After instigating cardiopulmonary bypass for an urgent procedure, it was noticed the venous return was not satisfactory to sustain full flow despite surgical manipulation. CPB was discontinued, the venous line disconnected at the inlet of the venous reservoir where a non-hospital standard luer cap was found lodged inside the venous inlet port. This was removed, CPB re-instituted and no further problems were encountered. No harm came to the patient.

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