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What is Malignant Hyperthermia? Patients frequently have concerns and misunderstandings. Patients wonder what the disease is, if it could possibly strike them during anesthesia, and how the disease would be treated.
The word “malignant” in Malignant Hyperthermia has nothing to do with malignancy or cancer. Hyperthermia is the medical term for high temperature, and Malignant Hyperthermia, or MH, refers to an acute medical disorder associated with dangerously elevated body temperature. MH is rare, life threatening, and triggered by general anesthetic drugs. The disease runs in families. For this reason, if any of your ancestors or relatives died during anesthesia it’s important you reveal that fact to your anesthesiologist.
The inheritance is autosomal dominant, which means one of your parents must have had the disease for you to inherit it. To manifest MH, you must have both the gene for MH and also be exposed to one of the triggering anesthetic drugs. The triggering drugs are succinylcholine (a paralyzing drug/muscle relaxant) and the potent inhaled anesthetic gases sevoflurane, desflurane, isoflurane, or halothane.
The incidence of MH varies from 1:5000 to 1:100,000 anesthetics. Most MH cases appear during a patient’s first anesthetic, therefore most MH cases appear in children or young adults. I’ve performed 25,000 anesthetics over 30+ years, and none of my patients have developed MH. Nonetheless, every anesthesiologist must be knowledgeable and ready to diagnose and treat an MH crisis should one occur.
The clinical signs of MH are increased temperature, increased heart rate, increased breathing rate, and increased carbon dioxide production. These changes are caused by increased metabolism within muscle cells. The onset of MH causes individual muscle cells to become hypermetabolic, which leads to increased heat, increased carbon dioxide production, and acidosis in the bloodstream. As temperature increases, the heart beats faster and the lungs hyperventilate to blow off the excessive carbon dioxide and acid production from the muscle cells.
Early diagnosis can be difficult. There is no specific blood test to diagnose the disease. If a child receiving his first anesthetic develops a temperature of 104 degrees Fahrenheit, a heart rate of 180 beats per minute, and a respiratory rate of 60 breaths per minute, the diagnosis is apparent. As well, the patient’s jaw, trunk, or total body may become rigid. However, in some patients the initial presentation may only include increases in heart rate and respiratory rate, and high temperature may be a late sign.
A hallmark of diagnosis is evidence of increased carbon dioxide production. During surgery, anesthesiologists measure the carbon dioxide concentration of every breath you inhale and exhale. If the carbon dioxide concentration increases steadily in the context of increased heart rate and respiratory rate, with or without an increase in temperature, the anesthesiologist must suspect MH. Late clinical findings include hypertension, abnormal heart rhythms, poor blood supply to the extremities (skin turning bluish in color), and sudden unexpected cardiac arrest in children.
Blood tests drawn during MH show low pH (both metabolic and respiratory acidosis), elevated potassium, and elevated muscle enzymes (elevated CPK). The urine will become cola-colored (colored by myoglobin in the urine).
The emergency treatment for MH:
- Notify the surgeon. Stop the surgery as soon as possible.
- Call for help from all available MDs and RNs in the vicinity.
- Stop the triggering anesthetic drug(s).
- Administer dantrolene. Dantrolene is a specific inhibitor of the MH cascade within the muscle cells. All anesthetizing locations are required to have a supply of dantrolene on site. The drug is manufactured in a powdered form, and must be mixed with sterile water to form an injectable solution. Large doses of dantrolene (2.5 mg/kg, which is 8 vials of dantrolene powder for an average-sized man) must be given IV as soon as possible. Doses may be repeated as needed, for a total dose up to 30 mg/kg if necessary.
- Administer sodium bicarbonate IV to buffer acidosis.
- Cool the patient. This can be done by applying bags of cold fluid to the skin surface, administering cold IV fluids, or by immersion of the body into an ice bath if available.
- Treat abnormal heart rhythms with appropriate IV cardiac drugs.
- Treat elevated potassium levels with hyperventilation, and empiric administration of calcium chloride, insulin, and glucose IV.
- Draw blood tests for electrolyte levels/arterial blood gas determinations, insert a catheter into the bladder to monitor urine output, and insert a catheter into the radial artery at the wrist to monitor blood pressure and for intravascular access for rechecking the levels of acidosis and potassium in the blood.
- Prepare for transfer to an intensive care unit.
If a family member of yours died during anesthesia and you don’t know if they died because of MH, your doctor may advise you to have a muscle biopsy to determine if you are MH susceptible. This biopsy of the anterior thigh muscle (quadriceps) is done under local anesthesia. You are not at risk of developing MH during local anesthesia.
If a family member of yours died during anesthesia and you don’t know if they died because of MH, and you choose not to undergo a muscle biopsy, you should wear a MedicAlert bracelet that states that you are susceptible to Malignant Hyperthermia, and all your anesthetic care should be done with trigger-free anesthetics (as listed below).
If you have a positive muscle biopsy test for MH, or if a family member of yours had well-documented MH, you should wear a MedicAlert bracelet that states you are susceptible to Malignant Hyperthermia, and all your anesthetic care should be done with trigger-free anesthetics (as listed below).
A trigger-free anesthetic includes no succinylcholine, sevoflurane, isoflurane, desflurane, or halothane. A trigger-free anesthetic includes any of the following:
- Local anesthesia, with or without sedation with IV drugs such as Versed, fentanyl, or propofol.
- Regional anesthesia, such as spinal anesthesia, epidural anesthesia, or a regional nerve block, with or without sedation with IV drugs such as Versed, fentanyl, or propofol.
- A general anesthetic without succinylcholine, sevoflurane, isoflurane, or desflurane. A typical recipe would include all intravenous drugs, e.g. Versed as a premed, propofol for anesthetic induction, rocuronium for paralysis/muscle relaxation, fentanyl or remifentanil infusion for pain relief, and possibly ketamine. The gas nitrous oxide can also be used.
In the 1980’s, prior to the availability of dantrolene, the mortality from an MH episode was greater than 80%. In the 21st century, the mortality from an MH episode should be less than 5%.
For further information, I refer you to http://www.mhaus.org, the website of the Malignant Hyperthermia Association of the United States.
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Published in September 2017: The second edition of THE DOCTOR AND MR. DYLAN, Dr. Novak’s debut novel, a medical-legal mystery which blends the science and practice of anesthesiology with unforgettable characters, a page-turning plot, and the legacy of Nobel Prize winner Bob Dylan.
In this debut thriller, tragedies strike an anesthesiologist as he tries to start a new life with his son.
Dr. Nico Antone, an anesthesiologist at Stanford University, is married to Alexandra, a high-powered real estate agent obsessed with money. Their son, Johnny, an 11th-grader with immense potential, struggles to get the grades he’ll need to attend an Ivy League college. After a screaming match with Alexandra, Nico moves himself and Johnny from Palo Alto, California, to his frozen childhood home of Hibbing, Minnesota. The move should help Johnny improve his grades and thus seem more attractive to universities, but Nico loves the freedom from his wife, too. Hibbing also happens to be the hometown of music icon Bob Dylan. Joining the hospital staff, Nico runs afoul of a grouchy nurse anesthetist calling himself Bobby Dylan, who plays Dylan songs twice a week in a bar called Heaven’s Door. As Nico and Johnny settle in, their lives turn around; they even start dating the gorgeous mother/daughter pair of Lena and Echo Johnson. However, when Johnny accidentally impregnates Echo, the lives of the Hibbing transplants start to implode. In true page-turner fashion, first-time novelist Novak gets started by killing soulless Alexandra, which accelerates the downfall of his underdog protagonist now accused of murder. Dialogue is pitch-perfect, and the insults hurled between Nico and his wife are as hilarious as they are hurtful: “Are you my husband, Nico? Or my dependent?” The author’s medical expertise proves central to the plot, and there are a few grisly moments, as when “dark blood percolated” from a patient’s nostrils “like coffee grounds.” Bob Dylan details add quirkiness to what might otherwise be a chilly revenge tale; we’re told, for instance, that Dylan taught “every singer with a less-than-perfect voice…how to sneer and twist off syllables.” Courtroom scenes toward the end crackle with energy, though one scene involving a snowmobile ties up a certain plot thread too neatly. By the end, Nico has rolled with a great many punches.
Nuanced characterization and crafty details help this debut soar.
Click on the image below to reach the Amazon link to The Doctor and Mr. Dylan:
LEARN MORE ABOUT RICK NOVAK’S FICTION WRITING AT RICK NOVAK.COM BY CLICKING ON THE PICTURE BELOW: