Preventing MH - An Anesthesia Protocol
This protocol is intended as a guide for anesthesia
practioners and other health care professionals to be
prepared to recognize, treat and prevent malignant
ROUTINE PRE-OPERATIVE QUESTIONING
All patients about to undergo general anesthesia should
be asked these specific questions as part of a medical
- Is there a family history of MH?
- Have there been unexpected deaths or complications
arising from anesthesia (including the dental office)
with any family members?
- Is there a personal history of a muscle disorder
(e.g. muscle weakness)?
- Is there a personal history of dark or cola-colored
urine following anesthesia?
- Is there a personal history of unexplained high fever
The following precautions should be taken in order to
detect MH in its early stages, when it is usually
amenable to treatment without sequelae:
- A written treatment plan should be posted in a
conspicuous place. A plan is available from MHAUS.
- A kit or cart containing drugs necessary for the
treatment of MH should be immediately available to all
operating rooms. Each kit should contain 36 vials of
water for injection, and bicarbonate. MHAUS offers a
brochure listing the recommended supplies.
- A refrigerator unit near the operating room should be
stocked with iced saline. Ready access to an ice
machine is important.
- All operating and recovery room personnel should be
trained in the recognition and treatment of MH.
Periodic dry-runs of an MH emergency are recommended.
In-service materials can be provided by MHAUS.
- Evaluate any unexpected hypercarbia, tachycardia,
tachypnea or arrhythmia (e.g. arterial and venous blood
gases). Avoid suppressing tachycardia with beta
blockers until MH has been ruled out.
- Core temperature should be monitored in all patients
given general anesthesia for 30 minutes or more.
Acceptable core temperature sites include: distal
esophagus, nasopharynx, axilla, rectum, bladder and
pulmonary artery. Skin temperature may not adequately
reflect core temperature during MH episodes. Consider
MH in the differential diagnosis of any temperature
- Stop inhalation anesthetic and succinylcholine if
masseter rigidity occurs. If surgery must continue,
immediately switch to non-triggering anesthetics.
- Do not give triggering agents to patients with
Duchenne Dystrophy, Central Core Disease, Myotonia and
other forms of muscular dystrophy.
- Sudden cardiac arrest in a young male with normal
oxygenation should be considered as secondary to
hyperkalemia and so treated.
TREATING THE KNOWN OR SUSPECTED MH-SUSCEPTIBLE PATIENT
- Anesthesia machine:
- Remove vaporizers, if possible. Otherwise, drain
and disconnect or tape in the off position.
- Flow 10 L/m O2 through circuit for at least 20
minutes. If fresh gas hose is replaced, 10 minutes
is adequate. During this time a breathing bag
should be attached to the Y-piece of the circle
system and the ventilator set to inflate the bag.
- Use new or disposable breathing circuit.
- Take a preoperative creatine kinase (CK) and CBC.
- Place a cooling blanket on the table.
NOTE: Dantrolene can worsen
muscle weakness in patients with muscle disease and should be used with
caution. For procedures with local anesthesia only,
dantrolene prophylaxis may be omitted.
- Dantrolene prophylaxis should be
considered on an
individual patient basis but is not recommended for
most MH susceptibles. When used, dosage is 2.5 mg/kg
IV starting 30 minutes prior to anesthesia. For
consultation, contact MHAUS.
- Techniques of choice
- Spinal, epidural, regional or local, if possible.
- Safe drugs
- Local: No local anesthetics trigger MH; thus
any type of regional anesthesia is safe for MH
- General: Benzodiazepines, opioids,
barbiturates, propofol, ketamine, nitrous
oxide, etomidate. Pancuronium, atracurium,
vecuronium, pipecuronium, mivacurium,
doxacurium, or curare may be used for
relaxation. Neostigmine and atropine are used
for reversal by some; others disagree on their
- Unsafe drugs/MH triggers
- Halothane, Enflurane, Isoflurane, Desflurane,
Methoxyflurane, Ether, Cyclopropane,
- Essential: blood pressure, central
temperature, ECG, pulse oximeter, and
capnograph or capnometer
- Strongly suggest respirometer
- Use arterial line, CVP or other invasive
monitors as appropriate for the surgery
- If the anesthetic course has been uneventful:
- Continue to monitor temperature and ECG for 1
to 2 hours. No further dantrolene is
- If MH has occurred:
- Recover patient in an ICU for 24-48 hours.
- Continue IV dantrolene for 48-72 hours,
titrated to alleviation of muscle rigidity,
tachycardia, acidosis, and CK levels. Suggested
dantrolene dosage is at
least 1 mg/kg q 6 hours IV.
After that, 1 mg/kg may be given q 6 hours orally x
- Monitor the patient's coagulation status,
watching for DIC.
- Look for myoglobinuria and renal failure, and treat as
- Use potassium-containing solutions with caution.
- Monitor potassium and CK levels q 6 hours at least.
- Monitor urine output.
- Register patient with North American MH Registry.
Forms are available by contacting North American MH
Registry, Pennsylvania State University, College of
Medicine, Dept of Anesthesia, PO Box 850, Hershey, PA
17033-0850, (717) 531-6936.
- Alert family to the dangers of MH in other family
- Refer for testing at nearest center (list
available from MHAUS).
Names and phone numbers of on-call anesthesiologists
available to consult in MH emergencies may be
obtained 24 hours a day through:
MEDIC ALERT FOUNDATION INTERNATIONAL
(209) 634-4917 Ask for Index Zero
This brochure was written and produced by the MALIGNANT
HYPERTHERMIA ASSOCIATION OF THE UNITED STATES (MHAUS).
MHAUS serves MH-susceptible individuals and medical
professionals. MHAUS is a non-profit organization
under IRS code 501(c)(3). Its services are provided
free. It operates solely on contributed funds. All
contributions are tax-deductible and should be sent to:
PO Box 1069
Sherburne, NY 13460-1069
This protocol may not apply to every patient and must
of necessity be altered according to specific patient