Malignant Hyperthermia


 
BACKGROUND:
 
Malignant hyperthermia is a potentially fatal syndrome.etic; 
Although the incidence of the MH trait in the general 
population is quite low, reportedly ranging from 1:4,500 
(when succinylcholine is used) to 1:60,000 anesthetics, the 
incidence varies depending on the prevalence of the gene(s) 
for MH in any given geographic area, the type of general 
anesthetic given and a multitude of patient factors. MH is 
reported worldwide and affects all racial groups; however, it 
is rare in infants and the incidence decreases after 50 years 
of age. Most cases occur in children and young adults. Males 
are more frequently affected than females, although this may 
be related to other demographic factors such as the incidence 
of emergency surgery in this group.
 
It is characterized by a rapid elevation of temperature as 
high as 42.8 C to 44 C (109 F to 111 F).  The complication is 
triggered by the anesthetic agent.  The patient with the 
tendency to be affected apparently has an inherited defect in 
the muscle cell membrane allowing the above chemicals to 
trigger a sudden release of calcium within the muscle cells. 
The increased amount of calcium sets off a series of 
biochemical reactions that increase the patient's metabolic 
rate, eventually liberating heat.  Muscle contractures also 
increase, liberating more heat.
 
Symptoms of malignant hyperthermia include elevated end-tidal 
CO2, rigidity, tachycardia, hypercarbia, tachypnea, cardiac 
dysrhythmia, respiratory and metabolic acidosis, fever, 
unstable/rising blood pressure, cyanosis/mottling of the skin 
and myoglobinuria. 


 
 
None of the agents known to be Malignant Hyperthermia 
triggers are currently in use in this facility.  The protocol 
for management of a Malignant Hyperthermia episode is 
included to raise consciousness in the medical industry of 
Malignant Hyperthermia Syndrome.
 
The following (2) questions have been recorded from the 
Malignant Hyperthermia Association of the United States 
(MHAUS): www.mhaus.org
 
WHAT DRUGS TRIGGER MH?
 
The volatile gaseous inhalation anesthetics (e.g., halothane, 
enflurane, isoflurane, sevoflurane and desflurane, 
methosyflurane, cylopropane) are MH triggers, as is the 
depolarizing muscle relaxant succinylcholine.
 
ARE OTHER ANESTHETICS SAFE?
 
Yes, Some examples of safe anesthetics are: local 
anesthetics, narcotics, propofol, thiopental, curare, 
atracurium
 
POLICY:
 
The prescribed protocol recommended by the Malignant 
Hyperthermia Association of the United States will be 
immediately implemented to reverse malignant hyperthermia.  
Patients will be transferred as soon as possible to an acute 
facility for continuing specialized treatment.
 
Medical protocol (from MedicAlert & Malignant Hyperthermia 

 
Association of the United States) is attached.
 
Acute Phase Treatment:
 
1.  GET HELP.  GET DANTROLENE.  Immediately discontinue all 
    volatile inhalation anesthetics and succinylcholine.  
    Hyperventilate with 100% oxygen at high gas flows; at 
    least 10 L/min.  The circle system and CO2 absorbent need
    not be changed.
 
2.  Administer dantrolene sodium 2.5 mg/kg bolus rapidly.  
    Continue bolus administration as needed until signs of MH
    (e.g. tachycardia, rigidity, increased end-tidal CO2, and
    temperature elevation) are controlled.  Occasionally, a 
    total dose greater than 10 mg/kg may be needed.  Each 
    vial of dantrolene contains 20 mg of dantrolene and 3 
    grams mannitol.  Each vial should be mixed with 60 mL of 
    sterile water for injection USP without a bacteriostatic 
    agent.
 
3.  Administer bicarbonate to correct metabolic acidosis as 
    guided by blood gas analysis.  In the absence of blood 
    gas analysis, 1-2 mEq/kg should be administered.
 
4.  Simultaneous with the above, actively cool the 
    hyperthermic patient.  Use IV iced saline (not Ringer's 
    lactate) 15 mL/kg q 15 min X 3.
 
    A.  Lavage stomach, bladder, rectum and open cavities 
        with cold saline as appropriate.
    B.  Surface cool with ice and hypothermia blanket.
    C.  Monitor closely since overvigorous treatment may lead
        to hypothermia.

 
 
5.  Dysrhythmias will usually respond to treatment of 
    acidosis and hyperkalemia.  If they persist or are life 
    threatening, standard anti-arrhythmic agents may be used,
    with the exception of calcium channel blockers (may cause
    hyperkalemia and CV collapse).
 
6.  Determine and monitor end-tidal CO2, arterial, central or
    femoral venous blood gases, serum potassium and other 
    electrolytes, urine output, PT/PTT and calcium for 
    baseline values.  Repeat as clinically indicated.
 
7.  Hyperkalemia is common and should be treated with 
    hyperventilation, bicarbonate, intravenous glucose and 
    insulin (10 units regular insulin in 50 mL 50% glucose 
    titrated to potassium level or 0.15 u/kg regular insulin 
    in 1 cc/kg 50% glucose).  Life threatening hyperkalemia 
    may also be treated with calcium administration (e.g. 2-5
    mg/kg of CaCl2).  Check blood glucose every two hours if
    insulin has been given.
 
8.  Ensure urine output of greater than 2 mL/kg/hr by 
    hydration and/or administration of mannitol or 
    furosemide.  Consider central venous or PA monitoring 
    because of fluid shifts and hemodynamic instability which
    may occur.
 
9.  Sudden Unexpected Cardiac Arrest in Children: 
    Children less than about 10 years of age who experience 
    sudden cardiac arrest after succinylcholine in the 
    absence of hypoxemia should be treated for acute 
    hyperkalemia first.  In this situation, calcium chloride 
    should be administered along with other means to reduce


 
    serum potassium.  They should be presumed to have 
    subclinical muscular dystrophy.
 
 
 
Post-Acute Phase
 
1.  Observe the patient in an ICU setting for at least 24 
    hours since recrudescence of MH may occur.
 
2.  Administer Dantrolene 1 mg/kg IV q 4-6 hours for 24-48 
    hours post episode. 
 
3.  Follow ABG, CK, potassium, urine and serum myoglobin, 
    clotting studies and core body temperature until such 
    time as they return to normal values (e.g. q 6 hours).  
    Central temperature (e.g. rectal, esophageal) should be 
    continuously monitored until stable.
 
4.  Counsel the family and patient regarding MH and further 
    precautions.  Refer the patient to MHAUS.  Fill out an 
    Adverse Metabolic Reaction to Anesthesia (AMRA) report 
    available through MHAUS.
 
CAUTION; THIS PROTOCOL MAY NOT APPLY TO EVERY PATIENT AND 
MUST OF NECESSITY BE ALTERED ACCORDING TO SPECIFIC PATIENT 
NEEDS
 
NOTES:    Names of on-call physicians available to consult in MH 
emergencies may be obtained 24 hours a day through:  MHAUS 
EMERGENCY HOTLINE, 800/644-9737 OR by calling Medic Alert 
Foundation International, 209/634-4917, ask for Index Zero.
 

 
For non-emergency information and patient referrals, contact: 
 
 
Malignant Hyperthermia Assn of the United States (MHAUS), 
800/986-4287; PO Box 1069, Sherburne NY 13460-1069.  
E-mail: mhaus@norwich.net; Web site: www.mhaus.org; 
MH info-by-fax: 800/440-9990.
 
Approved By Governing Board    
EP.4    
Control #76.3
GUPTA GASTRO