Artificial liver is not a true name. Since modern science cannot yet recreate this organ. The liver is too complicated for this and performs a huge number of functions. For example, the main function of the kidneys is the secretion of excess water and substances from the body. It is the function of removing toxic substances that the artificial kidney performs. An artificial heart performs this function by a pump that pumps blood to all organs. The liver performs more than a hundred functions. To create a device that performs so many functions is almost impossible. However, devices exist, are manufactured in several countries, and have already helped many people. Let’s figure out what artificial liver devices do, how they differ from each other.
Liver failure
The main pathology of the liver, which doctors around the world face, is failure. The main causes are viral lesions - hepatitis B and C, alcohol intoxication, long-term use of drugs, mainly paracetamol, and poisoning by toxins can also cause pathology. Liver failure is a condition when an organ cannot maintain a constant internal environment and metabolism.
The complexity of the treatment lies in the fact that all the measures that a doctor can take (eliminating blood clotting disorders, hypoxia, normalizing the water-salt balance and acid-base state) do not improve the patient's condition. The basis of the course of the disease is the accumulation of toxic substances that are different in chemical composition, solubility and target organs. All these substances do not periodically enter the body, but are vital products of the body itself. This means that toxins continuously accumulate, and to maintain the patient's life, they must be constantly removed.
Modern methods of treating liver failure
The only radical way to eliminate liver failure is a liver transplant. However, even in Europe, about 15 thousand people die annually before this operation: the number of donors and recipients of the liver is completely different.
The course of liver failure is based on the death of liver cells (hepatocytes) under the influence of damaging factors (viruses, drugs, etc.). The appearance of clinical signs of liver failure suggests that 80% of hepatocytes are not already functioning. Liver cells are well restored, but for this they need to temporarily relieve the load and take on their functions. That is, the main task of treating patients is to create conditions for the regeneration of hepatocytes. For this, several extracorporeal (that is, “outside the body”) treatment methods are used in modern medicine. These methods can be divided into two groups: biological and non-biological.
Biological methods for maintaining liver function
The use of live hepatocytes taken from animals, stem or cancer cells is implied. The devices process such toxic waste products as ammonia, bile acids, and bilirubin. On the cellular principle, several liver support systems have been created: the “auxiliary liver” by N. Yu. Korukhov, the “auxiliary artificial liver”, the “bio-artificial liver support system”, and other biological systems.
The devices are hollow tubes with hepatocytes through which the patient’s blood or plasma passes. Blood during the passage through the tube is in contact with hepatocytes, which render it harmless. Then the purified blood returns to the human body.
The source of the cells is the most talked about topic. The most promising options:
- liver cells taken from live pigs have a short lifespan;
- stem cells taken from a human fetus raise ethical issues;
- cancer cells are a promising option.
The advantage of biological systems of an artificial liver is that they not only neutralize toxins, but also perform other functions of the liver: they participate in metabolism, synthesize a number of substances, deposit blood, and participate in antibacterial defense. The disadvantages of using living cells are the difficulty of working with them and, accordingly, the high cost of the systems, the need to include additional devices in the device to provide cells with oxygen.
Currently, several countries use an artificial liver device based on cancer cells developed in the USA - ELAD.
Non-biological methods for maintaining liver function
They imply the use of methods based on adsorption and filtration, replacing the neutralizing function of the liver. These include:
- hemodialysis;
- hemofiltration;
- hemosorption;
- plasma exchange;
- molecular adsorbing recirculation system ("MARS");
- fractionated plasma separation and adsorption (Prometeus).
These methods have their drawbacks: the first three methods of replacing liver function reduce the concentration of individual toxins in the blood, but generally do not ensure the survival of patients. Palazmo-exchange is more effective, but it requires a large amount of donor plasma, which leads to the risk of infection with viruses, including immunodeficiency and hepatitis. In addition, slightly reduces mortality. It is worth noting that the first four methods have many negative effects on the patient's body.
Prerequisites for the creation of "MARS" and "Prometheus"
The main cause of death in patients with liver failure is intoxication of the patient with waste products, causing jaundice, hepatic encephalopathy (brain damage), hepatorenal syndrome (simultaneous damage to the liver and kidneys), impaired hemodynamics and, in many cases, failure of many organs and systems. Mortality in acute liver failure reaches 90%.
Toxic products can be divided into two groups:
- water-soluble - ammonia, tyrosine, phenylalanine;
- water-insoluble, usually associated with albumin: bilirubin, bile acids, fatty acids, aromatic compounds.
Moreover, the liver synthesizes mainly substances of the second group.
Existing methods for extracorporeal support of the liver - hemodialysis, plasma exchange, hemofiltration and hemosorption - allow you to remove only predominantly water-soluble substances from the blood. Thus, water-insoluble toxic substances associated with albumin remain in the blood.
The development of modern medicine allows us to combine the applied extracorporeal methods of therapy and create a new generation of artificial liver. It is these life support systems that are now used in many countries.
Prometheus System
In 1999, an artificial liver system called Prometheus was developed in Germany. The principle of its work is based on a combination of two methods of extracorporeal treatment:
- hemadsorption - separation of blood plasma into separate fractions (separation) and adsorption of toxins on the albumin fraction;
- hemodialysis - blood purification filter.
The separation is carried out using a filter permeable to albumin, which is small in size and does not allow cells and large molecules to pass through. Further, albumin with toxins separated from the blood passes through the adsorbent system, where these toxins remain, and albumin itself returns to the patient’s blood. Thus, water-soluble substances are removed by hemodialysis associated with albumin - hemadsorption. Thus, the Prometeus artificial liver system supports the detoxifying function of the organ, thereby facilitating the regeneration of hepatocytes.
Devices "Prometeus" are used in many countries, including Russia. For example, it is used at the Surgery Center of the Ministry of Health of Russia.
Mars system
Artificial liver "MARS", developed in the 90s in Germany, like Prometeus combines sorption and dialysis. But the method of purification is different. The patient's blood enters the membrane, permeable only to small molecules of toxins. They pass through the membrane and bind to donor albumin. Purified blood is returned to the patient. Albumin bound to toxins is cleared through a complex of adsorbents and returned to the system. Thus, the difference and the main advantage of the artificial Mars liver is that albumin can be reused.
MARS has been successfully used in Russia since 2002. Artificial liver devices in Moscow are in several clinics, for example, at the Scientific Center for Cardiovascular Surgery named after Bakuleva is both Prometeus and MARS.
Despite the constant search for new methods of creating artificial liver apparatuses, some of them have already proved their effectiveness and are successfully used in many countries, including Russia.