Lactate: brain fuel in human traumatic brain injury: a comparison with normal healthy control subjects.
Level 3 - non-randomized controlled study
Prospective non-randomized comparative physiological study with healthy controls
PubMed 25594628 · doi:10.1089/neu.2014.3483
What was done
Dual isotope tracer methodology using intravenous [6,6-2H2]glucose and [3-13C]lactate infusions with simultaneous arterial and jugular bulb blood sampling was performed in 12 patients with nonpenetrating traumatic brain injury (mean 5.7 ± 2.2 days post-injury) and 6 healthy control volunteers. Cerebral metabolic rates, fractional extraction, and oxidation rates of glucose and lactate were measured.
What was found
Cerebral metabolic rate for glucose was significantly suppressed in TBI patients compared to controls (p < 0.001). Cerebral lactate fractional extraction approximated 11% in both healthy controls and TBI patients. Neither net cerebral lactate rate nor tracer-measured cerebral lactate uptake differed between groups. Lactate tracer oxidized and released as 13CO2 into the jugular bulb was 92% in controls and 91% in TBI patients. Direct lactate uptake and indirect lactate gluconeogenesis accounted for approximately 70% of carbohydrate consumed by the injured brain, with 75-80% of released 13CO2 derived directly from lactate.
Why it matters
This study demonstrates in humans that the injured brain maintains lactate extraction and oxidizes it as a primary energy substrate when glucose uptake is compromised, supporting the rationale for exogenous lactate therapy after traumatic brain injury.
Limits
The sample size was very small (12 patients, 6 controls). Arterial glucose tended to be higher in TBI patients, which could confound comparisons. The study evaluated acute metabolic kinetics at a single time window post-injury without measuring clinical neurological recovery.
Cited by
- context In patients with moderate to severe traumatic brain injury, elevated blood lactate levels correlate with better clinical and cognitive recovery if the blood-brain barrier is intact.
- supports Infusing lactate in patients with traumatic brain injury increases total cerebral carbohydrate uptake (glucose plus lactate).