The device of artificial circulation: the purpose and principle of work

The device of artificial blood circulation is a special medical equipment that is able to provide the processes of human life, if the heart or lungs cease to fully or partially fulfill their functions. The idea of the possibility of realizing the "preservation of any part of the body in a living condition" appeared in 1812, but the first primitive device, which consisted of a mechanism for injecting blood and oxygenation, appeared only in 1885.

The first operation on the open heart, where the device of artificial circulation was involved, was carried out in 1930. Since then, several basic methods of AIC have been used: artificial circulation of the whole body, regional, where a specific organ or site is provided with a biological fluid, and various variations in the auxiliary circulation.

Features of methods

A common artificial circulation is the complete replacement of the functions of the heart muscle and gas exchange in the lungs with special mechanical devices and devices. It is widely used in heart surgery.

Regional refers to the circulation of a certain organ or part of the body. This method is used to introduce a significant amount of drugs into the purulent infection or malignant tumor.

Regional artificial circulation has a variant used for short heart operations in combination with a deliberate decrease in human body temperature (hypothermia). This method is called coronary-carotid perfusion.

Features of devices

Modern apparatus of artificial circulation, the principle of which will be discussed below, must meet the following requirements:

• Support at the required level of minute volume of blood circulation in the patient's body;
• Quality oxygenation, in which oxygen saturation should be at least 95%, and the amount of carbon dioxide - 35-45 mm Hg. P.
• The filling volume of the apparatus is not more than 3 liters;
• The presence of a device for returning the patient's blood to the circulatory circuit;
• Do not injure blood as it passes through the structural elements;
• Material for the manufacture of mechanisms should be non-toxic, so that it is possible to disinfect and sterilize.

Device

Any apparatus of artificial circulation consists of a physiological (arterial pump, oxygenator, circulatory circuit) and a mechanical unit. From the patient's body, venous blood enters the oxygenator, where it is enriched with oxygen and purged of carbon dioxide, and then by means of an arterial pump it returns to the bloodstream.

Before the blood comes back, it passes through special filters that catch thrombi, air bubbles, calcium slices from the valve system, and also through a heat exchanger that maintains the necessary temperature regime. If the blood in the body is in the cavities, it is sent to the apparatus of artificial circulation using a special pump.

Essential elements

AIC has the following structural elements:

1. Oxygenators. There are mechanisms in which blood is enriched with oxygen by direct contact, and there are those where the interaction occurs through a special membrane.
2. Pumps. Valvular and valvular are distinguished depending on how the blood flows.
3. Heat exchanger. It maintains the temperature in the patient's blood and body. Correction of the temperature regime occurs with the help of water that washes the device.
4. Additional nodes. This includes traps, containers for keeping the cavity out of the cavity or the reserve blood.
5. Mechanical block. It consists of the device body, moving parts of the oxygenator, equipment for determining various indicators, emergency manual drive.

The artificial circulation apparatus HL 20 is one of the best examples. The perfusion system in this mechanism meets the highest standards and requirements. It combines safety and reliability, a perfect data collection system, flexibility and the ability to adapt to any manipulation.

Preparing and connecting the device

Before use it is necessary to check the readiness of the mechanism for operation. AIC (the device of artificial circulation) should have absolute purity and sterility of those surfaces that directly contact the blood.

All structural elements included in the physiological unit are treated with detergents or high-concentration alkali solutions with further washing with water. After sterilization is carried out. After complete assembly and filling the device with blood, it is connected to the patient at a certain stage of the operation.

To return blood to the body, access from the femoral or iliac artery, sometimes through the ascending aorta, is more often used. The apparatus receives biological fluid through the drained hollow veins. Before the blood enters the oxygenator, the patient is injected with heparin (2-3 mg per kilogram of body weight). To the patient was safe, access to the arterial system is carried out earlier than the catheterization of the venous bed.

Anesthesia and anesthesia

The use of the device of artificial circulation during operations has certain peculiarities, and therefore the anesthesia during this period is different.

1. Multicomponent premedication.
2. The period before perfusion requires artificial ventilation of the lungs with increased indices of inspiratory and exhalation pressure.
3. In the perfusion period, anesthetics enter the body through the AIC. Conduction of mechanical ventilation is characterized by increased exhalation pressure.
4. In the post-perfusion period, the parameters of hemodynamics are restored, long-term ventilation of the lungs is required.

Pathophysiology

When using the device of artificial circulation, the human body is in unusual conditions. Pathological reactions to perfusion can develop, because retrograde blood flow in the aorta, a decrease in pressure in the heart cavity, the absence of the work of the small circle of blood circulation - conditions that are not characteristic of the normal state of the body.

During the intervention, a person is in a state close to hemorrhagic shock. There is a decrease in blood pressure and total peripheral resistance. Under normal conditions, such a reaction is considered protective, but in conditions of AIC use it interferes with the normal restoration of blood circulation.

The consequence is the development of hypoxia and metabolic acidosis in the blood. Preventive maintenance of complications is based on improvement of microcirculation, elimination of the phenomenon of protective redistribution of blood.

Possible complications

The main complications are:

• Vascular embolism, which can be caused by blockage of thrombi, gas, lipids, calcium particles;
• Hypoxia - can develop due to insufficient work of the oxygenator or arterial pump, through which the blood must flow back into the body;
• Hematological complications - incompatibility of patient and donor blood in a group or Rh factor, patient's reaction to the infusion of citrated blood, traumatization of blood cells in the artificial circulation apparatus, clotting disorder.

The devices are constantly being improved to reduce possible complications during the procedure. Modern innovations, technologies and high qualification of the team of doctors are the key to successful intervention.