Dose-dependent effect of isoflurane on regional cerebral blood flow in anesthetized macaque monkeys

Area of Science:

• Neuroscience
• Anesthesiology
• Medical Imaging

Background:

• Isoflurane is a common anesthetic agent.
• Understanding its effects on regional cerebral blood flow (CBF) is crucial for patient safety.
• Cerebral blood flow autoregulation maintains stable brain perfusion despite blood pressure changes.

Purpose of the Study:

• To investigate the dose-dependent effects of isoflurane on regional CBF in cortical and subcortical structures.
• To assess the integrity of CBF autoregulation in different brain regions under varying isoflurane concentrations.
• To determine if isoflurane disrupts CBF-metabolism coupling in specific brain areas.

Main Methods:

• Utilized Continuous Arterial Spin Labeling (ASL) Magnetic Resonance Imaging (MRI) technique.
• Administered isoflurane to anesthetized macaque monkeys at concentrations of 0.75% and 1.5%.
• Measured regional CBF in various cortical and subcortical brain structures.

Main Results:

• High isoflurane concentrations (1.5%) led to a global increase in CBF and a decrease in blood pressure.
• Significant CBF increases were observed in the thalamus (39%) and cerebellum (55%) with rising isoflurane doses.
• CBF changes in the thalamus and cerebellum correlated linearly with isoflurane concentrations, suggesting impaired autoregulation.
• Cortical regions (anterior cingulate cortex, motor cortex, medial prefrontal cortex) and the caudate showed no significant CBF changes.

Conclusions:

• Isoflurane at maintenance doses (0.75-1.5%) preserves CBF autoregulation in cortical regions and the caudate.
• CBF autoregulation is impaired in the thalamus and cerebellum under these isoflurane doses.
• These findings indicate disturbed CBF-metabolism coupling and functional responses in specific subcortical regions during anesthesia.