Malignant hyperthermia is a rare but life-threatening anesthetic complication. If there is a genetic predisposition, it is triggered by various trigger substances, including some anesthetics.
What is malignant hyperthermia?
According to Gradinmath, the cause of malignant hyperthermia is a genetic modification of receptors in skeletal muscle. Normally, skeletal muscle contracts by releasing calcium ions from the sarcoplasmic reticulum, a calcium store in skeletal muscle cells. When a muscle contraction is to be triggered, an electrical signal is transmitted to the muscle cell via the motor endplate.
This activates a voltage-dependent ion channel in the T-tubules, i.e. in special cell membrane protuberances. This ion channel is adjacent to a calcium channel of the sarcoplasmic reticulum. This in turn is called the ryanodine receptor. It will be opened later. Calcium now rushes into the cytosol, allowing contraction of the muscle’s myosin and actin filaments. This results in a contraction of the entire muscle.
If malignant hyperthermia is present, the receptors mentioned are altered due to a genetic predisposition in such a way that calcium is released in the muscle even when certain trigger substances, including narcotics, are administered. However, this is much stronger than normal. Therefore, the muscle fibers are activated excessively.
This excessive activation is very critical, because the calcium that has been released must then be transported back into the sarcoplasmic reticulum. In addition, the contractile elements actin and myosin have to separate from each other again. The body needs ATP as an energy supplier for these two regenerative processes. Due to the disproportionality, there is quickly a lack of energy in the muscle cells.
The free calcium ions greatly increase cell metabolism, which in turn causes increased oxygen turnover and increased carbon dioxide and heat production. Initially, the processes mentioned take place exclusively in the skeletal musculature, in the further course it comes to necrosis and muscle breakdown due to the continuously deteriorating ability to regenerate.
Furthermore, harmful carbon dioxide and lactate accumulate, which cause the body to become acidic. In connection with this, the body temperature rises, which in turn damages other organs. The heart musculature is not primarily affected by the pathological changes associated with malignant hyperthermia, but the processes mentioned also damage the heart over the course of the course, so that death from circulatory failure can occur.
Symptoms, Ailments & Signs
The clinical picture of malignant hyperthermia is characterized by severe metabolic derailment, particularly in the skeletal muscles. The other symptoms are very different. Depending on the point in time, the clinical picture presents itself differently and not all signs always appear. Early signs of malignant hyperthermia are an increased concentration of carbon dioxide in the exhaled air and an increase in heart rate.
Muscle rigidity, a spasm of the masseter muscle, a general lack of oxygen and overacidification of the body can also occur. Only later does the eponymous significant increase in body temperature set in. Finally, cardiac arrhythmias, a drop in blood pressure, muscle breakdown and increased potassium release can also occur. It is essential to pay attention to the early signs, since malignant hyperthermia leads to death if no countermeasures are taken.
Diagnosis & course of disease
Because the development of malignant hyperthermia is acutely life-threatening, the diagnosis must be made as early as possible and then effective therapy initiated immediately. In any case, priority is given to stopping the supply of triggering substances. Inhalation anesthetics are discontinued and the anesthesia is continued with intravenous drugs. Normally, these do not have any effect that triggers malignant hyperthermia.
As a rule, this disease leads to a life-threatening situation that must be treated immediately by a doctor. Since this complaint usually occurs directly with anesthesia, it can also be diagnosed immediately by a doctor and ultimately treated. Those affected suffer from an increased heart rate and also from an increased concentration of carbon dioxide in the air they breathe.
Muscle rigidity also occurs and the patients suffer from a lack of oxygen. The undersupply of the organs with oxygen can lead to severe damage to the internal organs, which is usually irreversible and can no longer be treated. In the worst case, the patient dies if the complaint is not treated immediately. It comes to heart problems and eventually to cardiac death.
This condition is treated with medication. This alleviates the symptoms and stabilizes the circulation. In most cases, complications only arise if treatment is not initiated early. If the treatment is successful, there is no reduction in life expectancy.
When should you go to the doctor?
Malignant hyperthermia is a complication of anesthesia. It is therefore not a disease whose symptoms occur in everyday life and thus indicate the need for treatment. Since the patient is already under medical supervision during anesthesia, there is no need for action on the part of the person concerned.
In addition, the patient was rendered unconscious during this phase. It is therefore not possible for him to point out existing complaints or irregularities of the vegetative nervous system. The changes occurring within the organism are noticed by the hospital staff present and immediately passed on to the attending physician.
Consultation with a doctor is necessary as soon as a blood relative in the family has been diagnosed with malignant hyperthermia. To clarify whether the disease was inherited, special examinations and tests should be carried out on the offspring. Before any surgical intervention, those affected with an existing genetic disposition must consult the doctor treating them. He should be informed in detail about the incidents within the family and existing test results should be presented.
Treatment & Therapy
A specific drug therapy is possible with the active substance dantrolene. This is a substance given intravenously that inhibits calcium release from the sarcoplasmic reticulum. This is how malignant hyperthermia is treated causally. At the same time, symptomatic therapy also takes place.
This includes stabilizing the circulatory system, balancing the body’s acidification, supplying electrolytes and, if present, treating cardiac arrhythmia. Hyperthermia, i.e. the increase in body temperature, is a late symptom. For this reason, active cooling of the body is only necessary later on. Cardiovascular monitoring should be performed at all times by invasive blood pressure recording via an arterial catheter. Once the patient has stabilized, it is imperative that he be monitored in the intensive care unit for some time.
Outlook & Forecast
Left untreated, malignant hyperthermia leads to premature death of the affected person. Various complaints occur at the same time, so that in addition to severe disorders of organic activity, an acute lack of oxygen is to be expected. For this reason, the affected person must receive medical care as soon as possible. If there are delays or no intensive medical care, the chances of survival are extremely low.
Prognosis improves if circulatory stabilization is initiated promptly. Blood pressure needs to be monitored and the sufferer needs a supply of electrolytes. If there are other diseases of the cardiac rhythm system, the prognosis worsens. The diseases can lead to significant complications and also cause the death of the patient. If the life-threatening condition can be averted, the person concerned must be hospitalized for some time. His state of health must be checked daily for several weeks so that irregularities or changes can be documented.
In some cases follow-up treatments are necessary so that the organism is adequately supplied. Nevertheless, those affected who have survived this health emergency can usually be released from treatment after a few months without any symptoms. This applies in particular if no other diseases are present. Otherwise, the prognosis worsens and the patient needs long-term medical monitoring by a doctor.
Various measures are taken today to prevent the development of malignant hyperthermia. For each planned anesthetic, a possible occurrence of malignant hyperthermia in the patient’s family is asked in a preliminary discussion. If there is a suspicion of a corresponding predisposition, further tests are carried out at least before planned interventions.
Two important test procedures are in the foreground: the in vitro contracture test and molecular genetic diagnostics. In the in vitro contracture test, a muscle biopsy is taken, which is then exposed to the trigger substances caffeine and halothane. If patients have a corresponding predisposition, the sample taken will contract as a result. This test represents the gold standard in the diagnosis of malignant hyperthermia.
In molecular genetic diagnostics, a blood sample is taken from the patient and examined for characteristic genetic changes. This method is less complex than the in vitro contracture test. However, it is not that accurate either. In summary, vigilance on the part of treating staff and prior testing if predisposed are the best ways to prevent malignant hyperthermia.
In the case of malignant hyperthermia, those affected are in a life-threatening situation that must be treated immediately by a doctor. The undersupply of oxygen can lead to serious damage to the internal organs. The damage usually cannot be repaired. If the complication is not treated immediately, the affected person usually dies quickly as a result.
Aftercare focuses on gently reintroducing the patient to normal life. In addition to medical check-ups, which should be carried out regularly, it is sometimes helpful to have constructive conversations with loved ones in the immediate vicinity. In this way, the mental stress can be reduced a little and a self-confident handling of the experience can be encouraged. If the attending doctor gives the okay, the patient can go about his daily routine independently again.
You can do that yourself
In the event of an acute outbreak of malignant hyperthermia (MH) as a result of anesthesia, the patient must be treated in intensive care to prevent a fatal outcome. In this state there is no possibility for self-medication or self-help.
However, the patient has the opportunity to help prevent an acute crisis. Since it is a genetic predisposition, the patient is obliged to inform the anesthesiologist prior to an operation if there is a family history of MH. The doctor should also be aware of any muscle disorders. For example, MH can occur as part of various myopathies such as central core myopathy, multiminicore myopathy, periodic hypokalemic paralysis or other muscle diseases. The patient should also tell the doctor about unusual symptoms such as muscle paralysis, muscle weakness or frequent muscle stiffness in an anamnesis interview before anesthesia is necessary.
For people who have already been tested, it is also advisable to present test results from an MH laboratory and, if possible, an MH ID card. The most reliable examination method is the in vitro contracture test (IVKT). Before a test, it is urgently necessary for the patient to contact the test center in writing or by telephone in order to clarify which documents and test results must be submitted. Since the muscle sample can only be examined when it is alive and fresh, the patient must also make an appointment on site after submitting all the necessary documents.