JRSM >
Volume 97, Number 6 >
Pp. 284-285
1 Section of Surgery
2 Department of Anaesthetics, University Hospital, Queen's Medical Centre,
Nottingham NG7 2UH, UK
Correspondence to: Mr D N Lobo, Section of Surgery, E Floor, West Block,
University Hospital, Queen's Medical Centre, Nottingham NG7 2UH, UK
E-mail:
dileep.lobo{at}nottingham.ac.uk
Myotonic dystrophy is the most common inherited muscular disorder, and patients with this condition pose a challenge to surgeons and anaesthetists.
CASE HISTORY
A man aged 43 in whom myotonic dystrophy had been diagnosed at age 26 was judged to require cholecystectomy because of repeated attacks of acute cholecystitis; ultrasound showed a solitary medium-sized stone in the gallbladder. He had type 2 respiratory failure as a consequence of respiratory muscle weakness. Although not breathless at rest, he could not walk more than 100 m on the flat. Other relevant history included moderate to severe sleep apnoea and poorly controlled type 2 diabetes mellitus. His electrocardiogram showed first-degree heart block.
A laparoscopic procedure was decided on. After preoxygenation, anaesthesia was induced with intravenous alfentanil 1 mg followed by propofol 200 mg. Tracheal intubation was easily performed with a 9 mm cuffed tube and anaesthesia was maintained with oxygen, nitrous oxide and sevoflurane to an end-tidal concentration of 1.0-1.5%. Intermittent positive pressure ventilation was applied to maintain end-tidal carbon dioxide concentration at around 5 kPa and airway pressure was noted to be within normal limits. No neuromuscular blocking agents or further opioids were given. Ketorolac trometamol 15 mg was administered intravenously after induction and again at the end of surgery, when the wounds were infiltrated with 0.5% chirocaine hydrochloride.
At surgery, a standard 4 port technique was used. Because the patient was not given muscle relaxant it was difficult to maintain an adequate pneumoperitoneum at an insufflation pressure of 15 mmHg. The pressure was therefore raised to 20 mmHg with satisfactory results. Throughout the procedure, which lasted about 40 min, the patient remained stable and the operation was completed uneventfully. After return of spontaneous ventilation and removal of the endotracheal tube he was transferred to the high dependency unit for postoperative monitoring. A regimen of diclofenac sodium and paracetamol, by mouth or rectally, was prescribed for postoperative pain relief.
COMMENT
The myotonic dystrophy gene, on chromosome 19, codes for a regulatory protein kinase in skeletal muscle. Affected individuals usually have compromised respiratory function with globally reduced functional residual capacity, functional vital capacity and peak inspiratory pressures. They are exceptionally sensitive to neuromuscular blocking drugs,1 premedicants and opioids;2 moreover, the surgeon and anaesthetist must plan carefully to avoid precipitating myotonia by hypothermia, shivering and mechanical or electrical stimulation, before, during or after operation. The anaesthetic technique of choice remains uncertain. There are reports of exaggerated physiological responses3 and a myotonic state after propofol administration, but we are not the first to use it without ill effects.4 Other groups, too, have used this agent without muscle relaxants for laparoscopic cholecystectomy;5 however, in our patient an increase over the standard insufflation pressure was needed to overcome abdominal wall resistance. Clearly gas-less laparoscopic surgery, in which the abdominal wall is raised manually, will not be an option in patients with myotonic dystrophy, because it requires neuromuscular blockade.
Patients with myotonic dystrophy have a high rate of complications from surgery of all kinds, mainly respiratory complications.2,6 Men with this condition seem to be at excess risk of gallstone disease requiring surgery.7 Patient assessment should include detailed cardiovascular evaluation and full pulmonary function tests. Harper8 has published guidelines for the care of these patients before, during and after surgery.
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