Malignant Hyperthermia Vanessa Bone PA Dr. Masson Dr. Liao

Definition MH is a life-threatening pharmacogenetic disorder triggered by the administration of commonly used volatile anesthetics, the depolarizing muscle relaxant succinylcholine, or both . It is characterized by a hyper metabolic response to potent inhalation agents and succinylcholine resulting in increased CO2 production, oxygen consumption, fever, tachycardia, tachypnea, acidosis, hyperkalemia, increased CPK’s and myoglobinuria, MH is a genetic condition that when a person is given certain anesthetics, their body reacts ina certain way. The problem with MH is that you can not tell from outward appearences weather a patient is a risk for MH. Unfortunatly some of the best drugs are the ones that can cause MH. Elevation in body temp, muscle rigidity, sweating. Once this syndrome appears, it can progress very rapidy 15-30 minutes and you can go to a normal body temo to a body temo that can cause irreversible damage. It must be turned around immediately. Anesthesiaologists work nightmare.

Incidents 1 in 15,000 pediatric anesthetics 1 in 50,000 adult anesthetics Incidence has an apparent geographic variation – more prevalent in US 2/3 of susceptible patients manifest this syndrome during their first anesthetic The incidence of anesthetic-related episodes of MH is between 1 in 15,000 in children and 1 in 50,000 in adults

Genetics of MH Three modes of inheritance : Autosomal dominant Autosomal recessive Unclassified Dx: invasive muscle biopsy testing Since most often MHS is inherited as a dominant trait, when MH is diagnosed in one family member, all first-degree relatives are treated as MHS, despite there being only a 50% probability of transmission of a mutant gene in each individual case To diagnose an individual’s risk of MHS invasive muscle biopsy testing remains the gold standard for determining MH suseptibility

Anesthetic Agent Choice for the MH-Susceptible Patient The following anesthetic agents are known triggers of MH and are not safe for use in MH-susceptible patients: Unsafe Anesthetic Agents for MHS Patients   Inhaled General Anesthetics Desflurane Enflurane Ether Halothane Isoflurane Methoxyflurane Sevoflurane Depolarizing Muscle Relaxants Trigger MH Succinylcholine All other anesthetic agents outside of these two categories of Volatile anesthetic agents and depolarizing muscle relaxants are considered safe

Signs of Malignant Hyperthermia EARLY -Tachycardia -muscle rigidity (masseter spasm) -myotonia -cardiac arrythmias -steadily increasing end tidal CO2 levels -severe respiratory and metabolic acidosis LATE Muscle breakdownIncreased CPK levels – 20,000 I.U. myoglobinuria It’s highly variable, but there is strong evidence that fulminant MH episodes result from a very rapid rise in myoplasmic calcium caused by fundamental defect in the ability of muscle to regulate calcium (2). A fulminant MH episode consists of a hypermetabolic crisis manifesting as metabolic and respiratory acidosis, tachycardia, cardiac arrhythmias, skeletal muscle rigidity, and rhabdomyolysis.

Treatment Get Help, Call 911, Get Dantrolene, Notify the Surgeon D/c volatile agents and succinycholine Hyperventilate* Halt the procedure ASAP if possible Bicarb 1-2mEq/kg Cool the patient. If body temp is > 39 Celsius, lavage open body cavities, stomach, bladder or rectum. Apply Ice to surface. Infuse cold saline IV. Stop cooling once temp is <38 Celsius Monitor ETCO2, electrolytes, blood gases, CK, core temp, urine output, urine color, coags *note: Do not give calcium channel blockers Glucose, insulin and calcium should be available to treat hyperkalemia, bicarbonate to treat metabolic acidosis and a diuretic to maintain urinary output *100% O2 at flows of 10 L/min or more

Dantrolene 2.5 mg/kg large bore IV Or 1mg/lb Dissolve the 20 mg in each vial with at least 60 ml sterile H20 Repeat until signs of MH are reversed (able to give up to 30mg/kg)

Muscular Dystrophies Duchenne’s Becker’s Evan’s Central core disease Exercise-induced rhabdomyolysis Hypokalemic periodic paralysis NOT neuroleptic malignant syndrome Patients with muscular dystrophy and mytonia may have adverse reactions to triggering medications

Prevention of MH Get Hx of MH susceptibility, muscle diseases, family anesthesia problems CO2 and temperature monitoring during anesthesia Recognition of masseter rigidity Investigation of unexplained tachycardia, hypercarbia and hyperthermia

Pre-op Questioning is there a family or personal history of MH and/or any known atypicalresponse to anesthesia Is there a family history or personal history of a muscle or neuromuscular disorder (e.g.,muscle weakness, serious muscle cramps, etc.)? Have there been unexpected deaths or complications arising from anesthesia (including within the dental office) with any family members or blood relatives Is there a personal history of dark or cola colored urine immediately following anesthesia or serious exercise Is there a personal history of unexplained and unanticipated high fever either during or within the first several hours following surgery Is there a personal history or family history of high temperature or death during exercise

North American MH Hotline Emergency: 1-800-MH-HYPER 24/7 Routine: 1-800-98-MHAUS Registry: 1-888-274-7899 http://www.mhaus.org http://www.mhreg.org