Patient had their procedure completed.  There was a miscommunication/misdirection between the operating surgeon and the trainee perfusionist.  

The recirculation line was opened while the arterial cannula was still in situ.  The patient was accidentally exsanguinated, which was noticed by the anesthetist and immediately resolved by closing the shunt and re-transfusing.  

The patient did not seem to suffer harm and the incident was reported to the parents and hospital Datix.  The team de-briefed and reinforced need to have positive reinforcement of directions and understanding of stages.