|Myotonic dystrophy is an inherited muscle disease with several distinguishing features. First, the age of onset is extremely variable, ranging from the neonatal period and infancy to late adulthood. A second distinctive feature is that, in addition to muscular weakness, multiple organ systems may be implicated, leading, among other syndromes, to arrhythmia, intestinal dysfunction, extreme hypersomnia and peri- or postpartum atonic haemorrhage in women. The extent and nature of the symptom complex may vary widely from patient to patient and depends, among other factors, on the age at onset and duration of illness.|
Serious complications that occur during surgical procedures performed under general anaesthesia are notorious. Kaufman (1960) can be credited as the first to draw attention to this trend. The risk of complications is directly related to the severity of the condition. Anaesthetists are seldom informed of the potential complications associated with this skeletomuscular condition. Additionally, patients suffering from a milder type or those in whom no definitive diagnosis has yet been made also run serious risks as undiagnosed or unrecognised cases prevent precautionary measures from being taken.
||Anaesthetic complications and their causes:|
Complications that may occur in patients with myotonic dystrophy are:
1.Arrhythmia, which can lead to an acute cardiac arrest or circulatory problems.
2.Respiratory distress due to;
Weakness of the respiratory muscles and diminished cough reflex;
Deficient central respiratory drive, possibly triggered or exacerbated by the administration of certain drugs. Patients may have a heightened sensitivity to morphine-like analgesics or muscle relaxants
Choking or aspiration of liquids or gastric contents into the lungs, causing pneumonia.
3.Myotonic crisis is an extremely serious although rare complication during or following general anaesthesia. A crisis may be provoked by certain agents used to induce muscle relaxation (e.g. depolarising anaesthetics like succinylcholine), which drugs are thus contraindicated. It may also be triggered by low temperatures, which is why the room where the procedure is to be conducted needs to be adequately heated and the patient covered with a warm blanket.
It is crucial to inform both the anaesthetist and the surgeon of the presence of the condition prior to surgery to allow protocols to be adapted. One may need to consider the possibility of using local, spinal or epidural anaesthesia. These options reduce the risk of pneumonia and are less stressful to the heart. Preoperative examination of the heart and lungs is indicated to establish the feasibility of the procedure. In case of serious arrhythmia, placement of a pacemaker or ICD may be required. Preoperative testing of pulmonary functions and blood gases are recommended in patients in the more advanced stages of the disease. Respiratory patterns may be indicative of life-threatening respiratory arrest following anaesthesia.
If required, general anaesthesia is fully practicable provided the right drugs are used, e.g. continuous propofol infusion, rocuronium bromide (Esmeron®), or fentanyl. Short-acting muscle relaxants and inhalation anaesthetics are to be preferred over intravenous agents. Depolarising muscle relaxants like succinylcholine need to be avoided on account of the risk of myotonia of the laryngeal muscles and a myotonic crisis. Increased respiratory depression should be considered after administration of the usual dose of centrally acting analgesics and sedatives such as opiates, barbiturates, and benzodiazepines. It is important for the anaesthetist to know that there is no elevated risk of malignant hyperthermia.
Postoperatively, patients are to be monitored for at least 24 hours especially with regard to cardiac and respiratory functioning, which implies the availability of an intensive care unit bed. Postoperative aspiration pneumonia caused by choking, impaired productive coughing, and respiration depression induced by certain drugs are well-known complications. The patient should not be extubated in a too early stage to prevent pneumonia. Furthermore, physiotherapist-led breathing therapy may be considered.
In recent years the literature has seen numerous reports highlighting perioperative complications in myotonic dystrophy, with the number of complications ranging from 8 to almost 50%. To date, much is still unknown about their aetiology. More specifically, we still lack insight into why certain anaesthetics are so poorly tolerated. Possibly, fundamental research of the mechanisms of myotonic protein kinase and the effects of anaesthetics on the various tissues, particularly of the brain, will shed new light on causal or mediating processes. In general it is advised to take Harper’s observation to heart (1994): "The patient with myotonic dystrophy is best served by doctors that protect him from any surgical interventions that are not strictly necessary.
From: NMZ-bulletin May 2002
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