Procedures at Cardiovascular Clinical Associates

Intra-Aortic Balloon Pump (IABP)

A mechanical aid to the circulatory function of the heart that acts to provide internal "counterpulsation" COUNTERPULSATION. The basic components of the device are a catheter tipped with a 10-inch balloon and a pump machine that inflates the balloon with either helium or carbon dioxide. The balloon is inserted via a femoral artery cutdown and guided under fluoroscopic control to a position in the descending thoracic aorta just distal to the left subclavian artery. In some models, the balloon is tri-segmented. When inflation begins in a tri-segmented balloon, the middle segment is inflated first, then the distal ends inflate simultaneously; there is no occlusion of the aorta. An alternative type of balloon catheter consists of only one segment with a second small balloon just distal to the main one; the smaller balloon partially occludes the aorta only during diastole, thus providing directional flow.

The pump console contains signal processing, drive, and timing and control mechanisms for appropriate inflation and deflation. The system also contains a display and diagnostic unit.

The physiologic effect of the IABP is to improve coronary blood flow and systemic circulation. It does this by (1) augmenting aortic root pressure during ventricular diastole at the time of maximum blood flow, and (2) reducing the workload of the heart by decreasing the amount of residual blood in the aortic arch, thereby decreasing resistance to the flow of blood from the ventricle. Inflation of the balloon during diastole just after aortic valve closure, and deflation just prior to ventricular systole reduces the pressure workload of the left ventricle and lessens oxygen demand and consumption by the myocardium. Timing of the inflation-deflation cycle is based on the arterial pulse wave configuration seen on the console's display screen. Adjustments to the cycle are made according to the site of arterial wave sampling, heart rate, and the depth of diastolic dip.

Indications for employment of the IABP include cardiogenic shock or severe pump failure secondary to acute myocardial infarction or following open-heart surgery, unstable angina resistant to drug therapy, and refractory ventricular irritability after myocardial infarction. The effect of improved oxygenation of the myocardium can result in reversal of ischemic damage resulting from infarction, and limitation of the size of the myocardial infarction.

Following insertion of the IABP catheter and initiation of the pumping action, nursing care is focused on proper administration of medications, monitoring the patient's response and the function of the equipment for evidence of safe and effective pumping, observation for ischemia of the limb in which the catheter is inserted, and observation for side effects and complications, such as excessive bleeding from the insertion site or formation of a hematoma, wound inflammation and infection, abdominal or back pain, reduction in platelet count and hematocrit and other signs of clotting abnormalities, and thrombus formation.

Nursing care problems associated with IABP include patient anxiety involving fear of the procedure, concerns about coronary angiography and surgery, or lack of knowledge about the procedure and its purpose; the need for cardiovascular and respiratory support; physical discomfort; and limited mobility. The patient with an IABP requires highly skilled nursing care.