Malignant hyperthermia (MH) in the past has been a greatly feared anesthesia complication and a significant threat to the safety of a small but definite number of patients. Presented here is information about why this threat is much less today and also some background information about what is happening with MH.
The Malignant Hyperthemia Association of the United States (MHAUS) was founded in 1981 to provide information, education and assistance to health care providers and patients who have a special interest and concern with this inherited disorder.
MHAUS produces a newsletter (The Communicator) five times/year, brochures dealing with various aspects of MH, treatment guidelines, as well as periodic conferences for professionals and lay persons. An important aspect of the activities of MHAUS is a hotline service available with the cooperation of The Medic-Alert Foundation 24 hours a day (telephone (209) 634-4917).
Callers dealing with MH questions of an urgent nature may contact an MH expert and request advice and assistance. Each year, approximately 600 calls are handled by hotline consultants.
A representative sample of recent calls received by the hotline and summarized by Dr. Rory S. Jaffe, Assistant Professor of Anesthesiology at the University of California, Davis, is presented below. For further information about MHAUS, call (203) 8470407, or write to MHAUS, P.O. Box 191, Westport CT 06881-0191.
MHAUS received 152 Hotline reports in the Spring of 1993. Sixteen consultants from the United States and Canada submitted reports. Fifty-six calls were consultations for patient management: 14 episodes of postoperative fever, two cases of neuroleptic malignant syndrome, and 40 perioperative events of which 14 were masseter muscle rigidity. Two deaths, which will be discussed below, were reported.
The most remarkable call for help came from the friend of a parent of a child having femur and wrist fractures repaired. There was a language barrier; he called from Mexico City, and spoke little English. it appeared that the child may have had an MH reaction, and they were attempting to obtain dantrolene. The consultant suggested trying a teaching hospital or major medical center in Mexico City. The hotline consultant could not assess the need for dantrolene, asked for the patient’s doctor to call (with an interpreter), and contacted Proctor and Gamble about the availability of dantrolene in Mexico. No doctor ever called. A representative for Proctor and Gamble said that they do not sell dantrolene in Mexico. It can be obtained through an intermediary, which takes about one week. Nothing more was known until three days later, when the father called. They had unsuccessfully searched for dantrolene in Mexico City, and the little girl had died.
In some parts of the world, people have access to diagnosis of MH susceptibility and specific treatment of acute episodes. Prior to dantrolene, MH truly was malignant, with a death rate exceeding 70%. Without dantrolene, most patients died even with ideal supportive care. In the past, United States physicians have received calls for information from Mexico, and most did not realize that Mexican doctors and hospitals do not have ready access to dantrolene. In a country with limited resources, how many deaths should be tolerated to save money? In Mexico City, with about 21,000,000 residents, 1:10,000 to 1:40,000 MH susceptible, 500 to 2,100 people are at risk for triggering. Can they afford to stock dantrolene to help save those people? Should Proctor and Gamble donate a supply? There is no ready answer, but this girl would probably still be alive if she had her operation in another country.
Not Always MH
The other death was also quite unusual, although no one could have prevented the outcome. A 35-year-old woman with a tibial plateau fracture was given a general anesthetic including succinylcholine to relax her muscles for intubation and isoflurane for anesthesia. After tracheal intubation, she developed hypotension and tachycardia. Ventilation became difficult, and her temperature rose. She then suffered a cardiac an-est. The consultant was called during the resuscitation attempt. The serum potassium level was normal, and the blood gases were not appropriate for severe MH. The consultant felt that MH was unlikely, but a small dose of dantrolene was given. The patient died, and the autopsy revealed a massive pulmonary embolus. Fever and tachycardia are common with pulmonary thromboembolism, and induction does seem a time of increased risk for pulmonary embolism. Perhaps the increased risk is due to stirring up pelvic vein clot in an immobile patient with movement to the operating room table or muscle fasciculations with succinylcholine.
Fever either postop or not associated with an operation resulted in 14 calls to the hotline. None were thought to be MH although the consultant recommended measuring blood gases every 30 minutes in one patient. Several were thought to be drug fevers: one from radiologic contrast, and one from cefazolin.
Masseter Spasm
Masseter muscle rigidity was the cause of 14 calls to the hotline. Three of these patients received dantrolene, and one was felt to have experienced an MH episode. AU patients were referred for biopsy to exclude MHS. The consultants all recommended hydration and precautions against renal damage from myoglobinuria. AU patients recovered rapidly.
Of the other 28 consultations for acute management, six were considered acute MH, 12 possible MH, and six unlikely to be MH. These patients did well. Two calls were to request assistance for the management of neuroleptic malignant syndrome (EMS) and two were for myoglobinuria. Both patients with myoglobinuria were referred to a neurologist for evaluation of myopathy. Neither of the patients with NMS required dantrolene.
Ninety-seven calls were information requests. Besides general management questions, the most prevalent question asked was for an assessment of risk for a relative of someone either MHS or suspected to be MHS (19). Close behind was the frequently asked question ‘Are all local anesthetics O.K.?’ (13) One questioner was curious about using Edocaine for MH-induced arrhythmias, The consultant said it was fine. MHAUS literature still recommends procainamide for treatment of arrhythmias. This may cause some of the concerns regarding amide-local anesthetic use and may need reevaluation. The suitability of other drugs was also the subject of inquiries: propofol (4), mivacurium (2), hydroxyzine, potassium, vecuronium, chloral hydrate, cortisone, and OTC medications.
A request for post hoc evaluation of a recent case was the reason for 10 calls. Most were episodes of trismus. One patient had been discharged immediately postop and was recalled to the hospital after the consultation. Many of these patients were referred for biopsy.
One patient referred for biopsy had 12-14 uneventful general anesthetics, including one known to include succinylcholine and isoflurane, without trismus. She recently had two anesthetics and was difficult to intubate after succinylcholine both times. This was perhaps due to trismus, but cannot be definitely confirmed. After that last anesthetic, she had very severe myalgias. The peak CK was 920. Her physicians were questioning whether this represented MHS or a difficult airway. Her biopsy was strongly positive, including contractures of 6.38, 2.32, and 3.06g to 3% halothane.
Four calls to the hotline were regarding the duration of postop observations for MHS patients given nontriggering anesthetics. Twice callers were told no additional observation was needed, and twice consultants said that about six hours were needed. This represents an area where there is still little solid ground to base any recommendations upon. No MHS patient given a non-triggering anesthetic has ever been known to develop MH because of that anesthetic. Late development after operation is felt by many to be quite rare. But what if this MHS person was inadvertently exposed during anesthesia to a volatile anesthetic? How long is long enough to exclude accidental triggering?
Various syndromes were asked about: myotonic dystrophy (2), arthrogryposis, osteogenesis imperfecta, Freeman-Sheldon syndrome, Russell-Silver syndrome, McArdles syndrome and Sp+ syndrome. Reflecting current controversy, one caller was advised that myotonic dystrophy is probably associated with MH, and one was told it is not. Other questions were regarding tourniquet use in the MHS patient, dantrolene pretreatment (seven calls, all told “no’), and military acceptance of MHS applicants.
Nugget Mining
Two callers were preparing lectures; one requested urgent FAX transmission of all MHAUS literature for the lecture (It is assumed her donation to MHAUS is forthcoming). One caller was studying for the oral boards and mining the consultant for nuggets of information useful for the exam.
The MH experts who volunteered their time and talents in assisting these callers were Drs. Allen, Bikhazi, Chapin, Greenberg, Jaffe, Kaplan, Karan, Larach, Miller, Muldoon, Rosenbaum, Rosenberg, Sessier, Shutack, Watson and Wedel. MHAUS thanks them for their generous donation of time and expertise.
Dr. Rosenberg is Professor and Chairman of Anesthesiology at Hahnemann university, Philedelphia, and also the Vice President for Medical Affairs and Chairman of the Professional Advisory Council of MHAUS,