Anaesthesia and orphan disease: rocuronium and sugammadex in the anaesthetic management of a parturient with Becker's myotonia congenita.

Becker's Disease is an autosomal recessive type of myotonia congenita. Worldwide prevalence is about 1/100000. It is linked to mutations in CLCN1, the gene encoding skeletal muscle chloride channel. It reduces flow of chloride ions during repolarization and leads to sustained muscle contractions. Typical clinical symptoms are myotonic stiffness and “warm-up” phenomenon. 27 year old primipara with homozygote recessive mutation in CLCN1 (c.1437_1450del,p.480HfsX24) was indicated to elective caesarean section in 40 gestational week. In personal history she had thoracic stabilisation for scoliosis and hypothyreosis. We decided to provide the general anaesthesia with propofol in TCI mode (Schnider mode, C e =effective concentration 5 mcg/ml) and rocuronium 1 mg/kg IV for rapid sequence induction, monitoring the depth of neuromuscular blockade (NMB) on TOF WATCH SX device. The male newborn (APGAR score 9-10- 10) with no signs of pathology in acid-base balance in arterial umbilical blood was delivered. At the end of surgery (C e =1 mcg/ml, TOF=0, PTC=0) we administered sugammadex 4 mg/kg IV. It takes 2 min and 15 sec to reach TOF ratio 90% and subsequent extubation. After extubation she was breathing adequately, communicative, transferred to the recovery room and after two hours with no signs of residual NMB or respiratory problems back to the gynaecological ward to the monitored postoperative room. She was discharged home on 4 th day. This is the first report of anaesthetic management of a parturient with Becker's myotonia congenita who underwent CS under general anaesthesia. In this case we wanted to aware of using malignant hyperthermia (MH) triggering drugs, though the association with MH has been regarded as highly unlikely, suxamethonium which can cause total body rigidity and subsequent difficult airway management and neostigmine which can cause myotonic response.