Definition – What is cholinesterase deficiency?
Cholinesterase is an enzyme (a substance that speeds up chemical reactions in the body, usually a protein) and is produced in the liver. It plays an important role in the transmission of impulses from nerves to, for example, muscles (see: Motor End Plate). If the liver is damaged by any cause, the production capacity is also disturbed and a cholinesterase deficiency occurs. Thus, by determining the cholinesterase in the blood, it is possible to draw conclusions about liver function.
What are the causes of cholinesterase deficiency?
Since cholinesterase is produced in the liver, its production may be limited in a variety of liver disorders, resulting in deficiency. Such liver damage can occur, for example, when the painkiller paracetamol is overdosed. In addition, liver cell-damaging diseases such as inflammation of the liver (hepatitis), liver cirrhosis or hepatocellular carcinoma (hepatocellular carcinoma) can lead to a deficiency in the production of cholinesterase.
Not only hepatocellular carcinoma can have an effect on cholinesterase. In a large number of tumour diseases, patients become emaciated in advanced stages. This lack of physical reserves can also lead to reduced liver function and thus to a cholinesterase deficiency.
Two types of poisoning can also lead to damage to the liver cells. These are poisonings with the tuber leaf fungus or with the insecticide E 605. There is also a congenital form of cholinesterase deficiency.
Symptoms of cholinesterase deficiency
A cholinesterase deficiency alone cannot be detected by a disease-specific symptomatology. If the cholinesterase is reduced due to a causative liver disease, a wide variety of symptoms can occur, but these are more likely to be caused by the liver disease than by the cholinesterase deficiency itself. These symptoms include yellowing of the dermis of the eyes or skin (see: jaundice), itching, bleeding, visible veins in the abdomen or an enlargement of the liver, which becomes palpable.
These symptoms do not always occur when the liver is damaged and are not characteristic of cholinesterase deficiency. Specific symptoms only occur when a patient with an as yet unknown cholinesterase deficiency is administered a certain medication under general anaesthesia to relax the muscles. The consequences and causes of this are described in the following subchapter.
Effects of cholinesterase deficiency under anaesthesia
During anaesthesia, drugs for muscle relaxation are given as standard. These cause the muscles in the body to relax and thus facilitate ventilation during anaesthesia and also the operation itself. A group of muscle relaxants (succinyl type) achieve the effect of muscle relaxation by attaching to certain receptors on the muscle and over-stimulating it.
This overstimulation blocks further stimulation of the muscle and prevents further excitation of the muscle. This muscle relaxant is broken down by cholinesterase. This means that the cholinesterase splits the muscle relaxant that is bound to the muscle.
The cleavage product is then broken down via the blood. This mechanism causes the muscle relaxant to gradually lose its effect until normal excitability of the muscle is restored. If there is now a deficiency in cholinesterase, the muscle relaxant is broken down much more slowly. This information is important before performing anaesthesia with respiration, as another group of drugs is then used to relax the muscles, otherwise dangerous paralysis of breathing can occur, as the driving muscle for breathing (diaphragm) is also blocked by the muscle relaxant. This danger exists especially in the congenital type of cholinesterase deficiency.
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