Cardiopulmonary bypass machine

Cardiopulmonary bypass machine design

A cardiopulmonary bypass machine is a complex perfusion system whose fundamental task is to completely take over the maintenance of systemic blood flow and gas exchange. Structurally, this equipment includes several critically important functional units:

• Pump. It is the central mechanical element that takes over the myocardial pumping function. Its main task is to pump oxygenated arterial blood back into the patient's systemic circulation.
• Oxygenator. This crucial unit acts as an artificial lung. Inside the oxygenator, venous blood collected from the patient comes into contact with a gas mixture and becomes saturated with oxygen.
• Auxiliary devices. In addition to the pump and oxygenator, the system necessarily includes various regulating and recording devices. They are essential for precise control of all vital parameters of artificial perfusion during surgery.

Technique of venous cannulation (blood drainage)

The surgical technique for connecting a CPB machine requires precise knowledge of topographic anatomy. The first stage of the procedure always begins with exposure of the heart, which provides the surgeon with direct visual and manual access to the great vessels.

This is followed by the venous cannulation stage, the purpose of which is complete drainage of venous blood before it enters the right side of the heart. A system of two catheters is used for this:

1. The first catheter is carefully inserted into the lumen of the superior vena cava (SVC). The anatomical access point for its installation is the right atrial appendage.
2. The second catheter is placed in the inferior vena cava (IVC). In this case, the catheter is passed directly through the wall of the right atrium.

To prevent bleeding and displacement of the lines, both catheters are securely fixed in the tissues using purse-string sutures. A crucial nuance of this stage is the complete isolation of the heart from the venous return. To achieve this, special gauze tapes are passed around the SVC and IVC (veins are snared with tourniquets). When tightened, the entire volume of venous blood is forcibly directed exclusively into the catheters, completely bypassing the heart chambers.

Technique of arterial cannulation (blood return)

After the blood has passed through the machine's oxygenator and become enriched with oxygen, it must be returned to the patient's arterial bed. This final stage of connection is called arterial cannulation.

The surgeon chooses the optimal site for returning the arterial blood. According to the surgical technique, there are two main options for placing the arterial line:

• Into the femoral artery. In this case, access is gained in the thigh, strictly below the level of the inguinal ligament.
• Into the ascending aorta. This is the direct route for blood return: the cannula is placed directly into the initial segment of the aorta, from where blood is distributed under pressure to all systemic arteries.

Class and exam questions

What else to study on this topic

• Topographic anatomy of the right atrium and its appendage
• Surgical anatomy of the superior and inferior venae cavae
• Topography of the femoral artery and inguinal ligament
• Anatomical boundaries of the ascending aorta
• Technique of placing surgical purse-string sutures

Other topics in the section "Operations on the Chest Wall and Thoracic Organs"

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.