Management of prolonged QT interval during a massive transfusion: calcium, magnesium or both?

This case report describes the intra-operative management of a prolonged QT interval in the setting of massive transfusion.

A previously healthy, 45-yr-old man presented for repair of a class IV thoraco-abdominal aneurysm. The initial stages of the operation were relatively uneventful, with the exception of an estimated blood loss of 5.0 L. At this point the patient's QT interval became markedly prolonged, and subsequently narrowed in response to supplemental calcium and magnesium. A blood sample taken just before QT prolongation revealed an ionized calcium of 0.98 mmol x L(-1) and an ionized magnesium of 0.37 mmol x L(-1), indicating, that low magnesium may have contributed to the QT interval prolongation.

This case illustrates the importance of following both ionized calcium and magnesium in the setting of a massive transfusion.