Anesthesia increases circulating glutamate in neurosurgical patients

Area of Science:

• Neuroscience
• Anesthesiology
• Neurocritical Care

Background:

• Glutamate, an excitotoxic amino acid, can worsen existing neuropathology.
• Volatile anesthetics are known to elevate plasma amino acid levels.
• This study investigates the impact of isoflurane and propofol on glutamate levels in neurosurgical patients.

Purpose of the Study:

• To determine if isoflurane and propofol anesthesia increase plasma and cerebrospinal fluid (CSF) glutamate levels in neurosurgical patients.
• To compare the effects of isoflurane and propofol on glutamate concentrations.
• To assess the clinical relevance of these glutamate level changes.

Main Methods:

• Plasma glutamate levels were measured in discectomized patients during isoflurane anesthesia.
• Plasma and CSF glutamate levels were assessed in craniotomized patients during and after isoflurane or propofol anesthesia.
• CSF samples were collected upon dural opening, prior to surgical manipulation.

Main Results:

• Both isoflurane and propofol significantly increased plasma and CSF glutamate levels compared to controls.
• Isoflurane caused a more pronounced and sustained increase in plasma glutamate, especially in male patients and those with brain edema.
• CSF glutamate increases were more significant with isoflurane than propofol, particularly in patients with pre-existing brain edema.

Conclusions:

• Anesthetic agents like isoflurane and propofol can increase plasma and CSF glutamate, potentially contributing to excitotoxicity in patients with compromised cerebral homeostasis.
• Further research is needed to identify anesthetic agents that avoid glutamate-mediated excitotoxicity.
• Neuropsychological assessments are crucial to evaluate the clinical significance of transient glutamate level elevations post-anesthesia.