Understanding intraaortic balloon pumping: intraaortic balloon pumping is a complex procedure aimed at supporting a compromised heart. Carried out in many of the country's intensive care units, it is important that nurses understand the physiology and mechanics of the procedure so they can offer optimal nursing care.

Intraaortic balloon pumping (IABP) is an established treatment for the support of a failing heart. (1) It is undertaken in most level two and three intensive care units (ICU). Despite IABP appearing complex, the principles are straightforward. A sausage-shaped intraaortic balloon (IAB) about 250 millimetres long and 15 millimetres in diameter, is placed in the descending aorta and attached to an external pump. The external pump then inflates and deflates the IAB, in synchrony with cardiac contraction. The primary purpose is to support a compromised heart, with a simultaneous increase in myocardial oxygen supply and decrease in myocardial oxygen demand. (2)

As a nurse, it is worthwhile understanding the principles of IABP because nurses in ICUs often care for patients needing this intervention.

Physiology

The IAB is inflated at the onset of diastole, when blood ceases to eject from the heart. Inflation of the IAB results in displacement of blood volume within the descending thoracic aorta. Proximal blood is returned to the heart to oxygenate the coronary arteries, while blood in the distal descending aorta is circulated around the body. Intraaortic balloon deflation, however, is timed to occur immediately prior to the onset of systole before the heart commences ejection. This ensures afterload (the pressure in the arterial vessels) is reduced and blood is ejected into a partially empty aorta, thus reducing cardiac workload and the consequent demand for oxygen. This reduction in afterload also improves cardiac output and increases systemic perfusion. (2)

Primarily, IABP increases myocardial oxygen supply and decreases myocardial oxygen demand. Secondarily, IABP improves cardiac output, increases coronary perfusion pressures, increases systemic perfusion, reduces mitral regurgitation and reduces afterload, which will subsequently decrease left ventricular workload. (2,3)

Mechanics

The adult IAB is available in three sizes: 34 millilitre (ml) balloon volume; 40ml balloon volume; and 50ml balloon volume. (4) When the IAB is inflated, it has a diameter of 15 millimetres. Intraaortic balloon pumping requires the positioning of an IAB in the descending thoracic aorta (see figure 1). The IAB is located immediately inferior to the origin of the left subclavian artery and superior to the renal arteries. (2) The IAB is then attached to an external pump used to inflate and deflate the IAB in synchrony with cardiac contractions. (2)

[FIGURE 1 OMITTED]

Historical background

Diastolic augmentation to assist in the treatment of left ventricular failure was described for the first time in 1958. (5) Pioneering cardiovascular surgeon Dwight Harken suggested that the removal of blood from the femoral artery during systole, and its rapid replacement during diastole, would both assist cardiac output and unload the heart simultaneously. (5,6) Considering these principles, an IAB prototype was developed in 1962 and integrated into client care in 1968. (7,8) This experience was mixed, demonstrating an improvement in haemodynamic function but no significant alteration in mortality rate.

Intraaortic balloon development has continued since 1962 and practice has consequently changed dramatically. Technological advances have allowed easier IAB insertion, the provision of a smaller IAB and a more efficient external pump. Greater circulatory benefits and fewer complications are the result. Time has also seen change in IABP indications.

Indications

Accepted guidelines for IABP include: cardiogenic shock; left ventricular failure; stunned myocardium; myocardial contusion; unstable angina; failure to separate from cardiopulmonary bypass (during some cardiac surgery blood is pumped around the body by an external pump bypassing the heard and lungs); procedural support during coronary angiography and angioplasty; bridging to heart transplantation (IAPB is used to assist the heart until a replacement heart can be transplanted); septic shock; drug-induced cardiovascular failure; and prophylactic application in the event of pre-operative surgery, especially cardiac surgery or myocardial infarction. (2) Intraaortic balloon pumping has also been used successfully in the treatment of clients to augment cerebral blood flow in cerebral vasospasm, in the anaesthetic management of high-risk cardiac clients undergoing non-cardiac surgery, and for the management of myocardial failure after severe post-partum haemorrhage. (9,10,11,12,13,14,15)

Complications

IABP is not without risk. In recent times, technological advances have been responsible for a dramatic decrease in complication rates. Despite these advances, complications remain numerous. These include limb ischaemia, platelet activation, thromboembolism; aortic dissection; infection; IAB rupture; IAB entrapment; and vascular injury--false aneurism at the catheter insertion site, ie a tear in the arterial wall has separated the intima from the media, allowing blood to flow into this false tract rather than through the actual vessel itself. Arterial perforation, and renal or abdominal organ dysfunction are also complications. (16,17,18)

Summary

Nurses are accountable for their care. Understanding the physiology and process behind any intervention improves patient care, while also increasing nursing satisfaction and skill and IABP is no exception. An awareness of IABP will facilitate sound nursing care, ensure early identification of possible complications or patient compromise, and lead to patient and relative satisfaction. It will also assist in the transition from caring for a patient whose needs are relatively straightforward, to caring for one subject to this complex medical intervention.

CARING FOR A PATIENT WITH AN IABP

Principles of IABP may be reasonably simple. However, nursing care of a patient subject to this intervention can be complex. While care of the IABP creates a new nursing challenge, it is the secondary problem of heart failure which complicates care. Inadequate heart function will compromise any bodily system reliant on adequate cardiac function.

The impairment of the heart's ability to pump causes a decrease in blood pressure and the consequent onset of shock. The complications of shock are those which complicate nursing care. The patient is often mechanically ventilated, is almost certain to be receiving a medley of pharmacological support (eg, inotropes to support the heart, such as adrenaline; vasopressors to support the blood pressure and peripheral perfusion, such as glycerol trinitrate; diuretics to prevent renal failure, such as frusemide) and will be restricted to bed rest as a consequence of the IABP. The nurse must combine vigilance with careful and methodical assessment skills to care for this patient adequately. In caring for patients receiving IABP, the nurse must make sound clinical assessments and ensure accurate and consistent observations. Assessments and observations which must be undertaken are those specific to cardiac function, the IABP process and possible IABP complications. Assessments include blood pressure, heart rate, urine output, mentation (mental awareness), peripheral perfusion, lung function, and fluid replacement requirements. Blood should be drawn regularly to monitor electrolytes and dotting. Hourly documentation of these assessments provides a picture of how the patient is progressing, informing future patient cares. Documentation, in addition to assessments, should include the function of the external pump, ie the frequency which it inflates the IAB, and the augmentation it provides the IAB and systolic blood pressure, and dosage of any pharmacological interventions.

While specific skills are required to care for the IABP, the ventilator, multiple infusions and drains, the nurse must not lose sight of the human element of nursing. The nurse should not merely care and tend the interventions and procedures but also care and tend the patient. A patient must have confidence in the nurse, must trust and feel reassured by the nurse and must be continually educated by the nurse. This nurse/patient partnership, so evident in general nursing, must not be lost as the complexity of patient care increases.

References

(1) Christenson, J. T., Simonet, F., Badel, P., & Schmuziger, M. (1997) Evaluation of preoperative intra-aortic balloon pump support in high risk coronary patients. European Journal of Cardio-Thoracic Surgery; 11: 6, 1097-1103.

(2) Overwalder, P. (1999) Intra aortic balloon pump (IABP) counterpulsation [Web document]. The Internet Journal of Thoracic and Cardiovascular Surgery; 2: 2, http://www.ispub.com/journals/IJTCVS/ Vol2N2/iabp.html

(3) Bolooki, H. (1989) Emergency cardiac procedures in patients in cardiogenic shock due to complications of coronary artery disease. Circulation; 79: 1, 137-148.

(4) Krau, S. D. (1999) "Successfully weaning the intra-aortic balloon pump patient: an algorithm. Dimensions of Critical Care Nursing; 18: 3: 2-11.

(5) Harken, D. E. (1958) Presentation at the International College of Cardiology. Brussels, Belgium.

(6) Harken, D.E. (1976) Circulatory assist devices. Medical Instrumentation; 10, 215-220.

(7) Kantrowitz, A., Tjonneland, S., & Freed, A. (1968) Initial clinical experience with intra-aortic balloon pumping in cardiogenic shock. The Journal of the American Medical Association; 203: 113-119.

(8) Moulopoulos, S. D., Topaz, S., & Kloff, A. (1962) Diastolic balloon pumping (with carbon dioxide) in the aorta--a mechanical assistance to the failing circulation. American Heart Journal; 63: 669-674.

(9) Apostolides, P. J., Greene, K. A., Zabramski, J.M., Fitzgerald, J.W. & Spetzler, R.F. (1996) Intra-aortic balloon pump counterpulsation in the management of concomitant cerebral vasospasm and cardiac failure after hemorrhage: technical case report. Neurosurgery; 38: 5, 1059-1060.

(10) Masaki, E., Takinami, M. (1999) Anesthetic management of high-risk cardiac patients undergoing noncardiac surgery under the support of intraaortic balloon pump. Journal of Clinical Anesthesia; 11: 4, 342-345.

(11) Mayr, A., Lederer, W. et al. (1999) Successful treatment of severe myocardial failure after postpartum haemorrhage with the use of an intra-aortic balloon pump. Intensive Care Medicine; 25: 2, 223-225.

(12) Nussbaum, E. S., Heros, R.C. et al. (1995) Intra-aortic balloon counterpulsation augments cerebral blood flow in a canine model of subarachnoid hemorhhage-induced cerebral vasospasm. Neurosurgery; 36: 4: 879-886.

(13) Nussbaum, E.S., Sebring, L.A. et al. (1998). Intra-aortic balloon counterpulsation augments cerebral blood flow in the patient with cerebral vasospasm: a xenon-enhanced computed tomography study. Neurosurgety; 42: 1, 205-214.

(14) Rosen, C. L., Sekhar, L.N. et al. (2000) Use of intra-aortic balloon pump counterpulsation for refractory symptomatic vasospasm. Acta Neurochirurgica; 142: 1, 25-32.

(15) Sanborn, T., Sleeper, L.A. et al. (2000) Impact of thrombolysis, intra-aortic balloon pump counterpulsation, and their combination in cardiogenic shock complicating acute myocardial: a report from the SHOCK Trial Registry. Journal of the American College of Cordiology; 36: 3, 1123-1129.

(16) Haas Stavarski, D, (1996).Complications of intra-aortic balloon pumping. Critical Care Nursing Clinics of North America; 8: 4, 409-421.

(17) Shin, H., Yozu, R. et al. (2000) Acute ischemic hepatic failure resulting from intraaortic balloon pump malposition. European Journal of Cardio-thoracic Surgery; 17: 4, 492-494.

(18) Vonderheide, R. H., Thadhani, R. et al. (1998) Association of thrombocytopenia with the use of intra-aortic balloon pumps. The American Journal of Medicine; 105: 1, 27-32.

This article was reviewed by Kai Tiaki Nursing New Zealand's editorial reveiw committee in May 2005.

Peter Lewis, RN, RM, MN (Ed), Cert.CC, is a lecturer in the School of Nursing, Christchurch Polytechnic Institute of Technology.