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. Therefore, 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: To treat an MH episode, an initial dose of dantrolene at 2.5 mg/kg is recommended, with a suggested upper limit of 10 mg/kg. If a patient of average weight (approximately 70 kg) were to require dantrolene at the upper dosing limit, then at least 700 mg of dantrolene would be needed.
In addition, a review of cases has shown 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; higher doses may be required on rare occasions.
Thirty-six (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 or death 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: We suggest the expired dantrolene either be used for your institution’s MH practice drills, or be mailed to MHAUS. Expired dantrolene received by MHAUS will be donated to simulation training centers for MH practice drills.
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 MHAUS brochure Managing MH – Drugs, Equipment and Dantrolene to be found at www.mhaus.org.]
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. Based on a review of the literature and consensus of MH experts, we have determined that it does not, and thus, our MH experts have approved its 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. The patient will receive 0.375gm/kg mannitol when given 2.5 mg/kg dantrolene
Drugs and MH
Q: What drugs are known to trigger MH?
A: Unsafe drugs for MH susceptibles are the depolarizing muscle relaxant, succinylcholine (Anectine), and the potent inhalation agents (sevoflurane, desflurane, isoflurane, halothane, and 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, ketamine, droperidol, and etomidate. Nitrous oxide is safe.
Q: Can local anesthesia be used for dental work?
A: Yes, all MH-susceptible patients can safely receive any local anesthetic.
Management of MH-Susceptible Patients
Q: Are MH-susceptible (MHS) individuals at risk for MH symptoms/episode if exposed to triggering agents while working in an operating room or similar environment?
A: NO. 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 very 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 MHS 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 at www.mhaus.org.)
Q: How should I manage a patient with a family history of MH?
A: The family should be referred to a Biopsy Center Director or MH expert associated with MHAUS for discussion of testing options to determine MH susceptibility. Until proven otherwise, 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. Flow 10L/min 02 through circuit for at least 20 minutes. 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 will indicate absence of volatile agents in the anesthesia circuit. Changing the CO2 absorbent (soda lime or baralyme) is not recommended if these procedures are followed. However, newer anesthesia machines such as the Drager Fabius may require up to 60 minutes of preparation. Check with the manufacturer of the machine for suggested washout procedure.
A summary of the recommendations for the Drager Fabius machine is found in the following article: Gunter, JB et al. Preparation of the Drager Fabius Machine for the Malignant Hyperthermia Susceptible Patient. [Anesthesia and Analgesia; 2008: 107; 1936-1945.] This article also demonstrated that placing a commercially available charcoal filter on the inspiratory limb of the anesthesia circuit will promptly reduce anesthetic gas concentration to very low (trace) levels.
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 an additional hour in phase 2 PACU /step down unit 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 hyperkalemic cardiac toxicity during an MH crisis?
A: Either calcium gluconate or calcium chloride can be used to treat life-threatening hyperkalemia. Gluconate (10-50 mg/kg) is less potent, but is less irritating to peripheral veins. The higher potency calcium chloride (4-10 mg/kg) is more appropriate for the acute situation.
Q: What should I do to manage an acute MH case or suspicious MH case?
A: Advice regarding acute emergencies can be obtained through the MH Hotline at 800-644-9737. 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. 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 with hyperkalemic cardiac arrest may occur. Potent volatile agents may produce rhabdomyolysis in time, but most believe that brief exposure is a small risk. The anesthesia care professional prior to surgery should carefully evaluate patients with muscle disorders. 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. MH precautions are not necessary in NMS patients.
Q: Is Masseter Muscle Rigidity a response to Succinylcholine?
A: Masseter (jaw) muscle rigidity (MMR) denotes trismus to the extent that it is difficult or impossible to open the jaw. Mild and/or transient MMR is a normal response to succinyicholine and is considered to be of no prognostic significance with respect to MH. [Longnecker et al. Anesthesiology. Pg 1969. 2008.
The actual physiologic changes associated with the onset of MH such as rise in ETCO2 may be delayed for up to 15 minutes after MMR, but will occur if trigger agents are continued. Hence whenever MMR occurs following succinyicholine, elective surgery should be postponed. If the procedure is emergent, the anesthetic may continue with nontrigger agents.
All patients who develop succinylcholine-induced MMR will experience rhabdomyolysis over the ensuing 24 hours. Hence the patient should remain in the hospital and be monitored for signs of rhabdomyolysis such as myoglobinuria and myoglobinemia. CK levels and electrolytes should be checked every 8 hours until returning to normal.
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. (See question on monitoring after uneventful anesthesia.)
Q: When should MHS patients be discharged from ambulatory facilities after episodes of masseter spasm?
A: Masseter (jaw) muscle rigidity (MMR) denotes trismus to the extent that it is difficult or impossible to open the jaw. 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 with potent volatile agents 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. Access to arterial blood gas and electrolyte analysis is recommended. It is not essential to have the capability to perform blood gas analysis at an ambulatory site, but there should be a prior arrangement with a laboratory or hospital to perform such testing.
Testing
Q: May 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 non-triggering anesthetic technique used.
Q: Where should an MHS patient be biopsied?
A: A biopsy for MH should be performed at one of the
updated 5/15/2009
For Patients
For Medical Professionals
About MHAUS
MH Registry
NMSIS Website
Place Order
