Heart Lung Machine Lecture (9)

WHAT IS OPEN HEART SURGERY? Surgery in which the chest is opened and surgery is performed on the heart. The term "open" refers to the chest, not to the heart itself. The heart may or may not be opened depending on the particular type of surgery.

Heart-Lung machine Heart-Lung Machine – blood pumping machine that takes over the functions of the heart and lungs during surgery (i.e. open-heart surgery) Most commonly used to perform a cardiopulmonary bypass (CPB) CPB allows for the heart to stop beating, which makes it easier to operate on, and surgeons can operate in a blood-free area

PRINCIPLES OF CPB Deoxygenated blood (Venous) – to CPB machine for (Pump +Oxygenation) – Return back to the body SAFELY The surgeon can operate in a blood-free area, which is easier and can allow for more precision and less complications.

Parts Five pump assemblies Venous Cannula Arterial Cannula - dual-stream aortic perfusion catheter / meshed cannula Venous Reservoir Oxygenators Heat Exchangers Cardiotomy Reservoir and Field Suction Filters and Bubble Traps Tubing and Connectors

The heart-lung machine, or perfusion pump, is composed of a chamber that receives all the blood from the body, which is the responsibility of the right atrium of the heart. The machine then pumps the blood through an oxygenator, which is the function of the right ventricle.

The machine then continues by pumping the oxygenated blood back to the body, which is the function of the left atrium and ventricle.

This process is possible by a series of tubes that are connected to the patient by a team of surgeons. This oxygenator removes the carbon dioxide and adds oxygen to the blood, which is the typical function of the lungs.

The heart-lung machine itself is operated by perfusionists during the surgery. To end an operation, the surgeon gradually lets the patient’s heart resume its normal functions.

OXYGENATOR Takes place of the lungs Exchanges O2 for CO2 in the blood pumped from the reservoir Three types: - Bubble Membrane Heparin-coated

MEMBRANE OXYGENATORS Thin gas permeable membrane separates blood and gas flow Blood flow = 3-5 L/min Gas flow is 60% of blood flow

HEPARIN-COATED OXYGENATOR Heparin is an anticoagulant Avoid complications resulting from abnormal pressure gradient across oxygenator Reduces need for systemic herparinization

Five pump assemblies A centrifugal or roller head pump can be used in the arterial position for extracorporeal circulation of the blood. Left ventricular blood return is accomplished by roller pump, drawing blood away from the heart. Surgical suction created by the roller pump removes accumulated fluid from the general surgical field. The cardioplegia delivery pump. Emergency Backup of the arterial pump in case of mechanical failure.