Lipp Vis Nursing ChaptLWBK1630_C02_p013-068

66  Chapter 2 • Cardiovascular Care

A Closer Look at VADs

• It may pump regardless of the patient’s cardiac cycle. • Nonpercutaneous centrifugal

pumps, which are used for cardiopulmonary bypass. They are used primarily for

There are three types of VADs.

1. A right VAD provides pulmonary support by diverting blood from the failing right ventricle to the VAD, which then pumps the blood to the pulmonary circulation via the VAD connection to the left pulmonary artery. 2. With a left VAD, blood flows from the left ventricle to the VAD, which then pumps blood back to the body via the VAD connection to the aorta. 3. When a right and a left VAD are used, it is referred to as a biventricular VAD (BiVAD).

cardiopulmonary bypass during open heart cases and thus are not placed percutaneously. They cause too much hemolysis to permit long-term use. There are presently two centrifugal pumps available for very short-term use (less than six hours). • the Bio-Medicus • Sarns • Extracorporeal membrane oxygenator pumps While each device has a different design and operation, the following parameters of circulatory function are improved by all devices; however the degree of improvement varies between devices and patients. • End-organ perfusion • Reduction in intracardiac filling pressures • Reduction in left ventricular volumes, wall stress, and myocardial oxygen consumption • Augmentation of coronary perfusion As a result of treatment with these devices the following clinical parameters may be improved: • Prevention or amelioration of cardiogenic shock • Reduction in pulmonary congestion • Reduction in manifestations of myocardial ischemia • Reduction in infarct size

R I G H T VAD

L E F T VA D

VAD

VAD

is bypassed and oxygenated blood returns to the patient via an arterial or venous route. With venovenous bypass, ECMO is effective primarily as a therapeutic option for patients with severe respiratory failure. With venoarterial bypass, an extracorporeal pump is utilized to support systemic perfusion, thus providing a hemodynamic support option in patients with circulatory and respiratory failure. The ECMO systems involve placement in the central arterial and venous circulation using a large bore catheters that allow positioning of a cannula in the aorta and right atrium. Blood from the venous catheter is pumped through a heat exchanger and oxygenator and then returned to the systemic arterial circulation

via the arterial cannula. The ECMO systems can be used for support for up to 30 days. Indications for Use of ECMO • Hypoxemic respiratory failure. • Hypercapnic respiratory failure with an arterial pH less than 7.20. • Ventilatory support as a bridge to lung transplantation. • Cardiac/circulatory failure/ refractory cardiogenic shock. • Massive pulmonary embolism. • Cardiac arrest • Failure to wean from cardiopulmonary bypass after cardiac surgery. • As a bridge to either cardiac transplantation or placement of a VAD.

Extracorporeal Membrane Oxygenation (ECMO) is part of a larger term identified as

extracorporeal life support (ECLS) which is a cardiopulmonary support system that. ECMO moves blood forward, removes carbon dioxide and adds oxygen to venous blood using an artificial membrane lung. The pulmonary circulation