Pharmacological in-vitro studies in malignant hyperthermia in childhood

In 91 children the caffeine-halothane test was performed according to the technique used by Britt et al and Kalow et al. The muscles investigated, 12 mm long and 2 to 3 mm in diameter, showed concentration dependent contractures to caffeine and a distinct potentiation after adding halothane. Compared to adults children above the age of 2 show a higher range for caffeine-induced contractures but infants below this age responded the strongest in range and average. While children with neuromuscular diseases usually revealed contractures less than average compared to the reference group there are special myopathies and muscle conditions which lead to a normal reaction to caffeine but increased ones to caffeine plus halothane. The reason for this remains unknown but the patients concerned should be treated like individuals with the proven trait for MH. Out of 22 patients being possibly MH susceptible [9] or having survived an anaesthetic complication [13] 4 showed decreased caffeine thresholds and increased contractures to caffeine plus halothane which is in accordance with MH susceptibility. Basically the pharmacological in-vitro test may reveal false negative results due to diseased muscle fibres or a shifted sensitivity of the contractile elements to calcium. Practically most important however is the inconvertible diagnosis of MH in a given patient, which in the very end will allow decision on the validity of the pharmacological test being used.