The intra-aortic balloon pump (IABP) is one of the devices that you may see in your cardiology/cardiac intensive care unit rotations.
The physiology of the IABP is intuitive. In heart failure, factors such as increased afterload and decreased contractility are negatives, right? The IABP inflates during diastole and deflates during systole, which generates a suction-cup like negative force that propels blood forward out of the heart. Physiologically, this is like the “suction cup” effect that geckos, treefrogs, and other animals have.
Because of the increased forward flow, the IABP can increase myocardial oxygenation (the coronary arteries have more time to perfuse, too), increase cardiac output, and reduce LV workload. It also decreases pulmonary artery pressure (which is why you’ll see a PAP listed on the monitor).
Which patients get IABP? People who have been through cardiac shock, are post-MI, or have severe cardiomyopathy, valvular disease like MR, or high-risk patients who are awaiting stenting. The important common factor is that IABP is a bridge to something: whether that is cardiac surgery, interventional cath, or transplant. It is not meant to be used indefinitely.
How do you titrate the power of the IABP? The IABP’s power is measured in “augmented beats”: the ratio of how many times the IABP “works” to number of heartbeats. If the IABP is 1:1 for instance, that means that it is being activated with every heart beat. As you wean down a patient, you may see a ratio of 1:2 or 1:3 (which is basically equivalent to not having an IABP).
How can you improve IABP performance?
- make sure timing of balloon inflation is optimized: there is an ECG monitor and “trigger” system that can be used to determine how to time a patient correctly.
- make sure the size of the balloon is correct
- heart rate >130 reduces efficiency
- preserve kidney function
Warning signs and complications to watch for:
- limb ischemia caused by thrombosis at the insertion site…IABP may also be associated with a compartment syndrome or gut ischemia for the same reason
- aortic dissection or pseudoaneurysm…ahh!!
- if augmentation decreases, ask yourself about the possibility of whether this is due to improving cardiac function, or whether there could be new sepsis or balloon rupture
- thrombocytopenia (there is a well-documented hemolytic and thrombocytopenia that comes from mechanical shearing from the IABP), but sometimes you will be asked to rule out HIT which is just a pain in the rear
- infection (you may be asked to place the patient on vancomycin…to prevent antibiotic abuse you should make sure there is a plan in place for how long the patient will be on antibiotics for, and if it’s treating anything or just for prophylaxis)
- acute renal failure (blockage of the renal arteries, catheter migration)
- peripheral neuropathy
When and how can you wean the IABP? A complicated decision that basically is about: is the patient’s cardiac function improving? Will it remain that way even if you take them off the device? As far as weaning goes, it’s a process of reducing the ratio of augmented to non-augmented beats from 1:1 to 1:2 or 1:3 (which is the same as no support) or decreasing balloon volume. It takes 6-12 hours.