Intra-aortic balloon pump therapy—a primer for perioperative nurses

AORN Journal,  July, 2006  by Roberta Schultz Tremper

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The article "Intra-aortic balloon pump therapy--A primer for perioperative nurses" is the basis for this AORN Journal independent study. The behavioral objectives and examination for this program were prepared by Rebecca Holm, RN, MSN, CNOR, clinical editor, with consultation from Susan Bakewell, RN, MS, BC, education program professional, Center for Perioperative Education.

Participants receive feedback on incorrect answers. Each applicant who successfully completes this study will receive a certificate of completion. The deadline for submitting this study is July 31, 2009.

Complete the examination answer sheet and learner evaluation found on pages 47-48 and mail with appropriate fee to

AORN Customer Service

c/o Home Study Program

2170 S Parker Rd, Suite 300

Denver, CO 80231-5711

or fax the information with a credit card number to (303) 750-3212.

You also may access this Home Study via AORN Online at http://www.aorn.org/journal/homestudy/default.htm.

BEHAVIORAL OBJECTIVES

After reading and studying the article on intra-aortic balloon pump therapy (IABP), nurses will be able to

1. explain how IABP therapy works in relation to the physiology of the cardiac system,

2. identify indications for IABP therapy,

3. discuss issues pertinent to intra-aortic balloon insertion, and

4. identify primary causes of IABP malfunction.

The intra-aortic balloon pump (IABP) is a commonly used circulatory-assist device for patients experiencing unstable angina, left ventricular failure, mitral regurgitation, or cardiogenic shock. (1) The primary goal of IABP therapy is to improve left ventricular function by increasing myocardial oxygen supply and reducing myocardial oxygen demand. (2) By increasing coronary blood flow or perfusion and decreasing the workload of the heart (ie, afterload reduction), the left ventricle can rest and ideally will recover enough to take over the entire workload of the heart. (3)

When a patient requires intra-aortic balloon pump therapy in the OR, it can be a time of great stress and frenzied activity for the OR team. At some facilities, the perioperative nurse is responsible for setting up, timing, and troubleshooting problems with this device. At other facilities, the perfusionist or intensive care unit (ICU) nurse may perform these functions while the patient is in the OR. No matter what the facility requires, however, all perioperative nurses should have at least a basic understanding of the theory and mechanics of IABP therapy. Common terms related to IABP therapy are defined in Table 1.

PHYSIOLOGY

The cardiac cycle has two components: electrical (ie, rhythm) and mechanical (ie, systole and diastole). The mechanical component is stimulated by the electrical elements. Systole is ventricular contraction of the heart, which ejects blood into systemic circulation. (4) Diastole is relaxation of the ventricles as they fill with blood. (5) Cardiac output (CO) is the amount of blood, measured in liters, that is ejected from the heart each minute. (6) It is calculated by multiplying the heart rate by the stroke volume (ie, the amount of blood ejected from the left ventricle with each heartbeat). Stroke volume is dependent on preload, after-load, and contractility. (6)

PRELOAD. Preload is defined as the amount of blood volume or pressure in the left ventricle at the end of diastole (ie, the resting phase of the heart). (6) Factors affecting preload include

* aortic insufficiency,

* circulating blood volume,

* mitral valve disease, and

* some medications (eg, vasoconstrictors, vasodilators). (7)

AFTERLOAD. Afterload is the resistance that the heart must overcome in order to eject the blood volume from the left ventricle. (6) Afterload can be affected by

* aortic valvular stenosis,

* arterial vasoconstrictors and vasodilators,

* hypertension, and

* peripheral arterial constriction. (7)

CONTRACTILITY. Contractility is the ability of the heart to stretch and contract, which is affected by the health of the cardiac muscle, the autonomic nervous system, heart rate, and oxygen balance. (6) Many medications can increase contractility (eg, dopamine, dobutamine) or decrease contractility (eg, diltiazem). (6)

IABP THERAPY

The theory behind IABP therapy as a means to treat left ventricular failure was first described in 1958. (2) Although the first IABP was developed by S. D. Moulopoulous, MD; S. R. Topaz, MD; and W. J. Kolef, MD, in 1962, (8) it was not used in clinical practice until 1967.9 Today, it is the most widely used mechanical device for the treatment of left ventricular failure, with more than 70,000 intra-aortic balloons (IABs) inserted each year. (9)

The IABP consists of two components--a catheter with a polyurethane balloon and a mechanical drive system (ie, pump) that, when attached to the catheter, causes the balloon to inflate and deflate according to the patient's cardiac cycle (Figures 1 and 2). (10) The inflation and deflation pattern of the pump is the opposite of the heart's contraction and relaxation rhythm. As the heart rests (ie, diastole), the balloon inflates, which displaces blood volume into the coronary sinus (11) and systemic circulation (Figure 3). This is called diastolic augmentation because the coronary arteries are augmented with an extra volume of blood. The balloon deflates just before ventricular ejection (ie, systole) decreasing the pressure that the ventricle must eject against (ie, afterload reduction). This is called counterpulsation. Increasing perfusion to the coronary arteries enhances cardiac output and reduces afterload for the failing heart simultaneously. (2)