Pitfalls of electromyography (EMG) in parathyroidectomy: a case report of unrecognized pseudocholinesterase deficiency.

Background: It is well known that patients with a pseudocholinesterase (PChE) deficiency will have an initial negative electromyography (EMG) signal during parathyroid surgery. However, the time to return to normal EMG signals in a patient with PChE deficiency who received succinylcholine combined with the common obstacles to EMG monitoring is yet to be described in the literature. Here we present the diagnostic challenges in a patient with unknown PChE deficiency undergoing parathyroidectomy. Case Description: The patient was a 74-year-old female and presented for elective parathyroidectomy with intraoperative neuromonitoring. The anesthesia induction was performed with propofol, fentanyl and succinylcholine. During the case, EMG responses were present; however, upon emergence, the patient was noted to exhibit profound weakness. Train-of-four ratio (TOFR) was 0.8, and post tetanic potentiation fade was recognized. Sedation and ventilation continued until the patient regained sustained tetanus with twitch monitor stimulation. Follow-up PChE levels were later evaluated, and her level was found to be 952 U/L, with normal being 2,900-7,100 U/L, which is consistent with homozygous PChE deficiency. Conclusions: If the EMG signal is missing in the early phase or if the EMG amplitude increases over time, suspicion for PChE deficiency should be high. Reviewing the literature, we recognized that there are no comprehensive checklists for EMG signals during parathyroid surgery. Based on our case report, we recommend establishing evidence-based anesthesia checklists at institutions that perform EMG monitoring since false negative results can have safety and economic implications.