October 1, 2013 Volume 77, Number 10
ACE Question

A 26-year-old woman with postpartum cardiomyopathy presents for an open reduction and internal fixation of her fractured femur following a motor vehicle collision. She has a continuous-flow left ventricular assist device (LVAD) with a remaining battery life of three hours. You are called to the preoperative area because a blood pressure cannot be obtained noninvasively and the patient has no palpable pulse. The patient has a heart rate of 70/min on electrocardiogram. She is conversing with her family and is in no apparent distress. The MOST appropriate next step would be to:

(A) administer chest compressions.

(B) change the battery pack.

(C) increase the LVAD flow rate.

(D) proceed to the operating room.

Left ventricular assist devices (LVADs) are used as a bridge to heart transplantation or as an alternative to heart transplantation (destination therapy) in patients with end-stage heart failure. Certain LVAD systems, such as the HeartMate II, have nonpulsatile, continuous flow. Blood is removed from the left ventricle and returned via a pump to the ascending aorta, thereby decreasing left ventricular work. The LVAD pump is connected to an external controller via a percutaneous lead.

Noninvasive blood pressure monitoring and pulse oximetry may be difficult because of the narrow pulse pressure occurring in patients with a continuous-flow LVAD (eg, HeartMate II). Patients often have no palpable pulse. Patients with a pulsatile LVAD (eg, HeartMate XVE) should have a palpable pulse and a noninvasive blood pressure device should be able to obtain a blood pressure. Physical examination of a patient with a normally functioning LVAD should reveal a well-perfused, neurologically intact patient in no distress.

Under anesthesia, an intra-arterial catheter is useful for monitoring blood pressure. Normal mean blood pressure should remain between approximately 70–80 mm Hg. Increases in systemic afterload may result in decreased pump flow and should be avoided. Increasing the pump flow rate will increase diastolic pressure with minimal changes in systolic pressure. An indication of decreased ejection of blood from the native left ventricle increases the probability of thrombosis. This decreased ejection of blood would also lower pulse pressure further, making monitoring more difficult. While decreased pulse pressures are normal, a flat arterial tracing may herald hypovolemia or an obstructed ventricular cannula.

The battery life in a fully charged battery pack in some LVAD models is three hours. When available, the LVAD should be connected to a power supply in the operating room. Extra batteries should be identified in the preoperative setting in case of power failure.

In this scenario, the LVAD patient has a normal physical examination, appropriate mean arterial pressure, and adequate LVAD battery backup. She, therefore, should proceed to the operating room for her procedure.

Answer: D



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