Last Updated: 7/1/2005
This protocol is intended as a guide for anesthesia care providers and other health care professionals to be prepared to recognize, treat and prevent malignant hyperthermia (MH).
ROUTINE PRE-OPERATIVE QUESTIONING
All patients about to undergo general anesthesia should be asked these specific questions as part of a medical history:
- Is there a family or personal history of MH and/or any known atypical response to anesthesia?
- Is there a family or personal history of a muscle or neuromuscular disorder (e.g., muscle weakness, serious muscle cramps, etc.)?
ADDITIONAL USEFUL QUESTIONS MAY INCLUDE:
- 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?
INTRA-OPERATIVE PREPAREDNESS
The following precautions should be taken in order to detect a potential episode of MH in its early stages; i.e., when it is usually amenable to treatment without significant sequelae.
Planning Ahead
- A written treatment plan should be posted in several convenient or conspicuous locations in the OR and PACU area. A plan such as this 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 a minimum of 36 vials of dantrolene, several liters of sterile water without bacteriostatic agent for injection, bicarbonate and other medications to treat a crisis. MHAUS offers a brochure listing the recommended supplies.
- Ready access to bags of ice is important.
- All operating room and PACU personnel should be trained in the recognition and treatment of MH. Periodic drills of a simulated MH emergency are recommended. In-service materials can be obtained from MHAUS.
During Surgery
- Evaluate any unexpected hypercarbia, tachycardia, hyperthermia, tachypnea or arrhythmia. Consider obtaining arterial or venous blood gases early.
- Core temperature should be monitored in all patients given general anesthesia for 30 minutes or more. Acceptable monitoring sites (considered order of sensitivity) include: pulmonary artery, distal esophagus, nasopharynx, tympanic membrane, rectum, and bladder. Skin temperature may not adequately reflect core temperature during MH episodes. Consider MH in the differential diagnosis of any unexpected temperature or ETCO2 rise.
- Stop inhalation anesthetic and do not administer additional succinylcholine if masseter rigidity occurs. If surgery must continue, immediately switch to non-triggering anesthetics.
- Sudden unexpected and unanticipated cardiac arrest with normal oxygenation, with or without use of succinylcholine, should be considered as secondary to hyperkalemia and so treated unless proven otherwise.
TREATING THE KNOWN OR SUSPECTED MH-SUSCEPTIBLE PATIENT
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The following disorders have been shown to predispose a patient to MH:
Central Core Disease and Multiminicore Disease
These patients should not receive MH triggers.
Duchenne Muscular Dystrophy and Becker's Muscular Dystrophy patients
may develop life-threatening hyperkalemia with succinylcholine and / or
potent volatile anesthetic agents.
The vast majority of muscle and neuromuscular disorders do not predispose to
MH. However, succinylcholine may precipitate muscle breakdown and / or
rigidity (especially the myotonias). Succinylcholine should be avoided in all
patients with clinical muscle or neuromuscular discorders.
Pre-operative Preparations
- Anesthesia machine: Ensure that anesthetic vaporizers are disabled by removing or taping in the “OFF” position. Some consultants recommend changing CO2 absorbent (soda lime or baralyme). Flow 10 L/min O2 through circuit via the ventilator for at least 20 minutes. If fresh gas hose is replaced, 10 minutes is adequate. During this time a disposable, unused breathing bag should be attached to the Y-piece of the circle system and the ventilator set to inflate the bag periodically. New anesthesia workstations may require flow of oxygen for 40 minutes. Use new or disposable breathing circuit. The expired gas analyzer will indicate absence of volatile agents in the anesthesia circuit.
- Utilize a cooling blanket or have other means of cooling available.
Dantrolene Prophylaxis
- Dantrolene prophylaxis is not recommended for most MH-susceptible patients.
- Dantrolene can worsen muscle weakness in patients with muscle disease and should be used with caution. In general, for most procedures, including those requiring general anesthesia, dantrolene prophylaxis can be omitted.
Intra-operative Considerations
- Techniques of choice
Non-triggering general anesthesia, avoiding all potent inhalational agents and succinylcholine. Spinal, epidural, other forms of regional anesthesia, or local anesthetic infiltration, when appropriate. Intravenous sedation as indicated for patient comfort.
- Safe drugs
Local anesthesia: Local anesthetics do not trigger MH; thus, any type of regional anesthesia is safe for MH susceptibles.
Safe general anesthesia agents may include: benzodiazepines, opioids, barbiturates, propofol, ketamine, nitrous oxide, and etomidate. Pancuronium, atracurium, vecuronium, rocuronium, pipecuronium, mivacurium, doxacurium, or curare may be used for relaxation. Neostigmine and atropine or glycopyrrolate are used for reversal without problem.
- Unsafe drugs/MH triggers
Desflurane, sevoflurane, isoflurane, halothane, enflurane, ether, methoxyflurane, and cyclopropane.
Succinylcholine
- Monitoring
Essential: blood pressure, central temperature, ECG, pulse oximeter, and capnograph
Strongly suggest monitoring respiratory rate and volume if general anesthetic
Use arterial line, CVP or other invasive monitors only when appropriate for the surgical procedure and underlying medical condition.
Post-operative Procedure
- If the anesthetic course has been uneventful:
Continue to monitor vital signs for one to two hours. Perioperative dantrolene is not necessary if there has been no evidence of hypermetabolism.
The patient susceptible to MH undergoing outpatient surgery may be discharged on the day of surgery if the anesthetic has been uneventful. A minimum period of 1.0 hour in PACU monitoring vital signs at least every 15 minutes and 1.5 hours in phase 2 PACU/step down is recommended.
- If MH has occurred:
Recover patient in an ICU for at least 24 hours.
Continue IV dantrolene for at least 24 hours, titrated to alleviation of hypermetabolism (hypercarbia or hyperthermia), muscle rigidity, tachycardia, acidosis, and elevated CK levels. Suggested dantrolene dosage is at least 1 mg/kg q 6 hours IV by either bolus or continuous infusion.
Monitor the patient’s coagulation status, watching for DIC.
Look for myoglobinuria and treat as needed. If myoglobinuria develops, maintain urine flow of at least 2 ml/kg/hr. A quick test for myoglobinuria is to test the urine via hemetest strip. If positive and no RBCs are visible microscopically, myoglobinuria is likely.
Monitor potassium and CK levels q 6 hours. CK elevation may not be apparent for several hours.
Use potassium-containing solutions with caution.
Monitor urine output.
Register patient with the MH Registry of MHAUS. Forms are available by contacting:
North American MH Registry of MHAUS
Children's Hospital of Pittsburgh
Anesthesiology Dept, Room 7449
3705 Fifth Ave at DeSoto St
Pittsburgh PA 15213-2583
1-888-274-7899
www.mhreg.orgAlert family to the dangers of MH in other family members.
Refer for testing at nearest center (list available at www.mhaus.org).
Your support of MHAUS is absolutely essential in order to keep these services available.
Information Resources
MHAUS provides educational and technical information to patients and health care providers. Contact MHAUS at 607-674-7901 or e-mail to info@mhaus.org
Information is available via the Internet at: www.mhaus.org
North American MH Registry of MHAUS
The North American MH Registry of MHAUS registers information about specific patients and their families. The Registry is located at Children's Hospital of Pittsburgh at the University of Pittsburgh and Dr. Barbara Brandom is the Director. Health care providers are encouraged to report MH and MH-like episodes to the Registry. Contact the Registry office at 1-888-274-7899 for forms or information (see www.mhreg.org)
The best source of information and educational materials for health care professionals
and MH-susceptible individuals is MHAUS. Call or write:
Malignant Hyperthermia Association
of the United States (MHAUS)
P.O. Box 1069
Sherburne NY 13460
(607) 674-7901
All brochures may be purchased online through our eSHOP.
