Sir, Myotonic dystrophy is an autosomal dominant multisystem disorder characterised by progressive weakness and wasting of muscles, cardiomyopathy and cardiac conduction defects, restrictive lung disease, sleep apnoea syndrome, slow gastric emptying, endocrine disorders and cataracts. This condition is often associated with prolonged muscle contractions with defective relaxation (myotonia). There are two major types of myotonic dystrophy: Type 1 and type 2. These are caused by mutations in different genes. Anaesthetic management of this condition can be challenging due to the potential for these patients to develop perioperative cardiorespiratory complications and because they may demonstrate abnormal responses to sedative and neuromuscular blocking agents. We present a report of the successful management of a 60-year-old gentleman with myotonic dystrophy type 1, weighing 70 kg, who presented for elective laparoscopic cholecystectomy. His symptoms had included progressive weakness of the upper limbs with dysarthria, soft voice and mild static swallowing impairment. He had dilated cardiomyopathy and had a pacemaker/defibrillator in situ. The patient also had moderate obstructive sleep apnoea and was saturating at 99% in room air. This patient had never undergone general anaesthesia, and all his previous investigations had been performed previously under local anaesthesia with sedation. Pre-operative examination findings included the characteristic facial features of myotonic dystrophy and a modified Mallampati class III. On the day of surgery, no oral pre-medication was given other than his usual medications. Intra-operative monitoring included five-lead electrocardiography, pulse oximetry, capnography, invasive blood pressure monitoring with a right radial artery catheter and bispectral index (BIS). Magnet and external defibrillator pads were placed over his chest. Following adequate pre-oxygenation, induction and maintenance of anaesthesia were carried out with 0.5 mg of midazolam followed by propofol and remifentanil target controlled infusion titrated to BIS between 40 and 60 and haemodynamic status. After the initial administration of 50 mg rocuronium for intubation anticipating approximately 2 h procedure, we had planned to give subsequent doses guided by a peripheral nerve stimulator. A grade II b laryngeal view was obtained with direct laryngoscopy and a size 8.5 endotracheal tube was inserted. The maintenance phase of anaesthesia was uneventful, and no other analgesia was given intra-operatively. Upper and lower body forced air warmers were used throughout. The surgery was uncomplicated and lasted 45 min. At the end of surgery as no twitches were observed with train-of-four (TOF) stimulus after the initial intubating dose of rocuronium, the decision was made to reverse neuromuscular blockade with an initial sugammadex dose of 200 mg and further administer additional doses if necessary. Interestingly with the initial dose, all the four twitches to TOF stimuli appeared with no fade, merely within 30 s. Furthermore, there was no obvious fade with double burst stimulation. The patient was extubated when fully awake after a smooth emergence. His oxygen saturation was 99% with 5 L/min of supplemental oxygen. The patient was admitted to the Intensive Care Unit for observation and had an uncomplicated recovery. Patients with myotonic dystrophy often have respiratory muscle weakness resulting in an ineffective cough. This can co-exist with a decreased ventilatory response to hypoxia and hypercapnia. Pharyngeal muscle weakness and prolonged gastric emptying may increase the risk of aspiration. As a consequence, there is a possibility of increased postoperative pulmonary complications in this patient group.[1] Suxamethonium can result in exaggerated contracture in patients with myotonic dystrophy.[1] It may be difficult to predict the reaction to neostigmine in these patients as it can result in aggravation of paralysis or myotonia.[2,3] Peripheral nerve stimulation itself can also result in a myotonic response that may be misinterpreted, as sustained tetanus.[1] Residual neuromuscular blockade may further increase the risk of postoperative pulmonary complications in these patients. Sugammadex, a modified gamma-cyclodextrin, selectively binds with rocuronium or vecuronium to reverse the neuromuscular blocking effect. It is devoid of the risks of neostigmine and with better efficacy at reversal, has been suggested as a superior alternative.[4,5,6] We had decided to use rocuronium and sugammadex combination, to avoid the possible need for neostigmine to reverse any other relaxant as well as because of lack of quantitative neuromuscular monitoring with which we could ensure complete reversal. In contrast to the previous reports, where sugammadex was either given to avoid the possibility of residual paralysis[4] or less than normal dose of rocuronium was given for intubation,[6] we observed that using sugammadex, we could easily reverse a complete paralysis following the usual intubating dose of rocuronium (approximately 0.6 mg/kg). We therefore suggest that sugammadex, if available, should be considered for reversal of neuromuscular blockade with steroidal non-depolarising muscle relaxants in patients with muscular disorders such as myotonic dystrophy, particularly in facilities where advanced neuromuscular monitoring is unavailable.
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Jul 31, 2024
Disha Deshmukh + 4
Open Access