METABOLIC EVENTS WITH SPONTANEOUS MALIGNANT HYPERTHERMIA CRISIS IN ANANESTHETIZED PIG

Purpose: To analyze metabolic changes associated with a fulminant mali gnant hyperthermia (MH) crisis developed spontaneously in an MH suscep tible pig which was part of 12 pigs undergoing metabolic investigation (six MH susceptible and six controls) and had been anaesthetized with anon-triggering agent (pentobarbitone). Methods: The pig was placed i n a cradle and then inserted into a 4.7 T magnet bore, The semi-membra nosus muscle was submitted to three repetitive stimulation-recovery se ssions. 31-P magnetic resonance spectra and mechanical data were recor ded. Results: The pig developed a non-rigid MH crisis during recovery from the second set of experiments. Although no mechanical work was pe rformed, dramatic metabolic changes were noted. Twitch tension decreas ed progressively reaching zero while mouth temperature continuously in creased to 44.5 degrees C. Phosphocreatine (PCr) consumption was coupl ed to Pi accumulation. Also, a marked intracellular acidosis and a lar ge accumulation of phosphomonoesters (PME) were observed, probably as a result or massive glycolysis activation. Interestingly ATP level rem ained constant. Conclusion: These irreversible mechanisms may constitu te a metabolic dead-end coupling calcium pumping ATP-consuming process es and ATP synthesis through PCr breakdown and anaerobic glycolysis. T hey do not differ from metabolic changes previously reported in rigid forms of MH crisis.