Unexpected Prolonged Neuromuscular Blockage in a Pediatric Patient

Abstract

Background: Mivacurium is a selective, short-acting, non-depolarising muscle relaxant, which is used to facilitate tracheal intubation and provide skeletal muscle relaxation during surgery or mechanical ventilation. A standard intubating dose of 0.2 mg/kg in children (aged 2–12) causes complete neuromuscular depression in 1.5-2 minutes and spontaneous recovery is 95% complete in approximately 20 minutes. As mivacurium is hydrolyzed by pseudocholinesterase (PCE), a deficiency in this enzyme may result in a prolonged blockage. In this case, we present an unexpected prolonged neuromuscular block in a child after a single dose of mivacurium. Case report: A 7-year-old boy underwent bilateral adenotonsilectomy. The patient had not been anaesthetized in the past and there was no family history of adverse reactions to anesthesia. He did not take any medication and denied drug allergies. Physical examination revealed a healthy 32 kg male. For induction of general anesthesia 0.05 mg fentanyl and a single dose of 3 mg mivacurium were infused, followed by endotracheal intubation 2 minutes later. In this case, only half of the recommended dose (0.09 mg/kg) of neuromuscular blocker was used. Anesthesia was maintained with 1 MAC (minimum alveolar concentration) sevoflurane in oxygen. Surgery lasted 50 minutes uneventfully and anesthesia was continued in the operating room for another 20 minutes. However, complete recovery from anesthesia was complicated by respiratory failure due to residual action of mivacurium. For safe extubation, he was transferred to the intensive care unit. The P-SIMV- Ventilation Mode was continued, and consciousness was additionally sedated with intravenous midazolam 2.5 mg and propofol 50 mg doses. Full spontaneous respiration was restored after 230 minutes after a single bolus of 0.09 mg/kg mivacurium with safe extubation. Conclusions: It is currently not practical to screen for all presurgical cases of pseudocholinesterase deficiency if the patient has no family history of this disorder. Usually, for faster non-depolarising neuromuscular-blockage recovery, neostigmine is used as an antidote. However, the current use of this antidote is still under discussion because it may potentially prolong the mivacurium induced neuromuscular-blockage and should only be used when the majority of euromuscular activity has returned.