Enfermagem no contexto da hipertermia maligna: revisão integrativa

Objetivo: descrever, a partir da literatura, o perfil das publicações sobre enfermagem na hipertermia maligna. Método: trata-se de revisão integrativa com orientações do Preferred Reporting Items for Systematic Reviews and Meta-Analyses (Prisma), nas bases de dados da Literatura Latino-americana e do Caribe em Ciências da Saúde (Lilacs), Scientific Electronic Library OnlineHYPERLINK "http://www.scielo.org/" (SciELO), e HYPERLINK "http://www.scielo.org/"Medical Literature Analysis and Retrieval System OnlineHYPERLINK "http://www.scielo.org/" (Medline). Os descritores formam “hipertermia maligna” AND “enfermagem” e “malignant hyperthermia” AND “nursing”; com amostra consitituída de onze textos eleitos estritamente quando referissem à enfermagem no contexto da hipertermia maligna. Resultados: como perfil das publicações foram eleitos três eixos temáticos, a saber: suscetibilidade genética e risco à hipertermia maligna; sinais, sintomas e recursos para a intervenção na hipertermia maligna; e educação e treinamento aos profissionais da enfermagem diante da hipertermia maligna. Conclusão: a preparação e o treinamento da equipe de enfermagem torna-se importante estratégia no enfrentamento da hipertemia maligna. Além disso, a incorporação de aprendizagem baseada em simulação, ainda nos cursos de graduação, fornece uma experiência consistente e aumenta a segurança do paciente.

Preparation of Dräger Atlan A350 and General Electric Healthcare Carestation 650 anesthesia workstations for malignant hyperthermia susceptible patients

Background Patients at risk of malignant hyperthermia need trigger-free anesthesia. Therefore, anesthesia machines prepared for safe use in predisposed patients should be free of volatile anesthetics. The washout time depends on the composition of rubber and plastic in the anesthesia machine. Therefore, new anesthesia machines should be evaluated regarding the safe preparation for trigger-free anesthesia. This study investigates wash out procedures of volatile anesthetics for two new anesthetic workstations: Dräger Atlan A350 and General Electric Healthcare (GE) Carestation 650 and compare it with preparation using activated charcoal filters (ACF). Methods A Dräger Atlan and a Carestation 650 were contaminated with 4% sevoflurane for 90 min. The machines were decontaminated with method (M1): using ACF, method 2 (M2): a wash out method that included exchange of internal parts, breathing circuits and soda lime canister followed by ventilating a test lung using a preliminary protocol provided by Dräger or method 3 (M3): a universal wash out instruction of GE, method 4 (M4): M3 plus exchange of breathing system and bellows. Decontamination was followed by a simulated trigger-free ventilation. All experiments were repeated with 8% desflurane contaminated machines. Volatile anesthetics were detected with a closed gas loop high-resolution ion mobility spectrometer with gas chromatographic pre-separation attached to the bacterial filter of the breathing circuits. Primary outcome was time until < 5 ppm of volatile anesthetics and total preparation time. Results Time to < 5 ppm for the Atlan was 17 min (desflurane) and 50 min (sevoflurane), wash out continued for a total of 60 min according to protocol resulting in a total preparation time of 96-122 min. The Carestation needed 66 min (desflurane) and 24 min (sevoflurane) which could be abbreviated to 24 min (desflurane) if breathing system and bellows were changed. Total preparation time was 30-73 min. When using active charcoal filters time to < 5 ppm was 0 min for both machines, and total preparation time < 5 min. Conclusion Both wash out protocols resulted in a significant reduction of trace gas concentrations. However, due to the complexity of the protocols and prolonged total preparation time, feasibility in clinical practice remains questionable. Especially when time is limited preparation of the anesthetic machines using ACF remain superior.

Increased basal metabolic rate in mice susceptible to malignant hyperthermia and heat stroke

Ryanodine receptor type-1 (RYR1) and Calsequestrin-1 (CASQ1) proteins, located in the sarcoplasmic reticulum (SR), are two of the main players in skeletal excitation–contraction (EC) coupling. Mutations in the human RYR1 gene (encoding for the SR Ca2+ release channel) and ablation in mice of CASQ1 (a SR Ca2+ binding protein) cause hypersensitivity to halogenated anesthetics (malignant hyperthermia [MH] susceptibility) and to heat (heat stroke; HS). As both MH and HS are characterized by excessive cytosolic Ca2+ levels and hypermetabolic responses, we studied the metabolism of 4-mo-old mice from two different lines that are MH/HS susceptible: knock-in mice carrying a human MH mutation (RYR1YS) and CASQ1-knockout (ko) mice. RYR1YS and, to a lesser degree, CASQ1-null mice show an increased volume of oxygen consumption (VO2) and a lower respiratory quotient (RQ) compared with WT mice (indicative of a metabolism that relies more on lipids). This finding is accompanied by a reduction in total body fat mass in both Y522S and CASQ1-null mice (again, compared with WT). In addition, we found that RYR1YS and CASQ1-null mice have an increased food consumption (+26.04% and +25.58% grams/day, respectively) and higher basal core temperature (+0.57°C and +0.54°C, respectively) compared with WT mice. Finally, Western blots and electron microscopy indicated that, in hyperthermic mice, (1) SERCA (used to remove myoplasmic Ca2+) and UCP3 (responsible for a thermogenic process that dissipates mitochondrial H+ gradient) are overexpressed, and (2) mitochondrial volume and percentage of damaged mitochondria are both increased. In conclusion, the MH/HS phenotype in RYR1YS and CASQ1-null mice is associated with an intrinsically increased basal metabolism.

RYR1-related myopathies: Expanding the spectrum of morphological presentation

Mutations in the RYR1 gene are the most common cause of nondystrophic congenital myopathies. Mutations in RYR1 were initially identified in individuals susceptible to malignant hyperthermia, a pharmacogenetic disorder triggered by volatile anesthetics and succinylcholine. Shortly after, mutations in RYR1 were identified in patients with central core disease, which is the most frequent congenital myopathy, and in other muscle disorders, collectively referred to as RYR1-related myopathies. RYR1 mutations are also responsible of some acute pathological conditions triggered by heat- and exercise-induced stress, named exertional heat stroke and exertional-induced rhabdomyolysis, which, similarly to malignant hyperthermia, occur in otherwise healthy individuals with normal skeletal muscle functions. Hundreds of causative mutations linked to RYR1-related diseases have been identified. These mutations are clustered in three regions that are referred to as the N-terminal, central, and C-terminal hot spots. Recent developments in cryo-EM techniques have provided high-resolution reconstructions of the channel, allowing a much better definition of the structural domains within the large N-terminal cytoplasmic region and in the C-terminal domain containing six transmembrane helices and the pore region of the channel. RYR1 mutations may either activate or inhibit channel function or, in some cases, can reduce the expression levels of RYR1 protein. However, similar clinical phenotypes can result from mutations with opposing effects on RYR1 function, or little or no correlation can be found between the observed clinical phenotype and localization of mutations in the structural domains of the RYR1 channel, even though recent studies indicate that clinically severe cases are mostly recessive or due to mutations located in the bridging solenoid. Recent results on the identification of RYR1 mutations in patients with myopathies will be presented.