Pseudocholinesterase deficiency in ophthalmology: a systematic review

PURPOSE

Unexpected anesthesia-related complications are among the most feared outcomes of ambulatory surgery. One potential culprit is pseudocholinesterase deficiency, which most commonly presents with protracted apnea, necessitating prolonged mechanical ventilation. We report the first case of pseudocholinesterase deficiency in a Bengali person and the first systematic review of pseudocholinesterase deficiency in ophthalmology. This review analyzed the epidemiology, etiologies, presentation, evaluation, and treatment of pseudocholinesterase deficiency.

METHODS

Searches were conducted in PubMed, Embase, and Medline through August of 2022 for publications related to pseudocholinesterase deficiency in ophthalmology. In total, 689 studies were screened by two independent reviewers with 26 full-text articles examined for inclusion eligibility. Nineteen studies were eligible and included in the final analysis.

RESULTS

Of the 16 identified cases of pseudocholinesterase deficiency, nine (56%) were drug-induced, four (25%) were inherited deficiencies, and in one (6%) of the cases, the cause could not be determined. In two (13%) cases, pseudocholinesterase deficiency could not be confirmed or ruled out. The duration of post-operative apnea ranged from 10 minutes to 14 hours. Continued ventilatory support was the main treatment for all cases and all patients made a full recovery.

CONCLUSIONS

Pseudocholinesterase deficiency is a rare, but potentially fatal, anesthetic complication that results in prolonged apnea, respiratory distress, and dependency on ventilators. Ophthalmologists should remain aware of this condition, especially when planning outpatient procedures, as ambulatory centers may have limited resources for managing prolonged post-operative complications.

Optimal detection of cholinesterase activity in biological samples: modifications to the standard Ellman's assay

Ellman's assay is the most commonly used method to measure cholinesterase activity. It is cheap, fast, and reliable, but it has limitations when used for biological samples. The problems arise from 5,5-dithiobis(2-nitrobenzoic acid) (DTNB), which is unstable, interacts with free sulfhydryl groups in the sample, and may affect cholinesterase activity. We report that DTNB is more stable in 0.09 M Hepes with 0.05 M sodium phosphate buffer than in 0.1M sodium phosphate buffer, thereby notably reducing background. Using enzyme-linked immunosorbent assay (ELISA) to enrich tissue homogenates for cholinesterase while depleting the sample of sulfhydryl groups eliminates unwanted interactions with DTNB, making it possible to measure low cholinesterase activity in biological samples. To eliminate possible interference of DTNB with enzyme hydrolysis, we introduce a modification of the standard Ellman's assay. First, thioesters are hydrolyzed by cholinesterase to produce thiocholine in the absence of DTNB. Then, the reaction is stopped by a cholinesterase inhibitor and the produced thiocholine is revealed by DTNB and quantified at 412 nm. Indeed, this modification of Ellman's method increases butyrylcholinesterase activity by 20 to 25%. Moreover, high stability of thiocholine enables separation of the two reactions of the Ellman's method into two successive steps that may be convenient for some applications.

A survey of semen indices in insecticide sprayers

This study aims at clarifying the semen indices of insecticide sprayers who are exposed mainly to organophosphorus and pyrethroid insecticides. Eighteen male sprayers out of 54 working for 9 companies in central Japan and 18 age-matched students or medical doctors as unexposed controls participated in detailed reproductive check-ups conducted in summer and the following winter. The sprayers were exposed to insecticides more in summer, the busiest season, than winter, the off-season (p<0.05). Erythrocyte true cholinesterase activities in the sprayers were lower than in the controls in summer (p<0.05), and decreased in significant association with the increase in exposure frequency. Testicular volumes in the sprayers tended to be smaller than in the controls (p=0.06). The serum testosterone concentration in winter in the sprayers was higher than in the controls (p<0.05), though luteinizing hormone and follicle stimulating hormone concentrations were not significantly different. The sperm counts and vitality were comparable between the groups, but detailed sperm motility analysis in summer revealed that the percentages of slow progressive and nonprogressive motile sperm were twice as high in the sprayers (p<0.05), and that of rapid progressive sperm tended to be lower (p=0.06). Such differences were not observed in winter. Differential sperm morphology counts showed that interaction of group and abstinence effects were significant in sperm with normal morphology and with head deformity only in the summer check-up. Despite possible inherent differences between the groups, the above season-dependent differences suggested that the observed lower semen quality in the sprayers was associated with pesticide spraying work.

Improved determination of acetylcholinesterase activity in human whole blood

Determination of erythrocyte acetylcholinesterase (AChE) activity is the appropriate tool for the diagnosis of organophosphate exposure and intoxication. The original colorimetric Ellman procedure is disturbed by a high hemoglobin absorption at 412 nm. In our modified method the wavelength was changed to 436 nm. This reduced the indicator absorption to 80% and the hemoglobin absorption to 25%. The signal-to-noise ratio was further enhanced by reduction of pH and substrate concentration, thus making it possible to measure 3% residual activity. AChE activity was determined in whole blood samples in the presence of the selective butyrylcholinesterase inhibitor ethopropazine. Dilution of blood samples (1:100) stops secondary reactions in the presence of inhibitor (organophosphate) and reactivator (oxime). Normalization of the AChE activity to the hemoglobin content, determined as cyanmethemoglobin, prevented dilution errors. This modified approach provides a simple way for sensitive and precise determination of AChE activity in whole blood in the presence of organophosphates even with low-tech equipment.

Elevated amylase is related to the development of respiratory failure in organophosphate poisoning

1. A retrospective study of organophosphate (OP) poisoning in the intensive care unit was performed to analyze the incidence of respiratory failure. 2. The patients were treated initially with gastrointestinal decontamination including gastric lavage and the administration of activated charcoal with cathartic. Further management included intravenous pralidoxim and atropine and ventilatory support. 3. Of the 32 OP poisoning patients, 16 patients developed respiratory failure and received ventilatory support. 4. An increase in plasma amylase above the normal range on the day of admission was related to the development of respiratory failure. 5. In OP poisoning, the elevation of amylase level was predictive of the subsequent respiratory failure.

A semiautomated flow injection procedure for acetylcholinesterase and cholinesterase activities

A stopped-flow FIA adaptation of the classical Ellman's colorimetric procedure for the measurement of acetylcholinesterase or cholinesterase activity is described. The samples are injected into a flow analytical system which is provided with an electronic timer and an electrovalve in order to stop the flow when the sample is inside the measurement cell. In this way, the absorbance-time relationship is obtained with a savings of sample, time, and reagents.

Acetylcholinesterase in the human erythron. I. Cytochemistry

The successful demonstration and localisation of acetylcholinesterase (AChE), in cells by a cytochemical technique requires maximal expression of enzyme activity, minimal loss of AChE and precise, quantitative generation of reaction product at the actual site of the protein in vivo. These requirements are addressed in a standard technique that has been modified to avoid or optimise fixation and to exhibit enzyme activity under close-to-physiological conditions of osmolality, pH, and temperature. With these refinements and with the use of a variety of substrates and enzyme inhibitors of different specificities, true AChE was demonstrable on the membrane of erythrocytes and in the nucleus and cytoplasm of erythroblasts in bone marrow and of the constituent cells of erythroid clones in vitro. The activity in erythrocytes from umbilical cord blood was less than that in corresponding cells from the peripheral circulation of adults. AChE was observed also in human megakaryocytes and in leucocytes at all levels of differentiation, including the components of granulocyte-macrophage clones. Pseudocholinesterase was detected likewise across the spectrum of erythroid (and leucocyte) ontogeny, suggesting that these enzymes may exercise an important function in hematopoiesis.

Prolonged apnea after orthognathic surgery due to atypical cholinesterase

Prolonged apnea (9 hours) after elective orthognathic surgery occurred in a healthy adult female. The patient had previously undergone multiple general anesthetics without any adverse reactions or complications. Measurement of the patient's serum postoperatively confirmed both a qualitative and quantitative defect in the cholinesterase enzyme. The genetic background for an atypical cholinesterase phenotype is briefly reviewed. Treatment modalities for this rare condition are also discussed.