosis and timely management. We hypothesized that ONSD could have a role as an objective screening tool to predict and early diagnose ICP changes in septic patients.

Inclusion criteria

• Patient acceptance.
• Age 21- 70 years old.
• Patients diagnosed with sepsis For diagnosis of sepsis and septic shock, the third international definition and appropriate diagnostic criteria was used.

Sepsis was defined as life-threatening organ dysfunction caused by a dysregulated host response to an infection, and it is suspected in an acutely deteriorating patient in whom there is clinical evidence or strong suspicion of infection. Septic shock was defined as the need for vasopressors or vasoactive medication to maintain a mean arterial blood pressure of 65 mmHg or higher after adequate fluid resuscitation, with the presence of a high lactate (>2 mmol/l).

Exclusion criteria

• Patient refusal.
• Ocular wound
• History of prior ocular trauma or surgery
• Conjunctival edema or orbital edema
• Vitreous hemorrhage
• Central nervous system (CNS) infection
• Cerebrovascular accident
• Brain trauma
• Any previous neurosurgical procedure