COMPARISON OF NORTH-AMERICAN AND EUROPEAN MALIGNANT HYPERTHERMIA GROUP HALOTHANE CONTRACTURE TESTING PROTOCOLS IN SWINE

Different in vitro halothane testing procedures have been used in the European malignant hyperthermia (MH) Group Protocol (EMHGP) and the North American MH Group Protocol (NAMHGP), whereas the caffeine-testing protocols are very similar. The present study compares the two halothane-testing protocols in ten MH susceptible swine and in four control swine. Halothane contracture testing was conducted in vitro 12-52 days following the barnyard challenge that established the MH susceptibility of the swine. There was one false positive and one false negative halothane test by the EMHGP. The MH-equivocal category in the EMHGP, which is treated clinically as MH-susceptible, affords a margin of safety in such cases. In contrast, there were no false halothane tests by the NAMHGP. While some skeletal muscle strips from MH pigs were normal by both protocols (NAMHGP 30%; EMHGP 10%), the outcome of halothane testing by the NAMHGP was unaffected. The response to halothane 3% is reduced if preceded by the EMHGP, suggesting that simply adding halothane 3% to the end of the EMHGP does not permit a direct quantitative comparison to the NAMHGP. However, the diagnostic outcomes of the two approaches are similar.