The cardioplegia pump on the heart-lung machine accelerated uncontrollably during cardioplegia administration. Cardioplegia was administered through a twin-pump module on a Maquet HL20, one blood pump (master) and the other cardioplegia solution pump (slave). During this incident cardioplegia was being given via a vein graft to a coronary artery. The risk of an accelerating uncontrolled pump when delivering cardioplegia down this route is to damage the vessel it is being given down and/or damage to the vein graft to coronary artery suture site.

This is the units third such event in twelve months.

The cardioplegia pumps have the following alarms in place at all times:

• Arterial flow zero: so no cardioplegia flow is possible when there is no arterial flow detected on the HL20.
• Runaway: where the cardioplegia pumps speed is greater than the revs set. If triggered this should stop the affected pump.
• Pressure alarm: where a high and low pressure reached via the cardioplegia line pressure (280mmHg and minus10mmHg). If triggered this should stop the master cardioplegia pump (and therefore the cardioplegia slave as well).

In all of the units episodes (three episodes) there has been audible alarms either for Runaway or Pressure or both but the stop feature did not happen and in each episode the main power switch for that twin-pump module had to be turned off for the Runaway pump to be stopped. The same HLM was in use for each event operated by different perfusion scientists.

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