Malignant Hyperthermia
Malignant Hyperthermia
• Is an inherited disease
• Is an autosomal dominant trait-only 1 parent can
carry the trait to pass on disease to child
• In most cases, MH is caused by defect in the
ryanodine receptor.
MH Affects
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Humans
Certain pig breeds-autosomal recessive
Dogs
Horses
And other animals
Support Group
• WWW.MHAUS.ORG
• 1-800-644-9737-Hotline for Medical
Professionals
• Caffeine Halothane Contracture Test- “Gold
Standard” for determining if patient is at risk
for MH
MHAUS Recommendations
• Should have 36 vials of Dantrolene available for
MH crisis
• Glucose, insulin, and calcium should be available
to treat hypercalemia, bicarb to treat metabolic
acidosis and diuretics to maintain urine output.
Diagnostic Test Available
• Muscle Contracture Test: Caffeine Halothane
Contracture Test (CHCT)
• Genetic Testing (Ryanodine Receptor [RYR1]
gene sequencing
Muscle Contracture Testing
• Gold Standard
• Cost $6-10K
• 30 Approved Centers in World, 6 in US-Must be
performed at an approved MH Muscle Biopsy Center
• Requires 3-4 inch muscle biopsy taken from thigh,
patient receives general anesthesia, but no local at
biopsy site.
• Abnormally high levels or contractile force indicate MH
suceptibility
• Close to 100% accuracy, false negatives are rare.
Genetic Testing
• Involves isolation of DNA from patient (blood, muscle
cells, or other tissue sample)
• RYRI (ryanodine receptor) found, there are currently
29 MH causative RYRI mutations.
• Presence of causative mutation in RYRI gene is
diagnostic for MH susceptibility.
• Sensitivity based on population selected and
methodology of testing utilized.
• Cost: $800-4000K, some insurance companies may pay
for genetic testing.
Genetic Testing
Pros
• Pros
Less expensive than muscle biopsy testing
Less invasive than muscle biopsy testing
No need to travel to an approved center
If causative mutation found in family member,
other members can have predictive testing
carried out with high degree of accuracy,
without need for muscle biopsy.
Genetic Testing
Cons
• Absence of causative mutation does not rule out
MH susceptibility.
• Muscle contracture test would be needed to
confirm the individual is not susceptible to MH.
• Expensive
• Insurance may not cover testing expenses.
Unsafe Drugs
• Depolarizing muscle relaxants
• Potent inhalational agents (halothane,
isoflurane,
• Enflurane, desflurane, sevoflurane)
Safe Drugs
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Antibiotics
Antihistamines
Antipyretics
Barbiturates (thiopental methoexital)
Droperidol
Ketamine (inherent circulatory effects may mimic MH)
Local anesthetics (lidocaine, bupivacaine)
Nitrous oxide
Nondepolarizing muscle relaxants(pancuronion,
Rocuronium, vecuronium)
Opioids (morphine, mepiridine)
Propofol
Propranolol
Vasoactive drugs
Clinical Manifestations of MH
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Hypercarbia (most sensitive indicator of MH in OR)
Tachycardia
Tachypnea
Temperature elevation (usually late sign of MH)
Hypertension
Cardiac dysrhythmias
Acidosis
Hypoxemia
Hyperkalemia (should be considered 1st in cardiac
Arrest)
Skeletal muscle rigidity (most specific sign)
Myoglobinuria
Treatment for MH
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1. Call for assistance, management is involved,
Difficult for one person.
2. Stop triggering agents!
3. Hyperventilate patient with 100% 02.
4. Finish or abort surgical procedure.
5. Adminster Dantrolene (2.5 mg/kg bolus;
May repeat 2 mg/kg every 5 minutes, then 1-2 mg/kg/h)
6. Cool patient with cold IV NS, cold body lavage,
Cold NG lavage, cooling blankets.
7. Change to a clean circuit not exposed to volatile
Agents.
8. Monitor/treat acidosis, monitor ABG’s and administer sodium bicarbonate.
9. Promote urine output (lasix, mannitol)
10. Treat hyperkalemia
11. Treat dysrhythmias with procainamide and
Calcium chloride.
12. Monitor creatinine kinase, urine myoglobin, and
Coags for 24-48 hours.
Antidote for MH
• Dantolene
• FDA approved in less than 7 months
• Is a proven skeletal muscle relaxant, inhibiting
the release of calcium from the sarcoplasmic
reticulum in skeletal muscle.
• IV administration used in most major countries
around the globe.
• Dantrolene has dramitically reduced mortality
from MH.
Mortality Rates
• Within 30 years, 80% mortality rate has dropped
to less than 5% today!