Brain tissue oxygenation during transnasal endoscopic skull base procedures.

Area of Science:

• Neurosurgery
• Anesthesiology
• Neurology

Background:

• Extended endoscopic skull base surgery often involves controlled hypotension to achieve a bloodless field.
• Patients with arterial hypertension may have altered cerebrovascular autoregulation.
• Brain tissue oxygenation (PbtO2) is a critical indicator of cerebral perfusion and ischemia risk.

Purpose of the Study:

• To investigate brain tissue oxygenation (PbtO2) during induced hypotension in patients undergoing extended endoscopic skull base surgery.
• To assess the relationship between controlled arterial blood pressure reduction and PbtO2 in this surgical context.

Main Methods:

• Five patients with skull base tumors and arterial hypertension underwent extended endoscopic surgery.
• Measurements included intracranial pressure, arterial blood pressure, cerebral perfusion pressure, and brain tissue oxygenation (PbtO2).

Main Results:

• Three patients experienced PbtO2 below 15 mm Hg (ischemia risk) for extended periods (40-123 minutes).
• Two of these patients did not require significant hypotension (MAP <65 mm Hg) for surgical hemostasis.
• PbtO2 levels correlated with cerebral perfusion pressure, with a 40-60 second lag.

Conclusions:

• Moderate arterial pressure reduction during skull base surgery can lead to critically low PbtO2 in patients with a history of hypertension.
• This maneuver may pose a significant risk of cerebral ischemia in susceptible patients.
• Careful monitoring of PbtO2 is crucial during hypotensive anesthesia in these procedures.