Studies of tissue PO2 in normal and pathological human brain cortex

Area of Science:

• Neurosurgery
• Neurophysiology
• Cerebral Metabolism

Background:

• Maintaining adequate brain tissue oxygenation is critical for preventing ischemic injury.
• Understanding the relationship between arterial oxygen levels and brain tissue oxygenation is essential for patient management.

Purpose of the Study:

• To investigate brain cortex tissue oxygen partial pressure (PO2) in patients with normal and pathological brain conditions.
• To determine the correlation between arterial PO2 and brain tissue PO2 under various physiological conditions, including hyperoxia and hyperventilation.

Main Methods:

• Brain cortex PO2 was measured in 26 patients after craniotomy and dura mater opening.
• Patients were categorized into normal and pathological groups based on pre-operative imaging and intraoperative findings.
• Tissue PO2 was assessed under standard conditions, altered arterial PO2 and PCO2, and following 100% oxygen inhalation.

Main Results:

• No significant difference in tissue PO2 was observed between normal and pathological groups, except in cases of brain swelling.
• A strong correlation between tissue PO2 and arterial PO2 was found in the pathological group, particularly in the edema subgroup.
• Inhalation of 100% oxygen significantly increased tissue PO2 in the pathological group compared to the normal group, indicating impaired regulation.

Conclusions:

• The study provides evidence for regulatory mechanisms of brain tissue PO2, which appear compromised in pathological conditions.
• A significant correlation between tissue PO2 and arterial PO2 in pathological brains suggests a loss of autoregulation.
• Low tissue PO2 values in pathological brains indicate a heightened risk of inducing cerebral ischemia.