Intra-Aortic Balloon Pump What it is and what it does Don Stroup, CC/NREMT-P Poudre Valley EMS

Objectives This presentation is intended to increase your existing knowledge on the care and transport of patients receiving IABP therapy. Please keep in mind this information does not replace formal didactic and hands on training.

When IABP is used, and when it’s not Indications Cardiogenic Shock Pre-shock syndrome Threatening extension of MI Unstable angina Intractable ventricular dysrhythmias Septic Shock Cardiac Contusion Prophylactic support Bridging device to other mechanical assist Support during transport Contraindications Absolute Aortic Valve insufficiency Dissecting aortic aneurysm Relative End-stage cardiomyopathies Severe atherosclerosis End stage terminal disease Abdominal aortic aneurysm Blood dyscrasias Thrombocytopenia

The Cardiac Cycle The ventricles propel blood throughout the pulmonary and systemic circulation as a result of ventricular contraction. Fluid (blood) always flows from high pressure to low. The cardiac cycle is divided into systole (ventricular contraction) and diastole (ventricular relaxation and filling) http://www.nhf.org.nz/images/how_your_heart_works.gif

Preload vs. Afterload Preload refers to the amount of stretch on the ventricular myocardium prior to contraction. Starling’s law described how an increase of volume in the ventricle at the end of diastole resulted in an increase in the volume of blood pumped out. Preload is often referred to as “filling pressure”. Afterload is the resistance to ventricular ejection which takes several forms: The mass of blood that must be moved, measured by the hematocrit The higher the mass, the more inertia that must be generated. Aortic end diastolic pressure (AEDP). If the AEDP is 80 mm/hg, then the left ventricle must generate 81 mm/hg in order to open the aortic valve and generate blood flow. Arteriole resistance

Principles of the IABP A flexibile catheter is inserted into the femoral artery and passed into the descending aorta. Correct positioning is critical in order to avoid blocking off the subclavian, carotid, or renal arteries. When inflated, the balloon blocks 85-90% of the aorta. Complete occlusion would damage the walls of the aorta, red blood cells, and platelets. http://www.fda.gov/cdrh/medicaldevicesafety/tipsarticles/balloonpump.gif

Hemodynamics Helium is rapidly pumped into and out of the balloon (about 40ccs). When inflated, this balloon displaces the blood that is in the aorta. This is known as counter pulsation Helium is used because it is a soluble gas and will not cause an embolus if the balloon ruptures This sudden inflation moves blood superiorly and inferiorly to the balloon. When the balloon is suddenly deflated, the pressure within the aorta drops quickly.

Hemodynamics (cont.) Inflation of the balloon occurs at the onset of diastole. At that point, maximum aortic blood volume is available for displacement because the left ventricle has just finished contracting and is beginning to relax, the aortic valve is closed, and the blood has not had an opportunity to flow systemically. The pressure wave that is created by inflation forces blood superiorly into the coronary arteries. This helps perfuse the heart. Blood is also forced inferiorly increasing perfusion to distal organs (brain, kidneys, tissues, etc.)

Hemodynamics (cont.) The balloon remains inflated throughout diastole. At the onset of systole, the balloon is rapidly deflated. The sudden loss of aortic pressure caused by the deflation reduces afterload. The left ventricle does not have to generate as much pressure to achieve ejection since the blood has been forced from the aorta. This lower ejection pressure reduces the amount of work the heart has to do resulting in lower myocardial oxygen demand.

Timing As you can see, inflation and deflation timing is critical in order to obtain the maximum benefits from the pump. Incorrect timing can result in poor patient outcomes. During a cardiac arrest, the IABP can provide very effective perfusion in conjunction with external compressions. Since there is no ECG signal and no arterial pressure wave to trigger the pump, an internal trigger is selected. This trigger detects the flow of blood caused by compressions and inflates the balloon providing improved circulation. Good, consistent compressions are a must for this to work! Use of the Autopulse in these situations has not been studied.

Additional Resources For more information on counter pulsation and the use of IABPs, use the following link and review the information Arrow has provided. http://www.arrowintl.com/products/education/IAT009OL/

Resources Arrow International (2005, May). Counterpulsation applied: an introduction to intra-aortic balloon pumping. Arrow International Inc.: Pennsylvania