jueves, 8 de junio de 2017

Hipertermia maligna / Malignant hyperthermia

Junio 8, 2017. No. 2713

Estimad@ Dr@ Víctor Valdés:  

Chichen Itza

Rabdomiólisis por ejercicio  y golpe de calor: Tenga cuidado con la sedación volátil anestésica.
Exertional rhabdomyolysis and heat stroke: Beware of volatile anesthetic sedation.
World J Crit Care Med. 2017 Feb 4;6(1):21-27. doi: 10.5492/wjccm.v6.i1.21. eCollection 2017 Feb 4.
In view of the enormous popularity of mass sporting events such as half-marathons, the number of patients with exertional rhabdomyolysis or exercise-induced heat stroke admitted to intensive care units (ICUs) has increased over the last decade. Because these patients have been reported to be at risk for malignant hyperthermia during general anesthesia, the intensive care community should bear in mind that the same risk of life-threatening rhabdomyolysis is present when these patients are admitted to an ICU, and volatile anesthetic sedation is chosen as the sedative technique. As illustrated by the three case studies we elaborate upon, a thorough diagnostic work-up is needed to clarify the subsequent risk of strenuous exercise, and the anesthetic exposure to volatile agents in these patients and their families. Other contraindications for the use of volatile intensive care sedation consist of known malignant hyperthermia susceptibility, congenital myopathies, Duchenne muscular dystrophy, and intracranial hypertension.
KEYWORDS: Congenital myopathies; Exertional rhabdomyolysis; Heat stroke; Inhalational anesthetics; Intensive care sedation; Malignant hyperthermia

Hipertermia  maligna. Una revisión
Malignant hyperthermia: a review.
Orphanet J Rare Dis. 2015 Aug 4;10:93. doi: 10.1186/s13023-015-0310-1.
Malignant hyperthermia (MH) is a pharmacogenetic disorder of skeletal muscle that presents as a hypermetabolic response to potent volatile anesthetic gases such as halothane, sevoflurane, desflurane, isoflurane and the depolarizing muscle relaxant succinylcholine, and rarely, in humans, to stressors such as vigorous exercise and heat. The incidence of MH reactions ranges from 1:10,000 to 1: 250,000 anesthetics. However, the prevalence of the genetic abnormalities may be as great as one in 400 individuals. MH affects humans, certain pig breeds, dogs and horses. The classic signs of MH include hyperthermia, tachycardia, tachypnea, increased carbon dioxide production, increased oxygen consumption, acidosis, hyperkalaemia, muscle rigidity, and rhabdomyolysis, all related to a hypermetabolic response. The syndrome is likely to be fatal if untreated. An increase in end-tidal carbon dioxide despite increased minute ventilation provides an early diagnostic clue. In humans the syndrome is inherited in an autosomal dominant pattern, while in pigs it is autosomal recessive. Uncontrolled rise of myoplasmic calcium, which activates biochemical processes related to muscle activation leads to the pathophysiologic changes. In most cases, the syndrome is caused by a defect in the ryanodine receptor. Over 400 variants have been identified in the RYR1 gene located on chromosome 19q13.1, and at least 34 are causal for MH. Less than 1 % of variants have been found in CACNA1S but not all of these are causal. Diagnostic testing involves the in vitro contracture response of biopsied muscle to halothane, caffeine, and in some centres ryanodine and 4-chloro-m-cresol. Elucidation of the genetic changes has led to the introduction of DNA testing for susceptibility to MH. Dantrolene sodium is a specific antagonist and should be available wherever general anesthesia is administered. Increased understanding of the clinical manifestation and pathophysiology of the syndrome, has lead to the mortality decreasing from 80 % thirty years ago to <5 % in 2006.

Manejo de la hipertermia maligna. Diagnóstico y tratamiento
Management of malignant hyperthermia: diagnosis and treatment.
Ther Clin Risk Manag. 2014 May 14;10:355-62. doi: 10.2147/TCRM.S47632. eCollection 2014.
Malignant hyperthermia is a potentially lethal inherited disorder characterized by disturbance of calcium homeostasis in skeletal muscle. Volatile anesthetics and/or the depolarizing muscle relaxant succinylcholine may induce this hypermetabolic muscular syndrome due to uncontrolled sarcoplasmic calcium release via functionally altered calcium release receptors, resulting in hypoxemia, hypercapnia, tachycardia, muscular rigidity, acidosis, hyperkalemia, and hyperthermia in susceptible individuals. Since the clinical presentation of malignant hyperthermia is highly variable, survival of affected patients depends largely on early recognition of the symptoms characteristic of malignant hyperthermia, and immediate action on the part of the attending anesthesiologist. Clinical symptoms of malignant hyperthermia, diagnostic criteria, and current therapeutic guidelines, as well as adequate management of anesthesia in patients susceptible to malignant hyperthermia, are discussed in this review.
KEYWORDS: genetics; in vitro contracture test; malignant hyperthermia; succinylcholine; volatile anesthetics

Hipertermia maligna
Malignant hyperthermia.
Swiss Med Wkly. 2012 Jul 31;142:w13652. doi: 10.4414/smw.2012.13652.
Malignant hyperthermia (MH) is a subclinical myopathy, usually triggered by volatile anaesthetics and depolarising muscle relaxants. Clinical symptoms are variable, and the condition is sometimes difficult to identify. Nevertheless, rapid recognition and specific as well as symptomatic treatment are crucial to avoid a lethal outcome. Molecular genetic investigations have confirmed the skeletal muscle type ryanodine receptor to be the major MH locus with more than 70% of MH families carrying a mutation in this gene. There is no screening method to test for MH, as current tests are invasive (open muscle biopsy) or restricted to MH families with known MH-associated mutations (molecular genetic testing). The prevalence of the MH trait is unknown, because the clinical penetrance after contact with triggering agents is very variable. More recently, MH mutations have been associated with rhabdomyolysis following statin therapy or with non-pharmacological triggering, such as exertional heat stroke.

IX Foro Internacional de Medicina del Dolor y Paliativa
Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán
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