The Daily Dose • Monday, April 30

LVADs and Non-cardiac Surgery: What to Do When They Come to Your OR

By Dr. Linda Trapani, from the IARS 2018 Annual Meeting*

As the population continues to age, the number of individuals with circulatory support devices like LVADs has grown dramatically. As we better hone our management of these patients, more and more LVAD recipients are surviving with the devices as destination therapy for longer periods of time. For anesthesiologists, this means more individuals are presenting to the ORs for emergent, urgent and even elective surgeries. Dr. David Barbara presented a review of LVAD function and physiology, as well as relevant framework for the perioperative care of LVAD recipients undergoing non-cardiac surgery (NCS). He began his discussion with a case involving a 78-year old man who had been living with his VAD for six years–and now needed surgery for an intertrochanteric femur fracture.

The Left Ventricular Assist Device: Background and Basics

The LVADs purpose is to support circulation whilst allowing the patient to return to a more-normal way of life; primarily, these devices are used either as a bridge to transplant, or as destination therapy. Mechanically, these devices have evolved as we have observed their consequences for the patient. Better outcomes have been yielded with continuous-flow devices as opposed to pulsatile-flow devices, with the centrifugal continuous LVAD representing the newest generation of technology. Compared with the axial continuous flow device (which employs a “pump pocket” outside the heart), centrifugal continuous LVADs rely on a pump integrated into the apex of the LV. The impeller, which drives blood out of the device, relies on either hydrodynamic forces or magnetic levitation. Regardless of the technology in place, patients with an LVAD require significant anticoagulation and antiplatelet therapy, with aspirin being a universal requirement. Many device manufacturers recommend a second antiplatelet agent, as well as warfarin anticoagulation to an INR between two and three.

Pump thromboses represent one of the most feared complications in LVAD recipients. The anesthesiologist managing these patients should feel comfortable with the data provided by the LVADs software to assist in quickly identifying possible thrombi and other potential complications. Important mechanical values include the pump speed (measured in rpm; this value can manipulate CO, MAP and pulse pressure), pump power (measured in watts; an increase in this value can indicate a thrombotic event), pump flow (not directly measured; can be falsely elevated with thromboses), pulsatility index (reflect flow variability over the cardiac cycle). The anesthesiologist should feel comfortable with a “flow chart” of sorts for interpretation of various combinations of these values (a fantastic flow chart was provided by our presenter).

Key Points for Perioperative Management of LVAD Recipients Facing NCS

Monitoring is an obvious feature of any anesthetic, but for LVAD patients, it is of particular import. Luckily, every patient comes to us with her or his own console, able to provide a wealth of information in its own right. Beyond this, blood pressure monitoring can safely be monitored non-invasively for MAC-based anesthetics–as long as a backup plan is in place if the cuff is unable to read (interestingly, Doppler makes a good stand-in; practitioners should recall that in a more desperate situation, auscultation and palpation allow us to glean at least a subjective view of the patient’s pressure status in a pinch). However, for most general anesthetics, an arterial catheter is the most sensible choice.

Anesthesiologists should be prepared to provide defibrillation and/or cardioversion; dysrhythmias can negatively impact device function and cardiac output. In terms of cardiopulmonary resuscitation, non-standardized recommendations exist for LVAD patients. External chest compressions can damage the outflow conduit, and thus catastrophically obstruct flow. Recommendations vary between differing expert groups and device manufacturers; it is important that the anesthesiologist know the specific device’s warnings and suggested actions in the event that the patient requires CPR. Common to most expert recommendations: if the device is functional, external chest compressions should be avoided (cardiac massage, however, is an option if available).

Management of anticoagulation and antiplatelet therapy presents a unique set of considerations for the anesthesiologist. Literature from the last ten years has presented some variation in the respective groups’ management of this problem, but there are some clear trends: for example, active reversal of AC and AP was rarely performed in both endoscopic and surgical procedures. Substantial fractions of patients studied (anywhere from 47% to a “majority”) had some form of passive reversal. Regardless, practitioners should be prepared to transfuse blood products both during the procedure and in the ensuing acute post-operative period. Moreover, these patients are often best served by a cardiac critical care setting post-operatively, where physicians and nurses are comfortable with the demands of the patient’s device.

Care for LVAD patients requires a multi-disciplinary approach at a center equipped to care for those requiring leading-edge technology. Together with the prepared anesthesiologist, these facilities can provide a safe setting for LVAD recipients to undergo NCS. An understanding of the device’s mechanics and function, as well as the pharmacological requirements of these patients, can help us as providers provide quality care.

*Coverage of the Review Course Lecture, LVADs and Non-cardiac Surgery: What to Do When They Come to Your OR