For general anaesthesia, two techniques are currently proposed: inhalational anaesthesia or intravenous anaesthesia with or without muscle relaxant [14]. Intravenous techniques should be preferred in myasthenia gravis, as the effect of halogenated agents on neuromuscular transmission is more pronounced in patients with myasthenia gravis than in healthy subjects [14].

The use of muscle relaxants is limited to formal indications (e.g. facilitate tracheal intubation and the surgical procedure). The pathophysiology of myasthenia gravis explains the clinical characteristics of the disease and the modifications observed when muscle relaxants are used: the nicotinic acetylcholine receptor is the target of both muscle relaxants and the autoantibodies responsible of myasthenia gravis [8, 15]. The use of muscle relaxants is not contraindicated and should be adapted in order to allow withdrawal of ventilation at the end of surgery. There is a resistance to succinylcholine (depolarizing muscle relaxant), and the dose needed to achieve neuromuscular block is increased [16, 17]. Anticholinesterase therapy, if continued, reduces the metabolism of succinylcholine and leads to delayed recovery of neuromuscular blockade. Non-depolarizing muscle relaxants, regardless of their chemical classes and duration of action, require doses reduced by 50–75% because of a significant increase of sensitivity and therefore an increase in their duration of action. This reduction depends on the severity of myasthenia gravis. Neuromuscular function assessment by nerve stimulation (train of four, TOF) at the adductor pollicis prior to administration of a non-depolarizing muscle relaxant can predict sensitivity. In myasthenia gravis, a TOF ratio below 0.9 implies a higher sensitivity to muscle relaxant, whereas patients with a TOF ratio equal ou greater than 0.9 have the same sensitivity as healthy subjects [18]. Monitoring neuromuscular blockade is crucial to prevent overdosage and residual block and thus prolonged postoperative mechanical ventilation. Titration and monitoring enable a safe and optimized use of non-depolarizing muscle relaxants.

In these diseases, cardiac muscle involvement leads to overall cardiac failure (contractility disorder) associated with rhythm and conduction disorders with a high risk of sudden death. It is responsible for early death around the age of 25. Due to walking disorders, cardiac symptoms often do not arise despite the early involvement of cardiac pump function. The tolerance to a surgical procedure depends on the severity of the cardiac damage, especially for surgery with high risk of excessive blood loss.

Preoperative assessment has to determine the severity and extent of muscle damage, presence of deformities and retraction, deglutition disorder and respiratory or cardiac insufficiencies. Due to reduced physical activity, exercise tolerance is difficult to determine and the clinical severity of respiratory and cardiac function is often underestimated. Respiratory investigations (chest X-ray, pulmonary function tests and arterial blood gas analysis) and cardiac investigations (ECG, echocardiogram, stress testing, 24-h Holter ECG) are most often performed as part of the multidisciplinary follow-up of these children and should be available at anaesthetic preoperative assessment.

The degradation of cardiac and respiratory functions should be monitored by sequential evaluation of the left ventricle ejection fraction and pulmonary function tests. For a major surgical intervention (e.g. spinal surgery), the following pragmatic attitude is proposed based on the result of stress echocardiogram: a good prognosis is associated with an increased heart rate after dobutamine administration whether the ejection fraction is normal or impaired. However, the prognosis seems to be poor when the ejection fraction at rest is under 40% and decreases with dobutamine-induced tachycardia.

In the case of Duchenne muscular dystrophy, ventricular arrhythmias are associated with the progression of cardiac impairment and the risk of sudden death [26]. The echocardiography and the 24-h Holter ECG are useful in the evaluation of the surgical risk [27]. Several severe intraoperative complications are reported in the literature: respiratory failure (aspiration pneumonia due to impaired gastric emptying), cardiac complications (arrhythmias, heart failure, cardiac arrest), myoglobinuria and rhabdomyolysis [28, 29]. Dystrophinopathies are not associated with an increased risk of per-anaesthetic malignant hyperthermia (MH) (Table 15.2). However, syndromes mimicking an MH are reported and can probably be linked to the use of succinylcholine or halogenated agents or both. When used on fragile and pathological muscles, succinylcholine can cause massive rhabdomyolysis and death [35]. Therefore, in Duchenne muscular dystrophy and, by extension, in any primary muscular disorders, succinylcholine is absolutely and definitely contraindicated because of the risk of massive rhabdomyolysis. For general anaesthesia, anaesthetics drugs should be titrated because of variable interindividual sensitivity. Non-depolarizing muscle relaxants should be used only in case of imperative indication. If used, their sensitivity is increased. Therefore, reduced doses are required to avoid prolonged recovery [36, 37]. Nerve stimulator monitoring is mandatory and should be interpreted with caution because of both muscle atrophy and retractions. Residual neuromuscular blockade is frequent and pharmacological reversal is problematic. Neostigmine and atropine are difficult to use in dystrophinopathies due to their effect on secretions dryness (atropine), potential rhythm and conduction disorders (both), central effects (atropine), delayed onset and direct effects on muscle action potential (neostigmine). If an aminosteroid muscle relaxant like rocuronium is used, residual effect can be reversed using sugammadex. This strategy has been successfully evaluated [38].

Inhalational and intravenous anaesthetic agents can be used. Complications are reported with both [28, 29]. Intubation difficulties are more frequent [28, 29]. In case of major surgery, suitable hemodynamic monitoring is needed (invasive blood pressure in particular). Central temperature should be monitored as postoperative shivering can lead to rhabdomyolysis. Hyperthermia can also be observed independently of any MH symptoms as a consequence of massive rhabdomyolysis. The patient’s position on the operating table should be very careful to prevent any excessive pressure on muscles.