Administration of Anaesthetic Triggering Agents to Patients Tested Malignant Hyperthermia Normal and Their Relatives in New Zealand: An Update

Testing for malignant hyperthermia in New Zealand involves two tests—in vitro contracture testing of excised lateral quadriceps muscle and DNA analysis. In vitro contracture testing is regarded as the gold standard in malignant hyperthermia diagnosis but several publications have questioned the reliability of a normal result. Analysis of 479 anaesthetic records in 280 patients or their descendants throughout New Zealand who had tested negative for malignant hyperthermia, demonstrated there was no evidence of malignant hyperthermia episodes in this group who had been administered anaesthetic triggering agents. A wide range of anaesthetics were used over the study period. Analysis of each anaesthetic record was undertaken using the malignant hyperthermia grading scale which determines the likelihood that an anaesthetic event represents a malignant hyperthermia episode. Confirmation of the negative results was further supported by normal DNA analysis of patients in 48% of anaesthetics. There are advantages to using inhalational agents in certain situations and although demonstrating a zero risk of a malignant hyperthermia episode is not statistically possible, evidence in this large series suggests that the risk of an episode in these patients is extremely low and may be negligible. We suggest that anaesthetic triggering agents can be used safely in patients with normal in vitro contracture tests, and in their descendants.

Malignant hyperthermia in infancy and identification of novel RYR1 mutation

Malignant hyperthermia (MH) has been reported as non-existent in children less than 1 yr old, although several unconfirmed reports have been published. A case report of MH in a 6-month-old child is presented, with confirmation of MH susceptibility by in vitro contracture testing of quadriceps muscle at 13 yr old. Genetic analysis revealed a novel RYR1 mutation that substitutes arginine 2452 for tryptophan in a region of the calcium channel mutated in several other MH pedigrees.

Management of malignant hyperthermia susceptible parturients

The management of eleven women susceptible to malignant hyperthermia during twenty deliveries is presented. These women were managed over a six-year period following guidelines that were established in 1990. Initial problems identified were the management of labour and caesarean section, the use of sympathomimetics and potential problems for the newborn, viz placental transfer of drugs and the possibility of a stress-induced malignant hyperthermia reaction in the newborn. There was little evidence that the stress of labour produced hypermetabolic responses in either mother or neonates and the use of sympathomimetics increased throughout the six-year period with no evidence of adverse effects. A caesarean section using general anaesthesia was not required but the management of this situation is described in both the protocol and discussion sections of this paper.

Mutant with heat-sensitive capacity for phagocytosis in tetrahymena: isolation and genetic characterization

A mutant ofTetrahymenawith heat-sensitive phagocytosis was obtained using a tantalum-particle enrichment procedure. The mutant phenotype is most likely determined by a somatic (macronuclear) mutation(s). The inability of the mutant to sustain cell division and to phagocytize at 37 °C are most likely determined by the same mutation. The phenotype of the mutant is stably inherited under vegetative propagation at 30 °C. At 37 °C, the mutation affects the development of the oral apparatus, the phagocytotic organelle. This mutant has proven useful for the study of cellular functions related to phagocytosis.