Time is Right for Restrictive Transfusion Strategy in ECMO

Despite studies supporting a restrictive red cell transfusion strategy in many medical situations, a more liberal strategy is still widely used in patients who need extracorporeal membrane oxygenation (ECMO), Alexander Vlaar (Amsterdam UMC, The Netherlands) highlighted during ‘The Heart of Anaemia’ session.

The time has come to question the preponderance of the liberal strategy and conduct a randomized trial to prove the restrictive strategy is safe in all patients requiring prolonged cardiopulmonary mechanical support, he said in a pre-meeting interview.

“Within medicine, and especially within intensive care medicine in the past decade, it has become clear that a restrictive transfusion policy of red blood cells in the setting of anaemia is safe, and sometimes there is even a signal towards a better outcome than with a liberal transfusion policy,” observes Vlaar.

“This is quite counterintuitive,” he acknowledges, “because in the past, we were thinking if a patient is anaemic and is critically ill, we need to compensate the anaemia, to have proper oxygen delivery to the tissue. But then it turns out it’s actually the blood transfusion, which is allogenic probably, has so many downsides in the long term, that it is not making your patient better.”

A liberal transfusion strategy is one where patients with anaemia are given a blood transfusion only when their haemoglobin level falls below a threshold of 9-10 g/dL. “But 90% of patients on ECMO hit this threshold because they often have a severe disease in which they become anaemic,” says Vlaar. The restrictive transfusion strategy on the other hand is where a transfusion is given only once the hemoglobin level drops a little lower, under a threshold of about 7-8 g/dL.

“In many areas in the intensive care setting ­­– the general ICU patient, but also the patient with septic shock, the cardiac surgery patient have all been investigated in randomised trials – ­the restrictive transfusion policy has been shown to be safe in anaemic patients,” says Vlaar.

Patients with acute cardiac syndromes were kept out of those trials, however, because it was though that it was clear that if they had anaemia that this needed to be corrected. When a trial was finally done in this specific patient group it not only showed that the restrictive policy was safe, but that it might also be safer than the more liberal approach.¹

“Everything again, counterintuitive of what we have been taught in medicine in a way,” says Vlaar. “But that’s the issue that was never taken into account, that the correction of anaemia with an allogenic blood product  is actually so harmful.”

Patients are put on ECMO because they are critically ill, they have heart or lung failure and without it they would very likely die.

“It is a bridge to recovery, or a bridge to transplants, or a bridge to a decision, because sometimes it’s not yet clear whether we have a solution for those patients,” says Vlaar. “It’s one of the remaining areas in the ICU where we still apply a very liberal transfusion policy. But we want to challenge that.”

Vlaar and colleagues in The Netherlands and Belgium are set to do just that, by conducting a randomized trial that will see around 400 patients on ECMO being recruited to see if a restrictive or liberal transfusion strategy is safer for patients.

Why is the time right for this trial? It’s because firstly it’s an area where a liberal policy is still favoured and secondly it’s because trials in other patients such as those with sepsis or heart failure, have shown the approach to be safe.

“When you put a patient on ECMO, which is compensating for heart failure and lung failure, there is actually no reason anymore to think that compensating your anaemia is necessary,” he suggests.

Reference

1. Ducrocq, G, Gonzalez-Juanatey JR, Puymirat E, et al. Effect of a restrictive vs liberal blood transfusion strategy on major cardiovascular events among patients with acute myocardial infarction and anemia. JAMA. 2021;325(6):552-560.

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