2004 Volume 56 Issue 2 Pages 91-98
Synopsis Serum cholinesterase (ChE) or pseudocholinesterase has been recognized as an enzyme that hydrolyzes choline esters to choline and organic acid, and it can be found in the liver, blood, and various internal organs. This enzyme is generally accepted as being synthesized in the liver and has been routinely measured as a test of liver function and has been used as a preoperative parameter. Patients with low ChE generally have no signs or symptoms and can have a healthy life. However, when these patients must be injected with a muscle relaxant, such as succinylcholine, which is broken down by ChE, they may develop prolonged apnea because of the lack of this enzyme. Moreover, its' absence causes escalation of blood concentration of amino-ester type of anesthetics and eventually lead to convulsion. Thus, it is important to evaluate the levels of serum ChE. The cholinesterase activity in pregnant women is low and is about 70% of the normal range.
We had a patient who had absence of ChE. All other laboratory results were normal. The absence of ChE was just accidentally diagnosed when patient had serum level determination prior to elective cesarean section.
This case involves a 26 year-old woman G3P1 (1011) who was admitted in our hospital because of elective cesarean section at 37 weeks of gestation. Her fetus was in breech presentation and she had intramural myoma. Her serum cholinesterase was anomalously low at 2.0 IU/l (normal range=203~460 IU/l ; the substrate was 5-Methyl-2-thenoylthiocholine-iodine). The spinal anesthetic agent was changed from amino-ester type (usual choice) to amino-amide type. Surgery was uneventful. If we had to do emergency cesarean section under general anesthesia, depolarizing relaxant will be avoided.
The usual abnormality with ChE is very low level, hence this case was unusual because of the absence of ChE. We assumed that she is an atypical form of human ChE or deficiency of ChE. After obtaining informed consent for DNA analysis, we collected whole blood samples, and extracted white-blood cell DNA. Exons 2, 3 and 4, which encode the entire mature protein of ChE, were individually amplified by polymerase chain reaction (PCR). After confirming the sizes and homogeneity of the PCR products, we performed direct sequencing of the entire coding region of the ChE gene. Analysis of ChE gene revealed two-point mutations at nucleotides 1615 (exon 3) and 1543 (exon4), and both were homozygous. We suppose that these two homozygous mutations caused a decrease in ChE activity. Furthermore, we performed DNA analysis of her family because of this finding, with the probability of hereditary ChE deficiency or low ChE. There are very few reports of pregnancy complicated with ChE deficiency. Moreover, the two-point mutations which are homozygous have not been reported.
In conclusion, it is very important to determine ChE prior to administration of any anesthetic agent in order to avoid complications associated with cholinesterase deficiency. [Adv Obstet Gynecol, 56(2) : 91-98, 2004(H16.5)]
