Malignant Hyperthermia

Malignant hyperthermia (MH) is a rare but life-threatening medical emergency that can occur during general anesthesia with certain volatile anesthetics and depolarizing muscle relaxants. It is characterized by an uncontrollable rise in body temperature, muscle rigidity, and other systemic symptoms.

Causes and Risk Factors

MH is usually triggered by the use of specific anesthetic agents, including:

• Volatile anesthetics such as halothane, isoflurane, sevoflurane, and desflurane
• Depolarizing muscle relaxants like succinylcholine

Individuals with a family history of MH or certain genetic conditions, such as central core disease or King-Denborough syndrome, are at increased risk of developing the condition.

Symptoms

The symptoms of malignant hyperthermia can develop rapidly and may include:

• Rapid rise in body temperature (often exceeding 109°F)
• Muscle rigidity or stiffness
• Masseter muscle spasm (trismus)
• Tachycardia (rapid heart rate) and tachypnea (rapid breathing rate)
• Hypertension (high blood pressure)
• Metabolic acidosis (elevated levels of lactic acid in the blood)

Diagnosis

The diagnosis of malignant hyperthermia is primarily clinical, based on the presence of characteristic symptoms during anesthesia. Laboratory tests may be used to support the diagnosis and monitor the patient's condition, including:

• Arterial blood gas analysis to assess oxygenation and acid-base balance
• Complete blood count (CBC) to evaluate for signs of muscle damage or coagulopathy
• Creatine kinase (CK) levels to assess muscle damage

Treatment

The treatment of malignant hyperthermia involves immediate discontinuation of the triggering anesthetic agent, administration of dantrolene, and supportive care measures to manage the patient's symptoms and prevent complications. Specific interventions may include:

• Discontinuing the volatile anesthetic or depolarizing muscle relaxant
• Administering dantrolene (a specific antidote for MH) intravenously
• Providing oxygen therapy and ventilatory support as needed
• Controlling body temperature with cooling measures (e.g., ice packs, cooling blankets)
• Managing cardiovascular instability with fluids, vasopressors, or anti-arrhythmic medications

Prevention

To minimize the risk of malignant hyperthermia, it is essential to:

• Obtain a thorough medical history, including any family history of MH or genetic conditions that may increase the risk
• Avoid using triggering anesthetic agents in susceptible individuals
• Have dantrolene readily available in the event of an MH emergency
• Monitor patients closely during anesthesia for signs of MH

Prognosis and Outcome

The prognosis for malignant hyperthermia depends on prompt recognition and treatment. With timely intervention, the mortality rate can be significantly reduced. However, delayed or inadequate treatment can lead to severe complications, including:

• Cardiac arrest
• Respiratory failure
• Renal failure
• Disseminated intravascular coagulation (DIC)
• Death