**9. Weaning**

Following satisfactory cardiac recovery evidenced by minimal inotropic support, maintenance of pulse pressure greater than 15 mmHg, and MAP above 65 mmHg at ECMO flow rate of 2 L/min; the patient is considered for weaning from the ECMO support. Prior to this it is imperative to ensure that bleeding has resolved, any indication for delayed sternal closure should have been resolved, and central venous pressure should be within acceptable limits.

Several successful protocols have been employed for successful VA ECMO weaning. Once such protocol involves a turn down test performed under TEE guidance. The process of weaning consists of reducing the flow rate by 50% for 10 minutes; then, if the right and left ventricular EF do not deteriorate and no mitral regurgitation or distension of the left ventricle occurs, an additional 25% reduction of flow support is done for 5 minutes. If at this time, the TEE demonstrates good function, then weaning may commence. Recognizing that even minimal ECMO flows decompress, and hence may not completely test, the right heart function; the interim ELSO guideline on VA ECMO recommends Pump Controlled Retrograde Trial where the arterial flow probe is reversed, and 1 liter of flow is returned to the right heart through the venous cannula. Successful weaning is expected following a turn down test evidenced by mean arterial pressure above sixty mm Hg, left ventricular outflow track velocity time integral (VTI) above 0.12 m/s, tissue Doppler lateral mitral annulus peak systolic velocity of 6 cm/second and above, central veinous pressure of ≤10 mm Hg, and left ventricular EF ≥ 25–30% on minimal doses of one or two inotropes or pressors [64].

Another weaning protocol consists of progressively reducing the support daily and at least a daily TEE check. In this protocol, the support is initially reduced to 75% support for 24 hours, if the hemodynamics remain stable, a TEE is performed to confirm that ejection fraction remains greater than 40% with no left ventricular distension and MR. Weaning is advanced by further reduction to 50% support for 24 hours, and then 40% while ensuring stable vitals, inotropes and labs. It is acceptable to decannulate if parameters remain stable with 25% support for one hour [59].
