Comparison of the in vitro caffeine-halothane contracture test with the Ca-induced Ca release rate test in patients suspected of having malignant hyperthermia susceptibility.

Abstract

We compared the results of the in vitro caffeine-halothane contracture test (CHCT) according to the protocols of the North American Malignant Hyperthermia Group (NAMHG) and the European Malignant Hyperthermia Group (EMHG) with the Ca-induced Ca release (CICR) rate test in the same patients with suspected malignant hyperthermia (MH). Five normal controls and 16 patients suspected of having MH susceptibility were studied. Muscle biopsies were usually obtained from the musculus vastus lateralis. Diagnostic cutoff points and procedures for CHCT protocols were as described in the original and renewal versions of NAMHG and EMHGs. The CICR rate test was performed according to the protocol reported by Endo et al. All five normal controls and two patients with abortive MH, two with postoperative hyperthermia, and three with high serum creatine kinase levels were normal in the three tests. Three patients with MH reactions and one patient with a history of masseter spasm were classified as MH positive according to NAMHG criteria and MH susceptible and MH equivocal according to EMHG criteria. There were five cases with discordant results between the CHCT and CICR rate tests. We propose that muscle biopsy for diagnosis of MH susceptibility should combine the CHCT with the CICR rate test, which may identify the defective site of Ca release channels.