Cannula Positioning in an Infant on Venoarterial Extracorporeal Membrane Oxygenation: A Rare Cause of Reverse Differential Cyanosis.

• Reverse differential cyanosis in patients on VA-ECMO via carotid cannulation is very rare. • A malpositioned aortic cannula can cause cerebral perfusion with deoxygenated blood. • Checking oxygen saturations in the lower extremity alone can be falsely reassuring. • Document simultaneous upper and lower extremity saturations for all patients on VA-ECMO. • Echo is a useful diagnostic tool to confirm cannula position and guide adjustment.