From the Guidelines
Malignant hyperthermia (MH) should be diagnosed and managed promptly with immediate discontinuation of triggering agents and administration of dantrolene sodium at 2-3 mg/kg IV, repeated until symptoms resolve, up to a maximum of 10 mg/kg, as recommended by the most recent guidelines from the Association of Anaesthetists 1.
Diagnosis of Malignant Hyperthermia
The diagnosis of MH is based on recognizing a hypermetabolic crisis during anesthesia, characterized by unexplained tachycardia, hypercapnia, muscle rigidity, hyperthermia, acidosis, and hyperkalemia. Definitive diagnosis requires the caffeine-halothane contracture test on muscle biopsy or genetic testing for RYR1 mutations.
Management of Malignant Hyperthermia
Management begins with immediate discontinuation of triggering agents (volatile anesthetics and succinylcholine) and administration of dantrolene sodium. Supportive care includes:
- Hyperventilation with 100% oxygen
- Active cooling measures (ice packs, cold IV fluids)
- Treatment of hyperkalemia (calcium gluconate, insulin/glucose, sodium bicarbonate)
- Management of arrhythmias
- Correction of acidosis
- Monitoring for complications like disseminated intravascular coagulation and acute kidney injury
Post-Acute Crisis Care
After the acute crisis, patients should be monitored in ICU for at least 24 hours, with dantrolene continued at 1 mg/kg IV every 4-6 hours. All MH-susceptible patients should be registered with the Malignant Hyperthermia Association, wear medical alert identification, and receive genetic counseling. Future anesthesia should avoid triggering agents and include prophylactic dantrolene consideration for high-risk procedures, as recommended by the European Malignant Hyperthermia Group 1.
Key Recommendations
- Dantrolene should be available wherever volatile anaesthetic agents are used 1
- Activated charcoal filters should be available at all locations where general anaesthesia is administered 1
- Patients at increased risk of developing malignant hyperthermia must not be exposed to potent inhalation anaesthetics or suxamethonium 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. In the anesthetic-induced malignant hyperthermia syndrome, evidence points to an intrinsic abnormality of skeletal muscle tissue. It is hypothesized that addition of dantrolene sodium to the "triggered" malignant hyperthermic muscle cell reestablishes a normal level of ionized calcium in the myoplasm.
Diagnosis of Malignant Hyperthermia:
- Monitoring for early clinical and metabolic signs of malignant hyperthermia is indicated
- Signs of malignant hyperthermia include increased oxygen requirements, metabolic acidosis, and electrolyte imbalance
Management of Malignant Hyperthermia:
- Discontinue the suspect triggering agents
- Attend to increased oxygen requirements
- Manage the metabolic acidosis
- Institute cooling when necessary
- Monitor urinary output
- Monitor for electrolyte imbalance
- Administer intravenous dantrolene sodium as directed 2
- The administration of additional intravenous dantrolene may be necessary in case of attenuated malignant hyperthermia 2
From the Research
Diagnosis of Malignant Hyperthermia
- Malignant hyperthermia (MH) is a genetic disorder of skeletal muscle cells affecting myoplasmic calcium homeostasis, which can present with nonspecific signs of a hypermetabolic reaction 3
- Clinical manifestations of MH include CO2 increase, tachycardia, haemodynamic instability, metabolic and respiratory acidosis, profuse sweating, hyperpyrexia, CPK increase, myoglobinuria, kidney failure, disseminated intravascular coagulation (DIC), and ending in cardiac arrest 4
- Definitive diagnosis is achieved by the exposure of muscle fibres to caffeine and halothane 4
Management of Malignant Hyperthermia
- Dantrolene is the only specific drug for the treatment of MH, and all institutions where general anesthesia is a daily routine should have a stockpile of this drug 5
- Rapid evaluation and rejection of alternative diagnoses can lead to a prompt diagnosis and treatment, significantly reducing complications 3
- Patients should be observed for a minimum of 24 hours after the reaction because of the possibility of recrudescence 3
- Survivors and their family members should be referred to a specialized MH centre for further testing and counselling 3
Treatment with Dantrolene
- Dantrolene sodium is a ryanodine receptor antagonist, and inhibits the release of intracellular calcium 4
- The amount of dantrolene that should be available in facilities where volatile agents are not available or administered is still a topic of debate 6
- After treatment of acute MH, the amount of dantrolene that should be administered and for how long is still a topic of debate 6
Anesthetic Care for Patients with Suspected Malignant Hyperthermia Susceptibility
- Patients with suspected MH susceptibility may be excluded from surgery at ambulatory centers, and anesthetic medication options are reduced 7
- Non-triggering anesthetic techniques should be utilized in patients with suspected MH susceptibility 7
- Improving the documentation of index cases of MH and increasing referrals to clinical geneticists and genetic testing may be a viable route to decreasing the proportion of suspected MHS patients with a poorly characterized risk profile 7