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During focal ischemia, neurons can use lactate as an alternative source of energy through its oxidation into pyruvate by the lactate dehydrogenase (LDH). After cardiac arrest, the neurological consequences of this phenomenon are unknown. Experimental study. Experimental laboratory. Male New-Zealand rabbits. Animals were surgically instrumented and randomly divided into five groups receiving short infusion duration of either lactate or pyruvate or a pre-cardiac arrest infusion of oxamate (an inhibitor of the lactate dehydrogenase) or injection of fluorocitrate (an inhibitor of astrocytic tricarboxylic acid), or Saline (lactate, pyruvate, Oxa, FC and Control groups, respectively). After randomization, animals were submitted to 10 min of ventricular fibrillation and subsequent resuscitation. All animals were then either followed during 4 h, for the evaluation of the cerebral net uptake and concentrations of metabolites by microdialysis (n = 6 in each experimental group, n = 12 in control group), or during 48 h for the evaluation of their neurological outcome (n = 7 in each groups and n = 14 in control group). Cardiac arrest was associated with a dramatic increase in cerebral net uptake of lactate during 120 min after resuscitation, which was increased by lactate or pyruvate administration. This was associated with an increase in the mean neurological dysfunction score (66.7 ± 4.7, 79.0 ± 4.5 vs 57.7 ± 1.5 in Lactate, Pyruvate and Control group respectively) at 48 h after cardiac arrest. Oxamate and FC administration were associated with a lower lactate cerebral uptake after cardiac arrest and with an improvement of the neurological recovery (28.85 ± 9.4, 23.86 ± 6.2 vs 57.7 ± 1.5 in Oxa, FC and Control group respectively). After cardiac arrest, immediate isotonic lactate or pyruvate administration is deleterious. Pre-cardiac arrest LDH inhibition was potently neuroprotective in this setting. [ABSTRACT FROM AUTHOR]

: Aims We investigated whether rapid cooling instituted by total liquid ventilation (TLV) improves cardiac and mitochondrial function in rabbits submitted to ischaemia-reperfusion. : Methods and results Rabbits were chronically instrumented with a coronary artery occluder and myocardial ultrasonic crystals for assessment of segment length-shortening. Two weeks later they were re-anaesthetized and underwent either a normothermic 30-min coronary artery occlusion (CAO) (Control group, n = 7) or a comparable CAO with cooling initiated by a 10-min hypothermic TLV and maintained by a cold blanket placed on the skin. Cooling was initiated after 5 or 15 min of CAO (Hypo-TLV and Hypo-TLV15′ groups, n = 6 and 5, respectively). A last group underwent normothermic TLV during CAO (Normo-TLV group, n = 6). Wall motion was measured in the conscious state over three days of reperfusion before infarct size evaluation and histology. Additional experiments were done for myocardial sampling in anaesthetized rabbits for mitochondrial studies. The Hypo-TLV procedure induced a rapid decrease in myocardial temperature to 32–34°C. Throughout reperfusion, segment length-shortening was significantly increased in Hypo-TLV and Hypo-TLV15′ vs. Control and Normo-TLV (15.1 ± 3.3%, 16.4 ± 2.3%, 1.8 ± 0.6%, and 1.1 ± 0.8% at 72 h, respectively). Infarct sizes were also considerably attenuated in Hypo-TLV and Hypo-TLV15′ vs. Control and Normo-TLV (4 ± 1%, 11 ± 5%, 39 ± 2%, and 42 ± 5% infarction of risk zones, respectively). Mitochondrial function in myocardial samples obtained at the end of ischaemia or after 10 min of reperfusion was improved by Hypo-TLV with respect to ADP-stimulated respiration and calcium-induced opening of mitochondrial permeability transition pores (mPTP). Calcium concentration opening mPTP was, e.g., increased at the end of ischaemia in the risk zone in Hypo-TLV vs. Control (157 ± 12 vs. 86 ± 12 µM). Histology and electron microscopy also revealed better preservation of lungs and of cardiomyocyte ultrastructure in Hypo-TLV when compared with Control. : Conclusion Institution of rapid cooling by TLV during ischaemia reduces infarct size as well as other sequelae of ischaemia, such as post-ischaemic contractile and mitochondrial dysfunction. [ABSTRACT FROM AUTHOR]