Question

The temporary substitution of a pump oxygenator for the heart and lungs allows the surgeon to stop the heart and perform cardiac procedures under direct vision in a relatively dry, motionless field. It also allows the surgeon to manipulate the heart without the risk of producing ventricular fibrillation and reduced cardiac output that jeopardizes perfusion to the myocardial, peripheral, and cerebral tissues. In traditional cardiopulmonary bypass (CPB), systemic venous return to the heart flows by gravity drainage through cannulae placed in the superior and inferior venae cavae or through a single two-stage cannula in the RA into tubing connected to the bypass machine. Blood is oxygenated, filtered, warmed or cooled, and pumped back into the systemic circulation through a cannula placed in the:

a. femoral artery.
b. axillary vein.
c. descending aorta.
d. femoral vein.

Answer 1

During cardiopulmonary bypass surgery, oxygenated blood is reintroduced into the systemic circulation through a cannula placed in the descending aorta. This allows for direct distribution of blood to the systemic arterial circulation. b. axillary vein.

Step-by-step explanation:

In cardiopulmonary bypass (CPB) surgery, the surgeon utilizes a pump oxygenator as a temporary substitute for the heart and lungs. This crucial device allows for the cessation of the heart's activity, providing the surgeon with a clear and still field to conduct intricate cardiac procedures. The pump oxygenator ensures that blood remains oxygenated and circulates throughout the body, despite the heart not beating, thereby maintaining perfusion to essential tissues such as the myocardium, as well as peripheral and cerebral regions.

Systemic venous return enters the pump oxygenator through cannulae positioned in the superior and inferior venae cavae or via a single two-stage cannula in the right atrium (RA). Once inside the machine, the blood undergoes oxygenation, filtration, and temperature adjustment to match the body's needs. Subsequently, the reconditioned blood is reintroduced into the patient's systemic circulation. This re-entry point is critical to the success of the procedure and involves a cannulation site that can effectively distribute the oxygenated blood to the entire body.

The correct answer to the question of where the oxygenated blood is pumped back into the systemic circulation during cardiopulmonary bypass is through a cannula placed in the descending aorta (option c). Neither the femoral artery nor the veins (femoral or axillary) are typically used for this purpose, as they do not provide direct access to the systemic arterial circulation. The descending aorta is strategically positioned to ensure that the oxygen-rich blood can be efficiently distributed to the systemic circulation and reach all organs and tissues.