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Introduction implications of the inheritance of MHS
R=~UNION DE GRENOBLE
(~ Masson, Paris. Ann Fr Anesth R~anim, 8 : 390-391, 1989
Introduction Implications of the inheritance of MHS F.R. ELLIS
The predisposition to develop malignant hyperthermia (MH) is inherited as a Mendelian dominant characteristic. The familial pattern of inheritance, coupled with the results of the preliminary genetic studies using chromosome 19 bioprobes, suggest that this complex medical condition may be due to a single gene defect. MH is, thankfully, a rare complication of anaesthesia yet ironically exposure of susceptible individuals (MHS) to anaesthesia is much commoner. This discrepancy is for two reasons, firstly MH reactors have often received <
Usually it is not difficult to devise an anaesthetic regimen for a known or suspected MHS ,0 patient. Atracurium or vecuronium are almost as good as suxamethonium for a rapid sequence induction where suxamethonium has traditionally retained its crucial role. For non acute surgery suxamethonium can easily be dispensed with. Avoidance of inhalational anaesthetics is simple using continuous intravenous techniques although nitrous oxide would need to be administered from a designated vapour-free machine. Perhaps all anaesthetic departments should maintain such a machine which can equally be used in liver failures etc.
tion ot central core disease, there seems to be no relationship between MHS and muscle disease. In particular patients with myotonic muscular dystrophy do not develop MH, and vice v e r s a . Similarly thyroid disease is not associated with MH and MHS individuals do not seem to suffer from heart disease more frequently. When studied carefully, the incidence of sudden infant death syndrome (SIDS) does not correlate with MHS. From a recent evaluation of our data base of almost 2,000 patients investigated by muscle biopsy for MH, MHS people do not show a higher incidence of kyphoscoliosis, hernia, strabismus, orthopaedic abnormalities, greater muscle mass, greater athletic performance, or muscle cramps compared to a control population. The MHS subject is indistinguishable on preoperative examination. MHS AND STRESS
Apart from anecdote, there is no direct evidence that MHS subjects are more liable than others to develop stress reactions, nor that MH represents a perverted stress response to anaesthesia. Formal laboratory studies have either failed to identify differences, or the differences are so subtle as to be unlikely reaction for stress response variations. SOCIAL IMPLICATIONS OF MHS
The MHS label is not yet widely understood (or even recognized) by non anaesthetic medical specialists or family doctors. MHS individuals are therefore likely to experience difficulties when doctors either disregard the diagnosis and attempt to reassure them inappropriately or conversely to over-react and refuse to consider surgical treatments. Many MHS people have personal horror stories of how they were treated in casualty departments, etc.
MHS AND OTHER MEDICAL PROBLEMS
There is a disturbing tendency for doctors to fabricate association between rare diseases which prove to be unfounded. With the possible excep-
Tir~s ~ part: Dr. F.R. Ellis, Reader in Anaesthesia, Director of the Malignant Hyperthermia Unit, Leeds University, St, James's University Hospital, Leeds, LS9 7TF, U.K.
IMPLICATIONS OF MHS
They also live with anxiety concerning foreign travel. If doctors in their own country can't understand the problem, how much more difficult it will be for doctors in a foreign country with whom they cannot communicated freely due to language and cultural differences. MHS subjects are now suffering discrimination for certain types of occupation such as the armed forces, oil exploration, deep sea fishing etc. While from the medical point of view this seems quite reasonable, a person faced with a muscle biopsy investigation for MH screening is less than enthusiastic if confirmation of MHS status deprives him of his occupation, or abolishes his chance of promotion. MHS status can also reduce the attractiveness of the individual as a marriage/breeding partner - this is particularly so in Japan.
LEGAL IMPLICATIONS
With the recent increase in litigation, anaesthetists are forced to adopt more aggressive monito-
391
ring than previously. With good monitoring, malignant hyperthermia should be suspected long before serious complications have occurred. It could be claimed that a fulminating/classical presentation of MH is only possible if there is either inadequate monitoring, or if the anaesthetist has failed to react adequately and effectively to the developing signs of MH. Although body temperature is easy and cheap to monitor, most cases of MH will be suspected using alternate methods which seem to be gaining in popularity - - such as end tidal capnography and pulse oximetry. Even investigating unexplained tachycardia by measuring core temperature or CO2 output would be adequate most of the time. When MH is suspected, all patients should have acid base status investigated together with serum potassium, CK and urinary myoglobin measured. The anaesthetist must then refer the patient for further investigative screening to either confirm or refute the diagnosis, and also warn other members of the family of the possible diagnosis, and of its implications. Anaesthetists have a moral obligation to act to safeguard the patient and his family.
(~ Masson, Paris. Ann Fr Anesth R~anim, 8 : 390-391, 1989
Introduction Implications of the inheritance of MHS F.R. ELLIS
The predisposition to develop malignant hyperthermia (MH) is inherited as a Mendelian dominant characteristic. The familial pattern of inheritance, coupled with the results of the preliminary genetic studies using chromosome 19 bioprobes, suggest that this complex medical condition may be due to a single gene defect. MH is, thankfully, a rare complication of anaesthesia yet ironically exposure of susceptible individuals (MHS) to anaesthesia is much commoner. This discrepancy is for two reasons, firstly MH reactors have often received <
Usually it is not difficult to devise an anaesthetic regimen for a known or suspected MHS ,0 patient. Atracurium or vecuronium are almost as good as suxamethonium for a rapid sequence induction where suxamethonium has traditionally retained its crucial role. For non acute surgery suxamethonium can easily be dispensed with. Avoidance of inhalational anaesthetics is simple using continuous intravenous techniques although nitrous oxide would need to be administered from a designated vapour-free machine. Perhaps all anaesthetic departments should maintain such a machine which can equally be used in liver failures etc.
tion ot central core disease, there seems to be no relationship between MHS and muscle disease. In particular patients with myotonic muscular dystrophy do not develop MH, and vice v e r s a . Similarly thyroid disease is not associated with MH and MHS individuals do not seem to suffer from heart disease more frequently. When studied carefully, the incidence of sudden infant death syndrome (SIDS) does not correlate with MHS. From a recent evaluation of our data base of almost 2,000 patients investigated by muscle biopsy for MH, MHS people do not show a higher incidence of kyphoscoliosis, hernia, strabismus, orthopaedic abnormalities, greater muscle mass, greater athletic performance, or muscle cramps compared to a control population. The MHS subject is indistinguishable on preoperative examination. MHS AND STRESS
Apart from anecdote, there is no direct evidence that MHS subjects are more liable than others to develop stress reactions, nor that MH represents a perverted stress response to anaesthesia. Formal laboratory studies have either failed to identify differences, or the differences are so subtle as to be unlikely reaction for stress response variations. SOCIAL IMPLICATIONS OF MHS
The MHS label is not yet widely understood (or even recognized) by non anaesthetic medical specialists or family doctors. MHS individuals are therefore likely to experience difficulties when doctors either disregard the diagnosis and attempt to reassure them inappropriately or conversely to over-react and refuse to consider surgical treatments. Many MHS people have personal horror stories of how they were treated in casualty departments, etc.
MHS AND OTHER MEDICAL PROBLEMS
There is a disturbing tendency for doctors to fabricate association between rare diseases which prove to be unfounded. With the possible excep-
Tir~s ~ part: Dr. F.R. Ellis, Reader in Anaesthesia, Director of the Malignant Hyperthermia Unit, Leeds University, St, James's University Hospital, Leeds, LS9 7TF, U.K.
IMPLICATIONS OF MHS
They also live with anxiety concerning foreign travel. If doctors in their own country can't understand the problem, how much more difficult it will be for doctors in a foreign country with whom they cannot communicated freely due to language and cultural differences. MHS subjects are now suffering discrimination for certain types of occupation such as the armed forces, oil exploration, deep sea fishing etc. While from the medical point of view this seems quite reasonable, a person faced with a muscle biopsy investigation for MH screening is less than enthusiastic if confirmation of MHS status deprives him of his occupation, or abolishes his chance of promotion. MHS status can also reduce the attractiveness of the individual as a marriage/breeding partner - this is particularly so in Japan.
LEGAL IMPLICATIONS
With the recent increase in litigation, anaesthetists are forced to adopt more aggressive monito-
391
ring than previously. With good monitoring, malignant hyperthermia should be suspected long before serious complications have occurred. It could be claimed that a fulminating/classical presentation of MH is only possible if there is either inadequate monitoring, or if the anaesthetist has failed to react adequately and effectively to the developing signs of MH. Although body temperature is easy and cheap to monitor, most cases of MH will be suspected using alternate methods which seem to be gaining in popularity - - such as end tidal capnography and pulse oximetry. Even investigating unexplained tachycardia by measuring core temperature or CO2 output would be adequate most of the time. When MH is suspected, all patients should have acid base status investigated together with serum potassium, CK and urinary myoglobin measured. The anaesthetist must then refer the patient for further investigative screening to either confirm or refute the diagnosis, and also warn other members of the family of the possible diagnosis, and of its implications. Anaesthetists have a moral obligation to act to safeguard the patient and his family.