To assess for recirculation, what should be observed?

Monitoring for recirculation in patients on ECMO involves assessing the oxygen saturation levels at different points in the circuit. When recirculation occurs, it means that blood exiting the venous cannula is returning to the pump too quickly, leading to a mixture of oxygenated and deoxygenated blood.

When the patient’s arterial blood oxygen saturation (SaO2) is very similar to the pre-oxygenator blood oxygen saturation (SO2), it suggests that the oxygenated blood is not adequately mixing or that a significant amount of deoxygenated blood is being returned to the patient's circulation. This similarity in values indicates that recirculation is present because the blood going back to the patient is not getting enough oxygenation due to poor flow dynamics within the support circuit.

This physiological understanding underscores why option B is correct, as it directly reflects the potential impaired oxygenation resulting from recirculation, making it an important assessment parameter for ECMO management.

While bright red blood in both cannulas might suggest adequate oxygen delivery, it does not provide the same direct insight into the functioning of the circuit and potential recirculation issues. Increased levels of CO2 may indicate inadequate ventilation or other metabolic problems but do not specifically assess recirculation dynamics. Lastly