In vivo exploration of the injured human brain can be achieved through the intrace­rebral microdialysis (CMD) technique, enabling repeated sampling and direct mea­surement of the brain interstitial tissue concentrations of main cerebral energy metabolites, including glucose, lactate, and pyruvate. While it provides a regional assessment of brain metabolism—in contrast to neuroimaging techniques (magnetic resonance spectroscopy—MRS; positron emission tomography—PET) or jugular bulb venous catheterization, which offer measurement of global brain metabolic function—a major advantage of the CMD technique is its ability to enable an online semicontinuous (every 1–2 h) measurement of energy metabolites at the patient’s bedside. Furthermore, CMD provides immediate insights into dynamic variations of cerebral metabolic function and a timely response to therapy aiming at restoring energy metabolism function. The CMD, through the monitoring of the LP ratio (normal brain values 20 ± 3, as opposed to 10 ± 3 systemically)—the main biomarker of cerebral oxidative metabolism—and glucose, the main energy sub­strate (normal brain values 1–2 mmol/L), has thus evolved to become a trigger and target of therapeutic intervention and a robust predictor of patient outcome [30, 31].