Prolonging viability of swine muscle biopsy specimens in malignant hyperthermia testing

In North America, the caffeine halothane contracture test (CHCT) is the sta ndard test for the diagnosis of malignant hyperthermia (MH). Current CHCT p rotocol recommends that the test be completed within 5 h of muscle excision . The purpose of this study was to investigate whether the period of skelet al muscle viability could be extended to 24 h. We tested the gracilis muscl e 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 un der tension and were stored in Krebs buffer (pH 7.4) at 23 degreesC-25 degr eesC (clamped-warm) and 4 degreesC (clamped-cold), respectively. In Groups 3 band 4, the muscle strips were dissected, and the ends were tied with sil k sutures, cut from the clamp, and placed in Krebs buffer at 23 degreesC-25 degreesC (free-warm) and 4 degreesC (free-cold), respectively. The respons es 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 storag e method to correctly diagnose MH susceptibility in all muscle strips teste d. This finding was also confirmed in muscle stored,under clamped-warm cond itions and shipped overnight to another testing center for a parallel CHCT.