Metabolic events with spontaneous malignant hyperthermia crisis in an anaesthetized pig

Purpose: To analyze metabolic changes associated with a fulminant malignant hyperthermia (MH) crisis developed spontaneously in an MH susceptible 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 in a cradle and then inserted into a 4.7 T magnet bore, The semi-membranosus muscle was submitted to three repetitive stimulation-recovery sessions. 31-P magnetic resonance spectra and mechanical data were recorded. Results: The pig developed a non-rigid MH crisis during recovery from the second set of experiments. Although no mechanical work was performed, dramatic metabolic changes were noted. Twitch tension decreased progressively reaching zero while mouth temperature continuously increased to 44.5 degrees C. Phosphocreatine (PCr) consumption was coupled to Pi accumulation. Also, a marked intracellular acidosis and a large accumulation of phosphomonoesters (PME) were observed, probably as a result or massive glycolysis activation. Interestingly ATP level remained constant. Conclusion: These irreversible mechanisms may constitute a metabolic dead-end coupling calcium pumping ATP-consuming processes and ATP synthesis through PCr breakdown and anaerobic glycolysis. They do not differ from metabolic changes previously reported in rigid forms of MH crisis.