Intraaortic balloon pump

Published on 07/02/2015 by admin

Filed under Anesthesiology

Last modified 22/04/2025

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Intraaortic balloon pump

David J. Cook, MD and Eduardo S. Rodrigues, MD

The intraaortic balloon pump (IABP) is a mechanical device used to provide temporary circulatory support during a period of acute cardiac failure.

Equipment

Historically, the adult IABP consisted of an 8.5F to 12F catheter, the distal 30 cm of which was covered with a polyurethane balloon. For adult patients, 7F catheters also with 25-mL to 50-mL balloons are currently most commonly used, with the size of the balloon dependent upon the patient’s height. The pediatric catheter is 4.5F to 7F with a 2.5-mL to 12-mL balloon.

The catheter is inserted into the common femoral artery percutaneously by the Seldinger technique or by an open surgical procedure. It is then threaded proximally so that the balloon lies high in the descending thoracic aorta, just distal to the origin of the left subclavian artery.

The catheter is connected to a drive console that has a pneumatic pump that uses helium to rapidly inflate the balloon and, just as quickly, deflate the balloon after a brief period of time. Balloon cycling is triggered either from the electrocardiogram R wave, inflating with diastole and deflating with onset of systole (Figure 153-1), or from the aortic pressure waveform. It should be adjusted to inflate when the dicrotic notch occurs in the pressure cycle (Figure 153-2). The balloon can be set to trigger with every beat, every other beat, or some other pattern.

Hemodynamic effects

With balloon deflation at onset of systole, the peak aortic systolic pressure falls 10% to 15% (systolic unloading) and inflates immediately with appearance of the dicrotic notch. Balloon inflation can increase intraaortic diastolic pressure by approximately 70%. The cardiac index increases 10% to 15%, whereas the pulmonary artery occlusion pressure falls by a similar amount. Coronary blood flow increases as a result of increased diastolic pressure.

As the balloon deflates, a decrease occurs in the pressure in the aorta in proximity to the balloon, reducing the systemic vascular resistance, which, in turn, reduces myocardial O2 demand and a shift of the Starling curve to the right. These effects can last as long as 48 to 72 h after initiation of the balloon counterpulsation.

Indications

The IABP is used primarily for treatment of acute cardiac failure refractory to pharmacologic intervention. Most commonly, it is used for low-output states associated with acute coronary syndromes and after cardiopulmonary bypass. The pump can also be placed preoperatively when the surgical stress is anticipated to exceed the functional capacity of a diseased heart. In very high-risk heart operations, the elective preoperative placement of an intraaortic balloon and initiation of counterpulsation can improve the patient’s prognosis. In recent years, the IABP has also found use as a temporary bridge to cardiac transplantation, to placement of a left ventricular assist device, or to placement of a total artificial heart.

Approximately 3% to 4% of patients undergoing cardiopulmonary bypass need IABP support. If the patient is not hypovolemic and the heart rhythm is suitable for IABP use, the criteria listed in Box 153-1 can be used to determine appropriate initiation of IABP support.

Outcome

Clinicians have evaluated immediate and long-term prognosis following IABP support with the aim of identifying reliable determinants of survival but have made their assessments using nonrandomized groups. The primary determinant of survival after use of an IABP is early recovery (within 24 h) of cardiac function with maintenance of vital organ perfusion. Conversely, the use of inotropes, direct current cardioversion, chronic left ventricular failure, and the functional severity of the patient’s heart disease have been associated with poor outcome.

Theoretically, the predicted improvement in the O2 demand-supply ratio offered by IABP support can benefit patients with acute cardiac decompensation. Nevertheless, it remains to be determined to what extent IABP will improve survival and for whom this technology is best used.