N.B. This article appeared in the Winter 1996 Edition of Target MD and is recreated with permission If you wish to subscribe to Target MD please contact them by Email at targetmd@muscular-dystrophy.org
ANAESTHETICS
Dr P ) Halsall
and Professor F R Ellis
People with neuromuscular disorders must take great care if they are to have a local or general anaesthetic. Even someone with very mild, or non-existent symptoms, or someone who has a family history of a disorder; needs to let the anaesthetist know well in advance so that tests can be carried out and proper care after the operation can be arranged.
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Who should read this? •
Everyone
who has a neuromuscular disorder, even if their symptoms • Everyone who has, or had a relative, with a neuromuscular disorder. •
Professionals
involved with the care of people with NMD around Which are the neuromuscular disorders (NMDs)? Neuromuscular disorders include all the muscular dystrophies plus: myotonic disorders; congenital myopathies including mini-core, central-core and multi-core disease plus nemaline and myotubular myopathies; mitochondria! myopathies; lipid storage myopathies; inherited metabolic myopathies including glycogen storage disease; familial periodic paralysis; inflammatory myopathies including infective myositis; autoimmune myositides including polymyositis and dermatomyositis; spinal muscular atrophies; hereditary and idiopathic peripheral neuropathy (HMSN also known as Charcot Marie Tooth disease); inflammatory, autoimmune and toxic neuropathies including Guillain Barre syndrome and CIDP; disorders of the neuromuscular junction including myasthenia gravis. |
Anaesthetics and breathing
Doctors need to measure how weak the patient's muscles are, usually by assessing the amount of physical activity that the patient can perform, and by taking a blood test to measure levels of a muscle enzyme, creatine kinase (CK). Any anaesthetic agent which affects the muscles will also affect the muscles we use to breathe. Strong analgesic or sedative agents will affect these muscles indirectly, and muscle relaxants will have a direct effect on them. As breathing (or respiration) may already be difficult for patients with NMDs, these drugs should be used cautiously, and monitoring of breathing after the operation is absolutely essential. As a result, the patient is usually best cared for in a High Dependency Unit or Intensive Care Unit immediately after the operation. The muscles used for swallowing can also be affected which is another reason why good post-operative care is important.
Muscle relaxants
Muscle relaxant drugs should only be used if essential because they tend to have a more profound and prolonged effect in NMD patients compared to other patients. One type of muscle relaxant, called suxamethonium, should usually be avoided. It causes the release of potassium ions (K+) from the muscle tissue into the blood. In normal patients this is usually of little practical significance. In patients with NMD the muscle may normally leak K+ so that a further increase in the levels of K+ in the blood may cause abnormal heart rhythms. A pre-operative blood test to check K+ levels is therefore important.
Local anaesthetics
A local anaesthetic works by preventing the normal electrical activity in the nerve around which the anaesthetic agents are placed. For minor procedures, such as stitches for cuts, they are probably the first choice for patients with NMD because they have few if any side-effects. However for major local anaesthetic techniques, e.g. spinal or epidural, careful assessment of the patient is needed and the type of NMD considered well before the operation.
Changes in body temperature and pre-operative 'starvation'
Patients with NMD do not tolerate changes in body temperature or the starvation often associated with anaesthesia or surgery as well as normal patients, so steps need to be taken to minimise these problems by keeping the patient warm and well hydrated using drips.
Malignant hyperthermia (MH) and Central Core disease
Malignant hyperthermia (MH) is an inherited disorder which causes an unexpected, sometimes fatal, reaction in the patient to certain anaesthetic drugs. Because some patients with NMD have sometimes experienced similar problems
During anaesthesia there have been claims that patients with NMD may also have MH. However, it is generally accepted that the
only neuromuscular condition truly related
to MH is Central Core Disease (CCD),
although this is not always the case.
Patients with CCD should be
considered potentially susceptible to
MH unless proved otherwise by a special
type of muscle biopsy which screens for MH.
It is always a good idea to make sure hospital staff have copies of Fact Sheets about yourcondition, and if you are going to have an anaesthetic you could show your anaesthetist this article. Dr Halsall and Professor Ellis where writing a fact sheet specially for anaesthetists which should now be available.
To sum up ...
- Clearly
anaesthesia in NMD is
not to be undertaken lightly.
Such patients should expect the
anaesthetist to make a careful
and thorough assessment of
their particular condition and
their current state of health. - They are
not suitable to be
treated as 'Day Cases' because
doctors should carry out pre-
operative investigations, and
enough time and recovery
facilities should be available
after the operation. - It is absolutely essential that
the person affected by NMD
should inform the anaesthetist
even if there are only minor
symptoms, or no symptoms at
all. Occasionally a
neuromuscular disorder in a
person who had no symptoms
has come to light only because
of an unexpected problem with
anaesthesia, particularly in
young children. The anaesthetist
should also be warned if there is
an inherited NMD in the family.
·
If possible ask for the
anaesthetist to be forewarned
before admission to hospital and
consider wearing a Medic Alert
bracelet or similar in case of
accidents.
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* The article above contains
the text of a scanned copy of an article written in the Winter 1996
edition of Target md , this is intended for reference only as some of the
details may now be out of date although to the best of my knowledge it is
correct
If you wish to
subscribe to Target MD please contact them by Email
targetmd@muscular-dystrophy.org
Further information on the subject may also be found by searching on
the
I asked for permission and was told " You may link to the NLM information resources without obtaining permission. It is probably safest to link to http://www.pubmed.gov/ ."
Follow this link to one example
And this as another on the subject
A skeletal deformity such as scoliosis, or curvature of the spine, can also affect the way the patient responds to anaesthesia so it is important to consider that too.
Anaesthetics and the heart
An article printed in the Winter 1995 No. 20 edition of The Search, showed how people with NMDs can sometimes have associated heart disease. This can occur as a cardiomyopathy, when the heart muscle doesn't work effectively, or as a defect in the way the electrical activity of the heart is transmitted, a conduction defect. The anaesthetic vapours - the smelly agents such as ether and halothane which are inhaled -can reduce the effectiveness of the heart's muscle contractions and also aggravate any conduction defect. The vapours are all slightly different from each other, some having more effect on the heart than others. So it is important that the anaesthetist makes a good assessment of the heart's condition before the operation which would include the level of physical activity that the patient can manage, and an ECG. Occasionally a more extensive assessment is needed.
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Many people are afraid of having an anaesthetic, mainly through ignorance, but when we look at the rate of complications and even deaths arising from anaesthesia we see that it is in fact very safe. This safety is the result of a thorough understanding of the patient's medical condition with a careful assessment before the operation, marked technical improvements in monitoring facilities during the operation, and the provision of good recovery facilities such as High Dependency Units (HDU) and Intensive Care Units (ICU).
Patients with neuromuscular disorders (NMDs) deserve special attention when it comes to anaesthesia because many of the agents used (gases and chemicals) have effects on both muscle and nervous tissue. The main areas of concern are how the anaesthetic agents will affect the muscle and how they will affect the heart which is itself a muscle.