Chair, AAEM Critical Care Medicine Section
Staff Intensivist, Washington Hospital, Fremont, CA
[email protected]
Emergency Medicine Resident and MedED Enthusiast. Learning and teaching medicine one doodle at a time!
The Pre-brief
The left ventricle can be fairly forgiving after acute injury; it can regain substantial systolic and diastolic function over a matter of just a few months with an array of outpatient medications. The right ventricle, however, is extraordinarily unforgiving. There are two options when the RV acutely fails in the context of a pre-existing LVAD: systemic circulation VA ECMO or a temporary (external) RVAD, which I affectionately call a “REC! MO” since it is often an ECMO circuit–complete with an oxygenator–that only circulates blood through the right side of the heart. (Other mechanical circulatory support (MCS) options are used too, such as the Impella, but the principles described here are the same.) Unfortunately, neither option is strong, and the patient’s prognosis is usually remarkably poor (1, 2, 3)
ECMO for the Failing RV
First, if you take the option of systemic circulation VA ECMO for RV failure in the context of an LVAD, the management is fairly straightforward: treat the patient like a typical VA ECMO patient with a fancy (and very effective) LV vent (4). The problem with this approach, though, is that you are still using retrograde flow, which comes with a host of problems such as high arterial pressures, extremity hypoperfusion, higher risk of cerebral hypoperfusion, and an array of additional complications that occur when blood is being forced retrograde throughout systemic circulation (5). That is a different topic.
This article focuses on the R-ECMO approach, which creates “dueling banjos” as an attending of mine would call it. (Credit to Dr. Stephen Ruoss for the outstanding phrase.) There are a few ways of cannulating a R-ECMO, but the essentials are an inflow cannula (usually from the femoral vein or right atrium) and an outflow cannula (to the pulmonary trunk). It can be done with a resternotomy (remember the patient has an LVAD placed already) or a percutaneous approach (6).
The illustration below shows a common R-ECMO set up in which the inflow cannula is drawing from the RA, and the outflow cannula is sending blood anterograde into the pulmonary trunk (main pulmonary artery). There are two important concepts: 1) the lungs do not like being monkey in the middle and 2) you don’t actually know the cardiac output from the LVAD so you can’t just match flow in and out of the lungs.
The lungs, fickle creatures that they are, do not tolerate the same flow of incoming blood with flow of outgoing blood. Instead, the systemic flow (LV and LVAD drawing blood from the lungs) must be greater than the pulmonary flow (RV and R-ECMO pushing blood into the lungs).
Figure 1. Start at the right atrium, where there is a light gray cannula taking deoxygenated blood to the ECMO circuit (or it could be an Impella or other such device that would not include an oxygenator). From the ECMO pump and oxygenator, oxygenated blood then joins deoxygenated blood in the pulmonary artery and goes out the pulmonary trunk to the lungs. The lungs may or may not add significant oxygen; for this example the lungs do not. Mixed blood returns to the LA from the pulmonary vasculature and then either goes through the aortic valve with native contraction or through the LVAD, but it’s the same blood and it meets, moving anterograde in the ascending aorta. All flow here is anterograde.
Figure 2. Trying to send equal amounts of blood from the right side that will be drawn to the left side will often cause higher hydrostatic pressure than the pulmonary vasculature tolerates, causing capillary leak into the lungs.
Figure 3. The left side should be pulling slightly more (0.5-1 L/min) than the right side is pushing.
Here are some practical tips:
- Re-evaluate frequently with ultrasound and update the hematocrit in the LVAD flow calculations often if the patient is fresh post-op or otherwise being fluid resuscitated so the calculated flow is as accurate as possible. The intravascular fluid shifts can drastically change the dance music of the banjos.
- Keep something constant with regard to oxygenation–whether the mechanical ventilation or the oxygenator–so you can accurately see a change in oxygenation status. Balance that oxygenation status with flow alarms from the R-ECMO and the LVAD.
- If the lungs do become over-hydrated, use your suction alarms and pressure values of the R-ECMO and LVAD in addition to ultrasound to determine if you need to decrease your R-ECMO flow or increase your LVAD flow.
- The interventricular septum on ultrasound should be approximately center or a little bit shifted left (which would indicate more pull to the left than push from the right).
- On the topic of ultrasound, if an LVAD/R-ECMO patient comes out of the OR as a hot mess, I ask the anesthesiologist to leave the TEE probe in place so I can very easily check the septum as I change settings in the first few postoperative hours when the fluids are shifting. The first 4-ish hours tend to be the most active.
- Try NOT to touch the settings. Unless there are serious alarms, significant suction events, significant hypotension, etc, try to let things settle on their own as the fluid shifts occur postoperatively because you don’t want to overshoot.
- Accept “good enough.” Perfection is the enemy of success in this scenario because when you touch one setting, something else almost always changes, too, and there can be a great propensity to go in circles.
The Debrief
- RV failure in the setting of an LVAD has support options but each comes with some significant challenges.
- When using a R-ECMO circuit plus an LVAD, keep the LVAD flow slightly faster than the R-ECMO flow.
- When using a R-ECMO circuit, keep vigilant for fluid shifts; use the ultrasound frequently to keep the interventricular septum midline to slightly left-ward bowing.
References
- Lampert BC, Teuteberg JJ. Right ventricular failure after left ventricular assist devices. J Heart Lung Transplant. 2015 Sep;34(9):1123-30. doi: 10.1016/j.healun.2015.06.015.
- Kormos RL, Teuteberg JJ, Pagani FD, Russell SD, John R, Miller LW, Massey T, Milano CA, Moazami N, Sundareswaran KS, Farrar DJ; HeartMate II Clinical Investigators. Right ventricular failure in patients with the HeartMate II continuous-flow left ventricular assist device: incidence, risk factors, and effect on outcomes. J Thorac Cardiovasc Surg. 2010 May;139(5):1316-24. doi: 10.1016/j.jtcvs.2009.11.020.
- Meineri M, Van Rensburg AE, Vegas A. Right ventricular failure after LVAD implantation: prevention and treatment. Best Pract Res Clin Anaesthesiol. 2012 Jun;26(2):217-29. doi: 10.1016/j.bpa.2012.03.006.
- Cevasco M, Takayama H, Ando M, Garan AR, Naka Y, Takeda K. Left ventricular distension and venting strategies for patients on venoarterial extracorporeal membrane oxygenation. J Thorac Dis. 2019;11(4):1676-1683. doi:10.21037/jtd.2019.03.29
- Rupprecht L, Lunz D, Philipp A, Lubnow M, Schmid C. Pitfalls in percutaneous ECMO cannulation. Heart Lung Vessel. 2015;7(4):320-326.
