Prolonging viability of swine muscle biopsy specimens in malignant hyperthermia testing

In North America, the caffeine halothane contracture test (CHCT) is the standard test for the diagnosis of malignant hyperthermia (MH). Current CHCT protocol recommends that the test be completed within 5 h of muscle excision. The purpose of this study was to investigate whether the period of skeletal muscle viability could be extended to 24 h. We tested the gracilis muscle from normal (n = 8) and MH-susceptible swine (n = 8). After baseline (1-2 h after excision) CHCT, the remaining muscles were placed into one of the following four treatment groups. In Groups 1 and 2, the muscles remained under tension and were stored in Krebs buffer (pH 7.4) at 23 degrees C-25 degrees C (clamped-warm) and 4 degrees C (clamped-cold), respectively. In Groups 3 and 4, the muscle strips were dissected, and the ends were tied with silk sutures, cut from the clamp, and placed in Krebs buffer at 23 degrees C-25 degrees C (free-warm) and 4 degrees C (free-cold), respectively. The responses of the treatment groups to halothane (3%) and caffeine (0.5-32 mM) were tested 22-26 h after excision. The clamped-warm storage was the only storage method to correctly diagnose MH susceptibility in all muscle strips tested. This finding was also confirmed in muscle stored under clamped-warm conditions and shipped overnight to another testing center for a parallel CHCT.