Malignant Hyperthermia

Malignant hyperthermia is a life threatening increase of body temperature, usually by a hypermetabolic response to the simultaneous use of a depolarizing muscle relaxant and a potent volatile inhalation anesthesia. Among the manifestations include muscle rigidity, hyperthermia, tachycardia, tachypnea, rhabdomyolysis, and respiratory and metabolic acidosis. The diagnosis is made clinically; Patients at risk can be tested for susceptibility. The highest priority is given to treatments for rapid cooling and aggressive supportive care.

The muscle relaxant succinylcholine is usually involved, as well as the inhalation anesthetics halothane. But other anesthetics (eg. As isoflurane, sevoflurane, desflurane) may be involved. This drug combination results in some patients with muscular dystrophy and myotonia to a similar reaction. Although malignant hyperthermia may develop after the first exposure to these drugs, patients need three exposures on average.

Malignant hyperthermia is a life threatening increase of body temperature, usually by a hypermetabolic response to the simultaneous use of a depolarizing muscle relaxant and a potent volatile inhalation anesthesia. Among the manifestations include muscle rigidity, hyperthermia, tachycardia, tachypnea, rhabdomyolysis, and respiratory and metabolic acidosis. The diagnosis is made clinically; Patients at risk can be tested for susceptibility. The highest priority is given to treatments for rapid cooling and aggressive supportive care. The muscle relaxant succinylcholine is usually involved, as well as the inhalation anesthetics halothane. But other anesthetics (eg. As isoflurane, sevoflurane, desflurane) may be involved. This drug combination results in some patients with muscular dystrophy and myotonia to a similar reaction. Although malignant hyperthermia may develop after the first exposure to these drugs, patients need three exposures on average. Pathophysiology Malignant hyperthermia affects about 1 in 20,000 people. The vulnerability of this is inherited as an autosomal dominant and is of variable manifestation probability. In most cases, the causative mutation affects the ryanodine receptor in skeletal muscle, but> 22 others causing mutations have been identified so far. In susceptible people, this fabric is hyper reactive to calcium. The mechanism may be related to an anesthesia-induced potentiation of calcium excretion in the sarcoplasmic reticulum of skeletal muscles. As a result, calcium-induced reactions accelerated, severe muscle contractions and increase cause metabolic rate, resulting in respitatorischer and metabolic acidosis. In response to the acidosis patients breathe spontaneously and develop tachypnea, which only partly offsets. Complications hyperkalemia, respiratory and metabolic acidosis, hypocalcemia and rhabdomyolysis with elevated creatine phosphokinase (CPK) and myoglobinaemia may occur, as well as coagulation disorders (especially disseminated intravascular coagulation [DIC]). In elderly patients and patients with comorbidities increased DIC may increase the risk of death. Symptoms and complaints Malignant hyperthermia may develop during surgery or in the early postoperative period. The clinical picture varies depending on the drugs used and the patient’s disposition. The first sign is often rigors of the muscles, especially the jaw, followed by tachycardia, arrhythmias other, tachypnea, acidosis, shock and hyperthermia. recognized hypercapnia (due to increased end-tidal CO2), may be an early sign. The temperature is often at ? 40 ° C and can be extremely high (i. E.> 43 ° C). Urine can be brown or bloody if rhabdomyolysis and myoglobinuria have occurred. Diagnosis Clinical evaluation testing for complications tests to verify the susceptibility in persons at risk Suspected diagnosis after the occurrence of typical symptoms within 10 minutes to, occasionally, several hours after the start of inhalation anesthesia. Early diagnosis can be facilitated by fast detection of jaw stiffness, tachypnea, tachycardia facilitated and increased end-tidal CO2. While there is no direct confirmatory tests, but patients should be tested for complications, including an ECG, blood tests (complete blood count with platelets, electrolytes, urea nitrogen, creatinine, creatine phosphokinase (CPK), calcium, PT, PTT, fibrinogen, D-dimer) and urine tests to myoglobinuria. Other diagnoses must also be excluded. Perioperative sepsis can lead to hyperthermia, but rarely so soon after anesthetic induction. Inadequate anesthesia may increase muscle tone and tachycardia, but not the temperature. A hyperthyroid crisis and pheochromocytomas rarely manifest themselves immediately after induction of anesthesia. Susceptibility testing A test for susceptibility to malignant hyperthermia is recommended for people at risk, based on a family history or a personal history with a serious or incomplete pronounced negative reaction to a general anesthetic. The caffeine-halothane contracture test (CHCT) is most accurate. It measures the reaction of a muscle tissue sample to caffeine and halothane. This test can be performed only on referral in certain centers and requires the excision of about 2 g muscle tissue. Because many mutations can include to have genetic studies limited sensitivity (30%), but are quite specific; Patients in whom a mutation has been identified, do not need CHCT test. Treatment Rapid measures to cool and support dantrolene It is critical to cool the patient as quickly and effectively as possible (heat stroke: treatment) to prevent damage to the central nervous system and also to treat the patient supportive, to correct metabolic disorders. The result is best if treatment is started before the muscular rigidity is generalized and have before developed rhabdomyolysis, a severe hyperthermia and DIC. In addition to the usual physical cooling measures should i.v. dantrolene 2.5 mg / kg every 5 minutes as required up to a total dose of 10 mg / kg are given. The dose of dantrolene titrated based on heart rate and end tidal CO2. In some patients intubation (Restoring and Backing up the airways: Endotracheal intubation), paralysis, and coma induced necessary to control the symptoms and provide support. Intravenous benzodiazepine, usually in high doses, can be used to control the excitement. Malignant hyperthermia has a high mortality rate, and sometimes not even responds to early and aggressive therapy. Prevention If possible, the local or regional anesthesia is compared to the general anesthesia is preferred. Potent inhalation anesthetics and depolarizing muscle relaxants should be avoided in susceptible patients and in those with a strong family history. Non-depolarizing neuromuscular blocking agents are the preferred pre-anesthetic medication. Preferred anesthetics are barbiturates (z. B. thiopental), etomidate and propofol. should be available at the bedside dantrolene. Important points Malignant hyperthermia develops in genetically susceptible patients (usually more than once) a depolarizing muscle relaxant and a potent inhaled volatile Narkotiukum were exposed (most often halothane) simultaneously. Complications can u. a. Hyperkalemia, respiratory and metabolic acidosis, hypocalcemia, rhabdomyolysis and DIC are. If you suspect the diagnosis when patients jaw stiffness, tachypnea, tachycardia, or increased end-tidal CO2 innerhab of minutes or sometimes develop hours after the start of inhalation anesthesia. Test people with risk with halothane contracture test caffeine or genetic tests if those tests are available. Treat with an aggressive, early cooling and i.v. Dantrolene.

Health Life Media Team

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