The dialyzer in the backpack
Scientists of Sechenov University gave hope to patients with chronic kidney failure
The second Thursday of March has been declared World Kidney Disease Day. It is designed to attract people's attention to their own health, and politicians and managers to the problem of organizing treatment and prevention of diseases. According to estimates According to the World Health Organization, 2.6 million people received treatment for chronic kidney diseases – dialysis – in 2010, and developed countries spend tens of billions of dollars to help such patients. The need for dialysis may double by 2030 compared to 2010, which pushes for the development of new effective and safe "artificial kidney" devices.
Dialysis is prescribed to patients whose kidneys are partially or completely unable to perform their main functions: filter blood, maintain blood acidity and salt content, and excrete urine, with which metabolic products and toxic substances are excreted from the body. The causes of such a condition (kidney failure) can be injuries, inflammatory, infectious diseases, exposure to poisons or drugs. If kidney disorders become chronic and their functions cannot be restored with the help of medications and other types of therapy, hemodialysis, peritoneal dialysis or kidney transplantation can save the patient from poisoning by metabolic products.
Of the several types of dialysis, hemodialysis remains the main one – blood purification directly with the help of an "artificial kidney" device. Blood enters it from a vein or artery, passes through a dialyzer (a device with a semi-permeable membrane), there toxins and metabolites pass into a dialysis solution, which is drained into the sewer, and the blood returns to the human circulatory system. In chronic hemodialysis, the procedure is performed periodically (weekly) and takes several hours, which the patient spends lying or half-sitting at the device.
In peritoneal dialysis, the patient's abdominal wall is used as a membrane. The dialysis solution is gradually poured through a catheter into the abdominal cavity, where there is an exchange between the solution and blood in the vessels of the abdominal wall, after which the solution is drained and replaced with a new one. This method of dialysis can be used on an outpatient basis and during the procedure a person can go about their business. Scientific groups in several countries of the world are engaged in the creation of wearable devices for peritoneal dialysis. One of them works at the Institute of Bionic Technologies and Engineering of Sechenov University together with the Moscow Institute of Electronic Technology.
"Chronic renal failure is an acute problem for the world population, which is confirmed by the annual increase in the number of patients with such a diagnosis. For these patients, there are currently only two alternatives: kidney transplantation or dialysis. Transplantation is an option only for a limited number of patients, since the quantity and quality of donor material does not increase, unlike the need. Hemodialysis, in fact, chains the patient to a hospital bed and forces him to undergo lengthy treatment procedures. We offer an alternative mechanism to combat kidney failure through a wearable artificial kidney, which allows not only to increase patient mobility, but also to personalize treatment by controlling the process of peritoneal dialysis," commented Dmitry Telyshev, Director of the Institute of Bionic Technologies and Engineering.
For 5 years of work on the project, Russian scientists have created a prototype of a dialysis machine that weighs 3.5 kilograms and fits in a backpack, tested it on animals, and were able to make significant progress in understanding the mechanisms that make possible peritoneal dialysis with regeneration of the spent solution.
"Wearable equipment for artificial blood purification will overcome the shortcomings of existing dialysis devices and methods and is one of the most promising areas in the field of biomedical engineering of artificial organs," said Nikolay Bazaev, project manager, senior researcher at Sechenov University.
The device consists of a system of pumps and valves that circulate fluid through a system of filters for mechanical cleaning, sorption columns (to retain creatinine and uric acid) and an electrolyzer (to decompose urea), a container for excess fluid that is removed from the body, a battery and a control system. The fluid is collected and returned to the abdominal cavity through catheters, as when using stationary devices – cyclers of peritoneal dialysis. The device is controlled from a smartphone, monitors temperature, fluid pressure and other indicators and notifies the patient if the values go beyond the norm.
The operation of the device was tested on a test stand and laboratory animals. For the first in vitro experiments, a container modeling the human abdominal cavity was used: the liquid in it contained the main metabolic products (urea, uric acid and creatinine), the acidity level and body temperature were maintained. Every hour, more metabolites were added to the container to simulate their production by the patient's body.
One of the interesting results was that the level of acidity (pH) of the liquid after dialysis increased slightly, that is, the medium became more alkaline, while dialysis usually increases the acidity, which reduces the biocompatibility of the procedure and requires the use of an additional buffer solution. The combination of electrolysis and activated carbon helped to normalize the pH. In general, experiments have shown that the efficiency of liquid purification can be increased up to 10 times compared to existing methods.
Pigs were selected for in vivo experiments as sufficiently large animals with an abdominal volume comparable to that of humans. At the first stage, the device was used for dialysis of a healthy animal to assess the possible negative effect on blood composition. At the second stage, the animal was injected with a dose of a radiopaque substance that causes temporary acute renal failure, due to which, without dialysis, the body could die while the kidneys are regenerating.
The results of the experiments confirmed that the device can successfully remove and destroy urea, maintaining its content in the blood at a physiological level. Biochemical analysis of blood and dialysate showed that the device successfully removes the main metabolic products, and the blood composition is normalized 34 hours after the start of dialysis.
Tests of the device have shown that the creation of a sufficiently safe and compact dialysis device is possible, and it can increase the efficiency of blood purification several times.
"The work on the artificial kidney wearable device is relevant and promising, but it is more complicated than it may seem at first glance, and requires significant research, development, time and investment. At the same time, theoretically, the creation of such a device will achieve a significant social effect, reduce the cost of dialysis by the state and provide an additional choice for the treatment of chronic renal failure," Nikolai Bazaev added.
To complete the work on the device and make it accessible to patients, a lot of research needs to be done: carefully study the electrolysis process, find a replacement for expensive electrodes (will reduce the cost of devices), and select the composition of solutions that will maintain a more stable level of acidity and ionic composition of blood.
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