One of the big complications of VA ECMO is something called Harlequin Syndrome, also known as North-South Syndrome. It happens when the oxygenated blood being returned from the ECMO circuit mixes with the deoxygenated blood being ejected from the heart (there was a big reason the patient was put on ECMO, remember?). This is actually sometimes a good sign, because it means the heart is able to pump (you were on VA because of heart problems). But, the lungs haven’t really recovered yet, hence the deoxygenated blood being ejected. And so, despite the good news of better heart function, the patient still may end up in life-threatening hypoxia from this mixing.
As usual, countbackwardsfrom10 is our go-to for all things cardiac surgery, and he has a nice Instagram post explaining this phenomenon and what to do about it.