EVALUATION OF LACTATE PRODUCTION AND CLEARANCE KINETICS BY H-1-NMR INA MODEL OF BRIEF REPETITIVE CEREBRAL-ISCHEMIA

Pilots of high-performance aircraft are subject to repeated transient cerebral ischemia during high-gravitational stress maneuvers. Previous ly we have demonstrated that repeated episodes of transient cerebral i schemia and reflow are cumulative and lactate accumulations appear to be exponential. To evaluate the metabolic events determining the kinet ics of lactate accumulation, and therefore the rates of substrate util ization, we have used in vivo H-1 nuclear magnetic resonance with a 5- s time resolution to measure lactate production and clearance. The ind ividual rates for each animal were then used to predict the accumulati on of lactate in the same animal during 30 episodes of ischemia and re flow. Lactate accumulation was modeled as the balance between a zero-o rder production process during the ischemic period and a first-order c learance process. The predicted lactate accumulation showed excellent agreement with the observed time course, validating the predictive pow er of the simple model used. The highly reproducible nature of this mo del and its accuracy in predicting lactate accumulation should enable more accurate studies of the deleterious effects of lactate accumulati on in cerebral ischemia by providing a highly reproducible means for g enerating a specific level of lactate accumulation.