Alternative Strategies for Challenges in Veno-Arterial ECMO Cannulation
Extracorporeal membrane oxygenation (ECMO) for cardiac
failure is on the rise worldwide. Some challenges, such as limb ischemia and
thrombotic or hemorrhagic events, are well-recognized. Newer data suggests that
ventricle distension and upper body hypoxemia during veno-arterial (VA) support
may be harmful to patient recovery also. In this video series, we present two
clinical scenarios highlighting alternative strategies for optimal VA support.
Challenge #1: Poor drainage of the right heart with distension of the left ventricle (LV)
Solutions: The addition of a second venous drainage into the right internal jugular (RIJ) vein may improve volume return to the circuit. A left ventricular (LV) vent may also be considered, and could be placed percutaneously (ie: Impella, ABIOMED), or surgically (direct apical versus right superior pulmonary vein). LV decompression may also protect from ventricular thrombus by decreasing stasis.
The accompanying video details the addition of a second venous drainage cannula into the RIJ vein, and the importance of communication during transition.
Basic Steps: Addition of second venous cannula (VVA ECMO)
1. Communicate with team regarding anticipation of brief period of separation from support. Discuss titration of medications and alternative support during this period.
2. Standard access through RIJ vein with sequential dilation to cannula size. ECMO flow decreased during dilation to avoid entraining air.
3. Measure and pre-fill additional tubing to reach from groin to neck. Allow mild redundancy for transport.
4. Stop ECMO flow, clamp and splice y-connector into the circuit. Reconnect original tubing to y-connector and add the new tubing to the other arm (see video). Unclamp the lines at the groin and re-establish flow.
5. Connect the new IJ cannula to the new tubing arm, and establish flow after de-airing.
Challenge #2: Dual circulation/Upper body Hypoxemia
Fully saturated blood is ejected from the circuit mixing with blood being pumped from the heart The degree of respiratory failure determines the oxygenation of this blood, and the degree of myocardial dysfunction determines the location of this blood, the so-called “mixing cloud”. With poor myocardial function, the point of mixing may be in the proximal ascending aorta, but as the heart recovers this zone may migrate further down the arch and even into the descending aorta, leaving the head and upper body desaturated (ie: Harlequin syndrome).
Solutions: A second venous drainage cannula (see above) will decrease blood flow through the heart and lungs. A second arterial inflow cannula into the RIJ may also be added to increase the oxygenated blood being delivered through the lungs and ejected by the heart, thus improving upper body saturations. The technique is identical to that previously described, except the new RIJ cannula is spliced into the arterial side of the circuit rather than venous.
A surgically placed LV vent may also be spliced into the venous system, decreasing deoxygenated blood being ejected by the heart. A percutaneous device is less useful in this case, as the blood transported across the aortic valve is still deoxygenated.
Lastly, transition to VA ECMO with axillary arterial cannulation may improve cerebral saturations (82% versus 54%) as compared to femoral cannulation.
In summary, peripheral VA cannulation may support the acutely failing heart with several emerging nuances. Alternative strategies such as the addition of cannulas for either drainage or perfusion must be considered in cases of ventricular distention or of upper body hypoxemia.
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