Delayed Emergence Due to Prolonged Mivacurium Blockade in a Child with Markedly Reduced Butyrylcholinesterase Activity: A Case Report

Background: Delayed emergence after general anesthesia in pediatric patients is uncommon and requires prompt evaluation of pharmacological, metabolic, and neurological causes. Residual neuromuscular blockade remains an important reversible cause, particularly when short acting neuromuscular blocking agents dependent on plasma cholinesterase metabolism are used. Case report: We report the case of a previously healthy three-year-old boy who underwent elective adenoidectomy, tonsillotomy, and tympanostomy under general anesthesia with fentanyl, propofol, sevoflurane, and mivacurium. Following the procedure, the patient failed to regain spontaneous breathing, purposeful movements, or response to painful stimuli. In response, neostigmine was administered to reverse possible residual neuromuscular blockade; however, no immediate clinical improvement was observed, and mechanical ventilation was continued. Quantitative neuromuscular monitoring was unavailable. Therefore, residual blockade could not be objectively assessed, and the depth of blockade at the time of neostigmine administration remained unknown. The patient was transferred to a tertiary pediatric center for further evaluation. Several hours later, spontaneous breathing and motor activity recovered, and the patient was successfully extubated. Retrospective family history revealed prolonged recovery after anesthesia in the patient’s grandfather. Subsequent laboratory testing demonstrated markedly reduced plasma butyrylcholinesterase activity (2493 U/L; reference range 7000–19,000 U/L), raising a strong suspicion of inherited butyrylcholinesterase deficiency. Conclusions: This case highlights the importance of considering residual neuromuscular blockade in delayed emergence after pediatric anesthesia, maintaining airway protection, and obtaining relevant family history to guide future management.