Patient underwent aortic root, ascending aorta, aortic valve replacement and CABG. Following the initial bypass the patient remained in theatre for assessment for bleeding. Decision made to re-open the chest and a requirement for further cardiopulmonary bypass was needed in an emergent fashion to resolve bleeding. This was now out of hours with the 1st on call being occupied by a concurrent emergency leaving only the 2nd on call to respond. A circuit with an emergency checklist and full pre-bypass checklist was utilised. Heparin was added to the bypass prime once 'off and clamped' and circulated through the main re-circulation line (arterial to venous bridge). The bridge was not re-clamped and bypass initiated. Low blood pressure and low patient NIRS were recorded for a significant period of time. Roller pump flows (no flow probe post bridge) were increased beyond calculated full flow and troubleshooting commenced. The unclamped bridge was identified and full flow to the patient re instituted.