Successful anaesthetic management of a patient with prior history of malignant hyperthermia for corrective scoliosis surgery
A 14-year-old girl was scheduled for correction of idiopathic infantile right thoracolumbar scoliosis. The surgery was previously attempted at a different hospital 2 years before. But, because she developed features suggestive of malignant hyperthermia, the procedure was abandoned. She had apparently developed some features during the 3 h of intra-operative period; tachycardia, muscle rigidity, hypercarbia, dark-coloured urine and hyperthermia (1080 F). On laboratory evaluation, she was found to have respiratory acidosis and elevated CK levels, which settled over the next 3 days, for which she was treated symptomatically and discharged. Muscle biopsy performed at a later date showed congenital myopathy with type 1 fibre predominance.\nHer past history revealed delayed gross motor milestones, recurrent respiratory tract infections and progressive spine deformity with back pain. With a history of easy fatigability and dyspnoea on mild exertion and a breath holding time of 8-10 s, she presented a picture of gross respiratory compromise, which was confirmed by pulmonary function tests that revealed severe restrictive defect [forced expiratory volume in 1 second (FEV1) - 25% predicted; forced vital capacity (FVC) - 28% predicted, FEV1/FVC - 83% predicted] and not responding to bronchodilators. Other than being underweight, her general physical and airway examinations were normal. All laboratory investigations (complete blood picture, blood urea, serum creatinine, serum electrolytes, coagulation profile, liver function tests) and two-dimensional echocardiogram were normal. X-ray chest showed right thoracic scoliosis with left lumbar compensation, with a Cobb's angle of 90 degrees and normal lung fields. Baseline arterial blood gases (ABG) and CK were normal and urine tested negative for myoglobinuria.\nInformed consent was taken after counselling the family members regarding all the potential complications – recurrence of malignant hyperthermia, rhabdomyolysis, increased blood loss, haemodynamic fluctuations, delayed recovery, post-operative ventilator support and intensive care unit (ICU) stay.\nOn the day of the surgery, the anaesthesia workstation was flushed with 100% oxygen after removing the vaporizers. Fresh soda lime and anaesthetic circuit were used. Dantrolene, all other resuscitation drugs and ice packs were kept ready. Pre-operative vitals and arterial blood sample on room air were normal. She was wheeled into the operating theatre and anaesthesia was induced with inj fentanyl 2 mcg/kg and inj propofol 2 mg/kg. After confirming adequate ventilation, inj atracurium 0.5 mg/kg was administered and intubated with an oral cuffed endotracheal tube 6.5 and connected to the ventilator. The right internal jugular vein and the left radial artery were cannulated. She was then turned prone and the pressure points were adequately padded. Oral airway was placed to prevent tongue bite during monitored evoked potential (MEP) stimulus.\nApart from standard monitoring, neuromuscular monitoring was also performed using MEP. Anaesthesia was maintained using oxygen – air mixture 40:60 and propofol (125-150 mcg/kg/min) and fentanyl (1-1.5 mcg/kg/h). No further muscle relaxants were administered. The procedure lasted for nearly 7 h and was uneventful. MEPs were adequate during the procedure. Intra-operative blood loss was approximately 1500 mL and four units of whole blood were transfused. Intra-operative urine output was 1 mL/kg/h. At the end of surgery, the patient was turned supine and muscle relaxation was reversed. Extubation was performed as she was fully conscious, obeying commands and had stable respiratory parameters.\nPost-operatively, her ABG revealed respiratory acidosis. As she was conscious and co-operative, intermittent bilevel positive airway pressure (BiPAP) support was given for 2 days post-operatively. She was shifted out of the ICU on the 4th post-operative day and discharged on the 6th post-operative day.