Review
Copyright ©The Author(s) 2024.
World J Crit Care Med. Jun 9, 2024; 13(2): 91397
Published online Jun 9, 2024. doi: 10.5492/wjccm.v13.i2.91397
Table 1 Various proposed cerebral microdialysis substrates
Function
Substrates
ATP usageAdenosine, hypoxanthine, inosine, K+
Membrane dysfunctionGlycerol
Reactive oxygen speciesXanthine, uric acid, glutathione, cysteine
Nitric oxide formationNitrite, nitrate, citrulline, arginine
Brain swellingPotassium, taurine
InflammationIL-1, IL-6, GFAP, TNF
Blood-brain barrier Alanine, leucine, and valine
Neurotransmitters and amino acidsSerine, 5-HIAA, GABA, Glycine
Table 2 Near infrared spectroscopy-derived indices and clinical utility for the neurointensivist
NIRS derived indices
Utility
COx = correlation coefficient (rSO2, MAP)COx: This index is derived by correlating rSO2 with MAP. It is used to assess cerebral autoregulation, with a positive correlation indicating impaired autoregulation
TOx = correlation coefficient (TOI, MAP)TOx: Similar to COx, TOx is calculated by correlating the TOI with MAP. It provides information on the balance between oxygen supply and demand at the tissue level
HVx = correlation coefficient (rTHb, MAP)HVx: HVx correlates the rTHb, as measured by NIRS, with MAP. It is used to evaluate cerebral blood volume changes in response to blood pressure fluctuations.
BFAx = correlation coefficient (rCBFi, MAP)BFAx: BFAx correlates the rCBFi with MAP. A positive correlation indicates that cerebral blood flow is more passive to pressure, suggesting impaired autoregulation
CMRO2 = cerebral blood flow × (arterial O2 content - venous O2 content)Estimation of the CMRO2: Although the direct calculation of CMRO2 using NIRS is complex, NIRS data combined with other parameters can estimate CMRO2. This provides information on the metabolic state of the brain