Use of the caffeine-halothane contracture test for the diagnosis of malignant hyperthermia in Brazil

Malignant hyperthermia (MH) is a pharmacogenetic disease triggered by volatile anesthetics and succinylcholine. Deaths due to MH have been reported in Brazil. The first Malignant Hyperthermia Diagnostic and Research Center in Latin America was inaugurated in 1993 at the Federal University of Rio de Janeiro, Brazil. The center followed the diagnostic protocols of the North America MH Group, in which the contractures of biopsies from the vastus lateralis muscle are analyzed after exposure to caffeine and halothane (CHCT). CHCT was performed in individuals who survived, their relatives and those with signs/symptoms somewhat related to MH susceptibility (MHS). Here, we report data from 194 patients collected over 16 years. The Southeast (N = 110) and South (N = 71) represented the majority of patients. Median age was 25 (4-70) years, with similar numbers of males (104) and females (90). MHS was found in 90 patients and 104 patients were normal. Abnormal responses to both caffeine and halothane were observed in 59 patients and to caffeine or halothane in 20 and 11 patients, respectively. The contracture of biopsies from MHS exposed to caffeine and halothane was 1.027 ± 0.075 g (N = 285) and 4.021 ± 0.255 g (N = 226), respectively. MHS was found in patients with either low or high blood creatine kinase and also, with a low score on the clinical grading scale. Thus, these parameters cannot be used with certainty to predict MHS. We conclude that the CHCT protocol described by the North America MH Group contributed to identification of MHS in suspected individuals at an MH center in Brazil with 100 percent sensitivity and 65.7 percent specificity.

La contracción uterina inducida por carbacol es inhibida por melatonina / Uterine contraction induced by carbachol is inhibited by melatonin

La melatonina es el principal indol secretado por la glándula pineal.Además de su efecto antigonadotrófico, se han descrito diversos efectos fisiológicos no hormonales. Entre estos se han reportado la inhibición de la contracción de tejidos con musculatura lisa, aunque este efecto se ha sido descrito ampliamente. El presente estudio se realizó con el propósito de caracterizar el efecto de la melatonina sobre la contracción uterina inducida por carbacol. Se realizó un estudio in vitro empleando úteros de ratas estrogenizadas de la cepa Wistar. La contracción fue producida por carbacol en un rango de concentración de 5 x 10 a 10 M/ml, en ausencia y presencia de melatonina. De ésta se emplearon las siguientes concentraciones: 10, 2.5 x 10 M/ml. Los resultados obtenidos muestran que la concentración efectiva media de carbacol para inducir contracción uterina se incrementa significativamente en precencia de melatonina a las concentraciones de 10 y 10 M/ml. Las curvas log de la concentración- porcentaje de contracción máxima para carbacol en presencia de melatonina se desplazan a la derecha de la curva de carbacol en ausencia de melatonia. Se concluye que la melatonina inhibe la contracción producida por carbacol de manera dependiente de la concentración, comportándose como una antagonista fisiológico.