Acute model for the estimation of the cerebral energy state during or after hypoxia and complete or incomplete ischaemia.

The behaviour of fuels (glycogen, glucose), of glycolytic pathway intermediates (glucose-6-phosphate, pyruvate) and end-product (lactate), as well as the pool of labile phosphates (ATP, ADP, AMP, creatine phosphate) and the energy charge of the brain were studied in the motor area of the cerebral cortex of beagle dogs in hypovolaemic hypotension. These parameters were evaluated after acute hypoxia (obtained by altering the composition of the inhalation mixture), after acute hypoxia plus incomplete ischaemia, after acute hypoxia plus complete ischaemia, during post-hypoxic recovery (3, 15 or 30 min after the restoration of normal ventilation), during post-hypoxic recovery and recirculation. A comparative examination of the different conditions showed that the most dramatic fall in the cerebral energy state took place in hypoxia plus complete ischaemia followed, in the order, by hypoxia plus incomplete ischaemia and simple hypoxia. However, reversal was most difficult in hypoxia plus incomplete ischaemia. The different situations are discussed in this paper with regard to the changes taking place in cerebral biochemical events.