During administration of the first dose of cardioplegia the pump that mixes the cardioplegia drug with blood stopped. This was observed by the perfusionist running the heart lung machine. The blood pump (master) to which the cardioplegia pump is slaved continued to run.

The control knob of the master was turned to off and then twisted to restart administration but the cardioplegia pump would not start.

The surgical team was alerted and the settings of the cardioplegia pumps and module reviewed but with no observable cause.

The cardioplegia dual pump base was turned off and on again and the pumps restarted. This time the cardioplegia pump restarted but the flow was much faster than the flow ratio set in the cardioplegia module.

The perfusionist administered cardioplegia intermittently due to the high flow to achieve cardiac arrest. After an appropriate dose was administered, the perfusionist sought a second opinion of a perfusion colleague.

Within the settings on the cardioplegia pump A the master slave ratio was displayed as "NaN". By changing the flow ratio on the cardioplegia module this value was changed to a corresponding percentage and the normal operation returned. The pump was be quarantined and reported to the supplier and the MHRA.