A Glenn shunt is a connection of the superior vena cava to the pulmonary artery to provide pulmonary blood flow. This operation is the second step in the pathway to a single ventricle circulation. Patients are usually cyanotic with polycythaemia, which can cause hyperviscosity syndrome when dehydrated and coagulation problems. Anaesthetic management is determined by the underlying condition. For good flow through the Glenn keep well hydrated to maintain central venous pressure and carefully decrease the pulmonary vascular resistance with oxygen and mild hyperventilation as needed.