Medical Professionals' FAQs

Dantrolene

 Q: Should MHS patients be pretreated with dantrolene?

A: 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.  For most procedures, including those requiring general anesthesia, dantrolene prophylaxis may be omitted, provided non-triggering anesthetics are used, there is appropriate monitoring and an adequate supply of dantrolene is available.  

 Q: How much dantrolene should be stocked?

A: If any potent volatile agents are used, a full supply of dantrolene (36 vials) should be available on site.  If potent volatile agents are not used, and succinylcholine is available for resuscitation, a minimum of 36 vials of dantrolene should still be available.  If neither potent volatile agents nor succinylcholine are used or available, dantrolene need not be present.

 Q: Why is it recommended that we stock a minimum of 36 vials of dantrolene, rather than 12 or 24?  

A: Research has determined that in a “worse case” scenario of a very large person (i.e., about 100-110 kg or 220 – 250 pounds) having an acute MH incident, as much as 8-10 mg/kg will be needed for treatment.  36 vials of dantrolene will allow for initial stabilization and treatment while more vials are being acquired to continue treatment, as needed.

 Q: Must we stock 36 vials of dantrolene if our OR is very close to a fully equipped hospital and the patient could be transported there quickly?

A: Yes, a stock of 36 vials is recommended.  The patient experiencing an MH episode must be stabilized before being transported.  Stabilization of an MH episode may take 30 minutes or more with multiple doses of dantrolene because, in some cases, MH progresses with explosive rapidity.  The full 36 vials of dantrolene is inexpensive insurance against patient injury and a malpractice claim, which the facility will lose.  The full 36 vials of dantrolene should be available within five minutes of the diagnosis of MH.

 Q: What should we do with expired dantrolene?

A: Mail it to MHAUS.  We will find a place to send it.

 Q: What is recommended to be stocked on an MH cart?

A: Drugs: dantrolene sodium IV (36 vials), sterile water (without a bacteriostatic agent) to reconstitute dantrolene, sodium bicarbonate, furosemide, dextrose, calcium chloride, regular insulin (refrigerated), and antiarrhythmics.  [For complete details, refer to brochure Managing MH – Drugs, Equipment and Dantrolene.]

 Q: Why were procainamide and mannitol taken off the list of drugs to stock for an MH episode?

A: Procainamide, a secondary drug used in the treatment of arrhythmias, is not readily available, and people are generally not familiar with its use.  Lidocaine is a primary drug that all physicians have used for years; however, it was previously thought that lidocaine might aggravate MH.  We have determined that it does not, and it has been approved for use during an MH episode.  Mannitol has been taken off the list of drugs because dantrolene (Dantrium® IV) has 3 grams of mannitol included in each vial.

Drugs and MH

 Q: What drugs are known to trigger MH?

A: Unsafe drugs for MH susceptibles are succinylcholine and the potent inhalational agents (sevoflurane, desflurane, isoflurane, halothane, enflurane).  Older inhalational anesthetics such as ether, cyclopropane and methoxyflurane can also trigger an MH crisis.

 Q: What drugs do not trigger MH?

A: Local or regional anesthesia and monitored anesthesia care are safe.  Spinal, epidural and nerve block anesthesia utilize local anesthetics, and such techniques are safe to use in MH susceptibles.  Intravenous drugs are safe, including propofol, barbiturates, benzodiazepines, and etomidate.  Nitrous oxide is safe.

 Q: Can local anesthesia be used for dental work?

A: Yes, all MH-susceptible patients can safely receive local anesthetics.

 Q: Are MH-susceptible individuals at risk for MH symptoms/episode if exposed to triggering agents while working in an operating room or similar environment?

A: There are no cases reported of MHS patients having problems on exposure to waste anesthetic gases while working in the OR.  The usual OR procedures maintain low, trace amounts of the potent volatile anesthetics in the air.  During a mask induction, someone within two feet or so of the face of the patient may be exposed to somewhat greater concentrations, but that is easily avoided.  Further, the volatile agents are heavier than air and drift down to the floor, where the excellent ventilation systems efficiently clear the vapors.  In addition, the data from pigs indicate that very low concentrations of anesthetics do not trigger MH in these highly susceptible animals.  There is only one report of muscle cramps and fatigue in a person who worked in a factory where he was exposed to chemicals whose structure is similar to that of potent inhalation agents. (See Consensus Statement for MHS OR Personnel on this Web site.)

Management of MH-Susceptible Patients

   Q: How should I manage a patient with a family history of MH?

A: Manage as if MH susceptible with a non-triggering anesthetic technique.

 Q: How should the anesthesia machine be prepared before surgery for an MHS patient? 

A: Ensure that anesthesia vaporizers are disabled by removing or taping in the “OFF” position.  Some consultants recommend changing the CO2 absorbent (soda lime or baralyme).  Flow 10L/min 02 through circuit 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.  Use a new or disposable breathing circuit.  The expired gas analyzer willl indicate absence of volatile agents in the anesthesia circuit.

 Q: How should I prepare the pump on the machine used for cardiopulmonary bypass? 

A: Do not attach an anesthetic vaporizer; otherwise, no other changes.

 Q: How long should MHS patients be monitored after uneventful anesthesia?

A: 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 one hour and one-half hours in phase 2 PACU/step down is recommended.

 Q:  Is it necessary to purchase an ice machine?

A: In the absence of an ice machine, there should be an adequate supply of ice in the freezer or freezing compartment of a refrigerator and the ability to crush it.  Also, saline solution for central cooling in case of an MH crisis should be kept cooled in the blood or drug refrigerator.

 Q:  Can calcium gluconate or calcium chloride be used when treating an MH crisis?

A: Either calcium gluconate or calcium chloride can be used to treat life-threatening hyperkalemia.  Gluconate is less potent, but is less irritating to peripheral veins.  The higher dosage is more appropriate for the acute situation.

 Q: What should I do to manage an acute or suspicious MH case?

A: MH cases should be reported to the North American MH Registry of MHAUS.  Forms for data collection can be obtained from the Registry or MHAUS.  Advice regarding acute emergencies can be obtained through the MH Hotline at 800-644-9737.  MHS patients and their families should be put in contact with MHAUS to obtain more detailed information regarding MH and the risks for family members.

Muscle Disease Issues, Heredity & Links

 Q: Is MH linked to other serious medical problems?

A: MH itself is not usually associated with other serious medical problems, such as hypertension, diabetes or similar diseases.  MH or MH-like events however, have occurred in patients with underlying muscle diseases, such as muscular dystrophy and myotonia.  Such patients typically display muscle weakness.  MH has been linked to a rare disorder of muscle called Central Core disease and King Denborough Syndrome, a rarer muscle syndrome.
     Additionally, patients with certain forms of muscular dystrophy may develop life-threatening disturbances and muscle destruction on exposure to the triggering agents for MH.  The clinical event may resemble MH in many ways, but is not considered “true” MH.  In patients with Duchenne muscular dystrophy, succinylcholine should always be avoided or rhabdomyolysis may occur.  Potent volatile agents may produce rhabdomyolysis in time, but most believe that brief exposure is a small risk.  Patients with muscle disorders should be carefully evaluated by their anesthesiologist prior to surgery.
     Hypokalemic and hyperkalemic periodic paralysis are also associated with risk for MH.  Hyperkalemic cardiac arrest may occur when MH-trigger agents are administered to muscular dystrophy patients.
     Patients with osteogenesis imperfecta often develop fever during anesthesia.  Myotonic patients will develop muscle rigidity with succinylcholine.  There have been a few MH cases reported in patients with carnitine palmityl transferase deficiency and it is recommended to stay away from MH triggers in such patients.  Neuroleptic Malignant Syndrome (NMS) is a syndrome that resembles MH but is precipitated by drugs acting centrally on dopaminergic pathways in the brain.

Outpatient Surgery

 Q: Are MHS patients candidates for outpatient surgery?

A: MHS patients can safely undergo outpatient surgery using non-triggering anesthetics and 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 one hour and one-half hours in phase 2 PACU/step down is recommended. 

 Q: When should MHS patients be discharged from ambulatory facilities after episodes of masseter spasm?

A: Masseter spasm has a spectrum of severity from mild increase in jaw tension to “jaws of steel.”  A patient who exhibits marked rigidity of the jaw muscles should not be discharged.  Overnight observation for temperature rise, myoglobinuria, elevated CK levels or progression to an MH episode is required.  Patients who experience milder increases in jaw tension should be observed for signs and symptoms of MH for at least 12 hours. If there is evidence of myoglobinuria, dark cola-colored urine, increase in temperature, pulse rate, and abnormality of acid base balance, the patient should be admitted and observed overnight.

 Q: How do I supply a surgicenter for an MH emergency?

A: A surgicenter in which general anesthesia is administered should be equipped to manage MH.  Dantrolene sodium IV (36 vials), sterile water, other drugs and equipment, and a protocol to treat an MH crisis should be available.  The drugs and supplies should be assembled in an MH kit or cart (refer to brochure Managing MH – Drugs, Equipment and Dantrolene for complete details).  Surgicenters that propose to use succinylcholine as an emergency agent should also have 36 vials of dantrolene available and an appropriate MH crisis protocol in place.

Testing

 Q: Should surgery be done without a muscle biopsy test for MH?

A: If there is a question of MH susceptibility and a biopsy has not been done, the patient should be managed as if known to be MH susceptible and a nontriggering anesthetic technique used.

 Q: Where should an MHS patient be biopsied?

A: A biopsy for MH should be performed at one of the U.S. Muscle Biopsy Centers complying with a standard protocol for the caffeine halothane contracture test.  A listing can be obtained from the MHAUS office (607-674-7901 or www.mhaus.org).

Updated April 2007