What is the treatment for malignant hyperthermia (MH)?

From the Guidelines

The primary treatment for malignant hyperthermia is immediate administration of dantrolene sodium, with an initial dose of 2-3 mg/kg IV, as recommended by the most recent guidelines from the Association of Anaesthetists 1. When malignant hyperthermia is suspected, the following steps should be taken:

• Discontinue triggering agents (volatile anesthetics and succinylcholine) immediately
• Hyperventilate with 100% oxygen
• Administer dantrolene at an initial dose of 2-3 mg/kg IV, repeated until symptoms resolve, with a further 1 mg/kg every 5 min until treatment goals are reached, as recommended by the Association of Anaesthetists 1
• Supportive measures include active cooling (ice packs, cold IV fluids, lavage of body cavities), treating hyperkalemia with calcium, insulin/glucose, and sodium bicarbonate, managing acidosis with bicarbonate, correcting arrhythmias, ensuring adequate urine output (>1 mL/kg/hr), and monitoring for complications like compartment syndrome and disseminated intravascular coagulation
• After the acute crisis, continue dantrolene at 1 mg/kg IV every 4-6 hours for 24-48 hours to prevent recurrence, as recommended by the European Malignant Hyperthermia Group 1 Dantrolene works by inhibiting calcium release from the sarcoplasmic reticulum, interrupting the pathologic process where uncontrolled calcium release causes sustained muscle contraction, hypermetabolism, and heat production. Patients who have experienced malignant hyperthermia should be monitored in an ICU setting for at least 24 hours and require genetic counseling and testing for susceptibility, as recommended by the Association of Anaesthetists 1.

Some key points to consider in the management of malignant hyperthermia include:

• The importance of prompt recognition and treatment, as delay in commencing treatment is associated with increased mortality and the severity and number of complications 1
• The use of activated charcoal filters to adsorb inhalational anaesthetics, which should be available in every hospital where general anaesthesia is administered 1
• The need for active body cooling to reverse the malignant hyperthermia process, as a raised body temperature enhances muscle cell calcium release and sensitises the myofilaments to the effects of calcium causing generalised muscle rigidity, compromising perfusion and thereby delivery of dantrolene 1

From the FDA Drug Label

The use of Dantrolene Sodium for Injection in the management of malignant hyperthermia crisis is not a substitute for previously known supportive measures These measures must be individualized, but it will usually be necessary to discontinue the suspect triggering agents, attend to increased oxygen requirements, manage the metabolic acidosis, institute cooling when necessary, monitor urinary output, and monitor for electrolyte imbalance Monitoring for early clinical and metabolic signs of malignant hyperthermia is indicated because attenuation of malignant hyperthermia, rather than prevention, is possible. These signs usually call for the administration of additional intravenous dantrolene.

The treatment for malignant hyperthermia involves the use of dantrolene sodium in conjunction with supportive measures, including:

• Discontinuing suspect triggering agents
• Attending to increased oxygen requirements
• Managing metabolic acidosis
• Instituting cooling when necessary
• Monitoring urinary output
• Monitoring for electrolyte imbalance Administration of intravenous dantrolene is indicated to attenuate malignant hyperthermia, and additional doses may be necessary if signs of malignant hyperthermia appear 2.

From the Research

Treatment for Malignant Hyperthermia

• The primary treatment for malignant hyperthermia (MH) involves immediate discontinuation of the triggering anesthetics and administration of dantrolene sodium 3, 4, 5, 6, 7.
• Dantrolene is a specific antagonist that should be available wherever general anesthesia is administered 7.
• The dosage of dantrolene recommended is 2.5 mg/kg 6.
• Additional treatment includes managing complications related to the hypermetabolic response, such as hyperkalemia and arrhythmias 5.
• Hyperventilation with 100% oxygen is also crucial in the management of MH 3.

Management and Prevention

• Surgery should be canceled following the acute phase of MH, unless it is an emergency 3.
• The patient should be admitted to intensive care for at least 24 hours, and dantrolene should be continued as recurrence has been described 3.
• It is essential to counsel the patient and their family, provide Medalert bracelets, and encourage registration with the Malignant Hyperthermia Association of the United States (MHAUS) 3.
• Diagnostic testing, such as the caffeine/halothane testing of muscle biopsies or DNA screening, can help identify individuals susceptible to MH 3, 6, 7.

Importance of Prompt Recognition and Treatment

• Prompt recognition and treatment of MH are vital to prevent morbidity and mortality 5.
• The syndrome is likely to be fatal if untreated 7.
• Increased understanding of the clinical manifestation and pathophysiology of the syndrome has led to a decrease in mortality from 80% thirty years ago to <5% in 2006 7.