(401) From Anesthesia to Paralysis: A Case of Pseudocholinesterase Deficiency

Introduction: The pseudocholinesterase (PChE) enzyme, or butyrylcholinesterase (BChE), is produced by the liver and metabolizes choline-esters such as neuromuscular blocking agents (NMBAs). PChE deficiency is rare and results in prolonged paralysis and apnea when NMBAs are administered.

Description: A 19-year-old male with no known medical history or medication use presented with acute urinary retention. Physical exam revealed suprapubic tenderness. Laboratory studies were normal. Bladder scan showed urine retention of 500 mL, and foley catheter placement was unsuccessful. He therefore underwent cystoscopy under general anesthesia with Propofol and Succinylcholine. Post-operatively he developed prolonged emergence from the neuromuscular blockade despite administration of Sugammadex. He was kept intubated, sedated, and transferred to the ICU. After 4 hours, he was extubated and fully recovered. Analysis for BChE level and dibucaine inhibition revealed BChE level of 441 IU/L and dibucaine number of 30% indicative of prolonged apnea.

Discussion: PChE deficiency is estimated to occur in 1 in 3000 to 5000 individuals, with higher incidence seen in Ashkenazi Jews. The condition is inherited in an autosomal recessive pattern or may be acquired due to liver disease, renal failure, malnutrition, and pregnancy. It can be discovered when respiratory paralysis persists after administration of NMBAs. Neuromuscular blockade duration is dependent upon the genetic pattern, as heterozygotes will experience a moderate duration while homozygotes can experience paralysis lasting 2 hours or longer. The diagnosis is confirmed by measuring the plasma PChE activity assay. Normal levels range from 4,000 – 13,500 U/L while reduced levels indicate deficiency. The dibucaine number is another test used to assess the activity of PChE. Dibucaine normally inhibits the activity of PChE by 80%. Enzyme activity will be inhibited by 40-60% in heterozygotes, and by 20-30% in homozygotes. Lower dibucaine number is indicative of expected prolonged neuromuscular blockade. Management includes supportive care and mechanical ventilation. The prognosis is excellent with early detection and recovery is spontaneous. Thus, early recognition is imperative for prevention of complications during anesthesia in affected or high risk individuals.