Malignant Hyperthermia FAQ
MH Frequently Asked Questions
What is a Malignant Hyperthermia (MH) crisis?
A Malignant Hyperthermia (MH) crisis can occur when a susceptible patient is exposed to triggering anesthesia agents.
This exposure can lead to deranged muscle function, producing muscle rigidity, very high fever, deranged function or failure of other organs (kidney, lung), abnormal blood clotting and other life threatening complications.
If treatment with dantrolene and other measures is not started promptly, up to 7 out of 10 patients may die from a MH-crisis and its complications.
How common is Malignant Hyperthermia (MH)?
It is unknown how many people in the U.S. are susceptible to Malignant Hyperthermia since most of them are otherwise healthy.
A MH-crisis during anesthesia is a rare event; it is estimated to occur once in 15,000 anesthetics in children and once in 50,000 anesthetics in adults.
However, if a person is known to be susceptible, anesthesia with triggering agents must be avoided at all times.
Who gets Malignant Hyperthermia (MH)?
Susceptibility to MH is an inherited condition.
Presently it is unclear how many people in the U.S. actually have this condition, because they are otherwise healthy and do not have any symptoms as long as they are not exposed to triggering anesthesia agents.
If a person is susceptible to MH each of his/her children has a 50% chance to inherit this condition.
What is Dantrolene?
Dantrolene was introduced in the U.S. in 1979 as a treatment for MH. Today it is still the first-line drug to treat a MH-crisis.
Dantrolene is given through an intravenous line and is thought to reverse the effects of triggering agents on muscle function, thereby interrupting a chain of events that otherwise would likely lead to serious damage to multiple organ system and possibly death in the untreated patient.
If dantrolene therapy is started promptly in a MH-crisis, the risk of complications or death is substantially reduced.
What are "trigger" agents?
Trigger agents are drugs used to give general anesthesia that can cause an MH-crisis in a susceptible person.
Trigger agents do not necessarily trigger a crisis every time a susceptible patient comes in contact with them. That means an uneventful anesthetic in the past does not rule out MH-susceptibility.
Trigger agents currently in use in the U.S. are:
- Anesthesia gases: Halothane, Enflurane, Isoflurane, Sevoflurane, Desflurane
- Muscle relaxants: Succinylcholine
What are "non-triggering" agents or alternative anesthesia techniques?
Simply put: any anesthesia agent that is not a trigger agent. A few of the most commonly used are: propofol, thiopental, nitrous oxide, fentanyl, midazolam, vecuronium, and many others.
Alternative techniques avoid general anesthesia and trigger agents. Examples include: spinal & epidural anesthesia, nerve blocks and local anesthetics.
Why not use "non-triggering" agents for all patients?
The so-called triggering agents are used in thousands of patients every day, and they are generally very safe with the exception of the rare patient with susceptibility to MH. Therefore it would not be practical to avoid these agents in all patients, regardless, since an MH-crisis is such a rare occurrence in the operating room (as rare as 1 out of 50,000 anesthetics)
Also, under certain circumstances many anesthesiologists may prefer using one of the triggering agents provided the patient is not MH-susceptible.
Is Malignant Hyperthermia (MH) associated with any other medical condition?
People with certain rare neuromuscular diseases have a high likelihood of also being susceptible to MH. Examples of those diseases are central core disease and King-Denborough-Syndrome.
What is MHAUS?
MHAUS stands for "Malignant Hyperthermia Association of the United States."
MHAUS was founded in the mid-80s as a non-profit organization by individuals and professionals interested in MH.
MHAUS is active in the education of patients and healthcare providers about MH. It operates a medical identification bracelet program, a 24 hour phone hotline for health care professionals, and a register of MH-susceptible persons.