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The IABP is used to help stabilize acutely ill cardiac patients. Its role is to provide support until short‐term recovery or definitive care. The IABP works by decreasing cardiac afterload, augmenting diastolic perfusion pressure, and increasing coronary artery perfusion [2]. The decrease in afterload reduces the workload on the heart, and the improved coronary artery circulation can increase oxygen supply to the myocardium. EMS clinicians will encounter IABP patients during interfacility transfers, often for more advanced cardiac care or surgery.

The most common indications for an IABP are acute myocardial infarction, cardiogenic shock, ventricular aneurysm, left ventricular failure, valve or papillary muscle rupture, or a combination of these factors [3]. Absolute contraindications for an IABP include aortic dissection, abdominal aortic aneurysm, and aortic valve incompetence. Relative contraindications include bleeding disorders and atherosclerosis [2].

The IABP catheter is inserted via the femoral artery and then advanced into the thoracic aorta. The tip of the balloon should be positioned 1‐2 cm distal to the origin of the subclavian artery and must be above the branches of the renal arteries. If the balloon is not placed correctly, occlusion of coronary, subclavian, or renal arteries could occur [2]. On a chest x‐ray, the tip of the catheter should be visible between the second and third intercostal space. When inflated, the balloon should not completely occlude the aortic lumen, as this can damage the aortic wall, and blood components [2]. Most devices have different‐sized balloons to be used based on patient weight or height. It is important to ensure the appropriate balloon volume is being used.

IABP function is dependent on precise timing. The balloon is cycled in conjunction with the cardiac cycle. It is important to remember the balloon is inflated during diastole, and deflated just prior to systole. While the balloon is inflated, blood is pushed both back toward the heart, as well as distal in the aorta. The result is increased blood flow to coronary and carotid arteries and increased systemic perfusion. The balloon is deflated very rapidly, and this rapid loss of volume reduces the pressure in the aorta. The result is that the left ventricle does not contract as strenuously as it would otherwise. Cardiac workload and myocardial oxygen demands are subsequently reduced. If the timing is not correct, these advantages are lost, and the patient may be harmed [2].

An IABP can use different triggers to time inflation and deflation cycles. Most use the ECG or the arterial pressure waveform as a trigger. The IABP may also have an internal trigger in the event of cardiac arrest. To use the arterial pressure as a trigger the patient must have an arterial pressure catheter that is connected to the balloon pump. Some IABP devices have specialized fiber optic connectors to measure arterial pressures. The ECG can also be used as a trigger mode. Most devices have an “automatic” trigger mode, where the pump automatically switches between trigger modes if needed. An example would be a switch between ECG and arterial pressure modes if the ECG signal is lost. Most modern pumps can also compensate for arrhythmias such as atrial fibrillation and pacing modes [2].

With the trigger mode established, attention should focus on timing. Most patients are transported with a 1:1 frequency, where each cardiac cycle is assisted. In order to assess timing, it may be helpful to place the device in a 1:2 frequency (every other cardiac cycle is assisted) to get a better picture of the arterial pressure waveform landmarks. For transport, the operator should ensure that the balloon is set to inflate at the dicrotic notch and to deflate during the next isovolumetric contraction phase (Figure 11.1). The dicrotic notch phase on the arterial pressure waveform represents aortic valve closure and diastole. Once the timing is correct, the device can be placed back into a 1:1 frequency and put in the “automatic” mode if available [2]. Potential complications include limb ischemia, compartment syndrome, aortic dissection, bleeding, thrombocytopenia and red blood cell destruction, gas embolus, infection, and cardiac decompensation from improper timing. (Additional introduction to IABP can be found at https://www.youtube.com/watch?v=NYeA‐3AAQB4&t=100s).

Figure 11.1 IABP arterial pressure tracings with 1:1 augmentation and 2:1 augmentation respectively. A. Diastolic augmentation with increased coronary perfusion. B. Assisted aortic end‐diastolic pressure with decreased myocardial oxygen demand. C. Assisted systole. D. Unassisted aortic end‐diastolic pressure. E. Unassisted systole.

The interfacility transport team should examine the patient with particular attention to the insertion site, as well as to the extremity distal to the site. The insertion site should be examined for bleeding or protruding balloon. The catheter tubing should be examined for any blood or blood flecks, and for kinking. The limb should be examined for signs of ischemia. Any problems must be corrected before transport. Fresh ECG leads should be applied to the patient. The referring hospital balloon pump should not be disconnected or shut off until the transport pump is connected and tested. The transport balloon pump should be plugged into an outlet during this time and not run on battery power. The pump should also be plugged into the aircraft or ambulance power inverter during transport. Pure battery operation should be used only to transport the patient from the vehicle to the in‐hospital destination. Special caution must be taken when transferring a patient from one model of IABP to another. There may be a difference in the balloon size, and an adapter may be needed to connect a “Brand A” catheter to a “Brand B” IABP. The balloon size should be noted and adjusted on the pump if necessary.

In the event of cardiac arrest, the IABP will lose all trigger modes, give a “Trigger Arrest” alarm, and then stop counterpulsation. If not addressed, this could result in a thrombus formation. When CPR is initiated, the IABP should be switched to “Arterial Trigger.” Effective CPR should allow the IABP to function from the arterial pressures. In the event that arterial pressures are not sufficient, the IABP should be switched to an internal trigger. This last resort tactic provides asynchronous counterpulsation and helps prevent clot formation. “Internal Trigger” mode should be stopped if there is a return of circulation and the ECG or arterial pressure mode is restarted [3].

In the event of IABP failure during transport, a large Luer‐lock syringe should be attached to the quick connector to aspirate the balloon for blood. If there is blood, then the balloon has lost integrity. Injection of anything into it will result in an aortic arterial injection. If no blood is found, use air to inflate the balloon to the volume capacity of the balloon. Then quickly aspirate the air and deflate the balloon. Repeat four to five times every 5 to 10 minutes to reduce the likelihood of thrombus formation until the pump can be repaired or replaced [2].